Microwave electrical and generator

[Helmsman]

Ok. Today I ran the generator. Starting up, the amperage on the side which has the battery chargers and inverters surged up to 18 amps then dropped back quickly as it figured out the batteries were fully charged. After that, I started the two AC’s (one of the 30 amp feeds) and then I turned on the hot water feed. Then I added one stove top. Both together along with the fridge and the chargers drew 25 amps. I ran it this way for about fifteen minutes.

Then, I turned off the hot water and the stove. With the AC running, I put a bowl of water in the microwave, and the microwave ran just fine. First for three minutes, and then four minutes. Generator just purred along. Then I added the hot water heater and tried the microwave for 3 minutes. Again, everything worked fine. Amperage was fine and so was the generator.

I want to check the wire to the microwave as suggested by KM, and I also want to check the coolant in the generator. The problem occurred on the 4th in 95 degree weather after running the generator for about two hours. The oil is fine, the impeller is good, the strainer is fine.

It could be that we tried to put too much on the system at once in a too rapid time frame. Will keep tinkering to see if I can get it to run away again.

[AaHubb]

Ever watch the tv show Green Acres?

[Helmsman]

Source of the post Ever watch the tv show Green Acres?

Sure, but not since I was a kid. Where are you going with it?

[tomschauer]

When using the genny, or shore power for that matter, its all about power management. If you have a 7kw genny at 120 v you have about 58 amps available at full load. If you have twin 30amp shore power cords, you have about the same. Sometimes actually less, with old cords, old receptacles and old breakers with long wire runs to your pedestal.
Your water heater alone will draw 12.5 amps when its heating. Just turning the breaker on doesn't mean it is heating. You may have had it on long enough that it was satisfied and not heating, which enabled you to run the microwave.
Anyway, with shore power or the genny, you cant run everything at the same time and not trip a main. You want to be especially cautious when switching on the genny. Bring it on with little or no load and then turn on an a/c, then the second a/c if you have it. If not the inrush will at best lower the voltage and trip the breaker, at worst, overheat the compressor start windings and toast your a/c units. I always turn off the water heater breaker when using the stove or the microwave.
Keep an eye on your voltage meter, if it is constantly dipping down near 100v, it will damage your compressor containing devices (a/c, fridge, ice maker), so back off on load to keep the volage up.

[AaHubb]

What Tomschauer said.

[Helmsman]

Source of the post When using the genny, or shore power for that matter, its all about power management. If you have a 7kw genny at 120 v you have about 58 amps available at full load. If you have twin 30amp shore power cords, you have about the same. Sometimes actually less, with old cords, old receptacles and old breakers with long wire runs to your pedestal.
Your water heater alone will draw 12.5 amps when its heating. Just turning the breaker on doesn't mean it is heating. You may have had it on long enough that it was satisfied and not heating, which enabled you to run the microwave.
Anyway, with shore power or the genny, you cant run everything at the same time and not trip a main. You want to be especially cautious when switching on the genny. Bring it on with little or no load and then turn on an a/c, then the second a/c if you have it. If not the inrush will at best lower the voltage and trip the breaker, at worst, overheat the compressor start windings and toast your a/c units. I always turn off the water heater breaker when using the stove or the microwave.
Keep an eye on your voltage meter, if it is constantly dipping down near 100v, it will damage your compressor containing devices (a/c, fridge, ice maker), so back off on load to keep the volage up.

Thanks Tom! Part of the description above was testing. The water heater was on and in the heating phase during the above test to get the amps up to see if I could get the gennie to surge as part of what Viper suggested for testing. The stove was cutting on and off as the eye would heat up and switch off and on. The amperage never got too high while we ran the microwave under various loads.

I have been phasing in the AC’s and waiting for the compressors to start one at a time as a start up habit. Typically, we will have the AC on when days are hot. The fridge also, using the pass through with the inverter, so with the 110 powering the gennie. Then we will use the microwave for heating up stuff.

I have never seen the voltage go below 115 or so. When I measured the outlet the microwave is plugged into with a multimeter it showed 117 volts steady.

I am beginning to think that the new inverter (the new variable) which pulls high amps for about 3 to 4 minutes when shore power or the gennie is supplying power is the variable that sends things into a tail spin. By waiting a few minutes and adding things gradually I think we may get back to “normal” which to your point, is power management.

I did buy a Kill-a-Watt meter as someone above suggested. I will hook the microwave through it and watch the wattage to see if it goes crazy. Since I made it through a 4 minute test without an amp increase, I think I may try a little longer and see if we get an increase. I may pull the microwave and test it elsewhere, but not sure how to get it loose yet.

[Helmsman]

I took the boat out for the day today. We ran the gennie for AC most of the day due to the heat.

We also microwaved. This time, I just had one AC on, the fridge was getting power through the 12 volt connection, and the water heater and the stove breakers were off. We had no power issues at all. So, I think it was a power management issue.