AC Portable Generator Electrical Voltage Drop/Fluctuating

[Dingy941]

Purchased this used 2006 Ford E450 Toy Hauler a few months ago, had issues running roof AC I’d say the first time above 75 degrees, tried to have the roof AC serviced(has a service port already so they checked and added refrigerant) seemed to fix it for a few days maybe but didn’t. I gave up on the roof AC and bought a window AC 10,000 btu we “temporary” hung it out the side window and it worked great, iceicles in here! One day I broke the window AC(don’t ask), got a new one at Walmart the new one didn’t work anything like the first one, same installation practice but it didn’t get that cold and would trip/reset itself every 30-90 minutes or so, took it back and got a replacement which is now the AC we currently have, it works better than the second but not as good as the first one but it’s doing the same thing reset/trip every 30-90 minutes or less if I turn on other electrical devices like the battery charger or microwave. I should also mention that the mricrowave does not operate very well(not sure if it’s the microwave.?)

Running a Brute 3500 running 5250 starting watt portable generator that I installed in the original generator bay using a 12V fuel pump to feed from the RV fuel tank. The generator jumps up and handles the startup of either the roof AC or window AC now problem and the generator never boggs down or trips, the window AC simply beeps and resets itself then blows warm air for a few until the compressor kicks back in then it blows cold again.

During this frustration I have tested many things and tried to discover whether this is a generator issues or an electrical issue 😕

Here’s some of the other interesting things I’ve found;

At first testing I found that my floating neutral generator was putting out about 90V on HOT and 30V on NEUTRAL, I placed a jumper to ground the nuetral and now have a normal 122V on HOT

All 12V lights are not affected

Roof AC will startup and run off portable generator but acts similar to window AC and slows then boggs down until you reset it

Microwave light starts to flicker and go dim when the window AC starts to slow then bogg down

The window AC runs fine plugged into a normal 120v outlet shore power

Occasionally when I try to run the window AC along with a few fans the AC and the fans will all slow down to a crawl, I have tested and got about 62V on HOT and 62V on NUETRAL, once the window AC resets the voltage slowly goes back up to 122V~ and remains there unless the AC begins to slow down again

Window AC runs longer if plugged into generator directly and all RV breakers are turned OFF


From what I’ve researched I should have enough generator power to run two maybe even three 10000 btu ACs at once let alone just one and some fans, do I not have a big enough generator? Is it a grounding issue? It ran the first Window AC no problem while charging batteries and running fridge... nothing changed from window AC number 1 to 2 to 3 other than the window ACs themselves, once this problem persisted I started messing with everything trying to figure it out. Any and all help greatly appreciated!

[Dingy941]

So a little further testing last night...unplugged 30A RV cord from generator and ran the window AC along with 3 9” fans and 1 box fan off an extension cord(I know, I know). The window AC runs quite a while like this maybe an hour or two before eventually tripping/resetting(one loud beep, like you get when you first plug it in). It does not seem to run as long or I plug it into the RV power with every breaker off but one. I’m starting to believe this generator isn’t handling the load but how it’s rated at 3500 running 5250 starting. This window AC should be like 800-1200 watts...

[Chris_Bryant]

So the generator will work fine until you put a heavier load on it.
I still say cheap genset failing.

[DrewE]

63V on the hot and 63V on the neutral could very well mean 126V between them, or no significant voltage droop. You need to measure the hot to neutral voltage to tell if it's drooping or not.

Can you plug the window air conditioner into an outlet protected by a GFCI? Does the GFCI trip? If so, it may have a significant (and dangerous) ground fault, an internal short to ground somewhere.

[Dingy941]

A little more info... we have been for many nights now and are currently running all of the following on the portable generator with no issues or failures of any kind; rooftop (AC) fan only, window (AC) fan only, 1 box fan, total of 4 10” fans, fridge, battery charger(lights), and able to charge any/all of our devices(iPad, iPhone, and galaxy s9)

During all this if I switch the window AC to Cool it kicks in the compressor and runs and blows cold air for about 5 to 10 seconds then gradually everything starts to slow(bogg) down so I immediately switch the window AC back to Fan mode within another 5 to 10 seconds everything gears back up and runs normally. I should note that exactly the same thing happens when trying to run the Roof AC, and like this current issue, it originally ran for us off THIS generator not more than 6 months ago...

