Few Q's on installation options

[Moderatefan]

So, I've got couple of quotes to the tune of $4K+ for hpwc and ~$2K for 14-50. Main panel full, so new subpanel is a must; switch over two 240V curcuits to subpanel and add new curcuit to garage ~110 feet.

The prices are biting. And wondering about future capacity for multiple cars.
Do we have people here with electrical background, who can clarify what might be a cheaper or more efficient setup:

- Are multiple 14-50 outlets w/ 110 feet of wire each from a far away subpanel a cheaper option than 100amp wire connected to hpwc?

- If 100amp wire is run into garage, does it need there another subpanel, disconnect switch, fuse box etc. (Which is preferred/appropriate?) so the capacity can be split between multiple appliances? I'm not just talking multiple hpwcs, but maybe a backup 14-50 or other type of charger.

- why do different wires in the basement seem to use separate set of holes in joists to go through?(considering multiple 14-50 circuits) Is there a code that says they can't run nearby? In new houses they use those "glued wood chips" joists that seem only 1/2 inch thick if not less instead of 2 inch solid wood in older houses. These look incredibly flimsy to me and with holes all over them I am getting worried about floor giving way and having to fly down into the basement some day.

- wondering if due to high cost it would make sense for me to buy 3-3-3-5 SER cable and just fish it end to end myself, so an electrician can save time on this mundane task and maybe I can save like $1K on it?

Electricians seem to be not very forthcoming with info, so I'm wondering about true cost and what I can do to optimize this...seems to me that if an electrician makes $500 in labor on this in addition to material costs that'd be fair, no? And I can't imagine that materials would run more than $1500, most of which is 100 amp wire.

I may be severely mustaken, in which case I apologize, not much knowledge on this.

 

[Big Dog]

just had a sub-panel put into my 100 amp panel; no disconnect, but since its easily accessible in the garage, I only have to throw the breaker (no fuses) to cut the power. The parts totaled $550, which included 65' of Romex, for a 60 amp circuit. Two guys to run the cable thru the crawl space was $750 labor. (Both SoCal prices.)

btw: don't forget that you can put two HPWCs on the same circuit -- they'll talk to each other so only one runs at a time. And for future-proofing, you might consider a 60 amp circuit with appropriate guage wire. Labor would be the same, and parts only a few bucks extra.

 

[davewill]

Those engineered joists are made to have holes for plumbing and electrical, I wouldn't worry about that. A second set of holes a few feet away are not an issue. You can certainly run the wire yourself, then have an electrician do the rest of the job, you just need to be sure that your work will pass inspection so he doesn't have to redo it. I see no reason why you can't ask for a breakdown of parts and labor, or suggest what you're willing to pay and have them respond.

The subpanel makes a lot of sense and gives you more flexibility later. You have to decide whether you NEED flexibility or not. It's easy to spend a bunch of money "future proofing" only to end up moving before you can make use of it.

 

[Moderatefan]

Those engineered joists are made to have holes for plumbing and electrical, I wouldn't worry about that. A second set of holes a few feet away are not an issue. You can certainly run the wire yourself, then have an electrician do the rest of the job, you just need to be sure that your work will pass inspection so he doesn't have to redo it. I see no reason why you can't ask for a breakdown of parts and labor, or suggest what you're willing to pay and have them respond.

The subpanel makes a lot of sense and gives you more flexibility later. You have to decide whether you NEED flexibility or not. It's easy to spend a bunch of money "future proofing" only to end up moving before you can make use of it.

Thank you. I think I should have asked for detailed pricing, you're right. I just thought that they had the right to obscure as part of their business model.

Those joists already have holes every 1-2 feet pretty much, which looks excessive to me from the point of structural integrity. Do you know if there's a code that says you can't have 2 wires in 1 hole?

 

[eprosenx]

So, I've got couple of quotes to the tune of $4K+ for hpwc and ~$2K for 14-50. Main panel full, so new subpanel is a must; switch over two 240V curcuits to subpanel and add new curcuit to garage ~110 feet.

