PG&E EPSS and generator options

[wwu123]

Thanks for the additional advice. I bought a small (700W) propane generator a few years ago, and only had occasion to finally use it this spring when the big windstorm took power and Internet out for 2 days. But it fortunately started up and worked great, and gave me practice on filling and changing the oil, and running on propane.. Since I anticipate only using the whole-house generator once every year or so for longer 6+ hr outages only, I'm specifically planning to get dual-fuel and run only with propane on the 240V generator, so no worries about gas stability and gunk (will only use gas as a last resort if the big one hits). And will change out the oil at least once a season.

Different plan for the generator location now, on the other side of the house - basically in the front of the house, but a rainscreen fence shields it from the street view It's on the other side of the garage door from the panel, has a concrete pad and some wide eaves that will mostly keep the rain off (plus I'll buy the vinyl generator cover). The clearance in this location is only 20-21" wide, so the smaller model I'm eyeing is still critical, as it's 18" wide vs 24" on most other brands. I can then wheel it easily across the flat driveway, basically to the front door, where the 20' BPTM cable will reach over a 4' grade without me having to wheel the generator down the grade, or through any dirt/mud. The one negative is the generator exhaust is a few feet from the front door, but the area is well-ventilated, and honestly we never use the front door, nor are the main living areas close to there.

The original storage location idea would reach with 70' of cable, and it's flat and dry there too. But even if the cable is rated for the conditions, it's still 50' of muddy cable I'll have to wind up and store each time. From the new storage location, I could even reach with 70' of cable across the driveway, if I didn't want to wheel it, so a more flexible location in every respect....

 

[BGbreeder]

Propane is a great fuel for long term storage in my book, and it is much less taxing on oils as well.

If the space around the generator is tight, I would be mindful of where the exhaust is pointed, and that there is enough space for fresh air for cooling and for the engine. I would check the owner's manual for recommendations on clearances.

If there is a break in procedure, I would try to follow it. Most new engines don't respond well to 100% load right away, nor to 5% loads.

All the best,

BG

 

[wwu123]

So ordered and received 240V generator from Home Depot, and… sigh, a number of issues…so seeking input from @BGbreeder and other experts here. Please bear with me on the my lengthy debate…

First, it wasn’t actually smaller/lighter than others in its class, they just listed the wrong specs without the wheel kit attached in the manual and online. Lo and behold, the unit came with an updated manual, it’s 23” wide instead of 18”. So it won’t easily roll or fit in the hidden area in front of the house, I may have to wipe out a nice plant that’s narrowed the opening to about 18”, or I can almost lift the heavy guy through the gap, sans wheels.

Second, and more concerning, I looked at the wiring diagrams for the bonded neutral (there for the 120V GFCI outlet), it looked like it was just behind the alternator end cap. Videos for some other brands showed separating the neutral/ground wires there. But after removing the two screws, it appears this thin stamped metal cap is pretty tightly press-fit onto the alternator housing - any attempt to wrangle it off with tools will likely visibly mangle the thin metal, thus clearly voiding any warranty or returns. Although I can see some large gauge wires through the cap air slots, I’m wary in case I can’t actually find or separate the bonded wires, or the unit is defective.

It’s just within the weight I can lift to return to store (may yet have to rent a truck to fit). But there are so few other options meeting my specs, basically a few clones of this from other brands - at least one brand with floating neutral, but must order/return online (so a real pain if any issues):
-18-24” wide (so I can store in front)
-240V (required for transfer switch)
-dual-fuel preferred (but gas-only doesn't really expand the options much)
E.g. Champion, Generac don’t even have a 240V in this size, have to step up to 165+ lbs, 27" wide, and thus have to store and wheel it around steep, narrow (muddy) slopes I'd hoped to avoid.

So I’ve been reading up - what are the exact safety or functional risks of just running this one with the bonded neutral? I feel like the risk is remote, but manageable. Having the two neutral bonds forms a ground loop - the loop is strictly between the generator/frame (through the BPTM) and the main panel, and the risk is mainly shocking myself with any return current. I plan to run it sitting on a front concrete walkway, always wear leather gloves and rubber-soled shoes. The BPTM procedure is to cut the main panel switch before connecting/disconnecting the generator - so there won’t be any loads when I have to start/stop/connect the generator to the meter.

Can folks validate the following are NOT real issues with the double neutral bond?
-Will it trip the 120V GFCI outlet on the generator? N/A, the 120V outlet is not energized in 240V mode
-Will it trip the 240V GFCI outlet on the generator? N/A, none of the models I’m looking at have GFCI on the 240V outlet
-Will it prevent my hardwired gas furnace from running? No. Many gas furnaces need to sense ground (or at least non-floating neutral) to activate. Double neutral bond is still grounded. Though, one person posted online they suspected “stray currents” in the ground loop prevented their furnace from activating, until they disconnected the 2nd neutral bond in the generator.
-Will it trip the GFCI/AFCI circuits in my panel (which is almost all my 120V lighting/outlets)? No. The issue with simpler manual transfer switches is they run a single common neutral back from the transfer switch back to panel, bypassing the individual neutral return on individual GFCI/AFCI breakers, causing them to trip. The BPTM transfer is at the meter, doesn’t modify the GFCI/AFCI circuits, so the hot/neutral currents remain unmodified and balanced.
-Will it pass large return current of major household appliances through the rest of my house outlets? No, the ground loop is only from the panel to the generator, so even if stray return current is going through the ground loop, that is not passing through neutral or ground of my household outlets.
-Will it energize the grounded chassis on my stereo/TV/microwave and blow them up, or electrocute someone who touches it? No, same as previous. The chassis on non-defective device is grounded, it is not tied to neutral - if it is already wired defectively (the point of having ground) where stray hot/neutral current is passing to ground, it was already a hazard regardless. Though, there is some nonzero risk that the larger return current of another appliance could pass through a smaller shorting defective device, but that is irrespective of the generator ground loop…

