Community Forums

Unicorn Driver · 07-30-2018, 07:55 PM

Hi,

Can I cause damage to my air conditioner or generator if I set it cool with no power connected and then start up my generator later (while deiving)? And the same if I turn off the generator. This is for if I am driving myself.

I know the gen should start with no load.

Thanks,

Wayne M · 07-30-2018, 08:11 PM

That question is going to get a lot of answers. Which one is correct will be the question.

I was under the impression that the AC should be off when the generator is started and the generator should run for few minutes. That is basically what we do but I'm not alone. When hot out, I'll turn the AC off when on house power, start the generator and DW will turn it back on after a few minutes while I'm disconnecting the pedestal power. That was then!

This is now:
We have an auto start feature that works if we loose power or of there is a demand on the AC. We have been in the MH when the power has gone off from the pedestal. The AC's shut down, the generator starts and after a few minutes the AC's come back on. All the delays are built in. Similar to the Sticks & Bricks house, if you turn the AC off or set the thermostat to shut off and then turn it back on the AC will not start up for a few minutes. (When talking minutes it probably is about a minute or so-give or take).
I have noticed that when the generator kicks on, or is started, there is a also a delay before electricity is provided to the RV.

Try it. Turn the generator on, and have the system set to cool. Time the cycle when the AC comes on. If it is immediately I would not use that method but turn it on until the generator has operated for a couple minutes.

When using the manual mode and not driving I always turn the AC off before starting the gennerator, and if it has been running while traveling and I need to shut it off I'll turn off the AC ad after a while turn off the generator.

Let's see what others have to say.

Unicorn Driver · 07-31-2018, 06:01 AM

Thanks Wayne,

If I am going to run air con I normally fire the generator up first. Its just sometimes I get caught out. Normally I send the wife back.

tmw188 · 07-31-2018, 06:20 AM

There is usually a short delay before the transfer switch releases power to the house, usually not long enough IMO to let the gen warm up, but the powering on is instant when the contactor pulls in. The problem IMO is when you would turn the generator off, it is not instant, it whines down slow which is probably not good for the ac if the compressor is running at the time.

Sbrownstein · 07-31-2018, 06:48 AM

All of this is correct. I try not to shut down my generator with the AC running since the shutdown is probably not that instantaneous, as would be if the contactor dropped out from the thermostat. But, I don't always remember to do it.

There is a 15 to 30 second delay for the generator to stabilize before the transfer switch kicks in and powers the RV. I don't think the sudden load really bothers the generator, it may lug a little, but I am not a warming up kinda guy. It has a governor and is designed to run like that. Even the manufacturer says that the transfer switch delay will suffice.

What you want to avoid is an immediate load applied during startup. that is why transfer switches have a delay for the generator.

from the Onan Manual...
" Before starting, good practice to turn off air conditioners and large electrical loads especially in
cold weather
– Note: Most transfer switches take care of this"

Unicorn Driver · 07-31-2018, 06:59 AM

Thanks all,

This is what I thought already but was just confirming.

Cooperhawk · 07-31-2018, 07:03 AM

We do that all the time. No problem.

The genset will start up and run a few minutes until the switch powers the circuits. Then the AC will come on.

When I shut down I just hit the genset kill switch. I never leave the drivers seat.

Unicorn Driver · 07-31-2018, 08:24 AM

Thats good to know.

dadej · 07-31-2018, 02:51 PM

What is the model of your generator as some don't like to have a load when stopping?

Unicorn Driver · 07-31-2018, 02:57 PM

Its an onan Marquis gold 5.5 gas

consolenut · 07-31-2018, 03:09 PM

You don't want to shut down or start that marquis under load. Either or will kill the voltage regulator.

Wayne M · 07-31-2018, 04:47 PM

For a Scientific Wild A#* Guess (SWAG) call Onan and ask them. I'll wager they have the right aswerl

Unicorn Driver · 07-31-2018, 08:42 PM

Thanks both,

I will call both Onan and Coleman.

70ChevelleSS · 08-06-2018, 06:23 AM

Okay, my opinion. As mentioned the generator comes up to speed and stabilizes then the transfer switch closes. So there is a short delay there. Once the AC unit is supplied with AC current there is a delay before it will attempt to start a compressor, don't recall exactly how long the delay is. This delay is built in to almost all AC units. It's meant to handle case where you have power, AC is running, power goes out for a second or two then comes back on. You don't want to try and restart the compressor immediately because there is built up pressure on the high side, output side, of the compressor. The delay allows the refrigerant pressure to equalize before restarting the compressor.

To me those 2 delays are enough before throwing a load on the generator. Now shutting down the generator with the AC running is a bad idea. Lot of current running through the transfer switch. If it opens with current flowing it will cause arching of the contacts which can eventually ruin the transfer switch.