Can you send pictures of your main panel - of the breakers so you can read the values of the handles, of the list of circuits, and also of the label for the panel that describes what kind of breakers are allowed, all the panel specs, etc...

I want to verify there are no opportunities to install double breakers which increases the density without requiring a full panel swap.

The prices are biting. And wondering about future capacity for multiple cars.
Do we have people here with electrical background, who can clarify what might be a cheaper or more efficient setup:

- Are multiple 14-50 outlets w/ 110 feet of wire each from a far away subpanel a cheaper option than 100amp wire connected to hpwc?

How hard is the run from the panel to the plug locations? Is it in a basement or crawl space or something? I presume they are planning to run NM-B (Romex) style cable (Or SER cable)? Or would hard pipe EMT, etc... be required?

- If 100amp wire is run into garage, does it need there another subpanel, disconnect switch, fuse box etc. (Which is preferred/appropriate?) so the capacity can be split between multiple appliances? I'm not just talking multiple hpwcs, but maybe a backup 14-50 or other type of charger.

If you are running a wire direct into a HPWC (or to a single receptacle or some other EVSE) my reading of 2017 electrical code does not require a disconnect for 240v split phase service unless it is over 60 amps. And with that being said, my reading of NEC 625.43 just requires you to put a locking cage on the breaker if it is over 60 amps which allows it to be locked in the off position. The disconnect just has to be in a "readily accessible" location. (though your local AHJ - Authority Having Jurisdiction may have other requirements or interpret that differently)

If you want to split one wire to multiple HPWC units, they can share one breaker, but the wire needs to be "split" in an electrical box separate from the HPWC (it does not have enough space for two sets of conductors).

If you want multiple NEMA 14-50 plugs or you have multiple EVSE units that don't talk to each other you would need a subpanel to break it apart for multiple circuits. You can not put multiple 14-50 plugs on a single circuit for EVSE purposes.

- why do different wires in the basement seem to use separate set of holes in joists to go through?(considering multiple 14-50 circuits) Is there a code that says they can't run nearby? In new houses they use those "glued wood chips" joists that seem only 1/2 inch thick if not less instead of 2 inch solid wood in older houses. These look incredibly flimsy to me and with holes all over them I am getting worried about floor giving way and having to fly down into the basement some day.

They are fully engineered and designed to allow the holes to be used. ;-) They are strategically located in the CENTER of the beams since that is where the stresses are lowest (so it is safest to run cables through there). I think you can pretty much remove all of them and they still meet their engineered specifications (but refer to any documentation from the manufacturer). I am not sure about rules for running multiple wires together. I am not aware of any limits, but I could see heat reasons not to do it or inductive coupling reasons not to do it. I can't comment on it.

- wondering if due to high cost it would make sense for me to buy 3-3-3-5 SER cable and just fish it end to end myself, so an electrician can save time on this mundane task and maybe I can save like $1K on it?

Pre-purchasing and running the cable yourself could be a good way to save some $$$, though you would want to be darned sure you got the right cable and installed it properly. Often times the pro's could do something a lot cheaper and faster than you since they know the tricks and they have the right tools. Also, electricians may not want to be responsible for homeowner run cable...

Note that there is a vast difference between Copper and Aluminum wire. 3 AWG copper can power a HPWC at 100 amps (and that is how they tell you to do it) but aluminum takes a larger wire size for the same amperage rating. The HPWC I don't believe can accept larger than 3 AWG (though I have not seen that in writing anywhere - they just say to use 3 AWG copper for 100 amps).

I could see running 1 aught (one size larger than 1 AWG) cable to a sub-panel in your garage and then doing EVESE's or NEMA plugs off of that...

Others have rightly pointed out that you might not have much "calculated" load capacity remaining in your house due to other loads. Has a load calculation been done? Assuming a 200a main service you might not even be able to do a single 100 amp circuit (shared between multiple HPWC units or not).

