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Old 07-06-2019, 01:14 AM   #1
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Converting 240v wire used for garage baseboard heater for electric car charger


Hi, my nephew lives in a small 3 unit condominium building. He shares an open garage space with his 2 neighbours. However the garage space is equally divided in 3 areas where each have their own 240v baseboard heater, 120v plugs and lights. He wants to charge his electric car faster. I was thinking of recommending that he use the 240v circuit (20 amps) used to power the baseboard heater to charge his car. But to keep both the heater and charger from using the circuit at the same time I would add a 3 way 20 amp switch to switch between the charger and heater. Are there any flaws or code violations in this approach? Running a new wire from the panel to the garage is an option but will be more difficult and expensive. The charger will do a maximum of 12 amps at 240v.
Thank you for any advice in advance.
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Old 07-06-2019, 01:54 AM   #2
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Re: Converting 240v wire used for garage baseboard heater for electric car charger


What is the power requirement of the car charger ?
even 20A may not be enough.
Many require 50A or more.
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Old 07-06-2019, 02:21 AM   #3
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If it’s a Tesla he can for sure control the amps. Charging that low amps is still pretty weak though. On a 30 amp circuit I’m Only getting 22mi/hr (24amp charge).

You also would have to have to find a plug that accommodates that level of amps as a 14-50 would always attempt to full off a 50 amp circuit, and 10-30 attempts to pull on a 30 amp circuit, etc.

Short term you could do this setup but the benefit is marginal compared to upgrading to a 14-50 circuit.

Last edited by SDGuy; 07-06-2019 at 02:24 AM.
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Old 07-06-2019, 07:29 AM   #4
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Its the standard Chevy volt charger that can do 12 amps at 120 or 240v
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Old 07-06-2019, 10:02 AM   #5
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Re: Converting 240v wire used for garage baseboard heater for electric car charger


What you need is a line voltage thermostat that switches between heat (from electric baseboards) and cool (from an air conditioner) using the same 240 volt 20 amp line to feed them one at a time.

But I think such a thermostat does not exist.

The closest equivalent is a double pole double throw 240 volt 20 amp rated toggle switch. One throw side of the switch powers the baseboard heater, the other side powers a 20 amp 240 volt receptacle, possibly in the same 4 inch junction box.

Oops, you described all of that.

You will have to have a licensed electrician do the work and s/he will then pass judgment on whether that is legal. Mention the heat cool thermostat analogy and that might get him/her to find a loophole if it was not otherwise legal.

In most cities all work in a multifamily, commercial, or non-owner-occupied building has to be done by a licensed professional.

You can get away with an adapter (may resemble a short extension cord) with a matching higher amperage (female) receptacle and a 20 amp (male) plug to connect a plug in class 2 (240 volt) car charger to a 20 amp 240 volt circuit.

None of the above will work if your car charger does not have a control to limit its amperage draw to no more than 16 amps (maximum "continuous" draw from a 20 amp circuit) at your discretion, or inherently does not have such a limit.
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Last edited by AllanJ; 07-06-2019 at 10:10 AM.
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Old 07-06-2019, 10:08 AM   #6
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Quote:
Originally Posted by AllanJ View Post
What you need is a line voltage thermostat that switches between heat (from electric baseboards) and cool (from an air conditioner) using the same 240 volt 20 amp line to feed them one at a time.

But I think such a thermostat does not exist.

The closest equivalent is a double pole double throw 240 volt 20 amp rated toggle switch. One throw side of the switch powers the baseboard heater, the other side powers a 20 amp 240 volt receptacle, possibly in the same 4 inch junction box.

Oops, you described all of that.

You will have to have a licensed electrician do the work and s/he will then pass judgment on whether that is legal. Mention the heat cool thermostat analogy and that might get him/her to find a loophole if it was not otherwise legal.

In most cities all work in a multifamily, commercial, or non-owner-occupied building has to be done by a licensed professional.

