I know the ideal scenario would be to shut off the A/C at the thermostat prior to turning off the generator, but in practice I'm sometimes pulling into a gas station with the generator and air running and just kill the generator from the drivers seat. Is this doing any damage to the generator or air conditioner?It's an Onan 4k Microquiet, and a Coleman Mach 15 ducted A/C.Similarly on the other side of it, I restart the generator from the drivers seat after leaving the pump and the A/C comes back on. This seems less bad to me, as there seems to be some delay between the generator starting and 120v being supplied, I suspect there's some electronics in the generator that is waiting to supply power until it's up and stable. But that's just a guess. Am I right?Just trying to determine if it's worth the extra effort to get up and shut down the air conditioning before killing the generator. :B

I ALWAYS turn the acs off with the thermostat. When you start the genset your ATS delays switching over until the genset is stable. I leave my genset running when fueling just like the millions of reefer trucks do.

camperdave wrote:Just trying to determine if it's worth the extra effort to get up and shut down the air conditioning before killing the generator. :BYES. Going both ways.Shutting OFF.....the gen is very HOT from running.Immediately chopping the air flow over the engine might make it WAY hotter than it is supposed to be.It is always recommended that you start the gen a minute or two before applying a heavy load......especially when cold.You will be better off in the long run by doing it "right".

No ATS, my 30a cord is plugged directly into the generator.

camperdave,Don't be surprised when your generator goes belly up. It needs a cool down after running at close to full load with the air conditioner running. Read the owner's manual. Shutting it off when it's as hot as it can be is extremely bad practice. Onan recommends a 3 to 5 minute cool down:Onan MicroLite 4000 Owner's Manual wrote:STOPPING1. Turn off air conditioners and large electrical loads before stopping to allow the genset time to cool down. 2. Let the genset run three to five minutes. Failure to let the genset cool down can cause engine run-on or backfire. 3. Push the Star/Stop switch to the Stop position.You've been getting away with it so far but don't expect your luck to last forever.

Big Katuna wrote: When you start the genset your ATS delays switching over until the genset is stable. I leave my genset running when fueling just like the millions of reefer trucks do.Not everybody HAS an automatic transfer switch.And the generator on a refer semi is at least 20 feet from the fuel tanks, which take diesel fuel, which is nowhere near as volatile as gasoline.

shutting down generator with air conditioner running

Dusty_R
Explorer
Aug 22, 2019
Just ad a switch, within reach of the drivers seat, so you can turn the AC off first.
Depending the layout of your rig.
You could run a 2 wire cable/cord. Or, add a wireless relay.
I've done both, one each of two different mh's.

Dusty
maillemaker
Explorer
Aug 22, 2019
Amazing how many systems in an RV do not protect themselves but rather rely on operator for proper operation.

You think the transfer switch is a no-brainer, check this out. On my ancient 1990 Winnebago, there is a rocker switch on the dash. If you push it one way, it momentarily gangs the house battery to the engine battery for an emergency start. No problems there.

But if you push it the other way, it stays that way, and allows the alternator to charge your house batteries while the engine is running.

BUT if the generator is also running and you do this - it will smoke your vehicle voltage regulator. This is explicitly warned against in the owner's manual. I have accidentally smoked the VR this way before.

You would think there would be some kind of interlock that prevented this situation.

Steve
larry_cad
Explorer II
Aug 22, 2019
The ONAN Auto Genstart system for the ONAN generator has a function which monitors the temperature in the RV and starts the generator if the temp goes above a user preset. This function is particularly for boondockers. The idea is to have your AC set to "ON", and when the temperature rises, the genny comes on and runs the AC to keep the RV temp down, such as for pets, etc. I wonder why ONAN would contradict themselves regarding this practice??

BTW, I have been doing this for several years while boondocking. Thus far my ONAN seems to be handling it.
pianotuna
Nomad III
Aug 22, 2019
Best practice shut down the air conditioner. Wait a while (5 minutes) and then shut down the generator. The same applies to large inverters.

