why would v/m EF readings on a tester fluctuate?

Thread Starter

ThirtyWest

Joined Jul 15, 2017
140
Long story how/why, but I was playing with a GQ-EMF390 meter (no, I'm not starting a COVID ghost-hunting service).

I don't think the meter is/was calibarated/working because it always show a mG of 2.8 anywhere in the house and it always shows a minimum of 6 V/M on the EF readings.

However, those will change if I place it over things like the electric stove's line and such.

The QUESTION:
Sitting in a room, pretty much any room in the house, I get a standing 6-11 v/m. If it's calibrated poorly I can see that, however:

Why would it spike, every 5 to 8 seconds, to anywhere from 37 to <=70 v/m. Perfectly timed?


My house has a history of prematurely burned out incandescent bulbs too, and after discussing with neighbors I've got an unusually higher electric bill than most of them. I'm disciplined with regard to lights, and even though we are in SE TX (twin HVACs) we run the floors based on time of day.

Is this fluctuating v/m indicative of a cleanliness issue with my mains?
A DMM says the receptacles are providing what you'd expect (+ or - a few)
 
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SamR

Joined Mar 19, 2019
2,419
The only way to be sure is by placing a recording V & I meter on the mains at the panel. The "regular periods" are puzzling. I had similar problems, irregular power sags, until the power company replaced the mains feeder servicing our area with higher capacity and 3 phase service. Getting the Utility Company to address the problem is a whole 'nother issue.
 

Thread Starter

ThirtyWest

Joined Jul 15, 2017
140
Hi and thanks.
Were I to use a DMM at the receptacle do you think I’d see a spike at those intervals I mentioned?

measure EF EMF is new for me.
 

SamR

Joined Mar 19, 2019
2,419
Maybe, but seeing it and getting the utility company to acknowledge it without a recorded strip would be impossible. Even with one, it could be hard to get them to do anything. YMMV First step would be to determine whether it is an "internal, within the house" or "external, from the utility" issue.
 

Thread Starter

ThirtyWest

Joined Jul 15, 2017
140
Well I got home and put the DMM on a few outlets.
No correlation to voltage bumps with the EF v/m spikes.
Every 5-7 seconds it would go from 5 to about 14 in the kitchen.
I made sure to keep the DMM far from it.
Voltage on the outlet (single phase) was 125.1 to 125.3 throughout.
I’m guessing I don’t have to test the whole house this way.
 

SamR

Joined Mar 19, 2019
2,419
I doubt you would see such a wisp of a blip on a DMM. Small signals take careful processing to acquire. It could even be an artifact of the EF meter.
 

MisterBill2

Joined Jan 23, 2018
6,764
You are reading an electrostatic charge voltage, and that is affected by the integrity ogf the neutral to ground impedance/ voltage. So my first suggestion is to tighten all of the neutral connections. My reaoning is that if the neutral to ground voltage changes then also the phase to ground in the locality will change.
 

MisterBill2

Joined Jan 23, 2018
6,764
No, I mean the neutrals on the incoming power connection. That will not be very many places to check Meter box to breaker panel neutral terminal strip.Be very careful to avoid the line connections, they can be shocking.
 

MisterBill2

Joined Jan 23, 2018
6,764
If there is a poor connection of the neutral return side then the voltage of the inside neutral wires relative to actual ground potential will be able to change. That could cause the jumping. OR, your electrostatic field intensity meter could have a problem.
 

Thread Starter

ThirtyWest

Joined Jul 15, 2017
140
I shut the mains and didn’t see any neutrals on that strip that were unsecured. I wasn’t going to go grabbing up to the mains neutral though.

the meter still showed 6v/m anywhere in the house with the power off but as soon as the mains came online the 5 second pulses came back.

I need another meter to compare baselines.

96767E3D-3C42-4298-A29E-3DC04D7681F1.jpeg
 

MisterBill2

Joined Jan 23, 2018
6,764
OK, at this stage I suggest doing a similar test at another house. The reason is to see if any of it is an issue with your meter. I am presuming that the center wire to the top of the panel is a neutral. And I see that the feed wires are aluminum, which does have a tendency to corrode and make poor connections. Tightening the three setscrews in the three wire clamps a bit is another thing that I recommend, but they are constantly live and swutching off the mauin breaker does not change that. So to do it safely you need a well insulated tool, and eye protection in case of a spark. Tightening those connections is dangerous , although the center one should be neutral.
What I see that is disturbing is that it looks like the screw in the middle is already farther in than the other two. Based on that, I suggest switching off the mains breaker in case tightening the neutral wire causes it to break, or somehow be disrupted for a moment.
If you can get a voltmeter probe onto the neutral conductor just at the top of that connection lug, and then meter to the busbar with all the neutral connections, it should be about zero volts. If not, then there is a problem. The meter check is safer than tightening the setscrews.
 

MisterBill2

Joined Jan 23, 2018
6,764
those are the points that I was talking about, except on the neutral I was saying to probe the actual conductor, not the lug body. The problem may be the connection between the conductors and that lug body. It might also be the connection between the lug body and the bus-bar it is attached to. That is why the suggestion for the other probe is the body of the bar that all the white wires are connected to. So the two places circled are indeed what I was describing, except for trying to contact the actual wire of the neutral feed.
 

SamR

Joined Mar 19, 2019
2,419
There is a great deal of arguing about the termination of aluminum mains feeders. Canada requires wire brushing and doping with antioxidants before torquing the termination block. The US NEC does not. Aluminum wiring in "mobile homes" has been blamed for excessive home wiring fires and outlawed in some local jurisdictions. Aluminum feeders are much less expensive than copper ones and now commonly used along with aluminum feeders for high ampacity HVAC, water heaters, and such. YMMV

EDIT: Working in an Industrial Chemical Refinery located on the coast we required antioxidant coating even on our copper feeders due to a history of oxidation problems. A much harsher environment than found in typical residential or commercial construction. FWIW
 
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MisterBill2

Joined Jan 23, 2018
6,764
It checked to be 0.

Is 124v normal for 110-120? I'm finding every receptacle in the house is >=123.
OK, with a voltage drop of zero in your distribution panel it gets more interesting, since the most common cause is not found. The good news then is that it may be outside the house, except that you stated that when the mains were switched off the signal went away, and returned when the mains were switched back on. One moore test would be to measure the voltage between the house neutral and a ground rod in the ground not near the power connection or the water pipe connection to the house.
 
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