residential stray voltage - investigation procedures
residential stray voltage - investigation procedures
(OP)
I'm interested in seeing what information may be out there on utility procedures for investigating stray voltage complaints from residential customers. This is mainly involving 120/240 V single phase service from single phase transformers, so its really North American practice.
Common situations involve people getting shocked in a shower.
Most of what I've found relates to dairy farms and milking equipment. Also there's some dealing with swimming pools, but I'm really not interested in that.
Common situations involve people getting shocked in a shower.
Most of what I've found relates to dairy farms and milking equipment. Also there's some dealing with swimming pools, but I'm really not interested in that.






RE: residential stray voltage - investigation procedures
Keith Cress
kcress - http://www.flaminsystems.com
RE: residential stray voltage - investigation procedures
The symptom you describe is usually the result of a bonding or grounding problem in the customer's system. Not something a utility cares to get involved with.
RE: residential stray voltage - investigation procedures
We'll typically pull the meter at the residence and if the neutral to ground voltage drops to zero then we'll conclude that the problem is on the customer's side and then advise him to get an electrician.
RE: residential stray voltage - investigation procedures
On the wooden floor above, I could read about 40 volts. When someone tried to drink out of the tap, they got a painful shock in the mouth.
Bill
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"Why not the best?"
Jimmy Carter
RE: residential stray voltage - investigation procedures
Beyond that it becomes a regular hunt with a meter and some knowledge. I generally plug in a grounded extension cord somewhere distant, drag the other end over to the problem area and then using the tested,(hot to ground), ground socket as the ground anchor and a meter hunt down the problem.
Keith Cress
kcress - http://www.flaminsystems.com
RE: residential stray voltage - investigation procedures
JIM
RE: residential stray voltage - investigation procedures
So how am I am getting very. very low voltages on my "dead" AC 120v circuits? (Digital voltmeter reading 2-3 volts on isolated circuits. That seems too high for just random readings, but too low for any short in the ground side.)
RE: residential stray voltage - investigation procedures
RE: residential stray voltage - investigation procedures
RE: residential stray voltage - investigation procedures
I have seen the problem and it was the results of bad grounds at the utility transformer (pad mount single phase 7200-120/240).
The particular installations I looked at had a ground rod driven at the transformer. The service neutral and the concentric ground on the 7200 volt cabel were connected to the ground rod.
The concentric neutral around the primary cable provided more of the ground connection than people thought. As the concentric neutral corroded stray voltages appeared. Usually it was people getting tingled when touching the sink etc.
The same problem appeared when primary cabels were repalced with cables routed in Polyethelyne conduit ( directional drilling projects). The cables in the Poly pipe lost a lot CN ground connection.
The soulution was to suppliment ground rods with copper plates. They were 24" x 12". They worked most of the time, the area was one of the wettest in the US. In dry summers somtimes the proble would resurface.
RE: residential stray voltage - investigation procedures
Wayne440, for voltage measurement with hi-Z meters, check out the Fluke TL225 Stray Voltage Adapter at fluke.com.
RE: residential stray voltage - investigation procedures
I would imagine that unbalanced phase current would only cause an issue if the transformer neutral was not solidly grounded. If transformer was grounded then neutral would be held to ground potential, and I dont see how unbalanced current would cause issues with Neutral to ground readings.
RE: residential stray voltage - investigation procedures
RE: residential stray voltage - investigation procedures
RE: residential stray voltage - investigation procedures
You're on to step 2.
Initially someone is getting shocked. Pulling the meter will help determine if the fault is on the customer side of the meter or not. Since we run into a lot of wiring issues, this is an important first step.
Step 2 is to put what is called a beast of burden on the meter base. This a single phase heater load that can be switched between legs of the service. This will check the condition of the service neutral as well as test for an open hot leg.
RE: residential stray voltage - investigation procedures
When we receive complaints of people being 'shocked' in swimming pools (usually, its a woman with recently shaved legs experiencing a tingling sensation when touching a ladder), it is usually due to neutral currents returning through the earth. I haven't seen this in any swimming pools that are bonded in accordance with the requirements of the 2007 NESC.
Robert
RE: residential stray voltage - investigation procedures
Are the pool bonding rules in the NESC different from those in the NEC? Most pools are installed under the rules in the NEC.
RE: residential stray voltage - investigation procedures
RE: residential stray voltage - investigation procedures
Robert