You can get away with an adapter (may resemble a short extension cord) with a matching higher amperage (female) receptacle and a 20 amp (male) plug to connect a plug in class 2 (240 volt) car charger to a 20 amp 240 volt circuit.
Does the switch need to be double pole? Can't I use a normal 20 amp 3 way switch (SPDT). I.e just switch one of the legs instead of both?
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Old 07-06-2019, 12:03 PM   #7
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Re: Converting 240v wire used for garage baseboard heater for electric car charger


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Originally Posted by lmcancu View Post
Does the switch need to be double pole? Can't I use a normal 20 amp 3 way switch (SPDT). I.e just switch one of the legs instead of both?
Electrically, I don't know why not..... code wise I have nfi....


(I kinda wondered about that in a baseboard heat installation. As they make both single and double throw thermostats, I kinda assumed that either were NEC code compliant...except if there were county modifications to the NEC. Either way, we ran double throw thermostats.)
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Old 07-06-2019, 12:35 PM   #8
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Thinking about it more. Leaving a hot wire connected to a plug seems to be unsafe as someone can easily tamper with the plug. For a baseboard, wiring is hidden and enclosed so someone can't really tamper with it in a normal fashion. To play it safe a dpdt switch is required in this application
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Old 07-06-2019, 12:36 PM   #9
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Meant receptacle and not plug
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Old 07-06-2019, 12:42 PM   #10
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Re: Converting 240v wire used for garage baseboard heater for electric car charger


Quote:
Originally Posted by lmcancu View Post
Thinking about it more. Leaving a hot wire connected to a plug seems to be unsafe as someone can easily tamper with the plug. For a baseboard, wiring is hidden and enclosed so someone can't really tamper with it in a normal fashion. To play it safe a dpdt switch is required in this application

Imcancu.... Good Point....thinking about it I agree 100%.... still interested to know how NEC addresses the issue....
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Old 07-06-2019, 06:43 PM   #11
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Re: Converting 240v wire used for garage baseboard heater for electric car charger


Do you have access to the garage's electrical panel?
Is it a shared panel for all three?

Why not keep it simple and just wire it into the same circuit with the baseboard heater and just don't run them at the same time, especially if the baseboard heater requires 'human intervention' to turn it on and off? You're basically doing the same if you are adding a 'switch'.
What is the concern? Tripping the breaker? Do you fear he won't have access to it if it trips?
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Old 07-06-2019, 07:09 PM   #12
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Quote:
Originally Posted by NCmountainCabin View Post
Do you have access to the garage's electrical panel?
Is it a shared panel for all three?

Why not keep it simple and just wire it into the same circuit with the baseboard heater and just don't run them at the same time, especially if the baseboard heater requires 'human intervention' to turn it on and off? You're basically doing the same if you are adding a 'switch'.
What is the concern? Tripping the breaker? Do you fear he won't have access to it if it trips?
It's a 1500w heater which at 240 will pull about 6 amps when on. The charger is pulling 12 amps. So we are at 18 amps, above the 80% limit. He charges his car at night so he doesn't want to wake up and find the breaker tripped and car uncharged. With the switch he guarantees either that the car is charge or the garage is heated.
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Old 07-06-2019, 07:33 PM   #13
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Re: Converting 240v wire used for garage baseboard heater for electric car charger


From what I can tell, you are looking for is a way to transfer power from one use to another use. From the baseboard heat to a way to charge the EV Car.

You need a power transfer switch. Something like one of these:

While they are meant to transfer power from two different sources to one device (Grid power or Home Generator to a Water Heater for example) There is no reason they can't do the reverse. Other than your local AHJ saying they can't. Darn Inspectors!!



Or this:

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Old 07-06-2019, 07:40 PM   #14
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Re: Converting 240v wire used for garage baseboard heater for electric car charger


Change the heater to a smaller one that will work with the charger????
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Old 07-07-2019, 07:54 AM   #15
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Re: Converting 240v wire used for garage baseboard heater for electric car charger


yes, as I'm not really as sure what the 'issue' is with sharing the power, as the owner will either be 'without' HEAT, or 'without' CHARGING, while sleeping overnight... neither can happen at the same time, and if 'charging' is MORE important, then simply turn the heater off for the night. Your switch is doing the same thing, only you are adding more work to 'add it' to the equation.
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