shutting down generator with air conditioner running

[camperdave]

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

[wopachop]

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.

[pianotuna]

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.

[camperdave]

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]

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.

[jharrell]

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]

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]

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.

[Sam_Spade]

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 ??

[pianotuna]

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.

[dougrainer]

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

[dougrainer]

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

[pianotuna]

Phil,

Because the generator needs to cool down.

And my inverter/charger actually caught on fire internally. I have soot marks as proof.

[philh]

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?

[Chum_lee]

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