A/C amps

Trwolff · 08-24-2015, 08:59 PM

Ok, I'm an admitted newbie so I'm guessing one of you veterans will have an answer to this. I've got a 2005 Winnebago Voyage 38J with two A/C - heat pumps for HVAC. When on shore power and both units running, I pull 26 amps. However, when on generator and both units running, I'm only pulling 11 amps. My first thought was that the rear unit had tripped out and I was only running the front unit. Checked both the house and generator breakers and nothing had tripped. So I shut down both units and turned on just the rear unit. It was pulling just 3 amps, so I assumed it was just the fan blowing. However, in running it for a bit, it was blowing cold, so something was functioning. Turning the front unit back on, total amps jumped to 11, which is still way too low in my mind, but I'm getting cold air out of both units. Do I have a magical Onan or an A/C problem?

96 Wideglide · 08-24-2015, 09:06 PM

11A is low for just one AC. The 26A you saw on shore power with two running is possible. I'm guessing you have 13,500btu units?

Ray,IN · 08-24-2015, 09:10 PM

I'll venture to say the rear unit compressor is not working, the circulating fan is drawing 3A, and circulating cool air. If they are ducted into the same plenum it's pulling cool air from the plenum. My roof mounted air conditioners drew around 9.5A each while compressor was running, surged to around 15A at start-up. Turn off both units, wait 2 minutes then start rear unit, if it does not show an amperage surge over 10 at start-up, the compressor did not run.
It could be as simple as replacing the start and/or run capacitors, which cost <$20.

nothermark · 08-24-2015, 09:11 PM

Off hand I'd say one of the compressors was not working at the moment. I'd try tracking over 15 minutes or maybe less to see if the line jumped up then dropped off again. There is some thermal lag.

grtharris · 08-24-2015, 09:30 PM

Trwolff, do you have a 30 or 50 amp electrical system? And also do you have a EMS system?
Since it is late I will assume you have a 30 amp system with EMS. The EMS measures current on the neutral wire is the breaker box and that is what you see in the display and what the EMS uses to shed loads. When on shore power both the AC units are fed through the breaker panel. The front AC is fed directly from the breaker panel and the rear AC is fed from the breaker panel back through the transfer switch then to the rear AC.
When you run the generator one leg of the generator feeds the breaker panel and thus feeds the front AC. The other leg feeds the rear AC directly from the transfer switch and thus the current for that AC unit does not go through the neutral in the breaker box and will not show up in the EMS current display.
All that said you do not have a magical Onan or a problem!!

Johndale · 08-25-2015, 06:48 AM

If you look at your electric panel you will see a switch and it will say rear ac. On it it will say gen or shore yours is set to gen mode and will not read on display. The 20 amp breaker supplies the power to only the rear ac unit. It took me awhile on this. So if you are on gen and switch is set to gen and have the rear on you can have more things running on the main unit. If your unit is like mine 5500 kW read the tag and it will tell you 45 amps. I hope this helps you.

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grtharris · 08-25-2015, 07:32 AM

Johndale, OP's coach is not wired like yours, his coach has a auto transfer switch.

Trwolff · 08-25-2015, 01:37 PM

Thanks, guys! You are 100% correct! I must admit, though, I was really hoping I had a magical Onan.....

wa8yxm · 08-25-2015, 04:12 PM

How are you measuring the amps? That will make a difference.

Johndale · 08-25-2015, 05:24 PM

Quote:

Originally Posted by grtharris

Johndale, OP's coach is not wired like yours, his coach has a auto transfer switch.

And you think mine doesn't. It has ATS. So be carful on your corrections.

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shiggs68 · 08-25-2015, 07:30 PM

Quote:

Originally Posted by Trwolff

Ok, I'm an admitted newbie so I'm guessing one of you veterans will have an answer to this. I've got a 2005 Winnebago Voyage 38J with two A/C - heat pumps for HVAC. When on shore power and both units running, I pull 26 amps. However, when on generator and both units running, I'm only pulling 11 amps. My first thought was that the rear unit had tripped out and I was only running the front unit. Checked both the house and generator breakers and nothing had tripped. So I shut down both units and turned on just the rear unit. It was pulling just 3 amps, so I assumed it was just the fan blowing. However, in running it for a bit, it was blowing cold, so something was functioning. Turning the front unit back on, total amps jumped to 11, which is still way too low in my mind, but I'm getting cold air out of both units. Do I have a magical Onan or an A/C problem?

The only real way to determine if the compressors are running is to measure the voltage being applied to the actual compressor and measuring the current draw at the compressor. This requires taking the rooftop cover off and finding the wires.

It is not uncommon for only one to run when on generator. Often the generator is not sized to run both. With that said and was said above, they may be ducted together so one compressor cools everything with both fans running while on generator.

The other issue is depending on where your meter is detecting the current draw, it may not be accurate when on generator.

Every coach is wired differently. So without knowing the actual wiring, everything else is just a guess based on some experiences.

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grtharris · 08-25-2015, 07:45 PM

shiggs68, OP's AC units are running as designed. Read post #5.

grtharris · 08-25-2015, 07:49 PM

Johndale, sorry about that the drawings for your coach shows a plug box for the power cord to the generator.