AC tripping generator

Mdk0420 wrote:


It is a ducted system. Do these AC units just happen to draw a ton of current when starting?

It's always been hit or miss since I got the generator. I would say it starts about 90% of the time unless I purposely short cycle it then I can pretty consistently trip it.

I did test both the motor starting Capacity and the main capacitor and they are within spec. I tested the coils as well to make sure there aren't any resistances in the coils and all seems good. The unit does work most or the time after all, and it is cold. It's just unreliable.

The older, and even the newer, RV AC units from Dometic and Coleman Mach do have a high spike of inrush current when the compressor starts. As I showed, 37 amps inrush on a Brisk Air 13.5 K BTU roof unit is common from what I have found. Again, assuming you are in the 120 volt range. My Fluke amp probe has a peak feature, not sure what meter you have to grab that peak spike, your reported numbers were lower. When mine is in constant scan mode I can't see that high spike the display is flashing so quickly.

Since you have the ducted system, you can try this to see if it helps your genny handle the spike better. On the AC T stat, select the fan to be "on" in place of "auto". This will turn the fan on all the time. Then turn the T stat to cool and set your temp. The compressor will cycle on and off with the fan running all the time. The intent of this test/trick is to lower the inrush combo of both the fan and the compressor at the same time.

If that helps make your genny run OK, then well, it helps tell a soft start can help compensate for your gennys inrush spike problem. It may be, your brand of genny is more sensitive to a high spike than others. The soft start on mine took a high 37 amps down to 18 amps. It is just that the soft start does cost a good bit, but still less than a new AC unit nowadays.

OR, if the fan is on all the time when running the AC helps solve it, you can run it that way when on genny power. The only issue is the fan noise all the time. We like the AC to shut down totally when the T stat setpoint is satisfied to not hear the fan noise. Some folks like the white noise of the fan, and some can't stand it. Sort of a personal preference.

There is a cleaning procedure of the inside and outside coil that can help lower the fan power which "might" help you. That said, it will only lower the fan an amp or two, but it will lower a small bit of the combo inrush current. If this interests you, let me know I can link you to it, I have a post on the Sunline Forum showing how to do this. If yours has not been cleaned, well ever, it is good to do the cleaning anyway.

The new AC unit motors are a little more efficient. When the time comes to get a new AC unit, the Coleman Mach brand has more offerings for lower power use. The new Dometic AC's do not offer as many choices. Both brands will require the air box and the T stat control to be changed.

Hope this helps,

John