In summary, both the PG&E BPTM and similar GenerLink transfer meter list both floating and bonded neutral generator models as compatible, without any overt warnings about unbonding neutrals (only overt incompatibility are rare units with GFCI on the 240V outlet). I’d like to try leaving the neutral-bond in place for a year or two, before I mangle the alternator cap (and my warranty) to try to access the wires …

 

[BGbreeder]

So ordered and received 240V generator from Home Depot, and… sigh, a number of issues…so seeking input from @BGbreeder and other experts here. Please bear with me on the my lengthy debate…

First, it wasn’t actually smaller/lighter than others in its class, they just listed the wrong specs without the wheel kit attached in the manual and online. Lo and behold, the unit came with an updated manual, it’s 23” wide instead of 18”. So it won’t easily roll or fit in the hidden area in front of the house, I may have to wipe out a nice plant that’s narrowed the opening to about 18”, or I can almost lift the heavy guy through the gap, sans wheels.

Second, and more concerning, I looked at the wiring diagrams for the bonded neutral (there for the 120V GFCI outlet), it looked like it was just behind the alternator end cap. Videos for some other brands showed separating the neutral/ground wires there. But after removing the two screws, it appears this thin stamped metal cap is pretty tightly press-fit onto the alternator housing - any attempt to wrangle it off with tools will likely visibly mangle the thin metal, thus clearly voiding any warranty or returns. Although I can see some large gauge wires through the cap air slots, I’m wary in case I can’t actually find or separate the bonded wires, or the unit is defective.

It’s just within the weight I can lift to return to store (may yet have to rent a truck to fit). But there are so few other options meeting my specs, basically a few clones of this from other brands - at least one brand with floating neutral, but must order/return online (so a real pain if any issues):
-18-24” wide (so I can store in front)
-240V (required for transfer switch)
-dual-fuel preferred (but gas-only doesn't really expand the options much)
E.g. Champion, Generac don’t even have a 240V in this size, have to step up to 165+ lbs, 27" wide, and thus have to store and wheel it around steep, narrow (muddy) slopes I'd hoped to avoid.

So I’ve been reading up - what are the exact safety or functional risks of just running this one with the bonded neutral? I feel like the risk is remote, but manageable. Having the two neutral bonds forms a ground loop - the loop is strictly between the generator/frame (through the BPTM) and the main panel, and the risk is mainly shocking myself with any return current. I plan to run it sitting on a front concrete walkway, always wear leather gloves and rubber-soled shoes. The BPTM procedure is to cut the main panel switch before connecting/disconnecting the generator - so there won’t be any loads when I have to start/stop/connect the generator to the meter.

Can folks validate the following are NOT real issues with the double neutral bond?
-Will it trip the 120V GFCI outlet on the generator? N/A, the 120V outlet is not energized in 240V mode
-Will it trip the 240V GFCI outlet on the generator? N/A, none of the models I’m looking at have GFCI on the 240V outlet
-Will it prevent my hardwired gas furnace from running? No. Many gas furnaces need to sense ground (or at least non-floating neutral) to activate. Double neutral bond is still grounded. Though, one person posted online they suspected “stray currents” in the ground loop prevented their furnace from activating, until they disconnected the 2nd neutral bond in the generator.
-Will it trip the GFCI/AFCI circuits in my panel (which is almost all my 120V lighting/outlets)? No. The issue with simpler manual transfer switches is they run a single common neutral back from the transfer switch back to panel, bypassing the individual neutral return on individual GFCI/AFCI breakers, causing them to trip. The BPTM transfer is at the meter, doesn’t modify the GFCI/AFCI circuits, so the hot/neutral currents remain unmodified and balanced.
-Will it pass large return current of major household appliances through the rest of my house outlets? No, the ground loop is only from the panel to the generator, so even if stray return current is going through the ground loop, that is not passing through neutral or ground of my household outlets.
-Will it energize the grounded chassis on my stereo/TV/microwave and blow them up, or electrocute someone who touches it? No, same as previous. The chassis on non-defective device is grounded, it is not tied to neutral - if it is already wired defectively (the point of having ground) where stray hot/neutral current is passing to ground, it was already a hazard regardless. Though, there is some nonzero risk that the larger return current of another appliance could pass through a smaller shorting defective device, but that is irrespective of the generator ground loop…

In summary, both the PG&E BPTM and similar GenerLink transfer meter list both floating and bonded neutral generator models as compatible, without any overt warnings about unbonding neutrals (only overt incompatibility are rare units with GFCI on the 240V outlet). I’d like to try leaving the neutral-bond in place for a year or two, before I mangle the alternator cap (and my warranty) to try to access the wires …

I'm reminded of the old line, "trust, but verify"... I'm sorry that the size isn't right. How are you for cooling clearance and fire clearance with this width now?

My preamble: I am not a trained electrician or contractor. My expertise lies in other areas.

I think that your analysis looks right to me.

I agree that grounding is complicated. I have been working with grounding and grounding issues for more than a few years, and I still think it isn't simple or clear cut.

In my limited reading and experience, I think that there are several themes that run through the grounding literature;

• One, what is a safe path for high voltage to earth, e.g. lightning?
• Two, what is the best way to manage wiring and device failures that put voltage into ground instead of, or in addition to, neutral?
• Third, what might be the potential for low level stray currents and corrosion from having duplicate, but spatially distant grounds? (If one of your ground rods corrodes the other due to a ground loop, the second may become a less effective ground.)*
• Fourth, what are the risks of having a generator fault, or generator supported wiring fault, that connects a hot to the generator frame? Depending on where the powers to be sit, they have different views (I think) on these subjects, and draw up rules to match. Portable generators temporarily attached to homes seems to me, as a non-professional, not to have received the attention it might have. In the old days, you had grid power and you had off-grid portable generator uses. Now there are lots of in-betweens.

