Explanation of NEC article 680.26 section 3

[rjohnston]

What is the significance of the 4" measurement with regards to isolated parts?

 

[alehman]

If you are refering to 680.26.B.3, 4 inches is the largest dimension permitted for an isolated metal part within the swimming pool that is not required to be bonded. It is not a clearance requirement. For swimming pool installations, I strongly recommend consulting with a licensed electrical engineer experienced with swimming pools.

 

[rjohnston]

But why 4"? Why not 5" or 6"?

 

[alehman]

I assume it's because they feel like it is unlikely for something that small to accidentally become energized or that someone may be in contact with it.

 

[rjohnston]

The whole article reads:

"All metal fittings within or attached to the pool structure shall be bonded. Isolated parts that are not over 100 mm ( 4in.) in any dimension and do not penetrate into the poll structure more than 25 mm (1 in.) hall not require bonding."

Does that mean that if an isolated part is over 4", but does not penetrate the pool structure by more than 1", it also does not require bonding?

 

[peebee]

Read it again, it's pretty clear: If it pentrates by more than 1" then it does require bonding.

 

[rjohnston]

But what if it is larger than 4" and does not penetrate by 1"? Does it still require bonding?

 

[jghrist]

The rule has 3 conditions for not requiring bonding, all must be met:

1. The part must be isolated.
2. The part must not be larger than 4 in.
3. The part must not penetrate into the pool structure more than 1 in.

If any of these conditions are not true, bonding is required.

 

[peebee]

Oops, sorry, I was typing too fast, my intended post was:


If it pentrates by more than 1" OR if it's bigger than 4" then it does require bonding.

If you violate EITHER condition, then you need to bond it.

 

[rnd2]

rjohnston
I read your other post in the corrosion forum.
What are the large structures for, or can't you say?
The corrosion guys seemed to have got a handle on the corrosion potential.
Is it a swimming pool or do we evacuate the fish because of zinc poisoning?

 

[rjohnston]

rnd2

It is a pool (ie. chlorinated water). People will be swimming in it. There will be no fish.

As far as what the structures are lets just called it a large mechanical device with a lot of moving parts.

The SST pins are at the pivots.