NEMA 14-50 outlet with auto transfer switch?

[telos]

I'm trying to get a NEMA 14-50 outlet installed in a house with 100a service.

Because of the small service and high expense of expanding that to 200a, the electrician has recommended reusing the 40a electric stove circuit with a transfer switch installed that switches between the stove and new NEMA 14-50 outlet.
This could work because it's rare that you want to cook in the middle of the night while the car is charging.

The kitchen is all the way across the house from the garage. The breaker panel is in the garage and the electrician would like to install the manual transfer switch next to the breaker panel.

The problem is, I'd like to avoid having to have a manual transfer switch. Partly because of the inconvenience, but also because you lose the stove clock and settings when you throw the transfer switch.

I know there are devices like the Electric Range Buddy, which can automatically switch between the two loads (it always keeps the stove side live, and cuts the car off whenever the stove load exceeds 3.5a). Unfortunately, I can't use the Electric Range Buddy because it's not designed to be hard-wired into the circuit.

Does anyone know of any automatic transfer switches that can keep one load live all the time?

 

[DOCAL]

Maybe worth sending an email to Brad, his email is at the bottom of the page you linked.
I have a Dryer buddy, and found him extremely responsive.

 

[Jedi2155]

It sounds like you're just lacking breaker positions.

I don't suggest a transfer switch but rather a sub panel which is the common solution in your case. You'd put a 80A breaker in the place of the old 40A breaker, wire an 80A cable to the subpanel, and provide connections to both the EVSE and the electric stove simultaneously.

 

[telos]

It sounds like you're just lacking breaker positions.

I don't suggest a transfer switch but rather a sub panel which is the common solution in your case. You'd put a 80A breaker in the place of the old 40A breaker, wire an 80A cable to the subpanel, and provide connections to both the EVSE and the electric stove simultaneously.

The problem is the electrician did a load calculation for the house, and with a grand total of 100a electrical service, there's not enough amps left to add any more load, which is why he's suggesting sharing the 40a for the stove with the car using a double throw transfer switch.

Upgrading the house to 200a service would be super expensive, as they'd need to dig a new trench and bury a new service cable as well as upgrade the power transformer that supplies the house's electrical service.

 

[telos]

Maybe worth sending an email to Brad, his email is at the bottom of the page you linked.
I have a Dryer buddy, and found him extremely responsive.

Thanks, I'll send him some mail. The ideal solution would be a version of the Electric Range Buddy I could hard wire.

 

[ewoodrick]

While you may not cook at night, most folks plug in when you get home. And the dinner is cooked after.
Do you really need that much current?

 

[COlsen1]

I 'd really look into a 200amp service upgrade. 100 amp service isn't much power to have a 40-50 amp continuous duty load such as car charging added to it. Check with the power company on costs. A lot of the time the power company absorbs most of the cost for the upgrades from the meter to the transformer and you are just responsible for the upgrades from the meterbase into the house. The manual transfer switch solution would work but it's not the greatest and in the end you will become annoyed with it after forgetting to switch it a few times.

 

[MrMassTransit]

What about installing a DCC-10?

DCC-10 Avoids Major Home Electrical Upgrades for an EV Charging Installation

I also have a 100 amp panel but all of my major appliances are gas. My electrician gave me the option of a 30 amp circuit for charging or a 60 amp with a DCC-10. I went with the 30 amp option (the DCC-10 increased the install by a little over $1k and I really don’t need the faster charging).

I think the unit will do exactly what you need. It monitors the load on your panel, and when you are below a certain threshold provides power to the charging outlet. When the electrical demand is above that level, it cuts power to it.

 

[telos]

While you may not cook at night, most folks plug in when you get home. And the dinner is cooked after.
Do you really need that much current?

The idea with an automated transfer switch is I don't need to care. I plug the car in, and if there happens to be enough juice it starts charging. If someone turns on the stove, it cuts the car off. When they turn the stove off again, it starts charging the car again.