I'm leaving out automotive grounds and grounding which are another whole ball of wax, as are computer and RF grounding systems.

If it were me, I would call/contact technical support for your generator and have them walk you through what is required to remove the cap covering the bond. In my book, if the manual is so poorly drafted that a reasonable consumer can't figure it out, the company needs to foot the bill for the call. I suspect that your press-fit cap comes off pretty easily. You can get some nice plastic chisels from Amazon or Harbor Freight, but a block of wood will probably work. I would double check your generator manual about whether you can or should have a ground rod for the generator. For grounding, larger diameter and taller rods are better, but check with 811 before driving one.

I know of folks who have discovered some pretty significant things underground that weren't marked. Like the power company linesmen who were replacing an old power pole one day across the street from where I was living. They drilled a new hole 8" over from the existing one. Being the curious sort, I wandered over and peeked in the hole, and asked what the shiny stuff at the bottom was. "Trash" they replied. In other circles, that "trash" was known as the 20,000 conductor telephone cable for the town west of that point. It took the phone company a week with two technicians pair-wise matching splicing the cable back together 24x7, together with teams of technicians at other junction boxes all across town west of there. $$$$​

As an overall comment, without a ground rod and grounding at the generator, I would point out that until your cable is fully hooked up to the BPTM and the generator, you will have no ground or grounding at the generator, and once the cable is hooked up, you are dependent on the electrical continuity of the outlets, plugs, and wires in between.

With only grounding somewhere other than the generator frame, you run the risk that the generator frame may not be at ground potential with respect to the soil and/or house in the area of the generator. Given the narrow space that you want to use this in, I think that you run a larger risk of grounding the generator frame when you don't intend to, and you might want to take more precautions. I would also consider what might happen if the generator develops a fault and puts 120V, unfused, into the generator frame. Would you want a second ground at the generator? Regardless, I would be thinking heavy duty rubber gloves and rubber boots.

I'm not an NEC expert, and as far as code compliance and future fire insurance risks go, I think that you would want to show that you followed NEC and the generator manual.

Folks that I know with far more experience than me with portable generators always drive at least one ground rod, and connect it to the generator.

Finally, I would not believe everything that you read.

All the best,

BG

*Grid power transformers for 120/240 typically (ok should always) have the mid point of the 240 windings (aka the neutral) grounded at the transformer. Which to a non-professional could look a lot like a neutral ground bond. Which is curious, because that would make it look like doubly bonded grounds and neutrals might actually be pretty common. Personally, I certainly think it is desirable to ground the neutral at the transformer and to ground the neutral at the house for many reasons. One might ask why more ground neutral connections are desirable or not desirable. Those who are actually knowledgeable about the NEC can probably explain why this is not actually a double bond between neutral and ground. (@wwhitney or @Vines care to comment?)

In many respects, a portable generator is analogous to that transformer from the perspective of being a power source.

I can personally testify to what can go wrong in the nanosecond that the home ground to neutral bond is broken and the transformer ground to neutral is missing (due to a lightning storm a year earlier...). Lots of failures happened beforehand to contribute to those transformers (3!) blowing up. My point is that the improbable does occasionally happen, and it is prudent to assume that the improbable will happen.

 

[wwhitney]

I somewhat quickly reviewed this thread.

I know no hands on experience with portable engine generators, but I don't see the point of having an earth rod connected at one. What fault scenario is improved by having an earth rod there, other than a direct lightning strike?

As to using a generator with a neutral-EGC bond versus one without, for the BPTM it is moot. From the meter to the service panel there are only 3 conductors, two hots and a neutral, no EGC. So while the L6-30 cable between the generator and the BPTM likely has an "EGC" (more properly called a supply side bonding jumper in this case), I expect it is bonded within the BPTM to the neutral side. This covers the case that the generator is unbonded and bonds the generator case to the neutral. For the case that the generator is bonded, the L6-30 cable's neutral and EGC will be in parallel and both carrying neutral current, but as long as the L6-30 receptacle on the generator has no GFCI functionality, that's no big deal, since the loop is only within the cable, BPTM, and generator.

Cheers, Wayne

 

[cali8484]

The generator uses L6-30 to connect to BPTM? How does it provide 120V? L14-30 is the typical 240/120V generator plug.

 

[wwhitney]

The generator uses L6-30 to connect to BPTM? How does it provide 120V? L14-30 is the typical 240/120V generator plug.

Typo on my part, the rest of the post still holds.

Cheers, Wayne

 

[wwu123]

I somewhat quickly reviewed this thread.

I know no hands on experience with portable engine generators, but I don't see the point of having an earth rod connected at one. What fault scenario is improved by having an earth rod there, other than a direct lightning strike?

As to using a generator with a neutral-EGC bond versus one without, for the BPTM it is moot. From the meter to the service panel there are only 3 conductors, two hots and a neutral, no EGC. So while the L6-30 cable between the generator and the BPTM likely has an "EGC" (more properly called a supply side bonding jumper in this case), I expect it is bonded within the BPTM to the neutral side. This covers the case that the generator is unbonded and bonds the generator case to the neutral. For the case that the generator is bonded, the L6-30 cable's neutral and EGC will be in parallel and both carrying neutral current, but as long as the L6-30 receptacle on the generator has no GFCI functionality, that's no big deal, since the loop is only within the cable, BPTM, and generator.

