SOLVED: Both AC's run on 50 amp shore but not generator?

[rocrider50]

Both of my AC units will run on the 50 amp shore power with everything else running (Electrical fridge, hot water, etc.). I camped this weekend (94 in September in Michigan go figure) on the generator only. I needed both AC units to keep up. I turned off the other electrical systems and could not get the AC units to run at the same time. When the second unit is engaged I hear a lot of clicking/beeping and then the generator pops one of the two 30 amp breakers on the generator. Always the same breaker. It never pops the circuit breakers in the main panel.

Thoughts?

 

[LBR]

Re: Both AC's run on 50 amp shore but not generator?

Unplug shore power and check all lines and connections between generator and transfer switch.

 

[danemayer]

Re: Both AC's run on 50 amp shore but not generator?

You may just have a weak breaker on the generator.

 

[crussian]

Re: Both AC's run on 50 amp shore but not generator?

Or both A/C's are wired to a single 30 amp. It happens.

C&J

 

[avvidclif]

Re: Both AC's run on 50 amp shore but not generator?

My money is both AC's are on the same 30a breaker on the generator. It won't trip the house breakers as each AC is on it's own 20a and they don't exceed that but when both are on 1 30a on the genny, whoops. Plus no telling what else is on that same circuit.

 

[carl.swoyer]

Re: Both AC's run on 50 amp shore but not generator?

Both of my AC units will run on the 50 amp shore power with everything else running (Electrical fridge, hot water, etc.). I camped this weekend (94 in September in Michigan go figure) on the generator only. I needed both AC units to keep up. I turned off the other electrical systems and could not get the AC units to run at the same time. When the second unit is engaged I hear a lot of clicking/beeping and then the generator pops one of the two 30 amp breakers on the generator. Always the same breaker. It never pops the circuit breakers in the main panel.

Thoughts?

Are the ac thermostats set 2 ° apart? If they cycle on at the same time your available power/ amps may be insufficient causing the genset to pop a breaker.

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[NWILSON]

Re: Both AC's run on 50 amp shore but not generator?

Doesn't the generator provide power on 2 different legs much the same as a 50a shore connection? 5500 watt generator provides a TOTAL of 45 amps though or about 23 amps per leg.
I had a similar issue trying to use the fireplace, heat-strip and coffee pot at the same time. I wasn't exceeding total draw limit but certainly would be enough to trip the 30a breaker on the generator if all those devices were pulling off a single leg.
This is what I convinced myself caused the problem. Please correct me if I'm wrong

 

[rocrider50]

Re: Both AC's run on 50 amp shore but not generator?

Or both A/C's are wired to a single 30 amp. It happens.

C&J

Thanks Crussian, I popped the cover on the breaker box and moved one of the AC's to a different leg of the generator. Both AC breakers, the refrigerator and the electric HW were all on the same leg. It's the simple fixes in life that give us pleasure.

 

[crussian]

Re: Both AC's run on 50 amp shore but not generator?

Thanks Crussian, I popped the cover on the breaker box and moved one of the AC's to a different leg of the generator. Both AC breakers, the refrigerator and the electric HW were all on the same leg. It's the simple fixes in life that give us pleasure.

Glad I could assist.

C&J

 

[lasvegas99fan]

Re: Both AC's run on 50 amp shore but not generator?

Thanks Crussian, I popped the cover on the breaker box and moved one of the AC's to a different leg of the generator. Both AC breakers, the refrigerator and the electric HW were all on the same leg. It's the simple fixes in life that give us pleasure.

How could you tell and how did you move an A/C to a different leg?

 

[Oregon_Camper]

Re: Both AC's run on 50 amp shore but not generator?

How could you tell and how did you move an A/C to a different leg?

X2....picture please.

 

[lasvegas99fan]

Re: Both AC's run on 50 amp shore but not generator?

X2....picture please.

Here’s my power panel and wiring diagram. Looks like both my a/c are on the same leg

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[PondSkum]

Re: Both AC's run on 50 amp shore but not generator?

