Russs57
Senior Member
- Location
- Miami, Florida, USA
- Occupation
- Maintenance Engineer
I had an unusual occurrence the other day. There was water coming out of the asphalt in a parking lot. I’m not responsible for the building but was asked to look into the matter when it was discovered that the water was carrying enough voltage to shock someone. I traced the water leak to condenser water lines from a cooling tower. I ran an extension cord over to a nearby conduit and grounded it on the conduit and measured about a 100 volts when sticking the other meter lead in the water. Even some 20 feet away from the actual leak, where the water was running to a storm drain, I was still getting 20-30 volts. After the voltage source was removed, and repaired things, were dug up.
So, you have a pair of 6” welded steel condenser water lines which are bolted a pair of pumps which are well grounded. You have a broken 4” PVC conduit with what looks to be six 500 MCM cables in it. These cables are connected to the secondary side of a utility transformer (assume primary voltage of 13,800). There are the three phase, 480 VAC service for another building. I can’t say if there was a neutral or ground in the conduit. Being a service feeder perhaps it was intended for a ground rod to be driven in the building it served.
So I’m trying to get a handle on figuring out what amount of current I had to be supplying to be measuring 100 volts at ground level. I would say the steel pipes were about eight feet drop and the conduit at six feet. Building is what next to the Bay so at high tide conduit could be in salt water. Parking lot so crushed gravel. Plus condenser water is more conductive. Call it 1800 micro Siemens. But we would have been down to raw city water shortly which is around 250 micro Siemens.
Would have expected the 13,800 to be involved. Just goes to show ground isn’t such a great ground I reckon.
So, you have a pair of 6” welded steel condenser water lines which are bolted a pair of pumps which are well grounded. You have a broken 4” PVC conduit with what looks to be six 500 MCM cables in it. These cables are connected to the secondary side of a utility transformer (assume primary voltage of 13,800). There are the three phase, 480 VAC service for another building. I can’t say if there was a neutral or ground in the conduit. Being a service feeder perhaps it was intended for a ground rod to be driven in the building it served.
So I’m trying to get a handle on figuring out what amount of current I had to be supplying to be measuring 100 volts at ground level. I would say the steel pipes were about eight feet drop and the conduit at six feet. Building is what next to the Bay so at high tide conduit could be in salt water. Parking lot so crushed gravel. Plus condenser water is more conductive. Call it 1800 micro Siemens. But we would have been down to raw city water shortly which is around 250 micro Siemens.
Would have expected the 13,800 to be involved. Just goes to show ground isn’t such a great ground I reckon.