My Yamaha has a switch to shut down the power.
camperdave
Explorer
Aug 22, 2019
larry cad wrote:
The ONAN Auto Genstart system for the ONAN generator has a function which monitors the temperature in the RV and starts the generator if the temp goes above a user preset. This function is particularly for boondockers. The idea is to have your AC set to "ON", and when the temperature rises, the genny comes on and runs the AC to keep the RV temp down, such as for pets, etc. I wonder why ONAN would contradict themselves regarding this practice??

good question. I see no difference in the way Onan themselves handle the auto start vs me manually starting/stopping it from the cab with the A/C on.

I know it's not good to load a cold engine, and I know it's good to let a hot engine cool down, but these are not exactly precision pieces of engineering. I think they measure tolerances with a ruler lol.

Anyway, I guess my lingering question is what kind of circuit protection does Onan have built into the output of the generator.

For example, it seems to me that the A/C instantly cuts off when I press the off button, even before the engine starts winding down. I suspect it's a clean disconnection of power prior to any loss of RPM, but don't actually know that.
Chum_lee
Explorer
Aug 22, 2019
pianotuna wrote:
Best practice shut down the air conditioner. Wait a while (5 minutes) and then shut down the generator. The same applies to large inverters.

Agreed. Not doing the above once or twice probably won't be the end of the genny. It will just make the end eventually come . . . . . sooner. How much sooner? I don't know. Do you feel lucky?

The reverse applies for cold starting. Start the genny. Let it warm up a few minutes, then load 'er up.

Chum lee
philh
Explorer II
Aug 23, 2019
pianotuna wrote:
Best practice shut down the air conditioner. Wait a while (5 minutes) and then shut down the generator. The same applies to large inverters.

My Yamaha has a switch to shut down the power.

Why wait 5 minutes?
pianotuna
Nomad III
Aug 23, 2019
Phil,

Because the generator needs to cool down.

And my inverter/charger actually caught on fire internally. I have soot marks as proof.
dougrainer
Nomad
Aug 23, 2019
maillemaker wrote:
Amazing how many systems in an RV do not protect themselves but rather rely on operator for proper operation.

You think the transfer switch is a no-brainer, check this out. On my ancient 1990 Winnebago, there is a rocker switch on the dash. If you push it one way, it momentarily gangs the house battery to the engine battery for an emergency start. No problems there.

But if you push it the other way, it stays that way, and allows the alternator to charge your house batteries while the engine is running.

BUT if the generator is also running and you do this - it will smoke your vehicle voltage regulator. This is explicitly warned against in the owner's manual. I have accidentally smoked the VR this way before.

You would think there would be some kind of interlock that prevented this situation.

Steve

You had other things that caused your failure. Winne/Itasca used the SAME switch system from at least 1978 to mid 90's. I worked on Itasca/Winne (we were a dealer) from 1978 to 1991 when we dropped Winne/Itasca. We were a chassis shop also during that time. NEVER had VR's fail. This was thousands of Winne/Itasca's we sold and serviced. The DUAL switch was almost always left in the DUAL position by our customers. Doug
dougrainer
Nomad
Aug 23, 2019
After 40 years and still an RV tech, the ONLY practice I would follow is, Shut the LOAD (AC and such) OFF, then kill the Genset. Start the Genset. wait for Transfer from the ATS, Then start you AC units. The reason is, The Contacs on the ATS take a beating when starting and stopping on a LOAD. I have yet to see a failure of a Inverter or a Genset that COULD be attributed to shutting down under load. Cooling a AIR COOLED genset, I can see the advantage to running 5 minutes before shut down. But, a WATER COOLED Genset, I see no reason, any more so that running your Auto for 5 minutes before shutting it off. Inverter(Large) have cooling fan/s, so I see no reason to worry about them. Doug

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