Pump/Grid bonding, etc

[Backglass]

Hey All,

I have found what I believe to be improper bonding on the pool at our new house. The subpanel is connected to a ground rod near the pump AND the house main panel (isnt this incorrect?) The pump has two large green ground wire connected on the case...one appears to go to the pump pad, the other snakes off in the direction of the pool. The pump itself is grounded through the cord.

Here is the problem...I was following the green wire heading out towards the pool and pulling it out of the mulch as I went (it wasn't really buried...only an inch under the surface) when about 5 feet from the pool, it just stopped. It doesn't look severed like from as shovel, but a clean beveled cut...as if it never really did go any farther. I have dug around trying to see if I can find the other end, but it appears there isnt one. SO...the pump isn't bonded to the pool. This is an old pool (the CO says 1983) so how would I go about connecting to the grid (if any) after the fact? Should I be looking for a piece of rebar to clamp on to? How do you test to see if your bonding is actually working?

To date we have no issues (no tingling on pool ladders, etc) although the 220 GFI test button doesn't trip when pushed which may or may not be related.

Any bonding tips short of ripping it all out? :lol:

 

[chatcher]

I don't know of any way to verify with 100% certainty that a pool is bonded properly, but yours definitely isn't. The pump case should definitely be bonded to the grid surrounding the pool with solid copper wire, including all the rebar including that in the deck, steel walls for steel/vinyl pools, ladder and handrail anchors, light niche, metal coping, etc. In short, all metal parts of substantial size must be bonded together to form one equipotential grid, which is then indirectly connected to the electrical circuit ground via the pump, light niche, heater, automatic controller, SWCG, etc.

You could bond your pump to a piece of rebar, but you would never know if that piece of rebar was tied to all the others (steel tie wire is okay if tight). I would check for continuity between all accessible metal parts. If the ground terminal is exposed on the inside of your light niche (current code says it should be sealed in potting compound, but since it is an older pool I bet it won't be) you could check from there to your ladder.

I'd find out why the GFCI doesn't trip. Could be a defective breaker, improper installation, or a problem with the ground circuit.

As for the additional ground rod for the subpanel, there are some inspectors who would never allow it, others who would probably insist on it, and depending on which version of which code was in force during construction, it may have actually been prohibited, but I don't personally consider it a safety problem as long as the subpanel ground is also connected back to the main panel. That second wire on the pump case bonding terminal is not supposed to connect directly to the ground circuit, so you might want to see where it goes.

 

[JasonLion]

First, if the test button on a GFCI doesn't trip the GFCI then it needs to be replaced. This happens now and then and is probably unrelated to everything else.

As chatcher said, code varies from place to place, year to year, and inspector to inspector. The extra ground rod at the sub-panel won't directly affect the bonding system. I would leave it alone unless you are making changes sufficent to require reinspection, and then go with what the local inspector says.

To test the bonding you need a fairly long piece of reasonably heavy gauge wire and an ohm meter (multimeter). Firmly connect one end of the wire to the pump and then measure the resistance between the other end of the wire and the heater, SWG, and anything metal built into your pool (typically ladders, automatic covers, sockets in the deck the ladders connect to, etc). In all cases the resistance should be less than 5 ohms, hopefully quite a bit less; though not all ohm meters are particuarly accurate at low ohm readings and it is sometimes difficult to get a good connection to the item being tested. If all the readings are high, switch the wire from the pump to something else and see if anything is connected together.

Finding a bonding point on an old system is tricky. You could use a metal detector, if you have one, and scan around the edge of the deck for metal. Another approach is to use a wire tracer, which you are even less likely to have. Without either of those; random digging in likely spots might get lucky or it might just mess up your landscaping.