Pool Pump Grounding Issue

[mmn]

I have an in ground pool that's probably 30+ years old. I had to change out the filter pump motor the other day and ran into the first of a few issues.

It's a 240VAC circuit and there's only the two hot wires at the junction box, i.e. no ground wire! The metal conduit from the sub-panel contains 6 wires. There's 2 red for the 240VAC, a black and white for neutral and 120VAC, 2 other red wires that are the 12VAC for the light. No ground wire.

I'm kind of puzzled by this and not sure what to do about it. I was wondering if, in the days before PVC conduit, did they use the metal conduit for the ground and, if so, was/is that allowed by code? It's the only thing I can think of for how they grounded the pump and the light even though there's no ground wire running to the motor, and the ground wire coming from the light is open and not connected to anything.

There's also no bonding to the pool, but that's another issue. There's been recent excavation and renovation and I'm digging around the pump area to see if I can find a bonding wire.

Any insight would be helpful. I am familiar with the potential consequences of doing nothing.

Regards
Michael

 

[topher]

is it possible to pull a 14awg wire through the pipe? and ground it at your house?

 

[mmn]

is it possible to pull a 14awg wire through the pipe? and ground it at your house?

Would that it were that easy! Not really possible I think. That 3/4 inch conduit has 6 wires in it already.

I'm thinking of a test. I'd like to run an insulated test wire from the main panel ground bus out to the end of the metal conduit - it's about 50 feet. Then use my multimeter to a) check for potential between the test wire and the conduit, and b) check for continuity. If I have continuity and no voltage at least I have a working ground with the conduit, but what I won't know is how much current it could carry in the case of a fault.

Regards
Michael

 

[JohnT]

Conduit can be used as the grounding conductor, but I would be concerned in an outdoor environment and doubly so in a salty environment. It's too easy for a conduit connection to be broken by a repair, corrosion or just a fitting that wasn't tightened for me to feel comfortable with it.

 

[topher]

How long is the run? Tie twine to a wire. Pull the wire out the other end. Attach VERY SECURLY a ground, and the other wire. I use wire lube (yellow 77) and pull it through. As long the wires aren't rotted in there, and the pipe is in food shape you'll be fine.... Try to see if you have slack on the wires that are in there... Before you get to involved... Likewise you can try sending a fish tape through, and pulling a twine, but that does risk damaging existing wires. Using the conduit as a ground may work (assuming it's metal) bit not a good a ground, and does not classify as a bonding method which it needs to be. Also if the conduit ever breaks, so will your ground.

Sent from my HTC Ruby using Tapatalk 4 Beta

 

[topher]

Also just read this http://www.alanwire.com/tech/conduit.html tells you how many wires you can fit. In that pipe if it is 14awg you can fit a lot more than 6

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[mmn]

I did run that test wire 14 ga. from the main panel ground buss out to the junction box at the pump. There is continuity between the conduit and the panel ground. However there is also a potential of about 2 vac between the test wire and the conduit which tells me there's some impedance in the path. But its a pretty long run. 30 feet or so over to the house and a sub panel and then another 50 - 60 feet around the house to the main panel with a couple of junction boxes on the way.

Just to see I also tested for potential between the motor housing (ungrounded) and the test ground wire. 25vac! That was a -er- shock. Then I turned the motor off and tested again. 15vac! I think it's a single pole switch out there which means one of the 240vac is still hot with the switch off.

Lot of things to fix. Got a pool electrician coming tomorrow.

Regards
Michael

 

[Durk]

My 1946 vintage pool had no ground wires whatsoever. Of course, the entire piping system was steel galvanized pipe connected to an unlined steel wall pool, both buried in the ground. The poolhouse electrical system was grounded to the well plumbing (well piping also had a 2" feed straight to the pool), so any other grounding probably seemed superfluous. You would be running a wire from a plumbing component to an electric ground connected to another plumbing component. Once plastic pipe started taking over, and then pump bodies went plastic, too--that certainly changed things electrically. It probably took a while for the codes to adapt to this.

Bonding? An all-steel pool with all steel piping? Heh, forget about it.

I'm not endorsing this, I'm just sharing how it was done back then. It all worked fine until demolished in 2003.

 

[mmn]

I don't feel any stray ac getting in or out of the pool but I did measure a couple of volts between the water and my test ground wire.

The only metal to water contact is the 12vac light and the motor shaft where it connects to the impeller.

Regards
Michael