HELP!! Pool pump & booster pump wiring sizing

[marc deschenes]

Re: HELP!! Pool pump & booster pump wiring sizing

The romex I have been using has thhn for the conductor insulation. Where are you guys getting this Idea about romex being limited ? It is not the outer sheath but rather what surounds the copper wire it self that matters . A 12/2 romex only has 2 currant carring conductors not 3 so the raceway argument does not hold water . Unless the manufacturer limits its ampacity I can't find where the code does.
N.M stands for non matallic and is not an insulator of conductors

[ August 25, 2005, 07:10 AM: Message edited by: marc deschenes ]

 

[augie47]

Re: HELP!! Pool pump & booster pump wiring sizing

The romex I have been using has thhn for the conductor insulation

may I ask how you know this?
It has been my understanding from a wire mfg. that the insulation for NM conductors meets a specific requirement (dialetric strength, etc) and is not necessarily "w" rated.

 

[marc deschenes]

Re: HELP!! Pool pump & booster pump wiring sizing

I am not very computer savvy but this is why I assumed it was thhn though it does not say it is , it is rated at 90 degree. Sorry if I confused anyone . My point is that for de rating you can use the 90 degree column . Thanks for asking. I am confused , why you are looking for a W in thhn ?
http://appprod.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet6

 

[iwire]

Re: HELP!! Pool pump & booster pump wiring sizing

Originally posted by marc deschenes:
The romex I have been using has thhn for the conductor insulation. Where are you guys getting this Idea about romex being limited ?

334.80 Ampacity.
The ampacity of Types NM, NMC, and NMS cable shall be determined in accordance with 310.15. The ampacity shall be in accordance with the 60?C (140?F) conductor temperature rating. The 90?C (194?F) rating shall be permitted to be used for ampacity derating purposes, provided the final derated ampacity does not exceed that for a 60?C (140?F) rated conductor. The ampacity of Types NM, NMC, and NMS cable installed in cable tray shall be determined in accordance with 392.11.

 

[suemarkp]

Re: HELP!! Pool pump & booster pump wiring sizing

Originally posted by gudguyham:
I see the table you speak of, BUT, isn't that table for a single wire conductor in a raceway? (with less than 3 current carrying conductors) Some will argue that NM cable sheath is a raceway and therefore complies with this table, so then why is it that we only breaker branch circuits using #14 at a max of 15 amps?

The table is for up to 3 current carrying wires in raceway OR cable. The reason you use 15A breakers on #14 wire is because of 240.4 as augie47 mentioned. But that rule doesn't apply to motor circuits. This rule is an extra safety factor that is applied to most 15, 20, and 30A circuits, because these amp limits are even less than what the 60C column allows (except in the 30A case where it is equal).

Mark

 

[marc deschenes]

Re: HELP!! Pool pump & booster pump wiring sizing

suemarkp, you are absolutely right , a 12/2 romex is perfectly fine for this application.