The great thing about a HPWC (whether you have one or multiple) is that you can "dial in" the desired max current allowance and you can change it later if needed. So you could do a sub panel with a 100 amp feed breaker, and then do a 60a circuit off it into a HPWC for the moment (48amps usable charge rate after 80% derate - which is the max for a Model 3 LR or Model S or X standard range) and then later if you add another car you can say add a NEMA 14-50 on a 50a circuit and just turn down the HPWC to 50a with a settings change as well so it does not overload the 100a feeder (or the calculated loading).

Electricians seem to be not very forthcoming with info, so I'm wondering about true cost and what I can do to optimize this...seems to me that if an electrician makes $500 in labor on this in addition to material costs that'd be fair, no? And I can't imagine that materials would run more than $1500, most of which is 100 amp wire.

I may be severely mustaken, in which case I apologize, not much knowledge on this.

Yeah, some of those quotes seem a little high, but hard to say without a breakdown of what is included and how hard the work will be. There is a good chance the job would take two folks.

They have to cover the capital costs of their vans and insurance and time spent doing quotes, etc... so it can get expensive. Doing residential electric is probably a hard biz. A lot of the "good ones" do commercial I think. ;-)

 

[eprosenx]

just had a sub-panel put into my 100 amp panel; no disconnect, but since its easily accessible in the garage, I only have to throw the breaker (no fuses) to cut the power. The parts totaled $550, which included 65' of Romex, for a 60 amp circuit. Two guys to run the cable thru the crawl space was $750 labor. (Both SoCal prices.)

btw: don't forget that you can put two HPWCs on the same circuit -- they'll talk to each other so only one runs at a time. And for future-proofing, you might consider a 60 amp circuit with appropriate guage wire. Labor would be the same, and parts only a few bucks extra.

Am I reading this right that your main electrical service is only 100a? And you had a sub-panel installed so you could add a 60 amp breaker for a HPWC?

That 60a is a huge percentage of your overall service if so! Did they do load calculations to figure out if this met code?

 

[Moderatefan]

Can you send pictures of your main panel - of the breakers so you can read the values of the handles, of the list of circuits, and also of the label for the panel that describes what kind of breakers are allowed, all the panel specs, etc...

I want to verify there are no opportunities to install double breakers which increases the density without requiring a full panel swap.

I need 2 slots really, not 1 for the car. B/c range is disconnected.

How hard is the run from the panel to the plug locations? Is it in a basement or crawl space or something? I presume they are planning to run NM-B (Romex) style cable (Or SER cable)? Or would hard pipe EMT, etc... be required?

It's across the entire house. From unfinished basement subpanel(new) to the ceiling, through the joists across the basement, then need to drill a hole to enter garage at the floor level, go up to the ceiling on the finished wall (conduit), then along the unfinished section of the ceiling across the garage and come down on the other side on the narrow section of front wall.
I was considering copper SER so far for the whole 110 feet run, given that aluminum oxidizes and you need to regularly clean it, which most likely will be forgotten.

If you are running a wire direct into a HPWC (or to a single receptacle or some other EVSE) my reading of 2017 electrical code does not require a disconnect for 240v split phase service unless it is over 60 amps. And with that being said, my reading of NEC 625.43 just requires you to put a locking cage on the breaker if it is over 60 amps which allows it to be locked in the off position. The disconnect just has to be in a "readily accessible" location. (though your local AHJ - Authority Having Jurisdiction may have other requirements or interpret that differently)

If you want to split one wire to multiple HPWC units, they can share one breaker, but the wire needs to be "split" in an electrical box separate from the HPWC (it does not have enough space for two sets of conductors).

If you want multiple NEMA 14-50 plugs or you have multiple EVSE units that don't talk to each other you would need a subpanel to break it apart for multiple circuits. You can not put multiple 14-50 plugs on a single circuit for EVSE purposes.

Yep, thanks for that, I'm slowly getting the picture.
100amp- need extra disconnect switch.
60amp single hpwc or 50amp 14-50 - no disconnect switch.
If need multiple hpwcs or 14-50s, then need extra box.

Also, electricians may not want to be responsible for homeowner run cable...

That kinda rules it out... unless an electrician agrees upfront.

