Future proof wiring

[nwdiver]

It took me a while to grok it. The incoming feed are the two wires terminated on the 100a breaker (hots), the big black wire at the top (neutral), and the stranded bare copper wire (ground) at the bottom. The two black wires that are smaller than the neutral coming from the bus bars at the top (hots) are going to the Wall Connector as is the solid bare copper ground wire at the bottom.

Yep... Ah... I see the confusion now; Yeah the two hots on either side of the neutral aren't incoming... they're outgoing. The incoming lines are landed on the 100A breaker.

 

[eprosenx]

Yep... Ah... I see the confusion now; Yeah the two hots on either side of the neutral aren't incoming... they're outgoing. The incoming lines are landed on the 100A breaker.

Wow, this is really weird.

So is this being fed from a breaker at the house? Or are you saying it is directly tied in the the main 200a bus there? So to turn off power to the outside pedestal panel you would have to kill power to the entire house? I am not sure that meets code? But I guess maybe it does?

So then the power comes in that 100a breaker. Is that breaker position rated for backfeed operation? I know they make breaker "holddowns" which I think may be required for backfeed? Not sure what the NEC requirement is here. Siemens Backfed Main Breaker Hold Down Kit-ECMBR1 - The Home Depot

Then you are feeding the HPWC direct off that bus at 100a (80 after derate)? Is the HPWC set to draw up to 80a? How does that work load calc's wise since you have three other circuits off that panel (NEMA 14-50, TT-30, and 20a 120v). I guess if you consider them non-coincident loads that would work?

Just a "interesting" setup. ;-) Nothing particularly dangerous, but certainly not run-of-the-mill.

 

[nwdiver]

Wow, this is really weird.

So is this being fed from a breaker at the house? Or are you saying it is directly tied in the the main 200a bus there? So to turn off power to the outside pedestal panel you would have to kill power to the entire house? I am not sure that meets code? But I guess maybe it does?

So then the power comes in that 100a breaker. Is that breaker position rated for backfeed operation? I know they make breaker "holddowns" which I think may be required for backfeed? Not sure what the NEC requirement is here. Siemens Backfed Main Breaker Hold Down Kit-ECMBR1 - The Home Depot

Then you are feeding the HPWC direct off that bus at 100a (80 after derate)? Is the HPWC set to draw up to 80a? How does that work load calc's wise since you have three other circuits off that panel (NEMA 14-50, TT-30, and 20a 120v). I guess if you consider them non-coincident loads that would work?

Just a "interesting" setup. ;-) Nothing particularly dangerous, but certainly not run-of-the-mill.

It's being fed directly from the 200A bus on the main panel. The original plan was to land the 2/0 on the main lugs of the RV Box but I figured landing on a 100A breaker then feeding the HPWC from the main lugs was the safer route since that provided over-current protection to the RV Box bus which I believe is rated to 125A.

Good catch on the back-fed main holdback. That is something we need to add.

Not common for residences but it's kinda-sorta how RV Parks are wired... except RV pedestals typically don't have main breakers...

 

[eprosenx]

We pigtailed from 2/0 AL to 2/0 CU for the final run because copper is easier to bend. The neutral is the same size... I wasn't there for the final wiring so the pigtail might be a bit larger if that's what was lying around but 2/0 AL triplex was used which is 2/0-2/0-2/0

The wire rating changes depending on where it's used. This is how utilities can run #4 wire overhead to a 200A service drop...

I am curious what you used to pigtail from Aluminum to copper? Split bolts? (I have never done it - I am curious what kind of splices it takes - clearly it is important to have something that is approved for aluminum)

On the wire rating thing - this is where my code knowledge reaches its limits, however, my reading is that you would use Table 310.15(B)(16) which says that (assuming 75c rated terminals) 2/0 aluminum is only good for 135 amps. 2/0 copper is good to 175 amps. (not even a full 200)

However, the reason that 4/0 aluminum (good to 180 amps at 75c) and 2/0 copper (good to 175 amps at 75c) is allowed for 200 amp residential service entrances/feeders is due to 310.15(B)(7)(1) THROUGH (4) you are allowed to put in wire that is good to only 83% of the rated amount (as long as that service or feeder carries the entire load of the residence - it also says you never need a downstream feeder that is larger than the main service feed which makes sense). So all you have to plan for is 166 amps.

