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Current Transformer - Built in ammeter


Grampy OG
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I have recently realized that my analog ammeters that are built into the coach are not even close to accurate. Perhaps they never were. This is an 03 The Executive and the main display panel for tanks, electrical, generator, etc. are in a cabinet over the entry door. While trying to do some load balancing in a hookup location that only supplies 40 amps per leg  I realized that no matter how many items were turned on ( a/c, mwave, dryer ) each display only registers a max load of 10-11 amps when I know in fact that the load is between 25 and 35 amps on a leg. I am pretty good with electrical so I didn't have any trouble pulling the circuit panel covers and exposing the wires. The two CT (current transformer) donuts appear to be positioned correctly on each of the incoming legs. The analog meters are up front and the circuit panel is in the bedroom. So with all of that explained my question to the electrical gurus of the site: Is it possible that both CTs have failed or both analog meters? Seems odd to me so I don't know where to chase the problem. As a further input to the question I have verified amperage with a clamp on ammeter on each leg and the results match the numbers that are on my progressive surge meter out on the power pedestal. The progressive meters work well but what a pain to keep going out to the pedestal  to quickly check the system. Small digital current transformers are available at a low price and would be easy to install in the rear cabinet but I am the type that likes my coach to work as designed at the factory when possible. 

Thanks in advance,

Ken Wilcox

2003 The Executive

 

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Hi Ken -

I installed the small digital current  meters (meant to be mounted in rectangle cut-out in sheet of plastic or metal). I put the CTs on each leg , ran the wire to the edge of the breaker front, and put sticky magnet tape on the back of each meter. I added 3M body tape to keep the magnet attached to the meter.

Now the two sit on my breaker panel - easy to identify load. It is not factory original, yet it is accurate and handy.

IMG_4921.JPG.21e40c44bf33e28f04256371c02a79b3.JPG

Cheers,

Jeff - 2003 Camelot 38-PST

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Thank you Jeff,

Those are the exact ones that I have sitting in my Amazon shopping cart.  I planned to do it pretty much the way you were saying. I was just wondering (out loud I guess) if I had a double failure on the OEM meters or if I just never noticed until this weekend that they weren't reading above 10 amps. A double failure seems quite odd since the donuts are in essence just rolls of wire.  

About the meters you put in if I am reading the schematics right I still need to put a hot and neutral lead to the meters so that  they can power the display and measure voltage. From the looks of it that doesn't need to be more than at 16 or 18 gauge wire. Was that your experience?  

BTW: your install looks nice

Ken Wilcox - 2003 The Executive

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Hey Ken ,

Maybe someone else will chime in on the factory unit. My Camelot doesn't even report both legs when using 50 amp service. 😞

Power wire is either 18 or 20 - quite small - very low current at 120v. I doubt you need it, but let me know if you want me to pull the cover and take a pic of the wiring.

When you get yours in, I hope you share how yours comes out in pics.

Peace

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Should be able to test the current transformers with your clamp meter for reference amperage and then measure corresponding output of the transformer back in the panel.
I replaced all of the analog meters in my panel up front with digital and was able to find meters on Amazon that fit in the original cutouts. The new ammeters spec a different transformer though, so had to replace them also. 
Cheers

Walter

meters.jpg

Edited by wamcneil
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What a great looking setup. Were you able to use the existing cable runs?  I'm not sure what reading I would be looking for coming off of the existing transformers. Is that a reading that can be  checked with a VOM? When you say measure in the panel are you speaking of the circuit panel or the panel up front holding the meters?  Is there any wild chance you still have the links to the meters and transformers that you used as replacements? 

Thanks again - Ken

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Thank you Dale. I have only had the coach for four years and only gave them a nod until I actually wanted the info. You have confirmed my suspicions. 

 

Thanks - Ken

 

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16 hours ago, JDStew said:

Hey Ken ,

Maybe someone else will chime in on the factory unit. My Camelot doesn't even report both legs when using 50 amp service. 😞

Power wire is either 18 or 20 - quite small - very low current at 120v. I doubt you need it, but let me know if you want me to pull the cover and take a pic of the wiring.