This is so I don't have to expand the house's service, which costs way more money.

 

[telos]

What about installing a DCC-10?

DCC-10 Avoids Major Home Electrical Upgrades for an EV Charging Installation

I also have a 100 amp panel but all of my major appliances are gas. My electrician gave me the option of a 30 amp circuit for charging or a 60 amp with a DCC-10. I went with the 30 amp option (the DCC-10 increased the install by a little over $1k and I really don’t need the faster charging).

I think the unit will do exactly what you need. It monitors the load on your panel, and when you are below a certain threshold provides power to the charging outlet. When the electrical demand is above that level, it cuts power to it.

Oh wow, that sounds like exactly what I want. Even better, actually, since it tracks the power consumption of the whole house when deciding whether or not to enable the car charging.

 

[ivan801]

Would your load calculation allow for 20A 240V outlet? If so, I would try that first. I've been charging on 20A 240V for a while now, it works great, even through the winter (I drive 60+ miles per day). You can get a plug adapter from Tesla for $35, and the whole install should not cost much at all. Finding 6-20 outlet is kind of hard, but I did find it at my local Home Depot (Lowes did not have it).

 

[Rocky_H]

Does anyone know of any automatic transfer switches that can keep one load live all the time?

That would make it by definition not a transfer switch.

I do have a couple of thoughts on this. Since you're struggling for amp capacity, why are you doing a 14-50 outlet? Why not a 14-30?

The problem is the electrician did a load calculation for the house, and with a grand total of 100a electrical service, there's not enough amps left to add any more load, which is why he's suggesting sharing the 40a for the stove with the car using a double throw transfer switch.

There is a very easy, cheap, and fully official solution to this anyway. Have him redo the load calculation with the "noncoincident loads" provision. It's in the electric code that you can take two loads that are unlikely to be used at the same time, and count them as one item, with the load of the greater of the two. So since your oven is already in the load calculation at 40A, you can include a car charging circuit as the offset nighttime load that is 40A or less, and it does not increase your load calculation. The code reference for this is section 220-60.

So with that noncoincident load provision, you could install a 14-50 outlet on a 40A breaker. The UMC only draws 32A max, so the 40A breaker is allowed and appropriate. But just to leave a little more margin, I would probably do a 14-30 anyway if that were me.

 

[telos]

That would make it by definition not a transfer switch.

I do have a couple of thoughts on this. Since you're struggling for amp capacity, why are you doing a 14-50 outlet? Why not a 14-30?​

Sorry, I don't know what the correct terminology for this kind of switch would be.

The main use for this outlet is frequent day trips to visit family in Canada: drive there, stay for a few hours or a half day (and charge at the same time), and drive back.

I'd like to be able to recover the battery as quickly as possible, without having to go out of my way to find a supercharger (there aren't any near enough not to require a large annoying detour).

I guess a 14-30 would be ok, although that would only be charging at 24a, right? I think that would turn what could be a day trip into an overnight trip.​

There is a very easy, cheap, and fully official solution to this anyway. Have him redo the load calculation with the "noncoincident loads" provision. It's in the electric code that you can take two loads that are unlikely to be used at the same time, and count them as one item, with the load of the greater of the two. So since your oven is already in the load calculation at 40A, you can include a car charging circuit as the offset nighttime load that is 40A or less, and it does not increase your load calculation. The code reference for this is section 220-60.

So with that noncoincident load provision, you could install a 14-50 outlet on a 40A breaker. The UMC only draws 32A max, so the 40A breaker is allowed and appropriate. But just to leave a little more margin, I would probably do a 14-30 anyway if that were me.

Does section 220-60 apply in Canada? I'm unable to find a copy of CSA C22.1 for free anywhere online, so I can't check.

I'm guessing the electrician wants the double throw transfer switch as physical enforcement to make sure the main breaker is never accidentally overloaded?

