Our power was down at work all day today, probably will be again tomorrow. We have a mishmash of generators, including my Champions that I brought from home.

The Champions ran great. I ran into issues with an 8000 watt Troy Built.

We have 3 Magic Chef cheap microwaves in the break room. Looking at the labels and online specs, they say anywhere from 1000 to 1100 watts.

There are 2 circuits on this machine, but no matter how I ran the cords (12ga), it would kick out the breakers. I could only run one microwave at a time.

I figured there was something wrong with the generator, but it would run some stuff. After break I hooked it to a refrigerator (7.1 amp load) and it ran fine.

A while later, I heard the small air compressor kick on and was trying to figure out how my employees were running it. I walked out to the warehouse, and sure enough, my employees have connected a 10 amp pancake compressor to the same generator and are beating the hell out of it with a pneumatic carton closer stapler.

So the generator is handling 17 amps now, but couldn’t handle a couple of microwaves 30 minutes earlier? And all on the same cords!!!

So is there something in particular to microwaves that make them screw with the load on a generator? Are their loads higher than specified? Do they spike the voltage or something?

Kinda has got me stumped.

Nothing about microwaves should effect generators.  Many generators have 2 separate power circuits that run in parallel, so the power must be balanced between receptacles to get the advertised power out of the gen.  Check the manual.

Let’s make sure we’re on the same page.  The genny is 8k running watts?  Each microwave is plugged into a seperate circuit? What’s the circuit breaker amperage for each? 15?

Microwaves don’t have a difference between starting And running watts.

The refrigerator is probably 7.1 amps starting, not running.  Running it might only be 2 amps or even less, so 10+2=12 amps, not 17 (unless the fridge happens to kick on exactly when they airgun).  The microwaves total 18.3 amps at 1100watts.

Try changing the power level on one or both microwaves.  Maybe start with one at 100% and one at 50% and work up if it handles it. A power level on one of 60% should be around 15 amps running them both. Maybe it doesn’t want to put out more than 15 due to circuitry or something.

The wattage ratings on those microwaves might assume that the AC power source is big enough to avoid clipping the waveform on its peaks.

Generators tend to have trouble with this - the voltage sags as the waveform approaches the highest part (on both the positive and negative cycles).

Some loads draw a lot more than their rated current when this happens. Other loads just don't work nearly as hard as they should.

Folks who use generators to run large battery chargers in off-the-grid applications often encounter it - the chargers need all of the peak voltage in order to deliver rated charging current to the batteries.

We ran into that at work.   Management bought a 20KW generator to run the server room but didn't tell us that they also wanted to run other things when the power was out.    The server room was between 8K and 9K watts and then management gave us another list of things that they wanted to hook up.   They nearly crapped when we explained that it lacked capacity.   We had to hook up an oscilloscope to show them how the sign wave was being eroded by the draw only siphoning off the top (and bottom) of the wave.   So they bought a 70KW to run the rest of the office.    I explained that it was like a wave breaking over a break wall.   Only the top makes it over and that is all that you have to work with.

Just so I understand, you were trying to route/use extension cords to ensure 1 microwave was plugged into 1 leg and the other was plugged into the other leg, effectively balancing the loads across each "half" of the generator? Did you grab a multi-meter and make sure that's what was actually occurring? IE, check voltage from the hot on the first plug you're using to the hot on the 2nd plug. If it's 220, then your 110 loads, plugged into each of those receptacles should be using both windings on the genny. If you're only showing 110 then you're only using half of the generator and your capacity is halved.

I could be wrong, but I've NEVER seen a microwave that actually reduces the power of the microwave, it just pulses it on and off, usually in 30 second cycles. IE, 50% power would turn the microwave on at 100% for 15s and turn it off for 15s, then repeat. This won't help the OP's problem.

You are correct.   Setting the microwave at a lower power reduces the duty cycle.   It doesn't reduce the power used during the microwave operation.

2Hut8

I would even go as far as saying it would be worse than 100% power bc it would be cycling the main load off and back on every 30s which would continuously subject the genny to the higher in-rush or startup current needed to start the microwave.

That being said, in theory, as long as the clocks in the microwave were running in-sync you could possibly get 2 microwaves to run in opposite cycles at 50% or less power so one turns on right as the other turns off and vice-versa. But I don't think that would really buy you much.

I tried pulling everything off the generator, except two microwaves, and plugged each one into a different leg, and it still knocked out the breaker.

We were still on generators today, so we were down to one microwave again. It would pull one microwave and one refrigerator. After breaks/lunch, I would disconnect the microwave and run two full sized refrigerators off it.

I haven’t found my meter that measures Hz (Only 1 portable light in our office) so I don’t know what it’s running. My crew tried to hook it up to the time clock and UPS before I got there at 6:50 in the morning. The UPS basically puked and wouldn’t run it. It’s probably off. I have my two personally owned Champions that I’ve been bringing up there everyday and the UPS’s run fine off the Champions.

Power is “supposed” to be fixed tonight, but so far nothing. I might try to run two microwaves off the 3500 Champion and see what it does.

If that's a 110-only model don't be surprised if it works.

After 1 microwave gets powered up you would then have the entirety of the remaining capacity to get the other started... which may be just what you need in this case.

Most microwaves produce a large surge of current when they first start the magnetron which can be much higher than the nameplate wattage.

My 5500 watt generator struggles with a 1000 watt microwave. It's not just you.

I also had a different generator struggle to run a small window air conditioner. It should have worked but didn't. It's like the generator would never sense the load.

Panasonic Inverter microwaves are what you seek! And they're great IMHO.

skibane is right generators are rated for average watts not peak, the breaker cannot handle 200 amps for 3 percent of the cycle.

I have got around this by first starting an induction motor of similar rated watts (with no load) on the same circuit.
The motor acts as an ac battery.