Low Voltage on Refrigerator Circuit

[Norman Martin]

I have 109 volts on my refrigerator circuit when plugged in to 50-amp plug. When unplugged I have 120 volts on that circuit. I'm told there is a pass thru when plugged in, I haven't heard of this before. Any ideas where to look?

Norman Martin
2000 CC XL
#60408

[BGLogistics]

Have you checked voltage at the plug? May just be what is available. Pass-thru on mine is done internally within the inverters themselves once shore or generator is avail.

[Fratto]

Good Morning Norman

I agree with Billy, have you measured the voltage at the 50 amp connection? What does the voltage meter in the coach say you are getting from the 50 amp connection?

Are other large loads (air conditioning, water heater, etc.) also running when connected to the 50 amp and you are measuring the refrigerator voltage?

It may be that your 50 amp source has a low voltage and additional loads in the coach further reduce this voltage. When you unplug the coach, the larger loads drop off and the inverter regulates the voltage properly to 120 volts.

What brought this question up? What made you check the voltage at the refrigerator outlet?

Have you measured the voltage at another outlet that is also on the inverter? If so, what is that reading (both with the coach plugged in and not plugged in). This would help in isolating the problem if it is not the 50 amp source as described above.

[Norman Martin]

Voltage at the 50 amp plug was 120 and 240. The fridge was 50 degrees. checked voltage at fridge plug inside the coach was 109 volts. When plugged in to 50 amps coach meters read 123 volts on both legs. Plugged extension cord to a 120 volt plug in coach fridge returned to 36 degrees.
When unplugged going thru inverters fridge plug was 119 volts. When plugged in to 50 amp plug fridge plug was 109 volts. Fridge plug inside coach does not go thru the electric panel, it has a breaker in the compartment by the switch box. I have had two Prevost coaches, this is a new one for me.

Thanks,
Norman Martin
2000 CC XL
#60408

[Fratto]

That is strange. Do you by chance have the CC wiring diagrams?

On our previous 1998, each inverter served a small load center with breakers for the individual loads. Like yours, the refrigerator was on its own breaker.

I am wondering if the inverter serving the refrigerator has an issue when it is in in bypass connected to shore power. I would remove the cover of the load center with the refrigerator breaker and measure the voltage there. If the entire load center is at 109 volts, then I would be looking at an inverter issue. For fun, I would then remove the cover of the load center for the other inverter and measure it. If it is an inverter problem, it is possible that the outlet you used with your extension cord was powered by the other inverter so you had normal voltage.

[Norman Martin]

I checked both invertors when unplugged from 50 amp, had 120 volts on both of them. I didn't check them when plugged in. Will check a few more things and post results. I will check with the Magnum people too. Inverters are 3 years old.

Thanks,
Norman Martin
2000 CC XL
#60408

[Ck2hans]

Not a direct comparison but...
I have experienced low voltage on one leg and not the other and found the common power wire (white color in household wiring) was not connected tight enough.
Perhaps the outlet that your fridge is plugged into has loose or bad connections in it.
Chuck

[Norman Martin]

Found the problem. I had a bad 30 amp breaker that was sending 109 Volts to one of the inverters. I traced power from the 50 amp plug thru the cable to the transfer box. A real electrician would have found it sooner but I didn't know that the input going to the inverter got its power from the breaker panel in the coach.
Thanks everyone for the help. Hope this helps someone down the road.

Norman Martin
2000 CC XL
60408

[Fratto]

That makes sense! Nice job tracking it down.

[Norman Martin]

Thanks Mark.

Norman