Note that there is a vast difference between Copper and Aluminum wire. 3 AWG copper can power a HPWC at 100 amps (and that is how they tell you to do it) but aluminum takes a larger wire size for the same amperage rating. The HPWC I don't believe can accept larger than 3 AWG (though I have not seen that in writing anywhere - they just say to use 3 AWG copper for 100 amps).

I got that from talking to electrician. Wasn't planning on aluminum.

Others have rightly pointed out that you might not have much "calculated" load capacity remaining in your house due to other loads. Has a load calculation been done? Assuming a 200a main service you might not even be able to do a single 100 amp circuit (shared between multiple HPWC units or not).>

Two electricians suggested a 100amp subpanel and one 125amp, so I'm guessing I have enough. Some of those things won't be running concurrently.

The great thing about a HPWC (whether you have one or multiple) is that you can "dial in" the desired max current allowance and you can change it later if needed. So you could do a sub panel with a 100 amp feed breaker, and then do a 60a circuit off it into a HPWC for the moment (48amps usable charge rate after 80% derate - which is the max for a Model 3 LR or Model S or X standard range) and then later if you add another car you can say add a NEMA 14-50 on a 50a circuit and just turn down the HPWC to 50a with a settings change as well so it does not overload the 100a feeder (or the calculated loading).

I thought the max load can also be confugured in the car app. So, probably not critical to do this on hpwc.

Yeah, some of those quotes seem a little high, but hard to say without a breakdown of what is included and how hard the work will be. There is a good chance the job would take two folks.

They have to cover the capital costs of their vans and insurance and time spent doing quotes, etc... so it can get expensive. Doing residential electric is probably a hard biz. A lot of the "good ones" do commercial I think. ;-)

Yep. It's amazing though how little they are interested in new jobs right now. It's either you pay what they want or they got too much work already and not taking new jobs. Maybe it's not that bad to be an electrician.

I'm starting to think with these kind of prices I may be better off just doing 14-50.

 

[davewill]

View attachment 309002
I thought the max load can also be confugured in the car app. So, probably not critical to do this on hpwc.

It can, but it's a bad idea to depend on it for daily use. There are a couple scenarios that can cause the car to revert to full amperage. One is the fact that saving the setting relies on GPS, which is not 100%. Another is that software updates have been known to cause the car to forget. Better that the EVSE properly matches the circuit. I would even go so far as to say that depending on the car setting to keep from overloading the circuit is a bit reckless. If it's a non-critical use, or a one-time thing (like not trusting a public RV outlet to supply 40a), then limiting in the car is fine.

Yep. It's amazing though how little they are interested in new jobs right now. It's either you pay what they want or they got too much work already and not taking new jobs. Maybe it's not that bad to be an electrician.

I'm starting to think with these kind of prices I may be better off just doing 14-50.

I'm sure the 14-50 would be adequate. That last bit of charging capacity isn't going to make much difference. I've "limped" along on 30a for a long time.

 

[eprosenx]

View attachment 309002
I need 2 slots really, not 1 for the car. B/c range is disconnected.

Gah, I can't load anything but that thumbnail since I think the forum is being broken (it has been having issues with images lately). Can you also attach a picture of the detailed specs of the panel (should be on a label - probably on the door panel) - I want to see if some breaker positions will allow "double" breakers to be installed. Could save you from needing a subpanel.

Hopefully the forum will figure itself out and the picture you already uploaded will start working at some point (I have seen this happen several times now).

It's across the entire house. From unfinished basement subpanel(new) to the ceiling, through the joists across the basement, then need to drill a hole to enter garage at the floor level, go up to the ceiling on the finished wall (conduit), then along the unfinished section of the ceiling across the garage and come down on the other side on the narrow section of front wall.
I was considering copper SER so far for the whole 110 feet run, given that aluminum oxidizes and you need to regularly clean it, which most likely will be forgotten.

FWIW, I probably would want the run to the garage on the main panel directly and if needed I would kick other small circuits over to a subpanel. Typically I see the max size breaker you can put in for most manufacturers is 125a, hence probably the recommendation to do a 125a subpanel.

