Standby Generator and Microwave

[Wingman]

Why won't my 5500 watt (continuous) standby generator run my 1250 watt microwave? Even if the microwave is the only thing plugged in, it will not run correctly. The microwave comes on and then immediately "bogs" down, and the light gets very dim. The generator shows no adverse reaction when the microwave is switched on.

 

[Kruse]

You didn't say the brand name of your generator, but some generators send out a very dirty sine wave. Some electronic devices need a clean sine wave. Your microwave might be one of them.

 

[cchase]

Check to see if the generator is a pure sine wave generator or a "modified" sine wave generator.

 

[Ramblejam]

Generac?

 

[SwampSurvivor]

Agree with Kruse - the sine wave isn't good enough for it to work.

I bet if you were to plug a box fan into the generator, you would hear the fan motor buzzing.

 

[95busa]

Grid power is three phase...much cleaner pure sine.

 

[montr]

Originally Posted By: Wingman
Why won't my 5500 watt (continuous) standby generator run my 1250 watt microwave? Even if the microwave is the only thing plugged in, it will not run correctly. The microwave comes on and then immediately "bogs" down, and the light gets very dim. The generator shows no adverse reaction when the microwave is switched on.

Did you check if the generator governor is adjusted for the right speed? Most portable generator (except inverter models) need to run at 3600 rpm to generate 60 Hz. With the generator running the load, check if you get 60 Hz. A useful and cheap device to check this is a "Kill a Watt"
http://www.newegg.com/Product/Product.aspx?Item=N82E16882715001

 

[Wingman]

Sorry. I did not give enough information. It is a Troy Bilt generator. It has a 220 outlet. I have it plugged into my whole house via the 220 oulet and I load shed as necessary to keep the watt usage within capability. Everything in the house works fine except the microwave. So is it just a "dirty" output from the generator?

 

[Kruse]

Originally Posted By: Wingman
So is it just a "dirty" output from the generator?


That would be my GUESS. If you had an oscilloscope to hook up to the sine wave, you would know for sure. Some of outputs coming out of generators are square waves or the output may even be in the shape of a trapezoid. An incandescent light bulb really wouldn't care. An electronic circuit probably would.

 

[Chris142]

Our power went out about 30 minutes ago. Going to be testing. My 3200w hf generator at lunch time. Right now its running moms oxygen machine , blowet for the propane heater and the fridge

 

[RF Overlord]

Originally Posted By: Kruse
Originally Posted By: Wingman
So is it just a "dirty" output from the generator?
That would be my GUESS. An incandescent light bulb really wouldn't care. An electronic circuit probably would.
Which is exactly why inverter generators were developed.

A "regular" portable generator is primarily designed to power light bulbs, hand tools, and other simple resistive or inductive loads which don't care about the quality of the waveform. Electronic appliances like microwaves, televisions, computers, etc. can be more sensitive to needing "clean" power.

 

[mikered30]

Would a line conditioner fix the problem?

 

[Chris142]

My hf genny ran the microwave fine.

 

[flanso]

Plug an ac clock with a sweep second hand into generator power. Then compare the second hand speed with that of your watch. Adjust the generator's speed to get the second hand on the clock to match your watch's. That should give you pretty close to 60 cycle current. Then retry your microwave.

 

[JHZR2]

Any cheap generator puts out horrible dirty power. We were just doing experiments on energy storage tied to cots generators two days ago. It's amazing how lousy the power quality can be with funny transient and oscillating loads. The governors and voltage regulation can be quite poor, and step loads and inrushes can throw voltages down to 50 or up to 170V.

 

[Wingman]

Electrical knowledge is not my strong suit. Is there any device that can be added to "clean up" the power signal?

 

[exranger06]

Originally Posted By: 95busa
Grid power is three phase...much cleaner pure sine.

3 phase has nothing to do with how clean the sine wave is. Pretty much every house in America (not including apartment buildings) has only single phase service.

 

[eljefino]

If you have it wired up to the 220 on your generator you have to halve the power on any one of the two "legs"/ phases of your box. Either shed all the other load or plug the microwave in to another outlet in the kitchen.

You could have a weak winding in the generator, for example.

You should have a 110/220 switch on the generator, try running it on 110. It adds up the pair of windings to give 30+ amps all on one phase. Only issue will be anything that ran on 220 in your house will see zero.

 

[meep]

is it connected via extension cord? I'm thinking it's a cord and it's way too small gauge (too light duty).

if the problem was operating frequency being too low, the genset would bog when the microwave turned on.

 

[Wingman]

The generator is plugged directly into the main electrical panel (220V) for my home so the panel receives the power as if it was coming in from the main line. No extension cords are required.