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AC Amp Meter problem - Printable Version

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+--- Thread: AC Amp Meter problem (/showthread.php?tid=7059)


AC Amp Meter problem - kaptain - 11-06-2022

This is another electrical issue with coach 701, one of the AC Amp meters (L-1 line) at the overhead of the driver's seat shows an amp draw of over 100 amp!
While the L-2 line is about 2 amp. 

The reading of over 100amp on the AC L-1 line is apparently erroneous because my Hughes Transformers EPO at the 50A AC power panel reads just 8.1/0.2 Amps, and the Xantrex SCP (Xanbus System Control Panel) shows LOAD: 2 amp, and AC IN: 4 Amp. I don't have much running except the 110V pump that comes on occasionally, some interior lights on, and three outside yard lights that I could not turn off (unless I set the disconnect the "Auxiliary Battery" to OFF).

Picture of the draw readings: 

           

Any thoughts on what could be the cause of the issue and how to fix this?

RE: AC Amp Meter problem - Jack Houpe - 11-07-2022

The voltage for the d'arsonval amp meters in the panel will be a low DC voltage, I suspect that the source that feeds that meter is defective. Most amp meters use shunts and are in series with the power input then send a signal to the meter via low voltage wiring, in the case of AC amps it will use flux from a shunt as the signal.

RE: AC Amp Meter problem - Richard - 11-07-2022

If you remove the cover from your circuit breaker box, you will probably find two doughnut coils surrounding the two hot legs coming into the box. Those doughnuts generate the signal for the voltmeters up front.

RE: AC Amp Meter problem - bikestuff - 11-07-2022

Does the meter ever go to zero?  If not…then the meter is bad.

I had the same problem… See this Thread

Also check the donuts in the little box under the breaker panel.  (Be careful)

Bill

RE: AC Amp Meter problem - kaptain - 11-07-2022

(11-07-2022, 06:41 AM)bikestuff Wrote:  Does the meter ever go to zero?  If not…then the meter is bad.

I had the same problem… See this Thread

Also check the donuts in the little box under the breaker panel.  (Be careful)

Bill


Thank you @Jack Houpe @Richard, and Bill for your suggestion.

I turned off the shore power at the outside 50 amp AC breaker.  Yes, the meters do return to zero, well, not quite but almost zero.

   

So I used a screwdriver to adjust the no-power zero reading. Now the no-power zero looks better. 

   
Then I removed 8 screws to take down the meters mounting panel, then swapped the two wires at each of the two amp meters.

   

Then I switch ON the circuit breaker at the shore power AC 50AMP. Check AC AMP readings again. Strange enough, now the reading appears normal.

     

Hughes Transformer EPO reading
   

Xantrex SCP reading now, the AC amp showing a minus sign in the front, does this looks normal? 
   

I am going to switch back the 2 wires at the backside of the 2 amp meters and see if the bad reading on the Newell Amp meter returns or not.

RE: AC Amp Meter problem - kaptain - 11-07-2022

Swapped back the two wires at the back of the L-1 and L-2 AC amp meters. The bad reading is back on the L-1 Amp meter.

   

Then I went to the coach rear, opened the AC power panel, and found the two donuts/inductors. But I don't see any abnormality with them.

AC Power Panel in the coach rear closet.

   

Two Donuts at the backside of the power panel
   

My question is, are the two signals that two donut rings collect, which are likely a low/small AC voltage, fed directly to the amp meter or to some circuit board for processing/rectifying before feeding to the amp meter? In other words, is there any middle guy (some device or board) between the donuts and the amp meter?

well, I guess what I should do now is measure the AC voltage across the two donuts and compare.

RE: AC Amp Meter problem - kaptain - 11-08-2022

Upon further checking, here are some of my findings:



1), The Newell AC voltage meters are fed directly from the AC input from the AC transfer switch bypassing the rear AC power panel in the rear closet. This means even if you turn off the 50 AMP main circuit breaker in the rear coach, this 120V AC feed line is still alive at the overhead of the driver's seat, and the voltmeter remains active.



   



2)  The two Amp meters are fed directly from the two donut inductors because the AC voltage at the meter terminals and the donut wires are the same. And it's the same color-coded wire in the back all the way to the front. 
 
No Power Reading in the front
       

No Power Reading in the rear closet
   

Power On reading in the front and back, the observed reading fluctuates and not quite stable.
   
   

3), Swap the two 2 wires behind the L-1, and L-2 amp meter again,  the bad reading disappear. This seems to indicate the original wiring (from the previous owner rather than from the factory) was erroneous.  AND the two donuts behind the power panel in the closet and two amp meters have to be a different model. But this has to be confirmed. I just ordered an inductance meter. Once I get it will test it again.