Wire size for HVAC

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Chris Simms

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Cohutta GA
I have never had to pull the wiring for the Hvac b4 but the house I came in on to "finish" the hvac crew said it was in an agreement with the customer for the electrician to provide the wiring. The crews that were doing the entire installation ( plumbing, hvac, & electrical) were all from the same company. The home owner fired 2 of the 3 and kept the hvac for whatever reason now that they are finished they stop by and say I am supposed to run the wire to their units and comperssors. They say to run 4/4/2 for the 15kw unit upstairs. What is wrong with a pull of 6/2 and a pull of 10/2. this woud be easier to pull and not cost as much.
Chris
 
What does the label on the unit say? It will tell you the Minimum Circuit Ampacity, Max Fuse or CB, among other things.

I am not familiar with 4/4/2.

A 6/2wg for 2 banks of 5kw heat and a 10/2wg for 1 bank of 5kw heat & fan, would be typical for the units in this area.
 
Take the time to read the information that came with the unit. It will be the best 5 minutes you can spend on a job like that. Dont assume you can use #8s for a 50 amp circuit. Sometimes it will tell you the size wire to use based on the length of the circuit.
 
Chris, if you are under the 2005 code #4 SEU is good for 85 amps--assuming copper. If this is residential I am assuming a 240 volt service so the 15KW unit will draw about 62.5 amps. Multiply that by 1.25 and you get 78 amps.

#4 sounds correct to me.
 
Chris Simms said:
I called the guys that installed the units and they said to use #4 SE cable
to the units and a 6/2 to compressor 1 and 10/2 to compressor 2
Chris
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Ask for cut sheets on the equipment. 6/2 is a lot of wire for an A/C compressor. Name plate data will give you the proper sizes. They are different than T310.16. The # 4 for the heat strips will have to be broken up into 1 #6/2 and 1 #10/2 at the unit.
 
don`t play games

don`t play games

Chris Simms said:
I have never had to pull the wiring for the Hvac b4 but the house I came in on to "finish" the hvac crew said it was in an agreement with the customer for the electrician to provide the wiring. The crews that were doing the entire installation ( plumbing, hvac, & electrical) were all from the same company. The home owner fired 2 of the 3 and kept the hvac for whatever reason now that they are finished they stop by and say I am supposed to run the wire to their units and comperssors. They say to run 4/4/2 for the 15kw unit upstairs. What is wrong with a pull of 6/2 and a pull of 10/2. this woud be easier to pull and not cost as much.
Chris
Click to expand...
422.60(a) read ,understand & calculate you loads,wire type 310.16 your o.c.p x125% I `m sure willbe able to help you with the specs /nameplates for condenser & space heater
 
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