The breaker box is pretty old, it's made by I-T-E (which is guess is now Siemens?).

 

[Rocky_H]

Sorry, I don't know what the correct terminology for this kind of switch would be.

Well, you mentioned about a toggle switch, which is a thing you can do, but that is an A or B kind of thing. That's the point of it--to make sure only one outlet is powered at a time. But you mentioned wanting one of the outlets to stay powered all the time. Well, then it's not really switching anything if both of the outlets stay powered.

Does section 220-60 apply in Canada? I'm unable to find a copy of CSA C22.1 for free anywhere online, so I can't check.

Oh, that's a whole new thing I wasn't considering because I didn't know that was in the picture. I don't know Canadian code or how similar it is in most things to the USA one.

 

[Big Dog]

The problem is the electrician did a load calculation for the house, and with a grand total of 100a electrical service, there's not enough amps left to add any more load, which is why he's suggesting sharing the 40a for the stove with the car using a double throw transfer switch.

Sorry, that makes almost no sense to me. What's the difference from unplugging your stove (switch its breaker off) than just not using your range while you are charging? A sub-panel makes more sense to me, which is what our electrician added to our 100 amp house. (We added a 60 amp line to charge model 3 at 48 amps if need be.)

If you are not cooking at night which you wouldn't be with some sort of switch, the only other thing using a lot of juice is likely your ac. In any event, electrical demand would be lower at night.

btw: I'm guessing ranges are supposed to have a dedicated breaker. Does a switch even meet your local code?

 

[Rocky_H]

btw: I'm guessing ranges are supposed to have a dedicated breaker. Does a switch even meet your local code?

A toggle switch does always satisfy that code situation, because it ensures that only one of the two devices can ever be connected onto that circuit, so it is still "dedicated". And with that, you don't have to decide if they are noncoincident day/night offset loads, because it's fixed into the hardware that it's just not possible to run both at the same time. So they could be two daytime kind of appliances. But it's also a bit less convenient, because of having to go out to the garage or wherever to change that switch every time you want to use the other appliance.

 

[tich]

@telos what did you end up doing? I'm in the exact same situation that you in. Did the Dryer Buddy guy ever respond to you?

My situation is identical except for the fact that since I'm in a townhouse, I don't have the option of upgrading my 100A service or adding a dedicated EV subpanel. As of now I'm planning on doing a manual interlock kit but would love to hear if there are any automated options aside from a DCC-10.

 

[Msjulie]

Currently our house can not run our 50amp Juicebox charger along with things like the oven, etc - like OP

But also like OP, not only do we not run the oven between midnight and 7am, we rarely run the oven period. When solar went up, the house got some added breaker spaces to accommodate that and a line was able to be pushed to the garage. If we ever did try to run everything together, a breaker would simply trip. No one ever suggested we'd need to manually switch between one and the other, FWIW

 

[jeremymc7]

Conversation is a bit old but I’ve come across it due to similar situation.

There is possibly another option, at least in my case. If I use the improper terms or speak against code please forgive.

House has a 100A 220V supply.

Panel is full.

Load calc even with a 14-30 is within limits.

However with panel being full there is no free fuse slots. But you can double up in some cases. For AC outlet fuses this is not an option. For lighting fuses though I swapped every light inside and outside the house from incandescent halogen, etc to LED. This lowered the draw on the lightning circuits drastically allowing some doubling up without issues to the 15A fuses.

This doubling up on some of the lighting circuits freed up enough space while still within load limit to have a 14-30 without issue.

Also for those that have a dual fuel option if you have an electric range swap it out for a gas range. In all likelihood swapping the range would be cheaper than pulling extra amps from the pull, upsizing the panel, pulling wire, etc.

I also swapped my old electric dryer to gas since I had option of both which is cheaper (without solar) and without having to run wire or swap outlets.

 

[Jedi2155]

If your breaker panel is full you can always do a sub-panel to increase breaker spaces.