So my callout is that I don't think 2/0 aluminum is sufficient if only protected by the 200a mains per NEC. (but please prove me wrong!)

 

[nwdiver]

So my callout is that I don't think 2/0 aluminum is sufficient if only protected by the 200a mains per NEC. (but please prove me wrong!)

The splices are AL rated. Not sure where they came from it was something our electrician had. Similar to this; Not sure about the NEC table 310. It doesn't seem to give any credit to direct burial. As I posted upthread the vendor rates XLPE 2/0 Al triplex cable to ~245A with direct burial... it's possible this is a non-NEC rating... wouldn't be the first time an inspector missed something. But if it's good enough for the manufacturer it's good enough for me. That cable will never see >100A and if it's rated to 245A the main 200A will definitely trip before the wire is damaged.

The utilities play super fast and lose with NEC ratings... I was trying to figure out how running #4 Al wire to a 200A service is legit since my friend is having absurd voltage drops when he charges his car. After reading through some electrician forums I found this handy guide that they use to determine what size wire to run.

 

[goto10]

We are also building a new home and I've been back & forth on future-proofing. In the end I've decided to just run a 60A circuit for the HPWC on the hope that it can use the rear entry on the HPWC for a cleaner install (no gray junction box next to the HPWC - no hope of avoiding that with 100A). If/when I need more power in the future I'll just pay what it costs to run it. I did get 400A service to the house though because upgrading that later would be prohibitively expensive and tear up the whole yard.

 

[davewill]

We are also building a new home and I've been back & forth on future-proofing. In the end I've decided to just run a 60A circuit for the HPWC on the hope that it can use the rear entry on the HPWC for a cleaner install (no gray junction box next to the HPWC - no hope of avoiding that with 100A). If/when I need more power in the future I'll just pay what it costs to run it. I did get 400A service to the house though because upgrading that later would be prohibitively expensive and tear up the whole yard.

Actually on a new build, I would definitely put a decent sized subpanel in the garage, unless the panel was already in or just outside the garage. As far as "clean" goes...it's a garage. A little industrial chic is appropriate in my opinion.

 

[goto10]

Actually on a new build, I would definitely put a decent sized subpanel in the garage, unless the panel was already in or just outside the garage.

The main panel will be about 10 feet from the garage in an adjacent utility room.

 

[Thunder7ga]

I have an electrician coming out tomorrow to give me an estimate...I'm concerned as it appears my current panel is full....we'll see what options we have for a 14-50.

 

[GatorAdam]

I just had an electrician out today that said my panel is full and my main breaker is 200amps. It looks like I need a major upgrade.

 

[davewill]

I just had an electrician out today that said my panel is full and my main breaker is 200amps. It looks like I need a major upgrade.

Get another opinion. It's almost unbelievable that there is no room in a 200a service for some sort of EV charging. And there are ways to deal with a full panel as long as the service itself isn't isn't overloaded.

 

[eprosenx]

I just had an electrician out today that said my panel is full and my main breaker is 200amps. It looks like I need a major upgrade.

Post a picture please and we may be able to help!

One picture of the panel so we can read all the amperages of all the breakers. Plus make sure there is a picture that covers the breaker schedule (of what each one is for). Then one of the spec sheet sticker for the breaker that includes lots of gory details on it (usually on the door). And if you are comfortable and able to do it safely, take the panel cover off and take some detailed pictures of the wiring such that we might be able to guess at conductor sizes.

A lot of times things can be consolidated into double breakers to free up positions, or like in my house, I have a gas dryer and a gas range but I also had breakers for those, so I could have re-used those positions had I needed to.

There is the question of physical space, but then there is the "load calcs" for the building. It is not as simple as adding up all the breakers - it is based on the actual devices installed in your home, the square footage, and in some cases the number of specific types of circuits.

