Does it kill an A/C to run it off a generator?

Hi mlts22,

My microwave draws more than my air conditioner, which is why I use the toaster as a "warm up" device.

I would not want a built in genny--I'd prefer a large solar system. The dash air does a not bad job of keeping the living quarters on my class c liveable if I use the air conditioner on fan only to spread the air.

Of course, with the large inverter I can now run the roof air for a time before I stop for the day to increase the cooling. I've also done this with the generator--and that will be very easy to do in future as I now have a remote start kit on the Yamaha.

I also invested in an induction cooker and love how it works, so I'm in a position now to run my rv 100% electrically, saving on propane costs.

Once nice feature of the Magnum is to limit the shore power amps that can be used. No more blown shore power breakers when at a friends home!

Question: IS your start up sequence as follows:

ONE: Start generator
Two: Start A/C?

If so I have an answer for you... Here it is:

When you first start the generator in the morning the converter kicks in and starts sucking major power to re-charge the batteries.. Like 10 amps in my case (yours may be different) that's over 1,000 watts..

The A/C also draws like 13-15 amps running.. And the Yahama simply runs out of power.


The solution:

Wait at least 30 minutes to an hour between Varoom and Cool OR.

Turn off breaker for converter, THEN start A/C (This assumes it's hot in there) if the A/C has an "Emergency" mode, use it. .THEN turn on the converter.. This may work depending on just how close you are to overload on the genny.....

Option 2 would be a smaller converter.. I have two converters here. one is BIG (80 amp and as I said it draws 10 or more amps when batteries are low) the other is variable I can throttle it down to like 20 or 30 amps if I wish, or open it up to 99/100 (Which it hit the other night when.. well that's a long story)
Here is my story:
COnverter 1 (Factory installed) Is a Progressive Dynamics 9180 with wizard, it is a plug in model mounted as far from the batteries as possible.

Converter #2 is the charger module in a Xantrex Prosine 2.0 connected to the batteries with a short run of 0000 welding cable,, that's a whole lot of copper and a very short run, LESS THAN 3 FEET.

I prefer the 9200 for charging and maintaining the batteries for several reasons but that dang plug.. Well sometimes I snag it and pull it and so I did a few days ago.

In one bathroom (Bath and a half model) I have a battery monitor, on all the time, it was showing very low batteries.

Since it was like middle of the night (in fact I think it WAS midnight) I came out to the Xantrex Remote panel and CLICK, took a look and saw it hit 99 amps.

Divide DC amps by 10 and add 10-20% for AC amps.

(WE do not charge at 12 volt we charge at 13 or more 13.2 is 12 + 10%, and the converter is not 100% efficient so the 2nd 10%)

pianotuna wrote:
Hi mlts,

Warm up the generator for at least five minutes. Run a toaster or other high draw appliance and then switch on the air conditioner. Try it with the eco switch in the off position. Add a hard start capacitor to the air conditioner. Some folks have added relays so the fan motor starts after the compressor (or is it the other way round?).

I have a 13500 btu Dometic and the Yamaha 3000 iSEB. If I watch the voltage on starting in eco mode, the voltage sometimes drops to 90.

I just got my magnum "boost" inverter so I'm hoping that will take care of this low voltage event. I'll probably try to write a report about it soon.

You read my mind. I don't use eco mode with the A/C (as I know the generator won't spin up in time to eat 60 locked rotor amps that are thrown in its face.) I also run the generator in steps... firing it up, waiting 60 seconds, firing up the microwave for a minute on two cups of water, turning on the A/C fan (not the compressor), waiting until the microwave finishes, then after that, reaching for the thermostat and engaging the compressor. I leave my fridge in gas mode so it won't add its 300-400 watts to the equation when power comes on.

If I were keeping this rig for a long time, I'd pony up for the "hybrid" inverter you mention, which cures the voltage sag by drawing from the batteries.

However, I'm looking to move to a TC, short "C", or a "B" motorhome once I actually get vacation time (no point in bothering until then), and since I should have a built in genset with those, this problem will be moot then, although I would probably see about the Magnum converter/inverter if there is space for it, so my appliances are isolated from the surges/sags of shore power.

Hi mlts,

Warm up the generator for at least five minutes. Run a toaster or other high draw appliance and then switch on the air conditioner. Try it with the eco switch in the off position. Add a hard start capacitor to the air conditioner. Some folks have added relays so the fan motor starts after the compressor (or is it the other way round?).

I have a 13500 btu Dometic and the Yamaha 3000 iSEB. If I watch the voltage on starting in eco mode, the voltage sometimes drops to 90.

I just got my magnum "boost" inverter so I'm hoping that will take care of this low voltage event. I'll probably try to write a report about it soon.

I forgot to add that when testing one of my outlets as per a DMM, I get 120 VAC when the A/C is on, and 122 VAC when the A/C is off. There is a brief transition, but I've seen the DMM hit ~105 or so for a fraction of a second, but not lower.

Subsequent compressor starts/stops don't bog the compressor nor drop the voltage under 115, until the next day.

A/C compressor (and fan motor) are drawing voltage down upon start faster than generator voltage regulator can respond.
Lower voltage=higher amp draw=shortened life span

Get a simple plug in voltmeter...plug it into an outlet where it can easily be seen and check the voltage when starting the A/C using generator.

Most 'power protection' (surge guards) devices trip on low voltage at 102V but that is just way too low for me.
I don't like running my A/C when voltage is below 108V AC for any length of time.

Plug in voltmeter.....

An underpowered generator trying to run an A/C on a consistent basis will eventually spell trouble for the A/C which may or may not lead to replacement of the A/C...