Checking a recent pool circuit installation

[@ngeLCD]

A pool is being constructed at my house, and the electrical sub recently completed their task. I'm in Pennsylvania which is under NEC 2014 I believe. In reviewing their work, I had some questions, and was hoping to confirm my suspicions. Two 50A two pole breakers were installed in my main panel. One for the heat pump, and one for the pool control panel which in turn has the other pool equipment wired to it. The heat pump circuit is 240V only, and the other pool circuit is 120/240V. Accordingly two hots were installed for the heat pump circuit, two hots and a neutral for the other pool circuit, and a shared ground. All of the conductors installed as well as the shared ground are 8awg copper thhn. All 6 wires (5 current carrying, 1 ground) are in a single 1" PVC conduit and the run for both circuits is approximately 95' one way. My concern is with the size of the conductors that were installed. My read of the situation is that while Table 310.15(B)(16) rates the 8awg conductors at 55A, Table 310.15(B)(3)(a) requires an 80% adjustment factor due to 5 current carrying conductors sharing a conduit. Therefore the five current carrying conductors should be upsized to 6awg. In addition I have a voltage drop concern on the 120/240V circuit, but that's besides the point if my first concern is valid. I wanted to ask if my read is correct, or if I'm missing something that would make 8awg conductors acceptable in this application. Thanks!

 

[Dennis Alwon]

You are correct that a 50 amp breaker is not appropriate for the #8 however a change of breaker to 45 amps would make the install compliant as long as the calculated load is not more than 44 amps on either circuit. Not sure of the mca of the heat pump, that may be an issue

 

[suemarkp]

I think you only have 4 current carrying conductors instead of 5 (the neutral on a 120/240 circuit doesn't count as far as current based derating). But 4 current carrying conductors still has the 80% derating value...

I would think the heat pump circuit is fine. Look on its nameplate for its MCA (minimum circuit ampacity) value and Max Breaker value. I would expect the MCA to be in the mid 30's and the max breaker to be 50A. As long as the wires to the heat pump have adequate ampacity (44A is what they have) to cover the MCA value, and the breaker does not exceed the Max Breaker value, that circuit is fine. This is a code quirk for motors and HVAC in that the breaker can be larger than the wire amapcity -- more than just a round up value). For voltage drop, being a 240V load I wouldn't be concerned with a 100' run on #8 as long as the MCA value is under 40A.

The other panel would be limited to 44A. A 45A breaker is uncommon and may need to be ordered. It could be dropped to 40A as those are probably on the shelf even at a Home Depot. That can help limit the current to reduce your voltage drop fears. Is 40A enough (it should be for most pool panels)?

 

[infinity]

Not that it changes anything but ion your single raceway there are only 4 CCC's. As Dennis stated the largest OCPD you can use with the existing #8 conductors is 45 amps. If that works for the equipment involved then you can just change the existing 50 amp OCPD to 45 amps.

 

[@ngeLCD]

You are correct that a 50 amp breaker is not appropriate for the #8 however a change of breaker to 45 amps would make the install compliant as long as the calculated load is not more than 44 amps on either circuit. Not sure of the mca of the heat pump, that may be an issue

Thanks for the quick reply! The heat pump nameplate specifically states "Minimum Circuit Ampacity: 42A; Minimum Overcurrent Protection Device 50A". The other equipment circuit most likely was calculated, and maybe a 45A breaker would suffice there.

 

[infinity]

Thanks for the quick reply! The heat pump nameplate specifically states "Minimum Circuit Ampacity: 42A; Minimum Overcurrent Protection Device 50A". The other equipment circuit most likely was calculated, and maybe a 45A breaker would suffice there.

With an MCA of 42 amps and a MaxOCPD of 50 amps the derated #8 conductors (44 amps) and 50 amp OCPD are code compliant.

 

[Dennis Alwon]

The heat pump is allowed to have an overcurrent protective device larger than the conductor so that would be fine

 

[Dennis Alwon]

Looks like infinity and I posted at the same time.

The reason you can have a larger overcurrent protective device is because the heat pump has overload protection built into the unit so the breaker doesn't need to protect for over current as the overload device will handle that. The overcurrent protective device is there for ground fault and short circuit protection.

 

[@ngeLCD]

With an MCA of 42 amps and a MaxOCPD of 50 amps the derated #8 conductors (44 amps) and 50 amp OCPD are code compliant.

Perfect thanks!