# Wiring for a Garage Heater, 10/2 or 10/3?



## ski_rush (Jan 16, 2021)

I'd like to install a 240v, 5000 or 7500 watt heater in my garage. The electrician is letting me run the wire myself (to save labor cost) and he's going to do the connection to the fuse box/electrical panel. I asked him what wire to use and he said 10/3. However, when I watch videos on YouTube about this install, they all use 10/2 wire. The 10/2 wire seems like a pretty easy connection to do and the heating units seem like they are set up for 10/2 wire; that is, they have one white, one black, and ground wire connection (hence the 10/2).

I do not understand the 10/3. Where would that neutral wire go and why would it be needed? That doesn't make sense to me. Why would he recommend 10/3 over 10/2? At the heater connection, I'm not sure where to connect that neutral wire or why it would even be needed. 

Please help.


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## Jim Port (Sep 21, 2007)

A straight 240 volt heater only needs 2 hot conductors and a ground. No neutral is needed.


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## ski_rush (Jan 16, 2021)

Jim Port said:


> A straight 240 volt heater only needs 2 hot conductors and a ground. No neutral is needed.


Thank you for your quick response. What is the purpose of using 10/3 with the neutral wire?


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## Jim Port (Sep 21, 2007)

The neutral would be used for something like a dryer where there is neutral current from the motor and controls, while the heat is 240 only.


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## ski_rush (Jan 16, 2021)

Jim Port said:


> The neutral would be used for something like a dryer where there is neutral current from the motor and controls, while the heat is 240 only.


So, if someone did use 10/3, would the neutral just get pigtailed with either the white or black lead then?


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## Jim Port (Sep 21, 2007)

The white would just be capped off.


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## darren (Nov 25, 2005)

You say you may install a 7500W heater which is 31.25A. In Canada #10 is good for 30A, what is the rule in the USA regarding wire size.


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## rjniles (Feb 5, 2007)

darren said:


> You say you may install a 7500W heater which is 31.25A. In Canada #10 is good for 30A, what is the rule in the USA regarding wire size.


A 7500 watt heater would require #8.

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## Electriclife (Jan 16, 2021)

If I was in your shoes and not quite sure the heater unit or size I would run the #8. Better to have and not need than need and not have in my opinion.


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## mark_kershner (Mar 11, 2017)

Looks like 8/2 copper for the 7500 watt models I saw. Then as to the unused wire with 8/3, your electrician may not know what model you are considering. Better to have an extra wire than not enough. 


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## Electriclife (Jan 16, 2021)

If I was in your shoes and not quite sure the heater unit or size I would run the #8. Better to have and not need than need and not have in my opinion


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## ski_rush (Jan 16, 2021)

One other thing I'm confused about. My current electric panel is full. There are no available slots left. No tap outs left where I could see where a new breaker could be installed. The electrician looked it over and said he could move some things around and make room for a new 30amp breaker to power the 240v heater in the garage. What do you think he planned on doing here? He can't double tap a breaker, so do you think he planned on using tandem breaks to free up space for the new 30amp breaker? I'm trying to understand how most people would make this work with a full breaker box.


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## Electriclife (Jan 16, 2021)

Yup he'll just put in a few "skinny" breakers and make room that way.


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