Aims Power PWR120001212OS

Tell us what you have for house batteries and how the inverter is connected?

Wire size and length are important.

More likely too few batteries that were low on charge.
Alarm was most likely low battery voltage and eventually low voltage shut down.

Overload would shut down immediately.

You may have wanted to post this in "Tech Issues" or "Class A"
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KevinandHarvey wrote:
We are new Class A owners. Was running our furnace and coffee maker and our Pure Sine Inverter warning buzzer sounded a intermittent beep, then constant then shut down. Was I over loading the inverter? Thank you!

What size inverter? A 1K should run most any coffee maker.
A propane furnace fan, is 12dc and runs directly off of the batteries.
My guess is for low batteries and for whatever reason, if your inverter is of adequate size.
I'm assuming your converter charger is in combo with your inverter and either way, the battery charging function should be checked out firstly.
Using a voltmeter on the batteries and switching the charger off and on should show a difference. Also with the engine's alternator running.
If your batteries are shot, then they're not going to hold a charger, regardless.

..

Furnace runs on 12 volts but is a major power sucker. Still no where near the INVERTER when cooking with battery power (making coffee)

The beeps were the "voltage is droping" warning. the shut down was the battery protection circuit. Inverter was not overloaded and was operating as designed.

TO cure

You can try shutting off furnace when brewing your morning cup
Fire up Generator
Add more batteries (I favor GC-2 in pairs as they are six volt and 2 in series make 12) also make sure all connections are clean. I gained about 1 volt under load when I cleaned mine last.