EV Shared Power
user-5946022
| Posted in General Questions on
Separate garage, away from the main house panel, has a rarely used portable AC unit, powered by a 250v/20 amp circuit.
What type of switch would be a code compliant (safe) setup to switch between using this circuit for the AC and using it for a Level 2 charger to charge an EV to ensure both are never drawing power at the same time?
Would a 20 amp double pole double throw center off maintained contact toggle switch work for this situation , or a type of 3 way switch?
(None of the EVSE Smart Switches seem to be for 250v/20 amp; they start at 30 amp so don’t have the correct plugs)
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You would use a manual transfer switch to do this, such as this:
https://www.zoro.com/siemens-nonfusible-safety-switch-heavy-duty-600v-ac-3pst-30-a-nema-1-dtnf361/i/G8652892/?utm_source=google&utm_medium=surfaces&utm_campaign=shopping%20feed&utm_content=free%20google%20shopping%20clicks&campaignid=21427636968&productid=G8652892&v=&gad_source=1&gclid=CjwKCAiA3Na5BhAZEiwAzrfagHJbSVKZ6wV6zdrqqShGX30BjqUrHk8sMSu6rtF3sfNRgSzFvZrrgRoCFfQQAvD_BwE&gclsrc=aw.ds
Note that you'd just use two of the three contacts on the "3 phase" switch when using it in your application. You could possibly find a 2 pole switch too, I just posted a link to the first thing I found as an example of what I'm talking about.
It's much cheaper to just use a small electric panel like this though:
https://www.amazon.com/Siemens-E0408ML1125SU-Circuit-125-Amp-Surface/dp/B00002NB09/ref=asc_df_B00002NB09?mcid=b8e72fcf434a35afb552b89f93a80942&tag=hyprod-20&linkCode=df0&hvadid=693410589815&hvpos=&hvnetw=g&hvrand=1506806078878310277&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9016990&hvtargid=pla-362690116767&psc=1
Put a pair of 20A double pole breakers in that panel, one for the A/C, and the other for the EV charger. Only turn on the breaker for the device you want to use.
Note that you could just have both devices connected at the same time if they are both plug-in (not hardwired) devices. The existing circuit's 20A breaker will trip if both units try to run at the same time and overload the circuit. This is similar to having two hairdryers connected to one circuit: you can run either hair dryer without trouble, but if you turn them both on at the same time, the circuit will trip. It is safer to have some kind of interlock as you're asking about though.
BTW, most EV chargers are going to want a 240v 40A circuit to be able to charge at full power (some need even more than this). You can usually set the charger to tell the car to only draw up to xx amps though, so I recommend you "dial it down" so that it knows it only has a 20A circuit available, which allows for 16A in "continuous" (more than 3 hours) loads, which would include the EV charger.
Bill
Physically, you can have both connected to separate receptacles on the same circuit, but that's not code compliant: article 625 requires a dedicated circuit for EV charging. You can play games with saying you installed the receptacle for a table say and then plugged an EVSE instead, but when lying is part of the plan for how to meet code, it's not really meeting code.
With the small-panel solution, you can do it right by adding an interlock device for another $10 or so (as you know, but for the person asking the question, that's a mechanical widget that prevent both circuits from being turned on at the same time.)
True enough, and I didn't intend that as a recommendation to just plug everything in.
I don't think an interlock kit will fit that very small 4 space panel I mentioned. Interlock kits are usually used as a sort of poor man's transfer switch for generator installations. Do you know of an interlock kit that allows for two LOAD SIDE breakers to be interlocked so that only one can be on at a time? I've never seen a device for that, but it would be good to know about.
There are load management chargers available. These are meant specifically for houses where you don't want to do a panel upgrade. They usually go onto a 100A panel but check if they will work down to 20A. These measure the overall power use on the panel and automatically limit the charger to prevent overload.
Some adjustable chargers also go down to 12A, so you would have enough power left over to run an AC. 12A is not fast but plenty to re-charge typical drive distance overnight.
Specifically, in the US Wallbox, Emporia and Tesla offer that option. Emporia's implemenation has some limitations that mean it might not work here--it can only go to a minimum current, not to zero. It would be necessary to install a subpanel for that, so a possible way forward would be to install the subpanel with an interlock as a manual transfer switch, and get the Wallbox charger (Costco has a good deal on them). Live with that for a while, and then if it gets to be annoying, get the $300 accessory power meter for the Wallbox and set up the automatic management.
Setting it for 12 A and sharing a 20 A circuit doesn't actually meet code, as a dedicated circuit is required for the charging equipment.