Cheers, Wayne

So no one is talking about an actual earth rod at the generator, I simply mean a neutral-bonded-to-frame, which ground is also bounded to frame, when I talk about a 2nd neutral-ground bond at the generator. The only earth rod would be from the main service panel. The PG&E tech specifically said no need or desire to have an earth rod at the generator - that was clear enough, but I think that is what he interpreted as my question about a neutral-bonded generator....

I think you're saying the connection from pole to meter to service panel has no ground conductor, which makes sense. But cali8484 is correct, the generator has a 14-30 twist-lock, the BPTM cable has also four conductors on the meter socket side, so presumably is is passing ground as well - basically grounding the generator frame to the panel's ground and therefore to earth, regardless of whether there is a bonded-neutral at the generator.

So for the neutral bonded generator, I think the ground loop does extend from the generator to the BPTM all the way through to main panel. However, the neutrals on the individual circuits are still not within this loop (as I think they might be when using a manual transfer switch. Still no big deal, in your opinion, I hope?

Would it have been clever for the BPTM designers to have it test if the neutral and ground pins are tied (thus a neutral-ground bond) from the generator before switching all 4 pins, and then maybe NOT passing ground through to the main panel? Neutral and frame would still be tied at the generator, but there at least wouldn't be a ground loop going all the way through the cable and main panel. I don't think it does this though; however, the manual says it does have a number of other protections including - resettable overload breakers on each 120V line, voltage surge protection, intermittent connection protection, "lost phases" (I guess if only one 120V is live at the utility?)...

 

[wwhitney]

So no one is talking about an actual earth rod at the generator

BGbreeder mentioned the idea.

So for the neutral bonded generator, I think the ground loop does extend from the generator to the BPTM

Yes, if the generator has an EGC-neutral bond.

all the way through to main panel.

Maybe. I will elaborate in a followup as I don't want to run out of edit time.

Cheers, Wayne

 

[wwhitney]

Maybe. I will elaborate in a followup as I don't want to run out of edit time.

OK, ground is an overloaded term and I generally try to avoid it. It can mean the earth; the EGC (equipment grounding conductor); and it's part of the term for one of the circuit conductors, the grounded circuit conductor (neutral). Or upstream of the service disconnect, it can mean a "supply side bonding jumper."

The EGC system originates at the service disconnect and extends downstream (away from the utility). It does not exist upstream of the service disconnect. Upstream of the service disconnect, all boxes and conduit and so forth, which downstream would be bonded to the EGC, are instead bonded to the grounded conductor.

So whenever there's a metal path parallel to the grounded conductor upstream of the service disconnect, that parallel metal path will be carrying neutral current. Such as a metallic conduit connecting a meter enclosure to a service panel enclosure. This is an accepted side effect of the standard service bonding practices.

With an L14-30 cable, the 4th wire that isn't a hot or neutral is usually thought of as an EGC. But with the BPTM, this cable is upstream of the service disconnect, so it can't be an EGC. Instead it would be called a supply side bonding jumper (since it's on the supply side of the service disconnect). Its job is to bond the case of the generator when the generator has no neutral-"ground" bond. If it does have such a bond, then that creates another parallel neutral path. But as above, upstream of the service disconnect, parallel paths for the neutral (grounded conductor) are accepted practice.

What you would definitely want to avoid is additionally running a separate bonding jumper from, say, a terminal on the generator to an earth electrode that happens to be installed as an auxiliary electrode and connected to the EGC in a subpanel. That would create a neutral-EGC bond downstream of the service disconnect, which is disallowed. And it would put neutral current on the EGC system, which is not supposed to carry current during normal operation.

Cheers, Wayne

 

[wwu123]

I'm reminded of the old line, "trust, but verify"... I'm sorry that the size isn't right. How are you for cooling clearance and fire clearance with this width now?

My preamble: I am not a trained electrician or contractor. My expertise lies in other areas.

I think that your analysis looks right to me.

I agree that grounding is complicated. I have been working with grounding and grounding issues for more than a few years, and I still think it isn't simple or clear cut.

In my limited reading and experience, I think that there are several themes that run through the grounding literature;

• One, what is a safe path for high voltage to earth, e.g. lightning?
• Two, what is the best way to manage wiring and device failures that put voltage into ground instead of, or in addition to, neutral?
• Third, what might be the potential for low level stray currents and corrosion from having duplicate, but spatially distant grounds? (If one of your ground rods corrodes the other due to a ground loop, the second may become a less effective ground.)*
• Fourth, what are the risks of having a generator fault, or generator supported wiring fault, that connects a hot to the generator frame? Depending on where the powers to be sit, they have different views (I think) on these subjects, and draw up rules to match. Portable generators temporarily attached to homes seems to me, as a non-professional, not to have received the attention it might have. In the old days, you had grid power and you had off-grid portable generator uses. Now there are lots of in-betweens.

I'm leaving out automotive grounds and grounding which are another whole ball of wax, as are computer and RF grounding systems.

If it were me, I would call/contact technical support for your generator and have them walk you through what is required to remove the cap covering the bond. In my book, if the manual is so poorly drafted that a reasonable consumer can't figure it out, the company needs to foot the bill for the call. I suspect that your press-fit cap comes off pretty easily. You can get some nice plastic chisels from Amazon or Harbor Freight, but a block of wood will probably work. I would double check your generator manual about whether you can or should have a ground rod for the generator. For grounding, larger diameter and taller rods are better, but check with 811 before driving one.

