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A/C or generator issue??

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I posted this over on the RV forum but it's painfully aware that they aren't actually reading the symptoms and just posting whatever comes to mind first.



We just got back from a week of camping and have a new issue.


I have a Coleman Mach3 Plus 13.5K BTU A/C and a pair of Honda EU2000i's.

Over the course of 4 days an issue developed and got worse as the days went by.

The first day I was running my A/C and after about an hour the 20A breaker tripped. I heard the gen's rev up (they were barely above min rpm and went to max rpm) but they didn't go into overload before the 20A breaker inside the camper tripped. I reset the breaker and restarted the A/C. It ran fine for several more hours.

The second day the same thing happened and I reset it again, and realized that is was more than a coincidence at this point. It ran fine the rest of the evening.

The third day I hear the gen's rev up and then the overload tripped on the gen's instead of the breaker popping inside. I was actually inside the trailer when this happened and noticed some other things at the same time. During the 3-5 seconds that the gen's reved to max and the overload tripped I saw the fridge switch back to gas and the converter shutoff, but the A/C fan kept running at a very reduced speed. The A/C compressor didn't seem to be running. The compressor may have been humming but it was hard to tell over the sound of the gens and A/C fan.

So I had a voltage issue!! I wasn't sure if was a gen output issue or a A/C draw issue. At this point I started looking more into the issue. We took a small chest freezer with us and I wondered if the chest freezer was cycling and lowering the generator voltage to a point where the A/C compressor would stop and require locked rotor amperage, so I took the chest freezer out of the equation and it still made the generators go into overload protection mode. It sometimes would run 5 minutes and sometimes as much as 15. I'm not sure what was cycling to cause the issue.

Since day 2 I have only had it trip the generator overload protection and not trip the 20A A/C circuit break.

On day 4 I turned off all the AC loads and ran the A/C. It ran fine for over an hour. As soon as I turned the converter back on it caused the same low voltage issue. Oddly enough by switching the A/C from high to low fan allowed the compressor to get back up to speed and it didn't trip the overload circuit. I cycled the converter with the fan on low and it happened again, so it's not a function of the fan on high.

The A/C has a SUPCO SPP6E hard start cap and starts just fine every time and it sometimes will run for an hour before the issue presents.

Now that we are home I am back into troubleshooting mode. I cannot get the voltage to drop or the breaker to trip on shore power, but that alone doesn't tell me it's a generator issue as shore power isn't having minor voltage fluctuations to aggravate the compressor.

I got the gen's to go into overload protection mode and just before they shutoff they were holding 85V, hence everything dropping off and the fan slowing down. Same thing where it sounds like the compressor isn't running but it could be buzzing like it wants to.

I haven't been able to make the 300w fridge cause the low voltage issue but it seems to me it was the only thing that could have been cycling when the problem occurred. I am able to induce the issue with the converter and 400-500w of draw from it, but it's not the converter. I can have the converter breaker off and use other loads (such as an air compressor) and get the same result.

I have messed with each generator individually and cannot get them to have a low voltage issue. I have only put 1500w of load on them but if I have a issue it should still manifest as it seems that even 300-500w is enough to cause a voltage dip.

Basically when something cycles and there is a minor voltage change (which seems normal for a generator) the compressor motor appears to lock up and draw the 63 LRA. No voltage fluctuations on shore power so no issues.

The compressor motor is running very hot, but I am not sure what normal is. It was 100° out yesterday and I could only touch the compressor for less than a second before it was too hot. This could be a sign of a run capacitor, but it could be normal. I do think the thermal switch tripped once while the compressor was locked as neither the breaker nor the overload were tripped but the compressor stopped and stayed off for 5-8 minutes and then started fine. It wasn't the compressor delay on the thermostat either.

This is my 6th season with this setup and I know something is wrong. It's not an ambient temp/altitude issue, it's an electrical issue. I'm just not sure on what side. I am leaning towards the A/C thou.

Any thoughts on what's causing the issue?

Run Capacitor?

Generator?

I don't think it's the compressor as the breaker doesn't ever trip on shore power.

All 3 capacitors looks good, but I am leaning towards replacing the run capacitor.

Thank you
 
I assume you have the paralleling versions of the generators and are hooking them up as a 120v 30a supply?

I don't suppose one of the generators got switched to an Eco mode?

One downside of the inverter models is they don't handle brief overloads well.
 
Yes they are running in parallel mode. The issue occurs with eco mode on or off, thou it happens easier with it off for obvious reasons.

The overload is the byproduct of my issue, and not the cause... unless one generator is ceasing output but I haven't seen any indications of that.

I do know, from Honda, that overload doesnt trip right at 2000w.
 
Any chance to test on shore power just to test trailer and power usage?

I don't have the ability to measure amp draw. But I have used this setup enough to know that when operating normal it's normal all based on generator sound. The EU2000i's vary rpms/sound quite a bit and I can hear a difference with as little as 300w applied to them.

It has ran for hours on shore power without an issue, even when I try to get it to duplicate the issue. Shore power just has too constant of voltage. If the issue was there on shore power I think I would trip the breaker too.
 
