Bonding Mystery - Pool Light

[Chuck_Davis]

I have an in-ground concrete pool (epoxy paint finish) with an Amerlite underwater light. The chrome bezel continuously turns black. The tarnish can be scrubbed off, but always returns. (There is also an ongoing, low-intensity battle with minor metal stains, with no known source for the metal.)

The tarnish probably indicates a bonding problem, but.................

There is a bond wire from the light niche to the bonding lug on the pump. The bond wire is #8 *stranded*, however. The wire connects to the inside of the niche and runs up the conduit with the power cord. The attachment of the bond wire to the niche is slathered in some sort of caulk. Using a wire nut in the J-box, the stranded bond wire is connected to another run of #8 stranded wire that goes back to the pump. It is a 30-40 foot run from the niche to the pump.

While the pool was partially drained I used a VOM to test, and there is continuity from the niche to the bonding lug on the pump. I connected my test wire to the screw hole where the screw holding the bezel in place is inserted, so I can assume that there is continuity from the bezel to the pump.

There are two other bond wires (also #8 stranded) connected to the bonding lug on the pump. One comes from the heat pump. The other comes from the concrete pool deck, with a bond wire from the rebar in a hot tub slab that I poured spliced into it. I have no idea of the quality or condition of the bond in the concrete pool deck.

The only real weirdness that I can see is the bond wire connection inside the niche, possibly in contact with the water if the caulking has failed. Since the goal of bonding is to keep everything, including/especially the water, at the same potential, I'm not sure this is a problem.

Does anybody have any ideas or suggestions on how to diagnose or fix what probably is some sort of current flow causing the tarnish on the light bezel?

Thanks.

 

[JohnT]

I'd say what is happening is that the bonding is doing its job, and what you need to look for is the source of the current. Hard to guess what that could be. Reversed hot and neutral someplace or a loose neutral, defective underground power or phone wiring or maybe a problem with your utility's power delivery system.

 

[Chuck_Davis]

Thanks for your quick response.

Other than the niche and pool light, there is no metal in contact with the water. (No stairs, rails, etc.)

I had the entire pool system rewired by an electrical contractor. Beauzeax, my name for the previous homeowner who installed the pool.............and who owned a pool construction company (!), had totally screwed it up. An AFCI on the light, no GCFI's anywhere else, and the bond wires disconnected since they caused the AFCI to trip. (I wonder if there's a clue there.) The new GCFI has not tripped.

Beauzeax had reversed hot and neutral at the receptacles in a non-permitted buildout of the garage into an apartment, but I corrected that.

No Telco wiring since I'm using VoIP from my cable provider.

The pool and pool light are around 15 years old. Is there any chance the power cord to the light is failing and leaking some current?

Can you think of any test points to determine if/where there is a voltage differential? Is there any way to test for leakage from the pool light power cord with the pool now being refilled?

(Here's another laugh. Beauzeax ran 75 feet of undersized gas line from the meter to the (now removed) pool heater............USING PVC! The undersized pipe caused the burners in the heater to run cool and moist, which rusted out the burners and baffles.)

 

[JohnT]

I expect if you pull the bond wire off the pump you'll see a voltage. If you can find a place were you can measure a voltage, you can try switching things off to check for changes.

Even problems with a neighbor's wiring could show up in your pool.

Google "stray voltage" to get some ideas.

 

[Chuck_Davis]

There was no measurable voltage at the pump, although my VOM only goes down to a 2 VDC range. There is a slight amount of DC current (.002-.004 milliamps) between the bond wires from the light and the pool deck to the pump bonding lug. (The heat pump is currently disconnected from the pool plumbing.)

I'm thinking of installing sacrificial anodes on the pool light and in the main plumbing, probably near the heater. Potential brand: http://pooltool.com/anodes.html.

Does anybody have any recommendations for, against or alternatives?

Thanks.

 

[Richard320]

There was no measurable voltage at the pump, although my VOM only goes down to a 2 VDC range. There is a slight amount of DC current (.002-.004 milliamps) between the bond wires from the light and the pool deck to the pump bonding lug. (The heat pump is currently disconnected from the pool plumbing.)

I'm thinking of installing sacrificial anodes on the pool light and in the main plumbing, probably near the heater. Potential brand: http://pooltool.com/anodes.html.

Does anybody have any recommendations for, against or alternatives?

Thanks.

DVOMs are wildly inaccurate when measuring AC set on DC and vice versa. Borrow a meter with an AC setting.

 

[Chuck_Davis]

My (el cheapo Radio Shack) VOM has AC volts, DC volts and DC milliamps.

 

[Richard320]

My (el cheapo Radio Shack) VOM has AC volts, DC volts and DC milliamps.

Your pump is AC, correct? You said you measured it on the 2VDC scale. That's why I mentioned it.

 

[JasonLion]

.002-.004 milliamps is exceedingly low and nothing to worry about, assuming you measured it correctly (see Richard320's comments).

 

[Chuck_Davis]

Per the suggestion above from JohnT, I disconnected the bond wires and then measured between each bond wire and the bonding lug on the motor.

 

[sunngurrl]

A friend of mine had this exact problem. After numerous people changing the light and running electrical tests, etc. they found the problem. They did a 9 point test on his water and found he had copper in his pool water which was causing the problem. They poured a solution for metals into his pool and it was corrected. I hope this helps.

 

[Chuck_Davis]

Thanks, Sunngurrl. I just finished my annual stain treatment that lifts and sequesters iron and copper stains. In my case it may be a chicken or egg issue. Other than the heat pump and pool light, I have no source of metals. It may be galvanic corrosion that is putting the metals into the water. I have added sacrificial zinc anodes just upstream of the heat pump and attached to the pool light. We'll see what happens.

 

[sunngurrl]

He found out the source of copper was coming from the water out of his hose to fill pool. In older communities they still have copper piping that the city/county water runs through. Good luck!