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

pianotuna
Nomad III
Aug 23, 2019
Doug,

The cooling fans on my inverter are AC motors. Turn off the inverter, and you turn off the cooling. That is why mine caught on fire.
Sam_Spade
Explorer
Aug 24, 2019
pianotuna wrote:

The cooling fans on my inverter are AC motors. Turn off the inverter, and you turn off the cooling. That is why it caught on fire.

Wait a sec. here...........
Isn't the inverter supposed to produce AC power ?
Why would the cooling fans NOT be powered by the inverter itself ?
Am I missing something here ??
jharrell
Explorer
Aug 25, 2019
Sam Spade wrote:
pianotuna wrote:

The cooling fans on my inverter are AC motors. Turn off the inverter, and you turn off the cooling. That is why it caught on fire.

Wait a sec. here...........
Isn't the inverter supposed to produce AC power ?
Why would the cooling fans NOT be powered by the inverter itself ?
Am I missing something here ??

You are not missing anything, they are 12v dc fans lookup Magnum Inverter 44-0004 for the replacements, they do not run off 120v ac directly and do not require the inverter section to be on.
pianotuna
Nomad III
Aug 25, 2019
jharrell wrote:
do not require the inverter section to be on.

When the Magnum inverter is turned off the fans do NOT run. I know that for a fact.

I assumed they were 120 volt AC fans, so thanks for the correction.

It is a stupid design to have them turn off when the inverter is powered down--particularly if they are DC fans.

And yes the 12 volt DC supply to the inverter was still turned on.

Sam Spade wrote:
Why would the cooling fans NOT be powered by the inverter itself ?
Am I missing something here ??

They are powered by the inverter. But if you turn off the inverter the fans cease to run. Or, if 120 volt shore power is being used to charge the battery bank via the Magnum, is disconnected, the fans also stop running.
jharrell
Explorer
Aug 25, 2019
pianotuna wrote:

They are powered by the inverter. But if you turn off the inverter the fans cease to run. Or, if 120 volt shore power is being used to charge the battery bank via the Magnum, is disconnected, the fans also stop running.

The inverter is either running forward inverting making 120v or running in reverse charging using 120v. If it is doing neither than there is no need to actively cool the fets or transformer.

The inverter has temp sensors on the fets and transformer, it will run the fans based on temp alone so long as it has at least 9.5v at the battery terminals:

From the manual:

The inverter contains two internal cooling fans that are automatically controlled. The speed of
these fans is determined either by the internal temperature of the inverter or by the load on the
inverter. The inverter’s fans will come on under the conditions listed below:
• Fans run full speed if the internal transistors (FETS) or the power transformer reaches 176°F
(80°C), or the inverter is running at 100% of its rated load.
• Fans run medium speed if the internal transistors (FETS) or the power transformer reaches
140°F (60°C), or the inverter is running at 50% of its rated load.
• Fans run low speed when the inverter is running at 25% of its rated load.
The fans shut down if none of the above conditions are met, or if the battery voltage is < 9.5V.
Whenever the inverter is first connected to the battery, the fans start for about one second.
pianotuna
Nomad III
Aug 25, 2019
All I can say is that mine caught on fire, after being run for around an hour in a situation where it was charging at over 70 amps. The repair center took it apart and ordered a replacement.

I have confirmed that the cooling fans shuts down when there is no 120 volt power source, be that inverter, or shore power, even when the inverter is still connected to the battery bank.

The manual can say what ever it likes. Real life trumps the manual every time.

It is possible they have redesigned the circuit--but my warranty replacement does not run the cooling fans without a source of 120 volt power.
camperdave
Explorer
Aug 25, 2019
Back to generators, even with the 15k air running, a 4k generator is still at less than half load. The engine is not working that hard.

I do gather from these posts that it may be worth installing an ATS if for no other reason than to have the 30 second delay on generator start up.

I also like the idea of wiring an A/C on-off switch at the drivers seat, though I'm not sure how I'd do that. The thermostat is way back in the bedroom.

For those that shut off loads before starting/stopping the generator, are you turning off the converter too? At 60a that's not an insignificant load when the batteries need charging.
pianotuna
Nomad III
Aug 25, 2019
60 amps at 12 volts ~= 6 amps at 120 volts. In a perfect world--sure shut it down.

camperdave wrote:
For those that shut off loads before starting/stopping the generator, are you turning off the converter too? At 60a that's not an insignificant load when the batteries need charging.
wopachop
Explorer
Aug 26, 2019
What about installing a small 12v cooling fan to blow on the genny? Controlled by a switch up near the drivers seat.

I've been wanting to do something similar for super hot 110F+ camping trips. Would just need to figure out the natural path of airflow.

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