I am not sure the rules on SER cable. Do you need to protect it like you need to protect NM-B I assume? So yeah, in conduit anywhere it is exposed? Would be a pain to pull through conduit I bet at that gauge! (but doable) I assume if the entire thing is not in conduit that you have to use the 60c temp rating just like with NM-B?

I would not necessarily say you need to regularly clean aluminum cable. Oxidation and thermal expansion are your enemies with aluminum, but modern aluminum alloys are not as bad as they were before and the terminals on the ends are greatly improved as well. It is often recommended (but I am not 100% sure it is a code requirement) to coat the ends with special anti-oxidant - even brushing it in with a wire brush to all the conductor strands. Once installed though (with proper torque on the terminal ends) I am not sure it really requires any maintenance.

Yep, thanks for that, I'm slowly getting the picture.
100amp- need extra disconnect switch.
60amp single hpwc or 50amp 14-50 - no disconnect switch.
If need multiple hpwcs or 14-50s, then need extra box.

For over 60 amps you need a disconnect switch, but my reading (YMMV) is that you can just use the breaker down in the basement as long as you put a lockoff cage on it so it can be locked in the off position during maintenance. Or if you feed it from a subpanel in the garage, then a lockoff on that breaker.

That kinda rules it out... unless an electrician agrees upfront.

Meh, you could always run it and then come out and have the electricians quote things. The worst that could happen is they no-bid the job. ;-) There is just the potential for an expensive mistake if you run the wrong cable or something.

Two electricians suggested a 100amp subpanel and one 125amp, so I'm guessing I have enough. Some of those things won't be running concurrently.

Hrm, ok, sounds like maybe you have a 200a main service then? What is your main disconnect rated? (I can't see the breaker in the thumbnail)

I thought the max load can also be confugured in the car app. So, probably not critical to do this on hpwc.

As per Dave's comment - I would not rely on the car to suck less juice. It seems fraught with peril (for anything other than temporary use) and I do not believe it is code compliant. Way too easy to draw too much current accidentally. It is trivial to switch the setting on the HPWC (just need to remove some Torx screws and adjust a rotary dial switch).

Yep. It's amazing though how little they are interested in new jobs right now. It's either you pay what they want or they got too much work already and not taking new jobs. Maybe it's not that bad to be an electrician.

I'm starting to think with these kind of prices I may be better off just doing 14-50.

Yup! Hard to find folks right now. I did it all myself. Good luck!

 

[jamnmon66]

Those joists already have holes every 1-2 feet pretty much, which looks excessive to me from the point of structural integrity. Do you know if there's a code that says you can't have 2 wires in 1 hole?

Many of those TGIs (tongue & groove I-beams) have pre-drilled knock-outs every couple of feet for this purpose. No problem with structural integrity as long as you don't take a long slice out of it. The top cord is in compression and the bottom cord is in tension but the forces almost cancel out in the center which is why this is ok. I'm sure it's in the building code somewhere. You'd have to figure out which code your city/county has approved. The books aren't cheap and are very difficult to find what you're looking for if you're inexperienced with code books. But the local building inspector might look it up for you if you ask nicely.

 

[Dana1]

Has Tesla given you a quote? Up to 100 feet is same price (benefitting longer runs!). Mine was just installed today and they did a great job, though mine simpler than yours. 60a breaker in an outside ground floor electrical box, about a 60’ run outside and inside about 12’ off the ground. Not inside walls. Painted conduit. About $1400.

 

[Moderatefan]

View attachment 309461

Has Tesla given you a quote? Up to 100 feet is same price (benefitting longer runs!). Mine was just installed today and they did a great job, though mine simpler than yours. 60a breaker in an outside ground floor electrical box, about a 60’ run outside and inside about 12’ off the ground. Not inside walls. Painted conduit. About $1400.

I think Tesla does installs only in a handful of states. In others they have "recommended" electricians, who do the work in accordance with whatever minimal instruction Tesla provides and then send pictures of the work to Tesla, which somehow is supposed to help the warranty or help them figure out why your car burned while charging. I don't buy that and the quote I got from the top recommended electrician is so far highest to date out of 4.

