60-amp electric furnace wire size?
#1
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60-amp electric furnace wire size?
Hi,
I'm installing an electric forced-air furnace in my basement. The furnace is less than ten feet from the panel. The furnace requires a 60-amp breaker, and in fact it came with one pre-installed on the face of the unit to serve as the within-arm's-reach disconnect. I have a couple questions:
1. What size wire do I need to run for this unit? Most everything I read places 60 amps at about #6 but some sources claim #4 depending on a couple of variables. Which is it?
2. What size PVC conduit will this wire, plus a #12 neutral (for the condensate pump) fit in?
3. Do I need to install a second 60-amp breaker in the panel to make the termination or will the breaker mounted in the unit suffice, and I can hard-wire to the panel?
Thank you very much!
Darel Matthews
I'm installing an electric forced-air furnace in my basement. The furnace is less than ten feet from the panel. The furnace requires a 60-amp breaker, and in fact it came with one pre-installed on the face of the unit to serve as the within-arm's-reach disconnect. I have a couple questions:
1. What size wire do I need to run for this unit? Most everything I read places 60 amps at about #6 but some sources claim #4 depending on a couple of variables. Which is it?
2. What size PVC conduit will this wire, plus a #12 neutral (for the condensate pump) fit in?
3. Do I need to install a second 60-amp breaker in the panel to make the termination or will the breaker mounted in the unit suffice, and I can hard-wire to the panel?
Thank you very much!
Darel Matthews
#2
You really need to look at the nameplate on the unit, find the corresponding model # and find the MCA rating(minimum circuit ampacity) and the MOCP rating(max over current protection).
This will determine your circuit size. The 60 amp "breaker" is just a means of disconnect and has no bearing on the size circuit to be run.
The circuit for the condensate pump will need to be a separate 120 volt circuit than the AHU. You can't tap one leg of the AHU and pull a neutral for the 120 volt.
Also, there needs to be a GFI receptacle within 20 or 25' (can't remember exactly) of the AHU.
This will determine your circuit size. The 60 amp "breaker" is just a means of disconnect and has no bearing on the size circuit to be run.
The circuit for the condensate pump will need to be a separate 120 volt circuit than the AHU. You can't tap one leg of the AHU and pull a neutral for the 120 volt.
Also, there needs to be a GFI receptacle within 20 or 25' (can't remember exactly) of the AHU.
#3
What size PVC conduit will this wire, plus a #12 neutral (for the condensate pump) fit in?
However, you can't just run the #12 as a neutral unless the manufacturer's instructions on the furnace specifically call for that.
Do I need to install a second 60-amp breaker in the panel to make the termination
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Thanks for the replies so far guys. MCA is 55A and MOCP is 60A.
Why can't I tap one leg for 120v? Just curious.
Also, the GFI - are you saying the GFI needs to be protecting the condensate pump circuit? Or there just has to be one? I have one on the board the panel is mounted on, I can pull the 120v for the condensate pump off of it.
I am going to use 3/4 EMT since that's what I'm most used to. Therefore, I can use #6 THHN for the 60A circuit, right? Plus #12 hot and neutral and #10 ground.
Thanks a lot, guys!
Darel
Why can't I tap one leg for 120v? Just curious.
Also, the GFI - are you saying the GFI needs to be protecting the condensate pump circuit? Or there just has to be one? I have one on the board the panel is mounted on, I can pull the 120v for the condensate pump off of it.
I am going to use 3/4 EMT since that's what I'm most used to. Therefore, I can use #6 THHN for the 60A circuit, right? Plus #12 hot and neutral and #10 ground.
Thanks a lot, guys!
Darel
Last edited by Darel; 06-03-09 at 03:50 PM. Reason: typo
#5
In your case, #6 NM will be ok because your MCA is 55 and you can use a 60 amp breaker.
Reason you can't tap one leg of this circuit is because your going to have a 15-20 amp circuit/device protected with a 60 amp breaker.
As far as the GFI, no it's not to protect the condensate pump. It's just required as a general purpose receptacle for a technician. I would do as you say and branch off the load side GFI and let that serve 2 purposes
3/4 is only good for 3-6's so your fill of 2-6's,2-12's and a 10 may be overfill without doing all the cross sectionals for all that wire. I'll say just go to 1" or do 2 separate circuits.
Reason you can't tap one leg of this circuit is because your going to have a 15-20 amp circuit/device protected with a 60 amp breaker.
As far as the GFI, no it's not to protect the condensate pump. It's just required as a general purpose receptacle for a technician. I would do as you say and branch off the load side GFI and let that serve 2 purposes
3/4 is only good for 3-6's so your fill of 2-6's,2-12's and a 10 may be overfill without doing all the cross sectionals for all that wire. I'll say just go to 1" or do 2 separate circuits.