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Sub-Panel installation question. Furnace wire to run sub panel???? maybe?

Sub-Panel installation question. Furnace wire to run sub panel???? maybe?

Old 12-27-14, 12:07 AM
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Sub-Panel installation question. Furnace wire to run sub panel???? maybe?

I am new to electrical. I have a basic understanding but not vast. I know I need to install a sub panel for the work I will be doing in my home. The question is can I use the power line that currently runs to the furnace to supply the sub panel, then run the furnace off the sub panel. I am thinking this becasue it would be cleaner to avoid ripping down things and I want to put a sub panel next to the furnace anyway for a welder in the garage and some lighting in the basement. Also to save th cost of buying wire which I am sure is expensive.

The furnace runs off of a 90amp breaker. The wire to the furnace from the 90 amp breaker is E32071 (U L) 2-2-2 AL. TRIPLE - E ALLOY TYPE SE CABLE STYLE U TYPE XHHW CDRS 300V. TO GROUND.

This is overkill isnt it but can I do it?

The panel will supply power to

Furnace: 208/230 Volts
Dual Supply Circut
L1/L2 Heater Amps 36.2/40.0 Miin. Ampacity 53.8/58.5
max overcurrent protection 60/60
L3/L4 Heater Amps 18.1/20.0 Min. Ampacity 22.8/25.0
max overcurrent protection 25/25

Welder: 220Volt / 60 Hz / Single Phase / 24.5Amps 3-Prong, 220V AC, polarized, twist lock NEMA#L6-30

2-3 outlets in Garage and a couple on the inside of the wall inside if It is possible.
possibly a bathroom.

Any advice would be apprciated.
I can comprehend everything I have ever been told so far about electrical so I am 100% positive I can understand whatever you throw at me.

Old 12-27-14, 06:35 AM
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No, you can't use the existing cable for a sub panel.

Your existing cable is type SEU which only contains 3 wires.

You'll need type SER for a sub panel, which contains 3 insulated conductors and a bare ground.
Old 12-27-14, 08:30 AM
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The furnace circuit has no neutral conductor, just 2 hots and 1 ground. It appears you have a 2 circuit 15 KW electric furnace. I am wondering how those 2 circuits are powered by one 90 amp circuit. Since your SEU cable is only rated 300 volts to ground, I am assuming this installation is from the '80s or earlier.
Old 12-27-14, 09:07 AM
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In addition, the circuit for your air handler should remain dedicated.
Old 12-27-14, 10:16 AM
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The furnace running at full tilt will draw about 83 amps. There is not any ampacity available on that circuit.

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