Kinda messed up today. I had the generator running and the invertor switched on, ( usually turn the invertor off when running the generator) both AC units were running. The AC's cycled off and a few minutes later I was going to leave, so turned off the generator, forgot the AC's were on, but not running. The inverter was still on...........will this hurt anything........will the AC's try to run off the invertor? I have 4 house batteries. Do you think I hurt anything? I wasn't around, so don't know if the AC's tried to run or not off the batteries.I've always turned the AC's off prior to turning off the gen or making sure the AC switch is off before starting the gen. Does it hurt to turn the generator off with the AC's running?Does it hurt to turn on the generator with the AC switch "ON" so they'll try to start as soon as the gen comes online?

“Does it hurt to turn the generator off with the AC's running?”Read your manual. My generator booklet says to remove loads and run for a short time before turning off.

Best practice to start and stop a generator with minimum load. Hard on the regulator and engine to start and go immediately to high throttle. Hard on the regulator trying to maintain voltage as the engine winds down. 30 seconds is generally enough wait time.

our AC does not run off the inverter. yours is likely the same.

rk911 wrote:our AC does not run off the inverter. yours is likely the same.This. It would have to be a honking big inverter to run AC.

So far as the generator is concerned, the AC thermostat "on" but not actually cooling is no different than the AC thermostat "off." In both cases, the air conditioner is not running and hence not consuming power.As was said, best practice is to turn off loads before shutting down the generator. However, it's generally unlikely that failing to do so accidentally will cause trouble. It's in the category of things to avoid, but not in the category of things to keep you up all night worrying about should they happen.Shutting the thermostats off before starting the generator is strongly recommended; starting under load, especially a heavy load such as two air conditioners starting up simultaneously, is rough on the generator. Let it start up and stabilize (and ideally warm up a bit), then add the significant loads individually so far as it is practical to do so.

Turning off the generator with the AC going? | Good Sam Community

27 Replies

MrWizard
Moderator
Oct 31, 2020
RLS7201 wrote:
4x4van wrote:
All of the naysayers conveniently ignore RV's with automatic generator start systems that users use to keep their RVs cool when they are not there. Or am I missing something?

EXACTLY...............Do you have a degree in electrical engineering? Or just some good common ¢. GRIN

Richard

Here I go bursting bubbles again
The automatic generator start systems have timers, specifically to prevent startup shut down load problems, are not going to engage until the generator power is stabilized and are not going to shut down on board running generator while the tstat is calling for cooling, you could conceivably run out of fuel for the generator if it ran long enough, but that would not be a rather abnormal shut down

I do not know how much EMS support is installed with these auto start systems, for A/C use, but there must be some, in order to prevent generator shutdown or generator overload trip problems under what would be considered normal auto start conditions
4x4van
Explorer III
Oct 30, 2020
RLS7201 wrote:
4x4van wrote:
All of the naysayers conveniently ignore RV's with automatic generator start systems that users use to keep their RVs cool when they are not there. Or am I missing something?

EXACTLY...............Do you have a degree in electrical engineering? Or just some good common ¢. GRIN

Richard
Actually, both!:C
RLS7201
Explorer II
Oct 21, 2020
4x4van wrote:
All of the naysayers conveniently ignore RV's with automatic generator start systems that users use to keep their RVs cool when they are not there. Or am I missing something?

EXACTLY...............Do you have a degree in electrical engineering? Or just some good common ¢. GRIN

Richard
dodge_guy
Explorer II
Oct 20, 2020
The ACs will wait for 45 seconds to a minute to restart if left on. Also the auto changeover will wait about 30seconds before it switches over.
Best practice is not to do it, but if it happens once or twice there will be no harm.
4x4van
Explorer III
Oct 20, 2020
PastorCharlie wrote:
My EMS manages the loads and prevents any damage to system. There is a 3-5 minute delay on the A/C startup.
Understood, but how is that any different than without the EMS? When I start my generator, there is about a 30 second delay before it actually kicks in and provides power to the coach breakers. At that point, if my A/C is already turned on, it starts; exactly like if it was turned off and I turn it on at the thermostat. There's no difference -electrically- between turning the A/C on at the thermostat or at the breaker. The only negative that I can think of, is shutting down the generator while the A/C is on, since it doesn't instantly shut off, but rather it slows and the voltage drops. Does your EMS turn the A/C off prior to shutting down the generator? I don't think so (could be wrong).
PastorCharlie
Explorer
Oct 08, 2020
My EMS manages the loads and prevents any damage to system. There is a 3-5 minute delay on the A/C startup.
4x4van
Explorer III
Oct 08, 2020
All of the naysayers conveniently ignore RV's with automatic generator start systems that users use to keep their RVs cool when they are not there. Or am I missing something?
tropical36
Explorer
Oct 05, 2020
MrWizard wrote:
If you unplug shore power with the A/C running,
The arcing will be at the shore cord male plug and the campground RV outlet.!

If you shut a synchronous generator off while there is a substantial load (A/C compressor) ,
The arcing will be in the transfer switch contacts,
But the biggest danger is damage to the the generator head,
As the generator head winds down, voltage drops rapidly and amp load of the compressor increases,
When the voltage is too low to hold in the ats, it drops out aka open the contacts that this amp load is flowing thru, but the back EMF from the breaking open circuit causes a power spike in the generator head and the field control circuit
That is where the expensive damage accumulates until there is failure,
A winding down generator, is not the same as flipping a disconnect or pulling a plug

I've always thought along these same lines and keep wondering why my coach has a gen start next to the bed for the convenience of starting or stopping during the night, without having to get up?
Flyfisherman128
Explorer
Oct 05, 2020
have 42 years as a RV technician. I will state I know more about this than you do.

I have been an engineer for 45 years I have been wrong at some point as well.
MrWizard
Moderator
Oct 04, 2020
If you unplug shore power with the A/C running,
The arcing will be at the shore cord male plug and the campground RV outlet.!

If you shut a synchronous generator off while there is a substantial load (A/C compressor) ,
The arcing will be in the transfer switch contacts,
But the biggest danger is damage to the the generator head,
As the generator head winds down, voltage drops rapidly and amp load of the compressor increases,
When the voltage is too low to hold in the ats, it drops out aka open the contacts that this amp load is flowing thru, but the back EMF from the breaking open circuit causes a power spike in the generator head and the field control circuit
That is where the expensive damage accumulates until there is failure,
A winding down generator, is not the same as flipping a disconnect or pulling a plug