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Posted By: stevenbohrer 100A Subpanel - 12/29/04 10:30 PM
I'm putting in a 100A subpanel in a damp area. I'm running 1 1/4" Sched40 PVC from the main panel (sized from NEC Table C.10). Planning on using 3 - #3 copper THHN (from table 310.16). Reading 250.122 (and 250.4(A)(5) and (B)(4)), it sounds like #8 bare copper stranded is fine for the ground, but I assume I'm better off going larger?

Also, anyone out there up to date on pool equipment grounding/bonding requirements?

I've done alot of home wiring, but am using this project as my first opportunity to interpret the NEC codebook. Let me know where I screw up!


Posted By: HotLine1 Re: 100A Subpanel - 12/29/04 11:21 PM
Welcome to the forum. We try not to give DIY help here, but...
Where did you find 'table c10' ???

310-16 is for conductor sizes and ampacities, and Article 250 provides all ground answers.

As to pools, yes, I'm 'up-to-date' as I am an EC and AHJ. Read Article 680 for pools.

Remember, the NEC is not a design tool.....

Posted By: stevenbohrer Re: 100A Subpanel - 12/30/04 12:56 AM
Hi John,

Table C.10 is in Annex C.

I read telecommunication specs as part of my day job, so I'm trying my hand at interpreting the NEC codebook (gotta keep the brain busy). Since I've never done it before, I was looking for a sanity check to make sure I'm following the references correctly. But, if this isn't the right forum, please let me know.

The pool question is prompted because I have a contractor replacing some equipment and I get the feeling that the pool bond / equipment ground codes have changed a bit. And while I'd love to have blind faith, I'm a born skeptic. Specifically... I'm trying to understand section 680.26(B)(4).

That section says that pool pumps/heaters/etc should be bonded to the pool unless they are "double insulated." This section also states that the internal metal parts shall have an equipment ground to the panel.

Q1 - If the accessible metal parts of "double insulated" equipment are not bonded to the pool, shouldn't they be bonded to the panel ground? This section doesn't explicitly say that. Maybe I don't fully understand what "double insulated" means.

Q2 - If a double insulated pump is installed, then a #8 bond wire must be provided in the vicinity for a replacement motor (that is not double insulated I assume). This bond wire, if the pool bond is not connected to the equipment ground, should be connected to the equipment ground.

So if I read this correctly, a new pump that is not double insulated must be bonded to the pool and grounded at the panel, while a replacement pump (for a "double insulated" pump) could use the panel for grounding AND bonding?

I think I really just need to understand the purpose of the pool bond and why it is not required to be connected to the service ground. And if they are not connected, what is the appropriate bonding point for pool equipment.

You guys ever get headaches from this? [Linked Image]


Posted By: HotLine1 Re: 100A Subpanel - 12/30/04 01:28 AM
I wasn't trying to blow you away.

OK...the 'bond' on pools is to create an equal potential. The pool pump motor, as well as all other metal (4 sq in or larger) must be 'bonded' with/by a piece of solid #8 copper wire. THIS IN NOT THE EQUIPMENT GROUND. It does not get connected to a ground rod. You 'bond' all the metal together.

Double insulated pumps, may exist, I personally have not seen any, although some people try to convince me that their pump IS double insulated.

The equipment grounding conductor IS NOT a 'bond', it is a grounding conductor.

Does the contractor you are using have a Permit?? Are permits required in your area??
IF so, then the local AHJ will assure you that the work was in conformance with the current NEC in your area.

As to 'leaving' a bond for a replacement pump?? Yes, that is a real good idea.

Take care & Happy Holidays

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