I know of folks who have discovered some pretty significant things underground that weren't marked. Like the power company linesmen who were replacing an old power pole one day across the street from where I was living. They drilled a new hole 8" over from the existing one. Being the curious sort, I wandered over and peeked in the hole, and asked what the shiny stuff at the bottom was. "Trash" they replied. In other circles, that "trash" was known as the 20,000 conductor telephone cable for the town west of that point. It took the phone company a week with two technicians pair-wise matching splicing the cable back together 24x7, together with teams of technicians at other junction boxes all across town west of there. $$$$​

As an overall comment, without a ground rod and grounding at the generator, I would point out that until your cable is fully hooked up to the BPTM and the generator, you will have no ground or grounding at the generator, and once the cable is hooked up, you are dependent on the electrical continuity of the outlets, plugs, and wires in between.

With only grounding somewhere other than the generator frame, you run the risk that the generator frame may not be at ground potential with respect to the soil and/or house in the area of the generator. Given the narrow space that you want to use this in, I think that you run a larger risk of grounding the generator frame when you don't intend to, and you might want to take more precautions. I would also consider what might happen if the generator develops a fault and puts 120V, unfused, into the generator frame. Would you want a second ground at the generator? Regardless, I would be thinking heavy duty rubber gloves and rubber boots.

I'm not an NEC expert, and as far as code compliance and future fire insurance risks go, I think that you would want to show that you followed NEC and the generator manual.

Folks that I know with far more experience than me with portable generators always drive at least one ground rod, and connect it to the generator.

Finally, I would not believe everything that you read.

All the best,

BG

*Grid power transformers for 120/240 typically (ok should always) have the mid point of the 240 windings (aka the neutral) grounded at the transformer. Which to a non-professional could look a lot like a neutral ground bond. Which is curious, because that would make it look like doubly bonded grounds and neutrals might actually be pretty common. Personally, I certainly think it is desirable to ground the neutral at the transformer and to ground the neutral at the house for many reasons. One might ask why more ground neutral connections are desirable or not desirable. Those who are actually knowledgeable about the NEC can probably explain why this is not actually a double bond between neutral and ground. (@wwhitney or @Vines care to comment?)

In many respects, a portable generator is analogous to that transformer from the perspective of being a power source.

I can personally testify to what can go wrong in the nanosecond that the home ground to neutral bond is broken and the transformer ground to neutral is missing (due to a lightning storm a year earlier...). Lots of failures happened beforehand to contribute to those transformers (3!) blowing up. My point is that the improbable does occasionally happen, and it is prudent to assume that the improbable will happen.

Thanks for the detailed and thoughtful reply! Quite a lot to parse out, and with all possible faults and failure modes, grounding seems to be quite the stumper. I think I've read in some of the Powerwall threads recently that some scenarios even now demand a 2nd earth rod at least 15' from the main panel earth rod - that certainly confused me too.

Anyways, just some quick replies. I've decided to not be bothered by the sizing issue - BTW, the tight location is just to navigate past a bush, and to get under the eaves for storage. I would actually wheel it out of the storage location and be operating in an open area, so plenty fine for cooling, fire, and to not trip the CO sensor. I've also decided I can take out or relocate a bush as needed. So only the weight concerns me on the larger generators, getting above 130 lbs, I can't really lift or maneuver it, much less return it to store - but this one is OK at 120 lb.

I do have an e-mail inquiry in to the manufacturer (WEN), while they make no mention or label of either floating neutral or bonded neutral for most of their generators, they are pretty open in their wiring diagrams, and in their parts diagram. The neutral-ground bond is there, and corroborates having GFCI on the 120V outlet. The top of exploded view clearly shows the two screws holding the alternator end cap (38) on (though again the cap is really press-fit to the housing. I can easily chisel it off, but will damage it - so waiting to see if WEN supports floating the neutral, if they don't, likely they won't warrantee it with the visible end cap damage....

While I await WEN's reply (or lack of), a dual-fuel inverter generator just went on sale at Costco.com, it has a floating neutral. Twice the price, but better in almost all respects - larger wattage, remote start, quieter, narrower including wheels, only 10 lbs heavier. The downside is no-name Chinese brand with poor shipping protection, when it works it works, but lots of DOA units, and almost 100% chance of cracked plastic panel covers (but free replacement covers very do-able). Unbeatable Costco return policy, and I think they will even arrange home pick up for Costco.com returns.

I think I will roll the dice and see if I can get one with relatively little shipping damage, wait til then to decide which unit I want to start up, test and ultimately keep. Unless one is DOA, possibly can return unwanted unit still brand-new never started..

What I take from your grounding analysis is, given all the potential faults and failure modes, including the generator itself, more neutral ground bonds, and more ground to actual earth, might be preferable to risk of neutral-ground loops, as one of the biggest concerns is you yourself becoming that neutral-to-earth or ground-to-earth rod for the full generator output, rather than being in the return path of the household load current. Lots to consider.

Anyways, wrt to the generator faults, the BPTM sequence is 1) shut off main panel breaker, 2) connect up BPTM cable to meter and generator (the BTPM has NOT switched generator to panel yet) , then 3) power up generator, and 4) let BPTM detect and switch from utility (offline) to generator (you're handsoff). So at least when starting the generator, there is no live load, no panel connection, but as you say there's no frame-to-earth connection either so you're at the mercy of any generator faults. Also I guess, if it's a wet day, there could be slight conductiveness from the generator frame across a wet outside rubber sheath of the BPTM cable to the outside frame of the meter socket/combination panel - but hopefully the outside of the panel/socket is tied to earth ground.

 

[wwu123]

OK, ground is an overloaded term and I generally try to avoid it. It can mean the earth; the EGC (equipment grounding conductor); and it's part of the term for one of the circuit conductors, the grounded circuit conductor (neutral). Or upstream of the service disconnect, it can mean a "supply side bonding jumper."

