I let a friend of mine use a 6500 watt generator that ran my house great, when he brought it back he said it was getting hot and stalling but could run 110 plug. He blew up lots of appliances, how can I make sure its ok to use in my home now?

  • 3
    The first thing I'd do is find out what he meant by "he blew up lots of appliances" - in what way did they "blow up"? Next, I'd hook a voltmeter to the generator and run it with no load, then put a cheap 1500W heater or two on it and check voltage under load. My guess is that the generator can't keep up with heavy loads (or has a significant lag before it does), so when an appliance like a refrigerator turns on, the sudden load drags down the voltage, causing a "brown out" that damages the appliance.. – Johnny Feb 2 '16 at 22:33
  • Thanks for your answer, his oven, a TV and 2 charter receivers do not work anymore. He could plug in to the 110 outlet just fine, this generator was his before I bought it and ran his house before. I heard if you don't shut main off it could screw up the generator. – Dan Cowdrey Feb 2 '16 at 23:29
  • 12
    If you don't turn the main off, you can blow up the generator, blow up appliances in your house (and appliances in neighboring houses that are on the same power company circuit), not to mention being a hazard to power company workers, and probably illegal. Never connect a generator to a house unless using a transfer switch or approved interlock device that will ensure that the generator feed is never enabled at the same time the main power is on. – Johnny Feb 2 '16 at 23:34
  • 1
    If you back-fed utility mains into the generator, might that make its generating alternator into a motor and turn the engine into a compressor? If that happened while it was running, you're looking at an extraordinary amount of energy to dissipate as heat, potentially why it might get red hot. It's probably totalled. I wouldn't touch it! – Billy C. Jun 4 '16 at 4:32
  • 2
    I bet he overloaded it.... 6500 watts is not very large and if he was running an oven he likely overloaded it. That caused the output voltage to drop (I'm guessing here that it isn't a high end, well regulated genny). When the voltage drops (much like the dreaded "brown outs" in cities during the summer) many devices will draw more current, exceeding what they can handle (transformers in power supplies, motors especially) and they're toast... literally ;) – PaulBinCT2 Jul 27 '16 at 15:00

You don't use it "in" your home so that solves the most direct safety bit. Then you avoid ever loaning that friend your tools ever again, since he both doesn't treat them right and is dishonest about it or he just doesn't know any better, either way it equals abused broken equipment.(Its very common.) I don't see how it could damage a stove other than severely voltage spiking the electronic controller bits in a very modern stove, but even those are generally tolerant of brownouts and small over voltages and none of it cares much about frequency. Home stoves are most commonly on 50amp 240v circuits 50*240=12Kw I know my typical range the bake element is 2400w the broiler another 2400, small burners on high about 1500 and the large coils are about 2000-2200 which adds up past 6500 very fast.

Have a small engine shop check and tune the engine, fuel system, governor and such, or do it your self if you have the skill and tools.(this doesn't address the alternator half but with the exhaust being so hot it could be engine related)

Electrically: does it have a circuit breaker or fuses that need attention? Beyond that faults could be from burning the windings enamel insulation, brushes if it has mechanical brushes, shorting or high resistance(or both)caused by moisture or corrosion(rain, fog, damp storage, etc). All you can really do without significant electrical training is to get it running and check the voltage unloaded, and then again while loaded (with a known calculated load, preferably resistive, not a motor) the standard range is 115-125v and 230-250v. I don't know the details of the that generator's windings, if it is 240 with a transformer for 120 or true 2 phase 120/240, or split phase just like mains power. In split phase neutral is attached to the center of the 240v windings to get 120v.

And if your multimeter has frequency and power factor options or you have a friend with an oscilloscope check that it is maintaining close to 60hz(56-64 ish loaded and unloaded) and that the power factor is above .95 while powering a pure resistive load.(a simple heater or 2 large stove elements)

Lastly as a safety note be very careful doing this with a cheap multimeter the sub $50 jobbers don't have correct fusing(despite the self "certification" on the label) the also don't inspire confidence in the tested value and won't read the true RMS power.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.