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Old 05-20-14, 07:50 PM
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Help!!

I just had a central heating system installed to replace cadet heaters.
The installers are not electricians so I thought I would give it a shot my self since bids were coming in between $1800-$2400 dollars. I have done some electrical in the past. My main panel in sub level so I think I am going to have to use a sub panel on the outside of the house since my basement is finished.
The furnace calls for a 220 volt 60amp and a 30amp circuit, the heat pump uses a 220 volt 35amp circuit.
Removing the cadet heaters in my house I will gain 3 double spaces @ 20amps each space.
The other thing I want to do is run 220 volt 30amp circuit to my garage for an air compressor.
all this said since my basement is finished it will have to be run outside and then back inside the house.
What gauge wire would be required between main panel and sub panel?
What other information can I supply to get the required wire size for my loads?
Thank you for your valuable time.
Larry
 
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Old 05-20-14, 08:17 PM
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Welcome to the forums.

I'm praying that you have a 200A service there since you are adding over 100A of continuous duty load. Your service is 120v/240v.

So..... first off..... what size is your main service ?
What will be the total load on the new sub-panel ?

I can see at least 60+30+35+30= 155amps.
 
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Old 05-20-14, 08:20 PM
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Also, where is your main panel located? Can you post a picture of your main panel and your outside meter?
 
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Old 05-20-14, 08:21 PM
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Yes I have a 120/240 200 Amp main
Load on sub panel =155 amps
 

Last edited by orgkrsh; 05-20-14 at 08:44 PM.
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Old 05-20-14, 08:41 PM
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Pictures as per request, meter outside, service inside, in basement.
 
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Old 05-20-14, 08:54 PM
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A little whoops there with the insulation. That should be insulated better.
Unfortunately it's hard to tape as you cannot kill it without removing the meter.

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Old 05-20-14, 09:18 PM
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Had to be the contractors when built. lots of f'ups on this house when built.
I am surprised this housed passed inspection the way it was built
 
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Old 05-20-14, 09:22 PM
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I hope someone did a demand load calculation before you decided to add such a significant load.

While the breakers you are removing are 20 amps, that does not limit the new circuits to the same ampacity.
 
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Old 05-20-14, 09:34 PM
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I had 2 licensed electricians come out and look at what I have and what I am doing, I would have to assume they would have done that before giving me a formal estimate for the work.
 
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Old 05-21-14, 06:28 PM
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A little whoops there with the insulation. That should be insulated better.
Unfortunately it's hard to tape as you cannot kill it without removing the meter.
It also looks like the service entrance wiring is URD.

Yes I have a 120/240 200 Amp main
Load on sub panel =155 amps
The added load is a significant increase, but probably not as high as you may think. Based on the information you provided, you now have a 2 circuit 15 KW electric furnace which has a load of 63 amps plus the blower motor load, probably a 1/3 HP motor, and a heat pump, probably 3 to 3 1/2 tons. It's important to note that the heat pump doesn't run when the electric heat is energized, so the heat pump load is not added to the electric furnace load. I believe a 100 amp subpanel would provide youo more than enough power for the furnace, heat pump and air compressor and also provide some future capacity.
 
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Old 05-21-14, 06:36 PM
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It's important to note that the heat pump doesn't run when the electric heat is energized, so the heat pump load is not added to the electric furnace load.
Very good point Joe! You get a gold star for today! Nice catch!
 
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Old 05-21-14, 07:16 PM
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OK everyone, I have re assessed my situation. After looking at this it appears that my service panel is not below surface, (brain fart).
Next thing is bury the cable or pvc?
I would like to do the most cost effective way, labor is free.
here is the the length for each load. can someone confirm what I am using for cable?

Compressor 30 amps run of wire 95' 10 ga.
Furnace 60 amps run of wire 65' 4 ga.
furnace 30 amps run of wire 65' 10 ga.
Heat pump 35 amps run of wire 65' 8ga.
Thanks everyone for those of you that have chimed in.
 
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Old 05-21-14, 07:43 PM
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Very good point Joe! You get a gold star for today! Nice catch!
Ty Ty Ty. I'll be in Minnesota all next week, do you deliver?
 
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Old 05-21-14, 07:46 PM
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Compressor 30 amps run of wire 95' 10 ga.
Furnace 60 amps run of wire 65' 4 ga.
furnace 30 amps run of wire 65' 10 ga.
Heat pump 35 amps run of wire 65' 8ga.
I'd use #6 for the 60 amp furnace circuit. Check the heat pump electrical data label or installation manual for minimum circuit ampacity, I suspect you'll find that all you need for it is #10. And yes, you can use #10 with a 35 amp breaker if that's what the data calls for.
 
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Old 05-22-14, 12:11 AM
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You must consult the data that comes with the unit on wire size due to the continuous loading nature of the electric coils.
 
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