The EGC system originates at the service disconnect and extends downstream (away from the utility). It does not exist upstream of the service disconnect. Upstream of the service disconnect, all boxes and conduit and so forth, which downstream would be bonded to the EGC, are instead bonded to the grounded conductor.

So whenever there's a metal path parallel to the grounded conductor upstream of the service disconnect, that parallel metal path will be carrying neutral current. Such as a metallic conduit connecting a meter enclosure to a service panel enclosure. This is an accepted side effect of the standard service bonding practices.

With an L14-30 cable, the 4th wire that isn't a hot or neutral is usually thought of as an EGC. But with the BPTM, this cable is upstream of the service disconnect, so it can't be an EGC. Instead it would be called a supply side bonding jumper (since it's on the supply side of the service disconnect). Its job is to bond the case of the generator when the generator has no neutral-"ground" bond. If it does have such a bond, then that creates another parallel neutral path. But as above, upstream of the service disconnect, parallel paths for the neutral (grounded conductor) are accepted practice.

What you would definitely want to avoid is additionally running a separate bonding jumper from, say, a terminal on the generator to an earth electrode that happens to be installed as an auxiliary electrode and connected to the EGC in a subpanel. That would create a neutral-EGC bond downstream of the service disconnect, which is disallowed. And it would put neutral current on the EGC system, which is not supposed to carry current during normal operation.

Cheers, Wayne

Yes, I did parse BGbreeder's longer, earlier post AFTER yours, so I see where the generator earth rod was brought up now. Thank you for this detailed explanation - it is even more complex to wrap around.

But I think you are saying the supply side upstream of the service disconnect can have multiple places where the neutral wire is bonded to external metal, frame, enclosures - and accepted to carry return neutral current on the external surface, and NOT considered neutral-ground bonds. So using the BPTM, the neutral-to-frame bonded generator is on the supply side, is not a violation of NEC regarding a 2nd neutral-ground bond, because by supply-side definition it is not.

If I understand then, your conclusion is it would be acceptable to use a neutral-bonded generator with the BPTM, since it is on the supply side (assuming the generator is not faulty). No need to float the neutral, just be aware the frame can carry return neutral current. But don't let yourself become a path from generator-to-earth. But also acceptable to use floating-neutral generator. Would explain why neither GererLink nor PG&E BPTM seems to raise the subject as a concern.


Now I think BGbreeder is raising a different, and not necessarily contradictory scenario. He's postulating a generator fault that bring hot-on-frame, or hot-on-neutral - that something the utility supply-side would never normally do - for one, you pointed out the utility supply does not even bring a fourth ground conductor from the pole. So if you have a supply-side that is an entirely faulty generator, earthing the generator frame could save you from being path-to-earth - in that very specific faullt scenario...

 

[cali8484]

I think you are overthinking this. The general recommended practice is to unbond the generator when you connect to house wiring. But if your generator doesn't have 240V GFCI then it should work even with the bond. There is a small risk of shock so maybe you can put a warning on the generator to not touch it with bare skin when it's running in case other people are around it.

The whole unbonding hassle is one reason why I suggested getting a floating neutral generator a few posts back.

In any case, I don't see how NEC could be violated regardless of what you do with the generator because it's portable and not permanently wired to the house.

 

[BGbreeder]

I am not an NEC expert. I am aware that what is written in one place in the NEC may have a different section that may contradict or override many of the apparent meanings in any given section. I defer to those like @wwhitney and @Vines that have read the entirety of the NEC and truly understand the NEC. I know enough to know that I don't know the whole of the NEC.

One thing that I think gets lost in these grounding / earthing / bonding discussions and analogies to main service drops, is that the main service drop neutral wire and the transformer ground are bonded at the transformer. If you take that away by switching your transfer switch, you are 100% reliant on the house ground, and the house neutral, to carry any electrical failure at the generator. As I understand it, the utility and the NEC do not practice single point grounding and bonding. Both transformer and the main service panel are neutral bonded to a grounding system.

Your utility, and the code, require that main service transformer to be a) have a working ground, b) be bonded neutral to ground, and c) have the transformer case grounded. If you swap out the word "transformer" for the words "portable generator", the NEC code as I have seen it, takes you in some very different directions. (And there, as I understand it additional differences when the output power of the portable generator goes over a certain number of kW.)

This is one reason why I wrote above that I don't think that the current use cases of portable generators has been given the same sort of attention that the NEC as done for other areas electrical components. In my view, not entirely without reason, as not everyone has a portable generator and most folks don't use it for standby power very often (only during or after a storm, fire, hurricane, etc.) nor for very long (hours to days) so the total hazard exposure of the generator use (risk times the number of seconds exposed) is overall low. However, there are other folks who do use generators extensively, who rely on them in life critical ways, and they have come to conclusions that are different, not to say quite different, from the NEC, again, as I incompletely understand it. I have watched these discussions from the sidelines for many years, and my TL;DR version is that there are conflicting views.

BTW: the WEN 120/240 generator manual that I looked at requires a) that the transfer switch switch both power wires and neutral, (i.e. a three pole transfer switch) and that "The frame of the generator shall be connected to an approved grounding electrode."
https://cdn.shopify.com/s/files/1/0012/0350/3168/files/DF475T.manual.20230911.pdf?v=1694529267
That suggests that they expect no bond at the generator, but they do expect a ground rod attached to the generator frame.

With many of these rules, grammar matters; may, can, shall, must...

Oh, and @cali8484, the NEC does have more than a few things to say about portable generators.

There are also OSHA regulations, not all of which agree with the NEC to my understanding.