 

[countontom]

So, I've got couple of quotes to the tune of $4K+ for hpwc and ~$2K for 14-50. Main panel full, so new subpanel is a must; switch over two 240V curcuits to subpanel and add new curcuit to garage ~110 feet.

The prices are biting. And wondering about future capacity for multiple cars.
Do we have people here with electrical background, who can clarify what might be a cheaper or more efficient setup:

- Are multiple 14-50 outlets w/ 110 feet of wire each from a far away subpanel a cheaper option than 100amp wire connected to hpwc?

- If 100amp wire is run into garage, does it need there another subpanel, disconnect switch, fuse box etc. (Which is preferred/appropriate?) so the capacity can be split between multiple appliances? I'm not just talking multiple hpwcs, but maybe a backup 14-50 or other type of charger.

- why do different wires in the basement seem to use separate set of holes in joists to go through?(considering multiple 14-50 circuits) Is there a code that says they can't run nearby? In new houses they use those "glued wood chips" joists that seem only 1/2 inch thick if not less instead of 2 inch solid wood in older houses. These look incredibly flimsy to me and with holes all over them I am getting worried about floor giving way and having to fly down into the basement some day.

- wondering if due to high cost it would make sense for me to buy 3-3-3-5 SER cable and just fish it end to end myself, so an electrician can save time on this mundane task and maybe I can save like $1K on it?

Electricians seem to be not very forthcoming with info, so I'm wondering about true cost and what I can do to optimize this...seems to me that if an electrician makes $500 in labor on this in addition to material costs that'd be fair, no? And I can't imagine that materials would run more than $1500, most of which is 100 amp wire.

I may be severely mustaken, in which case I apologize, not much knowledge on this.

Could you share your final solution and the cost?

 

[Moderatefan]

Could you share your final solution and the cost?

I had trouble with even $2k quote electricians getting back to me. One of them looked at my panel load and said per calculations he cannot add a 2nd 14-50 in the future(200amp panel) if need to be, so I'd be limited to a single outlet he can add with all of the re-work of panel. That got me thinking in the direction of the dryer buddy, which lets you share 14-30 between the dryer and another outlet that you can use for EV (with extension cord) - for the future expansion.
Once I read up more on that site, I noticed they also have RV buddy/range buddy products that split 14-50 into two outlets.
There are 3 versions of these splitters:
1. Cheapest, just a Y splitter - if you accidentally use both outlets, then breaker in your electrical panel trips. Some people warn of risk of fire, so I probably wouldn't go with this one.
2. Manual switch on the box, so you ensure manually which outlet now gets the power.
3. Auto plus, which automatically detects if "primary" outlet starts drawing power and if so, disconnects the "secondary" outlet at the 3.5amp level. I.e. for a moment you may be drawing 43.5amps, which is ok for 50amp outlet for "under 3 hours", from what I gathered. However, I have a 40amp breaker on my 14-50 outlet, which currently serves 40amp sauna. I have 50amp wire, so no risk of overload, but I think breaker might trip with the auto option.

So, as a short term solution, I bought 75 feet extension cord for 14-50: https://www.amazon.com/gp/aw/d/B079JBWR6W?psc=1&ref=yo_pop_mb_pd_title

That should get me covered when the car comes in about a week. The cable is pretty thick. I had it attached to the joists of unfinished basement(would be the same thing if an electrician had to feed the wire into garage), drilled a hole into garage and have ~15feet of the cord available in the garage, which I haven't yet decided where to attach.

I think couple of months later before I start using sauna I will buy manual RV buddy for $330
RV Buddy Plus #1 Custom 50A 2-way switcher, 3.5' 14-50 plug cable to two 14-50 outlets, with kWh meter

The pictures are messed up for that item, but you can see the approx picture with the switch here
Upgrade pak from Dryer Buddy™ on order (waiting for build) to Dryer Buddy™ Plus

So, the buddy and extension cord will get me functional for 2 appliances on a single 14-50 outlet w/o the need to unplug/plug in dif. appliances(which is a risk of wear on the outlet - seems they don't last long) for less than $700. Maybe I could replace the breaker from 40amp to 50amp and get the AUTO version of the buddy.