When you say separate garage, it's not attached to the house and the wiring feeding it is underground? Is this this only circuit in the garage or are there also 120 V circuits for lights, receptacles, and door opener? If it's an outbuilding, code requires the ability to turn off all the circuits in the garage from one point inside or outside the garage. The usual way to do that is with a subpanel with a main breaker as the shutoff. You might not be in compliance and might need to bring it up to code.
I have a 20 amp EVSE
was common 3 years ago
I would find one and have one outlet, so no way to overload
Thanks for the responses.
The AC is not hardwired; it plugs into a 20 amp 250 v outlet. The EVSE will be the same. There is insufficient capacity for both, so only one device can be used at a time which is fine. The NEMA 6-20 plug for the AC is inside, the NEMA 6-20 plug for the EVSE will be outside.
There needs to be a mistake proof solution so there is never a situation where both loads are pulling power at the same time.
Looking for a switch to energize one outlet or the other; never both, and not allow inadvertent user mistake. They have all sorts of Smart Splitters for 30 amp and above loads, I just can't find one for 20 amp. Must be a simple solution??
.
As Charlie pointed out above, code requires that EV's be charged on a dedicated circuit. This means not shared with anything else, back to the panel. So in order to switch you would have to switch at the panel. The easiest way to do that is to use the circuit breakers as switches.
This device: https://www.amazon.com/dp/B0D875SJP9/
Is a piece of metal that goes between two circuit breakers and creates a physical obstacle to both of them being turned on at the same time.
@DCcontraian: If the panel is conveniently accessible and has space for another 20 amp breaker, this seems like a nice, simple solution. However, the link you posted (and all similar devices) are for a main breaker/sub breaker solution, both at 100 amps. To use this solution to switch between two 20 amp breakers, seems to require a subpanel with a 20 amp main and 20 amp sub breaker.
At that point, your post #18 solution is far more user friendly and similar cost.
There's no reason you can' t put a 20A breaker in a 100A panel.
A manual transfer switch, as I described in my first post, would do what you're asking. A manual transfer switch would allow the circuit to be connected to one or the other of the two receptacles, but not both at the same time.
Bill
The one you linked to was $800, that seems pricey.
And I'm not up enough on my code to know, but does a transfer switch meet the requirement for a dedicated circuit?
Manual transfer switches are unfortunately somewhat unusual, and typically pricey.
I would have to review the code book to be sure, but I would think this would satisfy the requirement for a dedicated circuit, since the transfer switch ensures that the circuit is "dedicated" to only one load at a time. The purpose of the code is to ensure safe operation, and avoid overloads, so the switch would allow for that to occur.
In my professional work, code issues with this sort of system don't come up, because the "under engineering supervision" part of the code comes up -- basically our final designs are considered "engineered systems", so the code doesn't apply quite the same way. This isn't the case in a typical residential setting though. Building to electrical code is similar to the "prescriptive method" in the IBC. With an engineer's stamp, you can do other stuff that may not quite fit the requirements of the prescriptive codes.
Bill
I'm with gusfhb, smart splitter is the way to go. RV suppliers will sell you adapters to go from any plug to any plug, get those to connect up what you need.
Simple and automatic. Nothing wrong with a 30A splitter on a 20A circuit.
Well, if you were going to use one of the regular smart splitters for dryer/EV they woul have to plug into the same spot. Since this is AC in the garage, one would assume this is not a big issue most of the year.
Also, there is nothing inherently unsafe about having a 20 amp breaker, 12 ga run then a 30 amp outlet. Cut the 6-20 plug off of the AC and put a 30 amp dryer plug on it. Same with the 20 amp EVSE. Install the smart splitter.
IF someone someday plugs a dryer into that outlet, it will pop the breaker and protect the circuit.
Everything else will involve some interaction on the user.
DPDT relay or switch could be wired but that seems over complicated.
Looking at the smart splitters, wonder if it is ok to connect them backwards, IOW give the EV priority
This is a good solution, and probably what I would do in my own home. But there's a couple problems from a code compliance perspective. First, you can't just cut the plug off of a UL-listed device and replace it with a different plug and keep the UL-listing. In particular, putting a 30-Amp plug on a 20-Amp device is a no-no.
Second, the NEC prohibits permanent installation of extension cords, so unless the charger can reach from where the plug is to where the car is that's not going to be compliant.
I consider these minor issues, like I said, I would do this in my own home.
My EVSE has a really long cord. Must be 8 foot cord and at least a 15 foot to the car
I am pretty surprised there is not more stuff out there for the lower output EVSE.