Grounding A Generator - Requirements As Per OSHA & NEC

Grounding a Generator - The guide will clear your doubts about portable generator grounding as per OSHA, NEC for neutal floating & bonded sets.

yourpowerguide.com

All the best,

BG

 

[wwhitney]

is not a violation of NEC regarding a 2nd neutral-ground bond

Again, ground is an unclear term here. The prohibition is on a second neutral-EGC bond, beyond the required neutral-EGC bond in the service disconnect enclosure that creates the EGC system.

So if you have a supply-side that is an entirely faulty generator, earthing the generator frame could save you from being path-to-earth - in that very specific faullt scenario...

A path from a generator conductor to earth is only dangerous if there is another path from a different potential generator conductor to earth. In fact, all "grounding" a voltage system means is to establish an intentional path to earth for one of the circuit conductors. [The choice of conductor to earth is semi-arbitrary; if the voltage system has a neutral point (conductor of equal potential to all other circuit conductors), then that is chosen just to minimize the voltage to ground of the other conductors.]

In other words, electricity is driven by the potential that generates it to return to its source. There is no general reason that current wants to go to earth. Your engine generator would work fine on a wooden boat or in space (if you provided it oxygen). If you have a standalone engine generator, and none of the circuit conductors is connected to the generator case or to earth, you have an ungrounded system, and that could be fine and acceptable as such.

The potential hazard of an ungrounded system is that one of the circuit conductors could fault to the generator case or to earth without any obvious sign that has happened. Then in the event of a second fault of a different circuit conductor to a different conductive object, you could come along and complete the circuit inadvertently. The NEC has rules allowing ungrounded systems in some circumstances, but it requires a series of monitored "ground" detectors in such cases, which provide a visible indication of the first fault, so that it can be tracked down and fixed before a second fault occurs.

Cheers, Wayne

 

[cali8484]

Oh, and @cali8484, the NEC does have more than a few things to say about portable generators.

There are also OSHA regulations, not all of which agree with the NEC to my understanding.

Grounding A Generator - Requirements As Per OSHA & NEC

Grounding a Generator - The guide will clear your doubts about portable generator grounding as per OSHA, NEC for neutal floating & bonded sets.

yourpowerguide.com

I wonder if the web site is authoritative. I don't care about it enough to find out. However, assuming it is, it states:

Requirement 1 would mean BPTM must transfer the neutral to work with bonded neutral generators in order to comply with NEC. I doubt BPTM does that and yet it's installed on many houses.

In any case, what I stated is about bonding config on the generator not being controlled by NEC which is still the case because NEC is not a product standard. The connectors and switches hardwired to the house for connection to portable generators are certainly part of NEC's scope.

 

[wwhitney]

Here's a little thought experiment that may be edifying: suppose we lived in a world in which the only conductive things are copper and people. Everything else is effectively an insulator, at least as far as conducting current through you. [Ignore the side questions this raises, like are there still integrated circuits, or batteries, etc.].

Electrical generators would still work and we can still use electricity. We'd just run (insulated) copper wires as the circuit conductors. That would be it, no earthing (it's an insulator), no bonding (nothing to bond together, they are all insulators). The only way you get shocked by this electricity is to grab two different uninsulated circuit conductors at two different potentials, completing the circuit and having current flow through you. You could walk around with one circuit conductor connected to you and there'd be no problem unless you contact another circuit conductor (bird on a wire).

OK, but we don't live in a world in which everything is an insulator. Instead we are surrounded by conductive surfaces like the earth itself, bare metal, etc. We could still use electricity the same way, and if all our wires were insulated and the insulation never failed, and circuit conductors never got connected to conductive surfaces, we'd have the same hazards as previously.

But insulation does fail and circuit conductors do fault to conductive surfaces. Some of these conductive surfaces are isolated, like a metal box on an insulating pole. Others are ubiquitous, like the earth. The worst case shock hazard would come about when two different circuit conductors fault to two different (insulated from each other) conductive surfaces in close proximity. Then you come around and unknowingly touch both surfaces, completing the circuit.

So what do we do to avoid this hazard? We add another conductor to our wiring, that runs alongside the circuit conductors. Its job is to connect together all these disparate conductive surfaces anywhere near our circuit conductors, which we call bonding. Since the earth is a big conductive surface, this wire is connected to earth as well. This wire is called the EGC, Equipment Grounding Conductor. In the previous example, when the second circuit conductor faulted to a conductive surface, the EGC would be connecting both conductive surfaces, so that completes a circuit, and enough current should flow to trip the circuit breaker, preventing the touch hazard from arising. This interconnected system of conductive surfaces that aren't supposed to be carrying current is what we'll call the "ground".

The above describes an ungrounded voltage system, and as I mentioned, it is allowed under the NEC. The remaining hazard stems from the uncertainty of how it is safe to interact with the circuit conductors. If there are no faults to ground, you could safely touch one circuit conductor without getting shocked. But if one circuit conductor does fault to ground, which would happen with no sign absent any further measures, and then you touch a different circuit conductor, as well as a nearby part of the ubiquitous ground, you would get a shock.

So there are two approaches to dealing with this uncertainty. One is to install "ground monitors" that tell you whether there has been a fault of any circuit conductor to ground, so you know what state the system is in, and you can find the ground fault and restore the system to the safer ungrounded state. When the NEC does allow ungrounded systems, it requires ground monitors.

The other approach is just to force the system into a grounded state by intentionally grounding one of the circuit conductors, and keeping track of which circuit conductor that is. Then you know that touching any of the other circuit conductors while touching ground is the primary hazard. [The grounded circuit conductor can still be a hazard in various scenarios, though.] This is a grounded voltage system, which is what we use residentially in the US.

Cheers, Wayne

 

[wwhitney]

I wonder if the web site is authoritative.

No.

