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Thread: Fluctuating voltage

  1. #1

    Fluctuating voltage

    Using a SureTest (ST-1P) circuit analyzer in a new house I got fluctuating voltage at various receptacle outlets. It would go something like this; 25, 70, 116, 85, 40, 0. Anyone have a clue what may be happening?

    Thanks in advance.

    Duane

  2. #2
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    Re: Fluctuating voltage

    Given all the recent goofy reports about the SureTest, I'm not sure that it has much value.

  3. #3

    Re: Fluctuating voltage

    If it is counting up and down on one receptacle, it's toast. That was a common failure mode of some multimeters I had several years back.

    Jim

  4. #4

    Re: Fluctuating voltage

    Thanks guys for your input. I'm a home inspector and I test circuits on new construction primarily looking for potential problems, and when found, defer it to a qualified electrician. I do not have troubleshooting experience due to SureTest findings and am hoping for some enlightenment from those who do.

    mdshunk said: "Given all the recent goofy reports about the SureTest, I'm not sure that it has much value." Can you elaborate just a little?

    Jim, This problem occurs only on certain outlets and is repeatable. Would that rule out a defective analyzer?

    Since the SureTest measures the circuit voltage under a load, could the fluctuations also indicate a poor connection in the wiring? I was testing the circuits in a new house when I ran across this fluctuation issue. I also had 0~14.9% voltage drop on the circuits at various receptacles, and on some duplex receptacles the voltage drop varied as much as 2.2% between the top and bottom outlets.

    Assuming that the SureTest is giving accurate readings, what are the most common causes of fluctuating current and voltage drop differential between the two outlets on a duplex receptacle?

    Thanks again!

    Duane

  5. #5
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    Re: Fluctuating voltage

    and on some duplex receptacles the voltage drop varied as much as 2.2% between the top and bottom outlets.
    Unless these are half switched outlets, I can't imagine a reason other than a defective tester that would show a different voltage drop for the top and bottom outlets of the same duplex receptacle.
    Don
    Don, Illinois
    "It is the first responsibility of every citizen to question authority." B Franklin

  6. #6
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    Re: Fluctuating voltage

    Originally posted by captain dick:
    mdshunk said: "Given all the recent goofy reports about the SureTest, I'm not sure that it has much value." Can you elaborate just a little?
    All I've ever seen about the SureTest is that upon occasion AFCI's won't dance to it's "fault" tune. Beyond that, what have you heard, MDS?

    Jim, This problem occurs only on certain outlets and is repeatable. Would that rule out a defective analyzer?
    Repeatable? Then I would tend to trust the tester, if it reliably acts up on a given receptacle. It might not be telling you the issue directly, but it seems to be on to something.

  7. #7
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    Re: Fluctuating voltage

    I've owned a sure test since the home inspectors started using them ( never had any problems, but keep the fluke meter handy). The first inspection report I recieved was from an inspector that didn't know how to use the Sure Test that was given to him by the company. Didn't read the instructions. Second he didn't understand that voltage drop adds up fast on #14 ( legal around here in some areas for residential ). Weird readings at a receptacle can mean nothing more than a loose connection at the receptacle. The way you hold the tester you tend to put pressure that will make and break connection. If you test too many receptacles in a row without a cooling period you may get strange readings ( the new one says 20 seconds ). And to be fair, only the washer circuit need to be tested at 20 Amps. for voltage drop. The rest are 15 Amp. receptacles, so even if they are on a 20 Amp breaker there is not going to be a 20 Amp load. The only problem that I have found with the Sure Test is they try to walk off if your not careful. Just like Fluke meters.
    "A sight for sore eyes to the blind would be awful magestic"---Wax Fang

  8. #8
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    Re: Fluctuating voltage

    Growler, I was going to post last night but I haven't seen one of these before so I didn't. You make a lot of the same points that I was going to.

    I think it's a great idea to test circuits under load. My method is to use my big drill, just as a way to know theres substantial current there.

    With the trend moving toward unqualified installer ( :confused: ) doing electrial who knows what's there to be found.

    It sounds like this thing is hand held and inserted into the receptacle with an adjustable load applied. I don't like that idea a lot. I get the impression it wouldn't be very difficult to cause some arcing on the receptacle contacts, and destroy their surface conditioning. Even put arc pits in them. I would much prefer a cord for attachment. I'm thinking that receptacles aren't designed with operating at full rating while the attachment plug is being wiggled around in mind.
    Sam, San Francisco Bay Area

  9. #9
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    Re: Fluctuating voltage

    Back to the Sure Test. I'm not sure what type of load they use to measure voltage drop but it's only momentary. There is no arcing because the device is securely plugged in with a short cord ( about 8"). But just plugging in with a new receptacle there is a certain tightness and this may make or break a poor connection. I just left a house where the previous homeowner had changed out all the receptacles, switches, and fixtures. I knew that I had a loose neutral but the first ten connections that I tightened didn't solve the problem. People use the screw terminals and don't bend the wire in a clockwise direction. They only give the wire nuts a couple of turns. It's not hard to find a bad connection its just hard to find the right one. And to make things fun they mix up all the wires in a multi-ganged switch box. They don't break out the tabs when wiring convenience receptacles. After I finish a job I like to use the Sure Test to check myself. If so much a ground touches a neutral it will tell you.
    "A sight for sore eyes to the blind would be awful magestic"---Wax Fang

  10. #10
    Join Date
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    5,156

    Re: Fluctuating voltage

    Ok, I'm a lot happier that it has cord then.
    Sam, San Francisco Bay Area

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