Everyone seems to think they need to charge at 40 or more amps
Agreed
A 20 A double pole double throw switch seems like a great solution to me, certainly much less expensive than a transfer switch, circuit breaker sub-panel, or load splitting widget and new plugs/receptacles.
Except it's not code-compliant.
Well, once you plug something into an outlet, not really code anymore, but as I said, over complicated. You have to build a device, as I have never seen a DPDT 240v building type switch. More like what is linked above, big arse expensive thing.
Connected devices are covered under the NEMA requirements and are generally certified by a nationally recognized testing lab such as UL, CSA, etc.
Building a switch is certainly possible, but using unlisted devices (such as a regular DPDT switch) can pose problems if you ever have an issue and have to make an insurance claim. Insurers will look for ways to deny the claim, and any suspicions that your home made device caused the problem are a way for them to deny the claim.
Bill
Would this work?
https://www.homedepot.com/p/Leviton-20-Amp-Industrial-Grade-Heavy-Duty-Double-Pole-Double-Throw-Center-Off-Maintained-Contact-Toggle-Switch-White-1286-W/301447135
Yes it would!
Note that those take a lot of room in the box. I'd use a 4" square "deep" box (the 2-1/8" deep kind), with a single gang mud room to give you plenty of room for the wires and connections. Trying to squeeze this into a regular single gang box is a bad idea, and will likely exceed the box fill rating.
Bill
OK, here's my submission as a code-compliant solution:
It's OK to have a sub-panel on a switch. The car charger needs to be on a dedicated circuit, the minisplit doesn't. Put a double-pole double-throw switch ahead of the minisplit, one side goes to the minisplit and one side goes to a small sub-panel, you can get a six-space one on Amazon for $28. Then the sub-panel feeds an outlet for the car charger.
For extra credit, instead of the DPDT switch use a current sensing relay to turn off the minisplit power whenever the charger circuit draws power.
For extra-extra credit, have the current sensing relay control the thermostat on the minisplit instead, so it shuts down gracefully instead of just kicking off.
Thank you all for the replies. For clarity,
-AC is not a minisplit, just an old plug in portable AC; rarely used.
-Primary goal is safety including precluding someone accidentally plugging in two loads at the same time, which could cause a fire if the breaker does not trip. Also, for anything permanently wired, goal is code compliance.
If I understand the above correctly:
Option A
1. $52 Double Pole double throw (DPDT) switch installed ahead of current feed to AC outlet:
https://www.homedepot.com/p/Leviton-20-Amp-Industrial-Grade-Heavy-Duty-Double-Pole-Double-Throw-Center-Off-Maintained-Contact-Toggle-Switch-White-1286-W/301447135
(this one is 120/277v)
2. Install a new feed from DPDT switch to new $30 subpanel, such as this:
https://www.homedepot.com/p/PowerMark-Gold-40-Amp-2-Space-4-Circuit-Indoor-Single-Phase-Main-Lug-Circuit-Breaker-Panel-TL240SCUP/202978667
Add 20 amp breaker into new subpanel: +/- $20
3. Install a new feed from subpanel to new EVSE NEMA 6-20 outlet at exterior.
DPDT switch stays flipped to feed subpanel & EVSE outlet; when there is a need to use the AC, flip the DPDT switch and turn on AC; when you turn off AC, flip the DPDT switch again.
Option B (is this safe/code compliant?)
1. Plug NEMA 6-20 to 10-30 adapter into the existing NEM 6-20 outlet ($31)
https://www.homedepot.com/p/parkworld-1-5-ft-10-3-3-Wire-20-Amp-250-Volt-NEMA-6-20P-to-30-Amp-Dryer-10-30R-Dryer-Adapter-Cord-6-20P-to-10-30R-60363/331333509
2. Plug smart load splitter into item 1 above ($199)
https://www.homedepot.com/p/LECTRON-NEMA-Socket-Splitter-Power-Your-EV-Charger-and-High-Powered-Appliance-from-The-Same-Outlet-NEMA-10-30-to-10-30-10-30-LESSTNEMA1030-1030USN/328978976
3. Plug a NEMA 10-30 to NEMA 6-20 adapter into each plug on the load splitter ($55 each).
https://www.homedepot.com/p/AC-WORKS-30-Amp-3-Prong-10-30P-Dryer-Plug-to-6-20R-20-Amp-250-Volt-HVAC-Power-Tools-Adapter-AD1030620/308319941
4. Plug the AC into one adapter on the load splitter and the EVSE into the other adapter.
Option B involves many adapters and thus points of failure, and seems like someone who does not know what they are doing could accidentally plug a 30 amp load into that adapter...
