AC Units shutting down

samgallagher

Advanced Member
Joined
Mar 6, 2011
Messages
48
Checking systems before I leave for a trip tomorrow. Start my Onan Gen 5500, wait for the microwave beep noise to kick in, turn AC Zone 1 on (inside temp 100 degrees, outside 94 degrees), set thermostat at 80 degrees. AC unit starts putting out cold air. Turn Zone 2 on with pretty close temperature conditions and it starts up. Within 20 to 30 seconds both AC units shut down, then Zone 1 will statrt back up. It did this 3 times. So, I ran Zone 2 for about 15 minutes, then turned on Zone 1 and both ran without shutting each other off. I have never had to do this where I could not start 2 AC's on one after another and shutting down. I am thinking there is a load problem with the generator. I hear the generator change frequecies from running a nice solid noise to a sudden decrease, then back to normal with 2 AC's running. Not contantly but enough to get my attention.

I have 74 hrs on the generator, keep up with maintenance, use 87 octane ethanol free with Onan's stabilizer product, and exercise the generator at least 2 hrs a month.

Where I am going has shore power so I will be interested in seeing if I encounter the same cycling problem of shutting down. Not an expert but maybe I have a short somehwere; if not a generator issue. I am having the EC30W Energy Mgt System installed by Cummins when I return and will explain the problem to them. Gen still under warranty. They can put a load on it and check systems.

Any thoughts on this?
 
What was the load management system set to? If it was set to 30 amp then it will shut down one AC at a time and alternate them. I was giving my generator its monthly workout yesterday and watched the load management center to see the current demand. It was steady at 32 amps with Zone 1 and Zone 2 running at the same time. I did not try Zone 3 as I just wanted to load the generator for a 20 minute run.
 
+1- ran mine the other day set on 30a and AC 1 ran fine, AC 2 started, but then the Water Heater kicked on and AC 2 shut off. Selected Gen and all 3 items ran fine.


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Been gone for a week. Umm, I was so occupied with the heat that I did not even think to look at the display next to the thermostat to see what the load was set at. Tomorrow I will run both AC's with gen and ensure the load mgt system is set at 50amps. If both run then I agree the load was set at 30amp. Will let you know. Appreciate the thought.
 
Update. Thought my problem went away but...Was cleaning inside unit today. Ran AC #2 and #3 (garage). AC's putting out cold air. Heard a beep after systems running for about an hr on the generator. System shut down both AC's. Had Error Code E7 on the Dometic Thermostat. E7 error code is, "Loss of 120 VAC power to all power module boards on the system”. Since I was done cleaning and already have an appointment to have Cummins install their ECW30 Energy Management System on next Tue I will let them check the generator. Of course, all this happens within 1 month after 12 month warranty. But, if generator issue I believe it is 2 yr warranty. Could breaker or board issue. If generator checks ok as not the cause of the loss of power then I will head down the street to Camping World for them to check it out.
Will keep this thread up-to-date as it may help someone else.
 
Update: Cummins put ECW30 Energy Mangement System on the generator. All went well with that. Technican spent over 2 hrs trying to figure out why the AC's would shut down running the generator. No matter what combination we ran, AC #1 (bedroom) followed by #2 (Living Room), AC# 3 (Garage) with AC # 2 or 1, the ACs would shut off for about 30 seconds before coming back on...but only one would come on. It was always the AC#2. Other ACs would throw a code E7 on the Dometic Thermostate, "Loss of 120 VAC power to all power module boards on the system". Technican at some point asked where the Transfer Switch was and neith of us could find it. Thinking it is behind the wall in the garage compartment where the converter is located. Technican called his boss. Was told to take the cover of the 2 30, 20 AMP switches on the left side of the generator and ensure all is connected. When the technican grabbed the quick disconnect of all the wires he felt a little bit of play as though it was not fully seated. Ensured it was secure, he ran ohm, amp, voltage checks...as I would turn different combinations of ACs. Systems worked. We are hoping problem solved. I have since run the generator back home with 2 ACs running and no shutdowns. If issue occurs again will update this thread. Thanks to all for input.
 
Last weekend when I was camping in the heat (96deg) and limited to 30 amp service I had to learn to manage the AC units with power consumption. In various configurations of trying to get cooled down every time my "Mini EMS" went over 30 it shut down the garage AC first and then the "E7" code would come up on the thermostat/controller. After lowering the demand it would come back on after power cycling the therm. So in my case I think the "Mini EMS" was cutting the power to the AC unit which would sense power cut and throw the code.

So what I learned in case anyone cares.

Option 1 - I can run two 13.5 AC units at once on 30 amp service but only if fridg. is on propane, water heater off or on propane and pole voltage is at 118v or above.

Option 2 - I can run one 15 AC unit with fridg. & water heater on power and just fans in two 13.5s.

Pole voltage would fall below 118v during the day so had to go with option 2 during the day.

I'm sure glad I added the ceiling fan in the living room and maxxair in the bedroom. They helped a lot.

In the future I will avoid 30 amp only if it's going to be hot. Didn't get a chance to see how the system worked on the generator but I'm sure at some point I'll have to while boon-docking.
 
I can run 3 ac's with the 5500 Onan. I can normally run 2 ac's on 30 IF the water heater is not calling to run. If it does, the EMS shuts down the bedroom ac.


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Interesting... my EMS shuts down water heater then garage...

Do you have three 13.5 BTU units or two 13.5 and one 15 like I do?
 
I think it's 2 15's and a 13.5, but I'll have to check when I get home.


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I believe my EMS indicates I have 44 amps in generator. So depending on what cycles on and off, it could cause an AC to shut off if the compressor is calling to be "on". Not sure what the hierarchy is. In my 380' he transfer switch is behind the angled basement wall. You might also want to routinely check to make sure connections are tight.


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