Bizarre HZ imbalance

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Acxpert

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A few weeks ago my oven died and I installed a new one. Old one was 230v electric and new one is gas. Installed a new breaker and plug for 120v and all was good or so I thought. The oven would not keep proper time and the display scrambles sometimes when turning on the burners. So the appliance guy comes out under warranty and changes the board, same problem. He called this afternoon and said the factory said to look for dirty power and to check the HZ. I checked it with my Fluke clamp on and the leg feeding the question circuit is reading over 400HZ. Other leg and Neutral are both 60 HZ.

The panel in question is a 4 wire sub-panel and the ground is not bonded to the neutral. I tried turning off all the breakers and the HZ remains high. At the main coming off the meter both L1 & L2 are 60HZ.

Im not sure if the clamp on Fluke meter is picking up some garbage, any ideas what may be going on here?
 
You may have a polarity issue. Make sure your 120v circuit is wired correctly.

If you used the original range cable, you may well have made an error.
 
plug in an old sync motor electric clock and watch the second hand.

Do you hae ;an induction cooktop? Might be getting EMI fro that if operating when over goes haywire.
 
I have always checked frequency with the probes. If your meter allows frequency measurements with the clamp it could only mean that you are measuring the frequency of the current drawn by the connected device. So if that 400Hz is real, it is coming from the device- IE the control board or something else in the range connected to that 120V circuit.

However, if you turned off all breakers including the 120v to the range and you are still seeing 400Hz with your clamp-on there is something wrong because there is no current for the clamp to measure.

Sooo, I think you need to polish up your measurement and troubleshooting techniques and give us more accurate information.

-Hal
 
I just looked at the specs for your meter. The clamp-on requires at least 5A of current flow to trigger the frequency measurement at 60Hz, more than 10A @ 400Hz. So if you have less than that or no current on the conductor that you are measuring, you are just getting a meaningless ghost reading.

-Hal
 
hbiss said:
I just looked at the specs for your meter. The clamp-on requires at least 5A of current flow to trigger the frequency measurement at 60Hz, more than 10A @ 400Hz. So if you have less than that or no current on the conductor that you are measuring, you are just getting a meaningless ghost reading.

-Hal
Click to expand...

I have a Fluke 337. Similar requirements if not the same. I waved mine around in front of the well vfd with no results. It does read 60HZ on the input with about 3.2 amps but nothing on the output of 2.8 amps.

Somethings amiss.
 
ptonsparky said:
I have a Fluke 337. Similar requirements if not the same. I waved mine around in front of the well vfd with no results. It does read 60HZ on the input with about 3.2 amps but nothing on the output of 2.8 amps.

Somethings amiss.
Click to expand...

FYI, the polarity and ground are correct and it is a dedicated circuit with no splices. I think I am getting some garbage, when I load up the panel it goes to 60hz and bounces around when I take the load off. I tried moving the circuit (its 120v) to another breaker fed by the other leg and its still doing the same thing.

Interesting enough after I was done and put everything away I turned on a burner, the display scrambled and its putting out a code with an 800 number to call Looks like I got a lemon, Im going to go get a replacement in a few. Sucks because I have to do the propane conversion again which is not fun.... I will pick up a better meter though, Im curious now...

Thanks for all the responses guys!
 
Did you look up the code to see what it means?

I'm thinking that the burner igniter is putting out crap or the control board wiring is routed by mistake too close to the HV igniter wiring.

If you get another meter you want one that will measure frequency using the probes across the voltage. I use my old Fluke 87 from the 90's that does that. Other than checking the speed of generators I have never needed to measure frequency. I suppose if you do work with VFDs frequency measurement can come in handy.

Still, for something like this problem only a scope is going to show something.

-Hal
 
Uh-oh. My spidey-sense is tingling. A neutral issue?

Have you tried a volt-meter in parallel with the load?
 
Just finished installing a new oven. Works perfectly. The original one never kept correct time out of the box which was the first sign I had an issue.

BTW, the code was a fatal error and could not be reset. Fingers crossed it works this time or wifey is gonna have a fit come Thursday.... I will post again if any issues pop up.

Thanks guys!
 
The specs of the meter indicate a current level required to detect HZ. The stove igniter would be my SEWAG guess for the HZ, but it would not account for the current level required. IDK what loads he actually had on at the time of his tests.

I thought harmonics were associated more with three phase vs single.
 
I could be wrong, but my best guess is something like a spark igniter isn't drawing current or pulsing at 60Hz. That high frequency ripple or interference is getting picked up by the meter.
 
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