When you get yours in, I hope you share how yours comes out in pics.

Peace

It's very common to measure only the neutral wire which works fine on 20A or 30A or 120V gen. On 120/240 50A the neutral amps are the DIFFERENCE of the two hot leg amps and hence the display is turned off.

The PI HW50C displays the amps and voltage on each leg which is for me more information on what each leg is carrying and with the remote inside a cabinet I can leave the door open to view. One of the reasons I have the HW version. 

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5 hours ago, Grampy OG said:

What a great looking setup. Were you able to use the existing cable runs?  I'm not sure what reading I would be looking for coming off of the existing transformers. Is that a reading that can be  checked with a VOM? When you say measure in the panel are you speaking of the circuit panel or the panel up front holding the meters?  Is there any wild chance you still have the links to the meters and transformers that you used as replacements? 

Thanks again - Ken

Thanks!

Here are the meters I used. Not currently available on amazon, but I'm sure there are others with similar dimensions. These are real close to being an exact fit in the original panel, but they require a different scale current transformer than original. So I found those on ebay.  Any new meters you buy will either come with transformers or list a spec for them.

https://www.amazon.com/gp/product/B016KD4WTK/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B00H8K5WHQ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

If I were doing it again I would probably try and find meters that use the old current transformers and then make a new panel to mount them in. I don't remember exactly what the CTs cost me, but I bought good ones and they were a lot more expensive than the cheap Chinese meters... I bought the meters first to confirm they would work in the original panel, and then figured out the rest of the system later. 

I used the original cable runs back to the current transformers in the breaker box.

To test your CTs, disconnect wiring to CTs, put a known load on the circuit and connect a multimeter to the CT back in the breaker panel. Current transformers provide a certain output current at a specified throughput current.  Something like 50A main current produces 50mA in the CT. The ratio should be marked on the current transformers. 

Like others have said tho, I'd suspect meters, not the transformers.

Walter

Edited by wamcneil
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6 hours ago, amphi_sc said:

Hey Jeff (JDstew), how about a link to the displays/transformers you used.  Looks nice.

Of course. I used these parts (links):

I have found other uses for the Trim Tape - small pictures to walls, holding down trim pieces (go figure).

At some point I will buy this: Sense Energy Monitor – Track Electricity Usage in Real Time and Save Money – Meets Rigorous ETL/Intertek Safety Standards

I'm in engineering, so I chart my energy usage and would love to see the detail from Sense. Someday...

Enjoy!

Edited by JDStew
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When I added my PI HW50C  to the coach I found that it did not read the same from shore power to Gen power, Gen power is always lower than shore. 

I measured the output at the gen and then the transfer switch only to find the readings the same. I come out of  the transfer sw into the HW50C  and then out to the coach.

The reading out of the transfer sw is the same as at the gen so I contacted PI.. they had no answer other than it was designed to monitor shore power,  The gen is producing the correct voltage and hertz but something in there pickup coils/circuitry appears to not like the way the onan 10k is producing the power.   

 

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23 hours ago, gburgman2000 said:

When I added my PI HW50C  to the coach I found that it did not read the same from shore power to Gen power, Gen power is always lower than shore. 

I measured the output at the gen and then the transfer switch only to find the readings the same. I come out of  the transfer sw into the HW50C  and then out to the coach.

The reading out of the transfer sw is the same as at the gen so I contacted PI.. they had no answer other than it was designed to monitor shore power,  The gen is producing the correct voltage and hertz but something in there pickup coils/circuitry appears to not like the way the onan 10k is producing the power.   

RV Generators do not produce a true sine wave output.

On the conventional gensets, the distortion is mainly caused by the action of the voltage regulator, while the inverter generators simulate a sine wave, but there is still distortion and high frequency components caused by the switvhing action of the inverter. 

These meters are calibrated to read a pure sine wave accurately, but will be off a bit when the power source is distorted.

 

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The OP indicated a 10K gen, probably Owen. They are 120/240V gens and my understanding is that they are not inverter gens. However the voltage could be different or it's not a exact 60 Hz sine wave causing the different readings. 

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