Turning A/C off before generator

[WBBB1]

I have always turned the a/c off before turning off the generator? I also make sure the a/c is off before I start the generator. I just wish I could turn both of them off or on from the drivers seat without one of us having to walk to the back while driving down the road. Since it's just to two of us and the dogs, we only run the Ford a/c. I do like to start the generator and the a/c before we stop for lunch or a break. It's just a pain, I'd like to fit!

I know the a/c does come on until after the generator has been running for a while, but don't want to burn one of them up by dropping the voltage while running. We own the 35qba.

WHAT DO YOU DO?

[Ed_G]

I am not really sure what your concern is. If the AC is running and you turn off the generator, you have killed the power...and thus the AC will shut off. Not a problem. If the AC is already turned on, and you are driving down the road and decide to turn on the generator, I still do not see the problem. The AC does not actually get switched to the coach by the Power switch box for several seconds after the generator is running, so again, no problem. AM I missing something?

[Old Scout]

Dont know about your specific unit and generator but on starting, it seems the generator, the power transfer switch, and the A/C unit all have build in delays to let the genset come up to power before loading it. Accordingly, you should be able to leave the T-stat on and just start the genset when you want the A/C to come one. Might could do the same thing when shutting off the genset but I like to take the load off the genset and let it cool down a bit before shut-down....this may not be necessary but its what I do......

[gemini5362]

Originally Posted by Ed_G

I am not really sure what your concern is. If the AC is running and you turn off the generator, you have killed the power...and thus the AC will shut off. Not a problem. If the AC is already turned on, and you are driving down the road and decide to turn on the generator, I still do not see the problem. The AC does not actually get switched to the coach by the Power switch box for several seconds after the generator is running, so again, no problem. AM I missing something?

Actually there is a potential problem. When you turn on the generator with the AC on is not a problem because the compressor does not come on immediately on most AC units. The problem is turning off the generator with the AC running. If the compressor is running and you turn off the generator the power does not drop off instantly there is a very quick power down period when the voltate goes from 120vac to 0 during that period of time the compressor is expecting 120 volts x current to run if you drop the voltage down then the current is going to go up and it could conceivably get to a level that would damage windings.

[Ed_G]

Actually, I don't think that is a correct assessment. Power (Watts) is a combination of voltage x amperage. When you shut the generator down, the power immediately drops rapidly. That is BOTH the voltage and amperage source. The AC cannot draw excessive amperage simply because there is no current source from which to do so. Perhaps a generator or motor expert here can corroborate what I just said.

[gemini5362]

Originally Posted by Ed_G

Actually, I don't think that is a correct assessment. Power (Watts) is a combination of voltage x amperage. When you shut the generator down, the power immediately drops rapidly. That is BOTH the voltage and amperage source. The AC cannot draw excessive amperage simply because there is no current source from which to do so. Perhaps a generator or motor expert here can corroborate what I just said.

You could be correct one of the things I did not think about was that a lot of MH generators are inverters not generators. If it is a generator you still have current from the collapsing field. But for an inverter I would expect the current and voltage to be cut off almost immediately. So for inverter systems probably not a problem but for an actual generator I still see a small possibility of a problem. Not sure it would rise to a risk for someone to worry about but could be a problem.

[AFChap]

It is a good idea to run the generator for a couple of minutes, letting it warm up a bit before putting a large load on it. And it is important also to allow the engine to cool down for a minute or two at idle (after the large loads are removed) before shutting it down ...same with the generator engine as with the chassis engine. It won't make much if any difference in the short term, but treating the engine well WILL make a difference in the long term.

[Mich F]

Unless you had a remote for your A/C unit, I don't see how you could turn your house A/C on or off without going to the back and doing so. Carrier A/Cs had them while they were making RV A/Cs. As for the generator, many years ago (early 90's) I saw a Cruise America rental MH that had a remote start/stop for the generator on the headliner area in the cab, just in front of the driver -thought that was a really neat idea. I've thought of doing that on my motor homes, but never got around to it.
I also normally turn off the roof air before shutting off the generator, since I believe that's the recommended procedure to let the generator cool down without a load, before turning it off.

[DonDee]

FWIW, my Onan Op. manual shows: "If practical, allow unit to warm up before connecting a heavy load".
Nothing about shutting down.

[smiller]

I don't think that there is any practical likelihood of damaging the A/C by shutting down the generator while the A/C is operating (it's true that a voltage drop can cause more current to flow in the compressor windings but this occurrence would be far too brief to generate enough heat to cause any harm.) The concern that I would have though is not providing any cool-down time for the generator. Whether stopping the generator immediately after running under load would cause any cumulative harm or not would depend on the generator design and other factors, but generally it's best to provide at least some cool-down period if at all possible.

When starting, most transfer switches have a time delay that won't apply a load until the generator has run for at least 30-60 seconds. I think it's advisable to allow more time than this before throwing a heavy load on the generator (such as an A/C), plus it's a lot easier on the transfer switch contacts when they switch with no load vs. a large load.

So... while it may not do any immediate or obvious harm to let the generator/transfer switch 'turn on' the A/C, I don't think it is an optimal choice for maximum generator and transfer switch life. Personally I'd just get off my heinie and start/stop the A/C manually.

[wa8yxm]

I have killed the Generator while the A/Cs were runnign, usually when I do I have to reset at least one breaker on the genny when I re-start.

IT is best to turn them off first.. I wish I had a remote to do that but alas, Only one of 'em can be remoted from the driver's seat (Carrier Air V's with I/R Remotes)

[CW5DJS]

Its not a problem to start or shut down the gen set with Air on. The issue is when you forget to turn the AC to off position before hooking up Shore Power. I often forget ( getting old) to flip the breaker at the SP Pole and when you plug in 50 AMP with air on, you get quite a spark and possible damage to the coach.

[mccsix]

In my way of thinking no load thru the transfer switch means no arcing/sparking which will kill a transfer s/w over time(cycles).
So nothing on when plugging in/ disc shore power, or starting/shutting down the gen.

[mel s]

WBBB1
As with most forum topics your question is receiving 50/50 answers....(1/2 correct and 1/2 questionable, aka: WRONG)!
Take your pick.

Or do whatever your owners manual says...(if everyone did that everything would last a lot longer).

Mel
'96 Safari