Spa & Pool Sub Panel

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Old 09-06-07, 12:10 PM
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Spa & Pool Sub Panel

Installing a new Pool/Spa Heater. No breaker openings left on the main 200 amp service siemens panel. There is a 20amp 220V Double pole pool pump breaker on the main panel. I would like to replace the 20amp pool pump breaker with a 70 or 80 amp breaker and increase the wire size for the run to the pool pump area where the heater is also located. I will install a new sub panel in this area.

The heater requires a 50 amp breaker. I bought a spa sub panel rated to 125amps and it came with a 50amp GFCI breaker.
I plan to put a 20amp breaker in the sub panel also for the pool pump. The small pool pump wires presently run through the second floor crawl space in a thin corregated flexible light blue plastic conduit about 1 1/4"dia. I plan to use this same conduit for replacing the small wire with larger wire.

The question is: what size THHN or THWN-2 T90C separate stranded wires should I use? I have some 6ga I would like to use for this.

NEC table amp ratings are very different from a jacketed cable to separate wires in open air. Is this conduit considered open air?

Is the 70amp or 80amp sub panel supply breaker a good size choice for the heater and pump loads?
 
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Old 09-06-07, 01:00 PM
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If you want to use an 80 ampere breaker then nothing less than #4 wire is allowable.

Do not use the "conductors in free air" table when sizing conductors for use in conduit. "Free air" is exactly what it says, the wires are not contained at all.

The #6 would have a maximum ampacity of 65 amperes.
 
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Old 09-06-07, 02:15 PM
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The NEC data I got off the web for 6awg THHN or THWN-2 T90C was 75amps (3 wires in a cable) and 105amps single wires in open air, all at 86F. 104F derates them to 91%.

I don't have an NEC book but the last reply mentioning 65 amps max makes me question my web data. Maybe there is derating factors to make it 65amps?

If the 75 amps is correct, then I would like to use the 70 amp breaker to be safe.

I would really like to use the 6ga wire I have to supply the heat pump and pool pump if at all safe to do.

Thanks
 
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Old 09-06-07, 04:15 PM
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> for 6awg THHN or THWN-2 T90C was 75amps (3 wires in a cable) and
> 105amps single wires in open air, all at 86F. 104F derates them to 91%.

Those ratings are for 90C terminations, which are rare outside of industrial settings. Most residential and commercial terminations must use the 60C or 75C table. Because you have THWN-2 in conduit, you may use the 75C table which sets the ampacity for #6 at 65A. The NEC does allow you to "round up" to the next standard breaker size of 70A.

How long is this run? Because you are right on the edge of the wire ampacity you may need to upsize to compensate for voltage drop.

Also, what is the nameplate data from the heat pump (LRA, FLA)? This will help to determine if the #6 is sufficient.

If you do use the #6 for hots and neutral, the ground must be #10. If you upsize to #4 hots and neutral, the ground must be #8. In either case, the ground must be green, insulated copper. Bare ground wires are not allowed for pool/spa connections.

> thin corregated flexible light blue plastic conduit about 1 1/4"dia.

This conduit is ENT (electric non-metallic tubing); a.k.a. "Smurf tube".
 
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Old 09-07-07, 09:36 AM
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ibpooks,

Thanks

I'll check on the name plate tonight for LRA/FLA. What do they stand for?

It is a Jandy AE3000 heat pump(without chiller) and the manual says it has an 81k scroll compressor, if that helps?

Minimum Circuit Ampacity is 48amps and Max Over Current protection is 80Amps. Jandy's Sell Sheet lists a 50Amp Supply circuit.

The run is approx 47ft.

Do I need to make sure the GE Spa Sub Panel 50Amp GFCI Breaker and Siemens Main Panel 70Amp Breaker are 75C Termination Capable?
 
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