How much generator/inverter to run AC

[AZMont]

I am thinking of upgrading to an Onan P4500I inverter. Have any of you ever used a 4500W inverter to start an AC unit? I'm trying to figure out if I will also need to add a soft start kit. I am mostly interested in running the main living area unit. But would also appreciate information on running both AC units.

[Daryles]

I installed a SoftStartRV on my front air conditioner and ran it with my 2000w inverter successfully.
I believe a 4500w inverter should run both.
The issue is batteries. One AC unit pulls 89A, DC.

[AZMont]

I should have been more clear. I am planning on using an Onan P4500I gas powered inverter/generator and not a battery powered inverter. Apologies for any confusion and thanks for the quick reply.

[mlh]

That generator has 3700 running watts. My 15000 BTU AC pulls 1350 watts. Yours probably pulls about the same so yes it should run both. To be on the safe side I would install install soft starts. If you camp at any elevation you loose 3.5% for every 1000 feet. At 5000 feet you are down to just over 3000 watts.
Lynwood

One other thing if you look around you can find that generator for a couple hundred dollars less. I won’t be a Onan but the same unit made in the same factory.

[DutchmenSport]

Originally Posted by AZMont

...Have any of you ever used a 4500W inverter to start an AC unit? ...

Yes. I have 2 Onan P4500i inverter generators I run in parallel to run both AC's when needed.

Either one of mine will run one air conditioner with no effort. Neither of my Air Conditioners have been modified. They are original factory installed. One AC will start and run either the 13,500 BTU or the 15,000 BTU AC/Heat pump flawlessly. But one by itself will not run both. Then (single) generator will over detect an overload and will shut off out-going power. But the generator keeps running. It does now power down. It has a breaker relay (button) that trips. (Same as as 30 amp shore power).

The output of one generator by itself is more than 30 amps, more than adequate to run anything in your camper, EXACTLY the same as being plugged into 30 amp shore power.

Without modifications, the Progressive EMS will not pass power to the camper if running of the generator (single or in parallel). The EMS recognizes no ground. But, the generators have their own high and low power and surge protection, so when running power from the generator, there really is no need for the EMS. If your camper has a hard wired EMS, you'll either need to by-pass it, or do some extra wiring on the P4500i to fake out a ground. But I do not know how to do that on the P4500i. So I never bothered with it, considering my EMS is a portable.

If you run 2 of these generators in parallel, you can run absolutely everything in your camper, exactly the same as being plugged into 50 amp shore power. I have run both AC, the electric fire place, the electric water heater, 2 televisions, and an electric griddle all at the same time using both generators in parallel. And the generators were not maxed out yet.

The generators are variable speed when set on economy, and run steady when economy is set off. They ARE VERY quiet. I checked them with a decibel meter, and they have a decibel rating the same as a human conversation, even running both side-by-side. They have an 18 hour run time on economy on 3.4 gallons of gas.

They weigh in at 100 pounds dry weight. Add the oil and the gas and they are heavy. I use a ramp to wheel them up into the bed of the truck.

I made a modification and quit carrying them in the bed of the pick-up truck. I now carry them inside the camper itself. They absolutely do not leak any gas smells if the gas shut off is flipped and the carburetor was allowed to run completely dry and the generator shut itself off because the engine starved itself of fuel. (by the way, this is the absolute best way to turn the generator off so fuel will not gum up the carburetor. We had both generators stored inside the house, actually in the bathroom, most of last winter. On the trip we are currently on, they are inside the camper itself, in the space where the kitchen table and chairs sit. We've removed all that for space.

We absolutely love our's. They work great in all situations. We've used them camping and at home when we've had power outages. I have a total of 3 generators, 2 P4500i's and a 20 year old King Craft that is louder than a lawn mower with no muffler. But it works great too after all these years.

The question has been asked, what do you do with the generators when it rains. Answer, they run under the overhang of the fifth wheel, where the king pin in located. Never had a problem with them running there. Never had fumes inside the camper. I stretch the electric wire under the trailer as my plug in is in the very rear.

If you get the Cummings Onan P4500i, you will NOT be disappointed. But, I promise you, if you get two of them and get the parallel wiring kit, you love them even more!