Also, I just turned off every breaker but the one for the window AC and still have two 10” fans and one box fan going and when I turned the window AC to Cool it ran cold for about 3 to 5 minutes then proceeded to slow(bogg) down so I ran and switched it to fan only.

I know from my previous testing that when this bogg down of equipment happens I see about 63V on both the Hot and Nuetral wires in the main RV panel. The fact that the ACs WILL run for a brief time(longer with no other loads) and the fact that both types of AC worked previously with exactly the same setup, it’s seeming to me that this is some sort of electrical issue where current is finding the wrong path home and causing more draw on the generator and less voltage....?? Further help greatly appreciated! Thank you!!!

[Dingy941]

Chris Bryant wrote:
I think it’s a cheap generator not up to the task- maybe the capacitor they use for voltage regulation is getting hot and failing.

We were able to run the first window AC along with the fridge and battery charger no problem originally. This don’t start until we bought a second window AC(the same brand and model) and continued happening into our third window AC, also I don’t hear any struggle or anything from the generator it seems to handle the load fine even when I get 63V~ on Hot and Neutral the generator seems fine and never kicks the load or the breaker once the window AC is reset the voltage climbs and everything works fine.

[MEXICOWANDERER]

Test it independent of the RV. it simplifies things.

Beg borrow or nag 3 1500 watt electric heaters. Disconnect gen from RV

If those 3 heaters aggregated do not affect the generator you have a valuable clue. Think outside the cube.

[Chris_Bryant]

I think it’s a cheap generator not up to the task- maybe the capacitor they use for voltage regulation is getting hot and failing.

[DrewE]

A neutral to ground short would not cause the breaker to trip; indeed, bonding neutral to ground is shorting them together, by definition. They're expected to be at the same potential (if bonded). The short would cause an upstream GFCI to trip.

If your ground to neutral bond is broken or lacking, your generator output is floating and most any arbitrary voltage between hot or neutral and ground is not unexpected. The voltage between hot and neutral is what matters for appliances. In that case it makes little sense to reference your measurements to ground since the voltage being generated is not referenced to ground (or anything else). Similarly, a broken or bad ground connection between the generator and the RV would cause the output to float...but that in itself wouldn't cause the air conditioner and microwave to have trouble.

[Dingy941]

DrewE wrote:
I think possibly you have a loose or otherwise connection somewhere in your neutral line between the generator and the air conditioner, and probably between the generator and RV electric panel's neutral bus. Check that everything is good and tight. Do this sooner rather than later as a poor connection under load is a hot connection (hot as in high temperature).

I have not found any loose connections or broken wires or anything yet, I figure a short between neutral and ground would cause a break to trip either on my generator or the RV main panel, which is not the case. I will double check things though and look for any shorts between Hot Nuetral and Ground.

[Dingy941]

MrWizard wrote:
sounds like the generator is over heating

used the oem generator compartment

did you add any fans for cooling to the compartment

are you running it with the compartment door open for extra air/cooling circulation

in the previous RV-ClassA DP, in order to use a portable generator
i installed a sliding tray/drawer

and mounted the genny on the tray

slide out to use, slide back in to store

made it easy to service, and allowed maximum fresh air cooling

Nice try, lol, I did install two fans to help keep it cool and extended the exhaust outside the RV. I’m about 99.999% sure this isn’t a problem with the generator running/overheating/etc.

[DrewE]

I think possibly you have a loose or otherwise connection somewhere in your neutral line between the generator and the air conditioner, and probably between the generator and RV electric panel's neutral bus. Check that everything is good and tight. Do this sooner rather than later as a poor connection under load is a hot connection (hot as in high temperature).

[MrWizard]

sounds like the generator is over heating

used the oem generator compartment

did you add any fans for cooling to the compartment

are you running it with the compartment door open for extra air/cooling circulation

in the previous RV-ClassA DP, in order to use a portable generator
i installed a sliding tray/drawer

and mounted the genny on the tray

slide out to use, slide back in to store

made it easy to service, and allowed maximum fresh air cooling