 

[eprosenx]

The splices are AL rated. Not sure where they came from it was something our electrician had. Similar to this; Not sure about the NEC table 310. It doesn't seem to give any credit to direct burial. As I posted upthread the vendor rates XLPE 2/0 Al triplex cable to ~245A with direct burial... it's possible this is a non-NEC rating... wouldn't be the first time an inspector missed something. But if it's good enough for the manufacturer it's good enough for me. That cable will never see >100A and if it's rated to 245A the main 200A will definitely trip before the wire is damaged.

The utilities play super fast and lose with NEC ratings... I was trying to figure out how running #4 Al wire to a 200A service is legit since my friend is having absurd voltage drops when he charges his car. After reading through some electrician forums I found this handy guide that they use to determine what size wire to run.

View attachment 309409

I don't think manufacturers ratings matter at all for conductor sizing. As far as I know, the NEC tables are the master source of record.

The power companies get away with it quite simply because they are not bound by NEC. They can do pretty much whatever the heck they want. If they don't think you are going to need much power they don't put in big transformers and they don't put in big service conductors. Especially when the conductors are in open air (lots of cooling) they can overload the crud out of them. Your friend should call the power company and complain - they generally have groups that deal with voltage sag and flicker issues. This one should be pretty simple to resolve. They upgrade service drops and transformers all the time based on need.

I don't know that direct burial helps at all for heat dissipation. The ground is actually more of an insulator than wires in air (due to airflow and convective currents).

I very much question those manufacturers ratings - I suspect they do not apply to the in-conduit application and I don't know what temperature rating they were at (the forum won't load that picture now). :-( My reading of the NEC is that wire is good for only 135 amps in that application. (but you are right, *probably* won't be an issue)

 

[eprosenx]

I don't think manufacturers ratings matter at all for conductor sizing. As far as I know, the NEC tables are the master source of record.

The power companies get away with it quite simply because they are not bound by NEC. They can do pretty much whatever the heck they want. If they don't think you are going to need much power they don't put in big transformers and they don't put in big service conductors. Especially when the conductors are in open air (lots of cooling) they can overload the crud out of them. Your friend should call the power company and complain - they generally have groups that deal with voltage sag and flicker issues. This one should be pretty simple to resolve. They upgrade service drops and transformers all the time based on need.

I don't know that direct burial helps at all for heat dissipation. The ground is actually more of an insulator than wires in air (due to airflow and convective currents).

I very much question those manufacturers ratings - I suspect they do not apply to the in-conduit application and I don't know what temperature rating they were at (the forum won't load that picture now). :-( My reading of the NEC is that wire is good for only 135 amps in that application. (but you are right, *probably* won't be an issue)

Oh wait a sec, I am sorry. I was assuming this was *in conduit* in the ground. But I just realized it may have been *direct burial*? That would be a different rating - I would have to go find that table. Disregard if that is the case!

 

[GatorAdam]

Post a picture please and we may be able to help!

One picture of the panel so we can read all the amperages of all the breakers. Plus make sure there is a picture that covers the breaker schedule (of what each one is for). Then one of the spec sheet sticker for the breaker that includes lots of gory details on it (usually on the door). And if you are comfortable and able to do it safely, take the panel cover off and take some detailed pictures of the wiring such that we might be able to guess at conductor sizes.

A lot of times things can be consolidated into double breakers to free up positions, or like in my house, I have a gas dryer and a gas range but I also had breakers for those, so I could have re-used those positions had I needed to.

There is the question of physical space, but then there is the "load calcs" for the building. It is not as simple as adding up all the breakers - it is based on the actual devices installed in your home, the square footage, and in some cases the number of specific types of circuits.

I am getting a second quote tomorrow night.

 

[nwdiver]

Oh wait a sec, I am sorry. I was assuming this was *in conduit* in the ground. But I just realized it may have been *direct burial*? That would be a different rating - I would have to go find that table. Disregard if that is the case!

Yes 'Direct Burial'; 'in conduit' is 'in conduit' regardless of above or below ground...