[twindman]

If you had to use a ramp to get them into the truck, how do you get them in the 5er? Same ramp?

[AZMont]

Thanks for the detailed response! .

[DutchmenSport]

Originally Posted by twindman

If you had to use a ramp to get them into the truck, how do you get them in the 5er? Same ramp?

Yes. Actually, those ramps, side by side, fit the steps perfect. When camped on uneven campsites and the steps are up very high and that bottom step is like .... 2 feet up, I use the same ramps on the bottom step and they work great.

[BobStack]

I use a WEN 3800 watt with soft starts and run both 15000 AC’s and lights etc with no problem. Need to turn one off to use the microwave or the GF’s hair dryer.

[Mark7]

I do have one of the those gensets and I have tried to run both of my 13.5's on my rig and it will not start the second one. I DO NOT have soft start kits installed. I am told that if I add those kits I would be able to run both A/C's. Not sure if I will get that done anytime soon as I have only had to run both A/C's once in the last few years and I hd plenty of 50 Amp shore power!

BTW... it will run one A/C and anything else in the rig just fine, within reason. Like someone else pointed out, just like 30 Amp shore power.

[BobStack]

The soft starts are the way to go, it took approx 2 hours per AC to Install and once the learning process was complete I was able to run both AC’s and was at 80% with lights, residential fridge and TV All running.

[Old_Salty]

I also have a 4500 but the original Westinghouse (before Onan/Cummins). They have the same outputs - just a different color.

Dutchman Sport has a very good post on this.

When we had our 2012 3750FL, it would run one AC. It would trip out if attempting to run both. I can't speak to our new Montana...
Love the 4500 - quiet, not very thirsty, only complaint is the handles make it difficult for one person to lift into a pickup. Good luck!

[Foldbak]

I installed an Onan 3600 LPG built in. Couldn't find a 5500 LPG. It does great. Only runs one AC but gets very little use thanks to the solar.

[AZMont]

Have you ever ran the onans at higher elevations? If so, did you have any starting or running issues? I plan to use my generator at 600' elevation and at 7,000' elevation. The Onan manual talks about a "high altitude kit" that is basically a re-jet. The issue is that the jet change is a manual process and having to constantly re-jet could be a negative. I'd appreciate it if you or anyone else can share any experience with running the stock inverter / generator at higher altitudes.

[mlh]

Originally Posted by AZMont

Have you ever ran the onans at higher elevations? If so, did you have any starting or running issues? I plan to use my generator at 600' elevation and at 7,000' elevation. The Onan manual talks about a "high altitude kit" that is basically a re-jet. The issue is that the jet change is a manual process and having to constantly re-jet could be a negative. I'd appreciate it if you or anyone else can share any experience with running the stock inverter / generator at higher altitudes.

I ran my Honda at about 4000 feet last year. It is mounted to the back of my motor home. It didn’t run exactly right but it did run. I have ran it at over 8000 feet. Last year it blacked up the back of my camper. If you are going to run it at attitude you should get the high altitude kit. It is a smaller jet add will only take a few minutes to install. You take the front off the generator remove the float bowl. That is one screw and the jet that comes out of the same hole after the bowl is removed. Put the new jet in, bowl back on, front cover on and done. Nothing to it.
Lynwood

[Foldbak]

Another good reason to run an LPG generator. If its carbureted running at 7000 feet it's going to run rich and need the kit. If it's a newer fuel injected no kit needed. Electronic fuel injection will correct for elevation.

[AZMont]

I agree with the EFI comment. But, EFI is an emerging technology for inverter / generators. Especially in the 4500 Watt size. Hopefully, we will see more EFI offerings in the next few years.

[AZ Traveler]

I believe the Honda 7000 and 3200 watt gennies are fuel injected. What others are?

[Foldbak]

Originally Posted by AZ Traveler

I believe the Honda 7000 and 3200 watt gennies are fuel injected. What others are?

I don't know about the portable gens. I've always had an Onan built in. It's going to be interesting to see how the generator industry progress with this green push.

[AZMont]

The honda 7000 is EFI, but costs ~$6K and weighs in at 263 pounds. Ouch! Looks like a nice unit, but more than I can afford.