The buddy product seems to make sense; since electricians don't want to add another high power curcuit in the future, I will do the same with the dryer outlet when it's time for another EV and split 14-30 into two 14-30s (few people don't recommend to split 14-30 into 14-30 and 14-50, since EV will think you have 50amp available on the curcuit, which you don't and may overload if your limit set on the car is somehow reset).

So, I think I will have this 40amp option right now from my outlet ~60 feet away from garage and later another 24amp connection I will add the same way, which will be cheaper; My dryer is on 2nd floor, so I'll drop extension cord into the basement and feed into garage through the same hole, will probably be shorter extension cord and thinner - 30amp vs 50amp. This 2nd connection is my only option that electricians won't do for me.
I guess maybe I could split 14-50 inside the garage, so that each EV only gets half the power, but with buddies(RV and dryer) I'll have 2 separate circuits. No electrician needed

 

[drawfour]

3. Auto plus, which automatically detects if "primary" outlet starts drawing power and if so, disconnects the "secondary" outlet at the 3.5amp level. I.e. for a moment you may be drawing 43.5amps, which is ok for 50amp outlet for "under 3 hours", from what I gathered. However, I have a 40amp breaker on my 14-50 outlet, which currently serves 40amp sauna. I have 50amp wire, so no risk of overload, but I think breaker might trip with the auto option.

Does the unit itself have a way of setting a maximum amperage? 14-50 plugs can be wired either for a 50-amp or a 40-amp circuit. In fact, the UMC from Tesla plugs into a 14-50, but only goes to 32 amps (80% of 40). If the unit has a way of setting it to know it's on a 40-amp breaker, it could do the smarts at 32 amps.

 

[Moderatefan]

Does the unit itself have a way of setting a maximum amperage? 14-50 plugs can be wired either for a 50-amp or a 40-amp circuit. In fact, the UMC from Tesla plugs into a 14-50, but only goes to 32 amps (80% of 40). If the unit has a way of setting it to know it's on a 40-amp breaker, it could do the smarts at 32 amps.

Yes, sorry, forgot that UMC v2 is underpowered on purpose to prevent burn out issues people were having with v1 of UMC that pulled 40amps. So, I'll get AUTO buddy, cool! Can't believe I forgot about 32amps.

The buddies don't let you set the amperage. It's the UMC that limits the car, which could pull 48amps(LR) to 32 amps.

 

[drawfour]

Yes, sorry, forgot that UMC v2 is underpowered on purpose to prevent burn out issues people were having with v1 of UMC that pulled 40amps. So, I'll get AUTO buddy, cool! Can't believe I forgot about 32amps.

The buddies don't let you set the amperage. It's the UMC that limits the car, which could pull 48amps(LR) to 32 amps.

Does the buddy do a switch from one to the other (i.e. either plug gets full draw, but not both at the same time, except for a short overlap), or does it try to "share" if say both sides were only trying to draw 20 amps? Because if both sides were trying to draw 20 amps, totaling 40, and it thought it was on a 50-amp circuit, it could very easily allow that to happen continuously, and that won't work on a 40-amp circuit.

But if it only allows either one outlet or the other to be active, then since your car charging ramps up a little at a time, then when the second one came on, the buddy would have time to switch the first switch off before every reaching 40 amps, then you're OK.

 

[Moderatefan]

Does the buddy do a switch from one to the other (i.e. either plug gets full draw, but not both at the same time, except for a short overlap), or does it try to "share" if say both sides were only trying to draw 20 amps? Because if both sides were trying to draw 20 amps, totaling 40, and it thought it was on a 50-amp circuit, it could very easily allow that to happen continuously, and that won't work on a 40-amp circuit.

Maybe you can add another custom subpanel with 2 20amp breakers in it to reduce the risk of going above 40, but that is getting hairy and more work then buddies let you get away with, b/c it's pre-packaged solution that does not require electrical expertise.