Option A involves less cost in parts but more electrician labor, and ultimately results in a cleaner install and seems safer...
Option A would work fine, but I see no need for that subpanel. If I'm understanding what you have correctly, you have a 20A 240V circuit from your home's main panel, and that circuit is presumably protected by a 20A double pole breaker in the panel. The circuit should be wired with 12 gauge (or larger) wire. The circuit currently runs an outlet for a window mount A/C unit, so probably a NEMA 6-20R receptacle. You want to feed an additional 6-20R receptacle for an EV charger in the garage off of that same circuit, or you want to hardwire that charger (no difference in this case).
You would install that DPDT switch between the breaker box and the A/C outlet, then tap off from there to run the EV charger. The switch now connects EITHER, but NOT BOTH, of the A/C or the EV charger to the 20A circuit. I see no problem with that arrangement, since the switch prevents both loads from being connected at the same time. The DPDT switch satisfies the "mechanically held" requirement of the code for this application, and I don't see a problem using it here.
Option B would be considered a temporary setup, limited by code to a period of time not exceeding 90 days. I personally would consider this setup a kludge, and would not risk it. Cord-type receptacles (those molded into extension cords) are far inferior to the in-wall type, and tend to heat up and fail when running large loads like EV chargers for extended periods of time. I have seen this before, and even had it happen once myself while charging my volt with the 120V charger included with the car. The chargers usually say they need to be plugged directly into an outlet -- no extension cords -- and I think it is a violation of a UL rule to use an extension cord with these (I'm going from memory on that one though, so don't hold me to that :-).
I would choose the hardwire option and would absolutely NOT use temporary portable cordage here.
Bill
Bill --
I'm not an electrician, but here's my read:
625.40 Electric Vehicle Branch Circuit
Each outlet installed for the purpose of charging electric vehicles shall be supplied by an individual branch circuit. Each circuit shall have no other outlets.
Also:
Branch Circuit. The circuit conductors between the final overcurrent device protecting the circuit and the outlet(s)
It's seems pretty clear to me that the intent of that section is that the circuit breaker serve no other devices. "Each circuit shall have no other outlets" seems pretty unambiguous. That it says "final overcurrent device" says to me they expect there to be multiple chained circuit breakers, and that you can turn any circuit into a branch circuit by adding a circuit breaker.
I'd say we're probably playing a bit loose with the intent of the code here, as I do think the intent is for the charger to be on a dedicated circuit, i.e. for no other purposes other than charging.
Since the OP is asking about a retrofit though, and the switch ensures either one OR the other device is operating at any given time, I'd call that "better" compared to the alternatives. If I was inspecting that, I would OK it, but I would ensure that (1) the switch was a 20A spec grade switch (it probably is spec grade), and that (2) the entirety of the circuit was AT LEAST 12 gauge wire. I would also disallow the use of any backwired devices, if that's even an option here. My reasoning would be to minimize the chances of anything getting hot enough to fail. Backwired devices, and underrated devices (like using a 15A switch on a 20A circuit) are all weak spots here. I would allow this only if there was no reasonable option to run a seperate, dedicated circuit, which I'd consider to be the proper way to do it.
Hardwiring is going to be better than unplugging the A/C and pluggin in the charger. Doing that over and over again will wear out the receptacles and cause heating issues. Using all the temporary power cables is asking for trouble too, again, from heating.
Basically if the retrofit option is the only way to go, I'd go with the switch in the Option A mentioned above. I would NOT go with Option B under any circumstances, but I do agree that a completely new, dedicated circuit would be the way to go to ensure code compliance.
Bill
I agree that running a new, dedicated circuit is the proper way. We haven't really probed the OP's contention that a new circuit isn't possible.
I'll concede that from a practical perspective, it's hard to see any benefit gained from adding another circuit breaker on the other side of the switch. You could even argue that it makes the circuit less safe and reliable by introducing more connections and a second, duplicative circuit breaker that doubles the chance for nuisance trips.
If the work is going to be inspected I'd ask the inspector what he wants, maybe even lay out some scenarios for him.
I did not see that there were commonly available DPDT switches.
All of the pieces of that system meet code, but probably not the letter.
https://www.amazon.com/gp/product/B07HH4LJD2/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
This was the EVSE I bought 3 years ago, and it came with an 8 foot cord and says 20 foot charging cable.
It would have plugged into the 240 volt outlet I use for my compressor, and reached to the front of the garage, but I had already bought the outlet and breaker, so it is installed 'correctly'
I would never have had an issue with conflict with the compressor and charging.