Not sure if this is your issue or not, but I will share my experience. My 5500 Onan will run 2 A/C's just fine, as long as it isn't too hot outside. What I've figured out, is that the sun beating down on the unit on the roof has heated up the motor/compressor. That extra heat creates a higher amperage draw, which is apparently too much for either the genset or the Transfer switch to handle. If it's really hot outside (middle of the day) and I try to start the second A/C, the transfer switch does a lot of popping and the A/C's turn off. A guy I work with checked amperage on his RV A/C's and during the heat of the day, the draw was way higher than in the evening, or when the unit is in good shade. If you have not already tried, try kicking them both on in the evening after it has cooled down, or early in the morning before the sun starts blasting the units on the roof. If they still do not run, then you may have a weak breaker or transfer switch, or both units on 1 circuit.

 

[danemayer]

Re: Both AC's run on 50 amp shore but not generator?

That extra heat creates a higher amperage draw, which is apparently too much for either the genset or the Transfer switch to handle. If it's really hot outside (middle of the day) and I try to start the second A/C, the transfer switch does a lot of popping and the A/C's turn off.

PondSkum,

The automatic transfer switch should not be popping or contactors dropping regardless of how hot the A/C unit gets.

The contactor operation is a function of the voltage (not current) on L1. It's possible that when it gets hot, the power grid in the park or local area drops low enough to cause the contactors to drop. If not that, you have a problem in or with the transfer switch.

 

[PondSkum]

Re: Both AC's run on 50 amp shore but not generator?

PondSkum,

The automatic transfer switch should not be popping or contactors dropping regardless of how hot the A/C unit gets.

The contactor operation is a function of the voltage (not current) on L1. It's possible that when it gets hot, the power grid in the park or local area drops low enough to cause the contactors to drop. If not that, you have a problem in or with the transfer switch.

It does not do it on shore power, only on generator power. High amperage draw on startup stalls the generator, which drops the voltage output and causes the transfer switch to drop until the generator regains it's RPM. Now, I guess this could be a problem with my generator governor or something, but I know everything works fine unless it's super hot outside and the trailer is out in direct sunlight. Again, only on generator power, haven't had any drops or transfer switch issues while connected to 50A shore power.

 

[wdk450]

I'm wondering if high solar heating during the middle of a 100+ degree day was what caused my rooftop air conditioner to blow the 20 amp breaker several times this summer. Monitoring with the EMS meter showed that leg was dangerously near 20 amps at times.

My idea is to paint the air conditioner cover white or chrome to reflect solar heat. Any expert opinions on whether this would be worth the effort? My dad used a silver colored roof paint on our flat roof stucco house with raised sides (hiding views of the roof) in hot Southern California. He swore that it kept the roof cooler, and extended the life of the tarpaper. Many of the white colored RV roof treatments claim to keep the rig cooler.

 

[danemayer]

Re: Both AC's run on 50 amp shore but not generator?

It does not do it on shore power, only on generator power. High amperage draw on startup stalls the generator, which drops the voltage output and causes the transfer switch to drop until the generator regains it's RPM. Now, I guess this could be a problem with my generator governor or something, but I know everything works fine unless it's super hot outside and the trailer is out in direct sunlight. Again, only on generator power, haven't had any drops or transfer switch issues while connected to 50A shore power.

So lets say you have two A/C units and some other stuff pulling power from the generator. If you're pulling too many amps, one or both circuit breakers on the generator should trip. I don't think the generator is supposed to lug or stall, allowing voltage to drop.

So that suggests either your generator's circuit breakers aren't tripping when they're supposed to, or the generator is not able to supply full power for some reason.

Even if you had a problem with the A/C units pulling to much power, I don't think it's normal to be stalling the generator. So trying to fix it at the A/C units probably won't fix the root cause.

 

[LBR]

In all fairness during these tests, you should not be using the 120V hot water heater....xshut that breaker off and heat with gas....it draws a lot of amps and is a silent draw on the systems, just like the convertor is at times.