But if it only allows either one outlet or the other to be active, then since your car charging ramps up a little at a time, then when the second one came on, the buddy would have time to switch the first switch off before every reaching 40 amps, then you're OK.

My use case is I need one or the other outlet of the buddy to draw power and not both. I'll use AUTO buddy.
So, for 14-50 I'll set sauna as primary. For 14-30, the dryer will be primary. The secondary outlet can draw 32amps on 14-50 due to UMC max; as soon as sauna ramps up, it will turn off EV charging. I need full power for sauna. 32+3.5=35.5, that's below my 40amp breaker.
For 14-30, secondary outlet can draw 24amps for EV. As soon as dryer ramps up, it will turn off EV charging. 24+3.5=27.5, that's below the standard 30amp dryer circuit breaker.
So, on those rare days when primary outlet is used, EV charging time is reduced by 1-2 hours, the overall effect of this is pretty negligible.

If you want both outlets used at the same time on the buddy, then you have to use the cheapest version #1 or maybe splitter like this:
https://www.amazon.com/Parkworld-69...arkworld&qid=1537233424&sr=8-2&ref=mp_s_a_1_2
But you have to micro-manage the total load yourself to make sure it doesn't exceed the breaker value, for ex. set the max charging rate on each of 2 cars to 20amps. There will be tons of people here yelling at you not to do this, b/c maybe if the limits accidentally reset with a software push and the breaker is defective or something, then there is a non-zero risk of fire. Your wire on 14-50 can only carry 50amps max and if that happens for longer than 3 hours, then it's called continuous and should not exceed 80% or 40amps.

I guess you could add a custom subpanel with two 20 amp breakers or fuses in it to reduce the risk, but this is getting hairy and goes beyond the small amount of work that pre-packaged solution from dryer buddy lets you get away with (w/o electric expertise).

I think a more valid use case for 2 cars charging if you have a single 14-50 in the garage is to get a buddy with the manual switch(Plus w/o Auto), plug in both cars and alternate their charging days by moving the switch every day. This will prevent the wear on your 14-50 and it seems they burn up after too many plug/unplug cycles.

 

[Moderatefan]

A budget/working solution could be to use a regular 110V 15amp outlet for a car that doesn't get much use/mileage.

In terms of less daily headache/things to remember, I think adding a 2nd outlet on the dryer curcuit with the help of buddy is also pretty good.
Prob. $500-600 and if your panel doesn't support additional circuits to be added by electricians, that's something you still can do yourself and get a fast charging option.

 

[Rocky_H]

Does the buddy do a switch from one to the other (i.e. either plug gets full draw, but not both at the same time, except for a short overlap), or does it try to "share" if say both sides were only trying to draw 20 amps? Because if both sides were trying to draw 20 amps, totaling 40, and it thought it was on a 50-amp circuit, it could very easily allow that to happen continuously, and that won't work on a 40-amp circuit.

But if it only allows either one outlet or the other to be active, then since your car charging ramps up a little at a time, then when the second one came on, the buddy would have time to switch the first switch off before every reaching 40 amps, then you're OK.

There are three main versions. One of them does what you want, and it is the only version of Dryer Buddy I would recommend at all.

The plain version of Dryer Buddy has no protections or switching of any kind. If both things turn on, you could be drawing 40A from both sides at the same time, and hopefully your breaker will trip before really bad things happen. That is what breakers are there for, but I would hate to rely on that.

The Dryer Buddy "Plus" includes a toggle switch, so you have to manually switch which one is active. That is safe, but is going to be inconvenient.

The Dryer Buddy "Plus AUTO" has a primary, which is on most of the time, but monitors the other side. If the other side tries to turn on, it will switch and let the secondary take over while deactivating the primary. This is automatic, easy, and safe. I would recommend that if you need to get a Dryer Buddy.

Their ordering page is kind of complicated. You pick the basic product based on what outlet types you want and add it to your cart. Then you add the upgrade package of Plus or Plus Auto to your cart also for them to build it that way.