(1) its provisions only apply to transfer switches at or downstream of the service disconnect, not a transfer service upstream of the service disconnect, like the BPTM, and

(2) for such transfer switches, the NEC just says that either you use a bonded neutral generator and transfer the neutral or, more commonly for fixed generators, use a floating neutral generator and don't switch the neutral.

In any case, what I stated is about bonding config on the generator not being controlled by NEC which is still the case.

Disagree. The NEC covers your house wiring and anything you connect to it. If you want to connect a generator to your house wiring so you can use your house loads, you are subject to the NEC requirements on how to do that properly. If just want to run a small portable generator and plug one or two items into it directly, that's a different story.

Cheers, Wayne

 

[cali8484]

No.

(1) its provisions only apply to transfer switches at or downstream of the service disconnect, not a transfer service upstream of the service disconnect, like the BPTM, and

(2) for such transfer switches, the NEC just says that either you use a bonded neutral generator and transfer the neutral or, more commonly for fixed generators, use a floating neutral generator and don't switch the neutral.

That makes more sense. So, multiple neutral-ground bonds upstream of the service disconnect is NEC compliant?

Disagree. The NEC covers your house wiring and anything you connect to it. If you want to connect a generator to your house wiring so you can use your house loads, you are subject to the NEC requirements on how to do that properly. If just want to run a small portable generator and plug one or two items into it directly, that's a different story.

Not sure there is much disagreement. Your description is pretty much the reason for my opinion and I see not real conflict. If I understand you correctly, you are saying portable generators have many different uses cases and in some cases they need to be properly connected to the house per NEC. No disagreement there. What I meant is that NEC does not require what needs be done in the portable generator (e.g. bond vs unbond). What NEC does specify is the requirements for the components (e.g. inlet connector, transfer switch) hardwired to the house that interface with whatever type of portable generator one wants to use. Another way to look at is when was the last time inspectors actually inspected much less cited a portable generator vs a hardwired inlet or transfer switch for not being NEC compliant. So, in general, I don't view NEC as a controlling standard for what's required in portable generators.

On a related topic of compliance, I have not seen much mentioned about product safety standard compliance impact when someone unbonds a bonded generator that does not explicitly support the modification. It seems to be me making such modification could technically make the generator non-compliant with whatever product safety standard certification the generator may have. So, if NEC does in fact require bonding modification in a generator then it could cause violation of some product safety standards.

 

[wwu123]

I think you are overthinking this. The general recommended practice is to unbond the generator when you connect to house wiring. But if your generator doesn't have 240V GFCI then it should work even with the bond. There is a small risk of shock so maybe you can put a warning on the generator to not touch it with bare skin when it's running in case other people are around it.

The whole unbonding hassle is one reason why I suggested getting a floating neutral generator a few posts back.

Heh heh, I wasn't intending to overthink it, I just wanted the experts here to simply say what you said right there, that's it's not preferred but is OK. But the explanations were complex enough I couldn't be sure without re-summarizing.

I did remember and appreciate you suggested the floating neutral earlier, it would have alleviated the whole thought exercise completely. If I had found one that fit the size requirements and was returnable (in case of DOA) locally initially, I certainly would have gone with that to begin with!

BTW: the WEN 120/240 generator manual that I looked at requires a) that the transfer switch switch both power wires and neutral, (i.e. a three pole transfer switch) and that "The frame of the generator shall be connected to an approved grounding electrode."
https://cdn.shopify.com/s/files/1/0012/0350/3168/files/DF475T.manual.20230911.pdf?v=1694529267
That suggests that they expect no bond at the generator, but they do expect a ground rod attached to the generator frame.

With many of these rules, grammar matters; may, can, shall, must...

Oh, and @cali8484, the NEC does have more than a few things to say about portable generators.

There are also OSHA regulations, not all of which agree with the NEC to my understanding.

Grounding A Generator - Requirements As Per OSHA & NEC

Grounding a Generator - The guide will clear your doubts about portable generator grounding as per OSHA, NEC for neutal floating & bonded sets.

yourpowerguide.com

All the best,

BG

Yeah, the WEN I purchased is basically that, but with a CO sensor. I did see the manual talked about the grounding electrode, but funnily the OSHA/NEC link you provided basically says, "well, it depends":

Most owner’s manuals recommend that you ground your portable generator using a copper ground rod driven several feet into the ground. OSHA bases its recommendations on whether the system has a permanent connection to the grid or not. The systems are divided into two categories based on this condition.

But after that point I got lost, 1) because:

Most home applications fall in this category as the transfer switches do not open or close the ground connection, and the system ground is permanently connected to the grid ground.

What the heck is "grid ground"? I get there's a grounding point at the transformer, but wwhitney already clarified there is no ground conductor coming from the meter, so ....?

And also just because the BPTM is different enough from a regular transfer switch, in its location and what is being switched, I'm not 100% sure all the assumptions in that explanation would be satisfied. I'm pretty sure the BPTM DOES switch neutral from utility to generator, as one of the four conductors is neutral, and while it does not switch "ground", the fourth conductor is tying "generator frame" to .... wait, if a utility supply only has three conductors in the meter socket, what is this fourth BPTM conductor attaching to, exactly? Is the BPTM socket ring acting as a metal "supply-side bonding jumper" and ties it to the main panel enclosure, therefore tied to panel ground and earth rod, I guess?

Anyways, will leave it to you experts, but I do appreciate your concern that until the BPTM makes the switchover, the generator frame will not be tied to system panel and earth rod. I think I will take it during that brief period to be more like a Separately Derived System, as aside from any stray conduction on the outside rubber sheath of the BPTM cable, it is actually standalone without any connected loads - i.e. ground rod not absolutely required, but take appropriate precautions.