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40 amp circuit to garage for a welder/electric car charger.

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  • Jun 21st, 2016 9:19 am
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Deal Addict
Feb 16, 2013
1554 posts
1286 upvotes
Toronto

40 amp circuit to garage for a welder/electric car charger.

Hi guys.

I'm thinking of running a 40 amp 220V circuit from the main panel to the garage.
Insulation would be 90C, but I would like the lowest AMP breaker for safety.
It would be 8 gauge wire, but I can also go with 6 gauge for the higher ampacity, also 90C insulation.
The circuit is dedicated for a 29 amp max draw (nameplate) welder, with the option of re-purposing the circuit for car charging.

My question is this. If I should decide to buy an electric car down the line, will the circuit be able to handle the 32 amp car chargers?
Do you guys think they will come out with higher amperage 220V chargers?

Also are there any issues with using liquid-tite or flex for protecting the conductors in a residential setting?
Ground would be undersized by 2 gauges. That is, 6G conductors = 10 guage ground, etc.

I would have to core a hole from the house to the attached garage, I dont know if there are any code issues with fireproofing?
Does everything sound ok?
8 replies
Deal Fanatic
Apr 20, 2011
7747 posts
2706 upvotes
ON
The missing piece of the equation is length of run - if it's a longer run you may want to use the 6ga instead of 8.
Minimum size of breaker is irrelevant - you need a 40 to run that welder (if that is a continuous rated device) anyway.

If you only ever want to use the welder or EVSE at any one time, simply wire a future EVSE with the same plug/socket used by the welder and it is plug and play, ready to go.

A 32A EVSE will require a 40A circuit (8ga or better), about the same as your welder.
They're usually labelled in model # by the circuit rating as opposed to the actual running current. e.g. my LCS-25 is actually 20 running amps, 25A circuit. An EV-40 would be 32A running, 40A circuit
They already have higher amperage EVSEs, but there are diminishing returns on home use.
For starters, anything over 30-40 and you'll likely need to upgrade to 200A service. Secondly, you will probably never need that much power on a regular basis. Vast majority of people will be charging a vehicle while they sleep - 8h+ charge time.
32A@240V is 7.7kW, or about 7kW making it into your battery. That's 56kWh in 8 hours, or an entire Tesla 3 or Chevy Bolt battery charge (or 200+ km worth of driving at the worst of efficiencies)
Deal Addict
Dec 28, 2010
1252 posts
132 upvotes
Ajax
I'm also considering this. I own a Chevy Volt 2017. I know it only charges at 3.6kWh. Would it make sense to get a 30-32A (7.2kWH-7.7kWh) in the event I get another electric vehicle in the future? My panel is 100A new construction build. No electric range though. Would I have room in my panel?
Deal Expert
Jan 27, 2006
16732 posts
9505 upvotes
Vancouver, BC
If you are thinking about putting in additional power for multiple items in your garage, you should consider putting in a sub-panel in the garage so that you can easily add circuits when you want as well as have easy access to the breakers locally rather than having to go back to the house ie. run the 6 gauge to the subpanel and then run what every you need from there. You might even consider removing the the existing garage circuit from the main panel and just have everything in the subpanel.
Deal Fanatic
Apr 20, 2011
7747 posts
2706 upvotes
ON
Bellotts wrote: I'm also considering this. I own a Chevy Volt 2017. I know it only charges at 3.6kWh. Would it make sense to get a 30-32A (7.2kWH-7.7kWh) in the event I get another electric vehicle in the future? My panel is 100A new construction build. No electric range though. Would I have room in my panel?
If you have the wiring to support a 40 amp circuit, I would do the upsize. The relative cost difference isn't that much compared to a lower powered unit, especially if you're getting a rebate for some of the cost.

Room on your panel might need to consult with an electrician if you have a large home.
Mine is small and no large draw electric appliances (except AC), so I have tons of spare capacity.

Worst case, you'll need to be conscious to not run the stove+oven, dryer, and charge your car all at once.
Deal Addict
Dec 28, 2010
1252 posts
132 upvotes
Ajax
I've got AC and dryer. No electric range. I have a 100A panel. You think there'd be space for 40A for the EVSE?
Deal Fanatic
Jul 4, 2004
7504 posts
754 upvotes
Toronto
Bellotts wrote: I've got AC and dryer. No electric range. I have a 100A panel. You think there'd be space for 40A for the EVSE?
Post. A. Photo.
Deal Fanatic
Jul 4, 2004
7504 posts
754 upvotes
Toronto
craftsman wrote: If you are thinking about putting in additional power for multiple items in your garage, you should consider putting in a sub-panel in the garage so that you can easily add circuits when you want as well as have easy access to the breakers locally rather than having to go back to the house ie. run the 6 gauge to the subpanel and then run what every you need from there. You might even consider removing the the existing garage circuit from the main panel and just have everything in the subpanel.
This is the better option. I wouldn't pull the existing circuit from the panel, just leave it there (you don't want the lights to go out on you if you trip the subpanel's feed breaker in the main panel).

8/3 is good for 50A. That's a good subpanel feed to the garage. That's what I did. AC90 is maybe $0.50/m more than NMD90 at a wholesaler and will be more rugged as well as providing you with good mechanical protection for the wire.

6/3 copper or 4/3 aluminum at half the cost if you want to go 60A. I didn't bother for 10A.
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User avatar
Jul 23, 2004
2167 posts
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Montreal
Drew_W wrote: This is the better option. I wouldn't pull the existing circuit from the panel, just leave it there (you don't want the lights to go out on you if you trip the subpanel's feed breaker in the main panel).

8/3 is good for 50A. That's a good subpanel feed to the garage. That's what I did. AC90 is maybe $0.50/m more than NMD90 at a wholesaler and will be more rugged as well as providing you with good mechanical protection for the wire.

6/3 copper or 4/3 aluminum at half the cost if you want to go 60A. I didn't bother for 10A.
Did that a few years ago.

6/3 to the garage feeding a subpanel. 60A breaker in the main panel.

Small panels are really cheap (around 50$ for a 8-12 slots if I remembrer correctly).

Then with the subpanel in the garage you can add circuits as you wish.

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