A/C Not Working With Generator

[bobschultz]

A/C Is working with shore power 50 amp but has stopped working with generator power on this trip. The generator seems to be running fine.

We have a 2009 Winnebago Journey DP with inverter.  

Any ideas on what to look for and try?

 Thanks for any help. Bob

[wolfe10]

Bob,

Since it works on shore power, you can rule out from the ATS onward.

First thing is to check the breakers on the generator itself-- turn both off and back on.

Do all the other appliances work from the generator?

[elkhartjim]

Hi Brett, when my ATS failed the a/c worked on shore power but not on the genset.

[wolfe10]

Jim,

Absolutely correct.  Better wording would be "from the far side of the ATS onward".

The ATS is where shore power and generator input "meet" and only one goes on to the coach 120 VAC breaker box.

[kaypsmith]

Congratulations Brett, Carl will now present the GRAND DRAGON award, for your five thousandth post<LOL.  The ATS switch is most vulnerable on the genset side due to the time delay circuitry. Sometimes fails to bring on 240 volts, "or both 120 circuits". But checking the genset circuit breakers can also be a must.

[dickandlois]

 Hopefully some helpful notes on Generators when using AGS, switching from Shore Power to Generator or from Generator to shore power. Per Onan Handbook.

Not All RV.s are setup the same regarding time delay relays and ATS wiring, so one needs some basic understanding of the coach 120 / 240 (30 or 50 amp)voltage electrical systems.

Operating Motor Driven Appliances
     When using an appliance with a motor, turn it on and let it reach normal running speed before starting other appliances. Air conditioners, like all electric motors, can draw up to three times more power during the first few seconds of start up than during normal operation. While this is common for all electric motors, it is especially true for air conditioners if the compressor tries to start against built-up high pressure in its refrigeration system.

Air Conditioner “Short-Cycling”
     When an air conditioner runs, the compressor builds refrigerant pressure. When the compressor is then shut off, either manually or by satisfying thermostat demand, it must stay off for some period of time, usually 3-4 minutes, to allow pressure in the system to equalize before safely restarted. Trying to restart the air conditioner compressor before pressure equalizes is known as “short-cycling”.
A “short-cycled” air conditioner could 1) trip the air conditioner circuit breaker; 2) shut down the generator due to overload; or 3) trip the air conditioner due to thermal overload. The air conditioner thermal overload will reset itself after the compressor cools. Typically, you cannot manually reset.
Some, but not all, RV air conditioner thermostats have built-in time delays to prevent short-cycling. Short-cycling occurs in some RVs when the thermostat is mounted so that cold air blows directly on it. If this happens, the thermostat shuts the compressor off before the cabin has cooled, but quickly warms back up and signals the compressor to restart before refrigerant pressure equalizes. In this case, direct the flow of air from the air conditioner away from the thermostat or relocate the thermostat. You can prevent air conditioner short-cycling by always ensuring the air conditioner rests for 3-4 minutes after the compressor shuts off before trying to restart it.

Effects Of High Altitude And Extreme Temperatures
     If you travel at high altitudes or in extreme temperatures, your generator can lose power. In such lower-density air conditions, you can’t operate as many electrical devices as you could under normal operating conditions.
Power decreases 3.5% for each 1,000 feet above an altitude of 500 feet. For example, to operate at 4,500 feet (4,000 feet above rated generator altitude) multiply 3.5% x 4 (4,000 ft) = 14% power loss. Then multiply .14 x your
generator’s power rating: 4,000 watts x .14 = a loss of 560 watts at that altitude.
Power decreases in extreme temperatures by 1% for each 10°F (5.5°C)
above 77°F (25°C).

Rich.