Brand new 2016 RV next door went through this last summer. They couldn't get the AC to start on the generator, but, on shore power was fine. Cheap construction genset was exchanged several times before the dealer figured out the capacitor in the AC unit was bad. They bought the genset from the same dealer making finger pointing impossible...

Why the hard start capacitor? Is this due to a compressor that's failing to buy more time or just start on a lower power generator? The AC compressor may be ready to lock up if the hard start kit is to buy time. The longer the compressor takes to start the longer the surge amps last to a point the generator(s) can't surge that long and breakers trip. So a high friction compressor that's failing could cause this. With the fan noise it's hard to hear the compressor start so disconnect the fan motor to listen to the compressor. (Don't run very long as all you want to know is how it sounds and how long to start up.) Quality of capacitors is just horrible anymore making them the #1 AC repair out here: Home and RV. The blower motor also has a capacitor and it's suspect as well. Can you borrow a capacitor tester from an HVAC friend?

You can borrow another 4KW generator and see if it also has trouble per the example above of several gensets having trouble because they were not the problem. IMO you need a bigger load to test your gen setup, but, it's easier to use a big noisy single generator to eliminate the connected RV first. Two 1500w heaters for a 3000 watt load is a starting point in case one generator is having engine trouble. The max wattage for testing would vary with engine derate but Honda should have a published testing spec for full power.

One final thought: a failed startup attempt heats up the compressor motor making further attempts to start it, even 5 min later, harder.
 
Hard start capacitors are OE on nearly all but the cheaper RV A/Cs as they make a huge difference on generator starts. This one had it from the factory, but my previous unit didn't.

The failed capacitor on your neighbors RV was likely the hard start capacitor.

I have zero issues starting, none. The lockup only happens after it's been running which can be over an hour. As soon as there is a voltage fluctuation the compressor stalls, which is why I'm leaning towards the run capacitor but I'll likely replace the fan capacitor too. All 3 capacitors are cheaper than one hour of diagnostics and are also the most likely components to fail. This one just isn't 100% acting like a failed capacitor but more than anything else. Or so I think.
 
Not sure how much help this might be, but I'll throw it out-- I had a similar situation with 2 Honda 2000's in parallel 2 yrs. ago. Turned out the 5th wheel batteries were bad and were drawing too much to allow the gens. to continue to run the A/C. Easy to check at least.
 
I didn't catch the "stalling the compressor after it been running" with low 85v part. I would test the generator pair near full load or borrow a different 4KW generator before throwing money at things. Looks like the pair has 3200 running watts with 4000 watts surge. You should be able to maintain the AC running (1700w) on just one generator with the second needed to start the compressor. So a gummed up jet in just one of the genset engines would do it. Perhaps something is killing the second genset like failure of the parallel mode and putting the first in a small overload just to run the AC let alone anything else. My propane generator would stall out early due to a bad main propane regulator. Ran great till you asked full load from it. It simply lacked full power as it never stalled out completely - just hung at full throttle when you added enough load and sounded like it was starving for fuel as it was. So start with the 1500w heater and then add a second heater or microwave to get 3000W. Then add 500W (halogen lamp)more to put the generators into the surge power realm. If the hiccup is intermittent on the generator(s) you are in for some real fun tracking it down. Otherwise you need to get an AMP meter on it to see what's really going on when the AC compressor stalls. A clip on unit like this comes to mind: https://www.amazon.com/Auto-ranging-Digital-Clamp-Meter/dp/B001VGND88 After verifying you got full power from the twin generators you can move on to the RV itself.
 
I have a friend with a pair of EU2000i's that he is going to bring to work tomorrow so I can rule the gens out.

I'm still leaning towards the run cap; however, it's cheaper to rule out my gens first.
 
FWIW,
I have had a similar issue, but i don't get any breakers popped.
My trailer has a built in Generator, and when i start the AC it runs fine for the first cool down. Then when the pump cycles off, then back on it puts a heck of a load on the generator, it bogs down and almost stalls. and does not do this hooked to shore power unless using a 50' extension cord.
mine only does it when it's cycling the compressor back on. might look into it.
 
FWIW,
I have had a similar issue, but i don't get any breakers popped.
My trailer has a built in Generator, and when i start the AC it runs fine for the first cool down. Then when the pump cycles off, then back on it puts a heck of a load on the generator, it bogs down and almost stalls. and does not do this hooked to shore power unless using a 50' extension cord.
mine only does it when it's cycling the compressor back on. might look into it.

That's a bit different than my issue. It sounds to me like your hard start capacitor is either MIA or bad.
 
$299!! That's rather expensive, but intriguing.

It wouldn't do anything for my current issue but it gets some good reviews.
 
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Yeah, but it seems they are running on a single 2000. More will be told in forum discussions.

I saw that. The startup has always been the hard part on a singe 2000. The running watts are 1400-1700 so they should be able to sustain use after startup.
 
Not that I know much about A/C units but have you cleaned the condenser coils lately? If the coils are dirty then the system will slowly overheat and trip the thermal overload or draw too much power.
 
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