Generator no longer powers refrigerator. - Page 1
Forum section: electronics / general

author: mjk.kirschner
author_rank: Newbie
timestamp: September 23, 2020, 02:44:00 pm
content: Hello,A family member bought a cheap generator a year ago and tested it out with various household devices before putting it into storage. It worked fine at the time. In particular it powered a refrigerator and 1500 watt resistive heater no problem. It never seemed to play nice with the furnace though.It's been tested on propane only, this is the same or similar generator:https://www.homedepot.com/p/Sportsman-2-000-1-400-Watt-Dual-Fuel-Powered-Portable-Generator-Runs-on-LPG-or-Regular-Gasoline-801477/206507850Recently a storm knocked power out for an extended period of time and they tried to use the generator to power the refrigerator. Of course the refrigerator compressor failed to start this time.We hooked up a scope, but don't have much experience looking at generator output, but our feeling was it looked pretty terrible. The trace is without load. Under load the sin wave still has multiple smaller peaks, but the frequency gets closer to 60hz.Curious if this is a standard output for a cheap generator? Thoughts on if the generator has degraded in some way and if it's repairable, or if it's more likely somehow the refrigerator?

author: MarkF
author_rank: Super Contributor
timestamp: September 23, 2020, 04:00:49 pm
content: That waveform looks reasonable for anon-inverter type generator.It's not going to be pretty. I can't read the frequency; but, it should be close to 60Hz.Was the refrigerator the only thing plugged into it?You want to insure the refrigerator is the only thing plugged in and that the generator is running at full speed.The inrush current for compressor motors can be quite high.I suspect the generator is not big enough to start the compressor(and not being able to start the furnace hints to that also)Especially if it is a big refrigerator.To be sure you would need to measure the inrush current when it starts.(i.e. with clamp on meter with inrush capabilities)

author: David Hess
author_rank: Super Contributor
timestamp: September 23, 2020, 05:21:13 pm
content: Quote from: mjk.kirschner on September 23, 2020, 02:44:00 pmDid you use a longer or thinner extension cord to connect the refrigerator to the generator? Extra resistance could prevent the compressor motor from starting.

author: Technomaniac
author_rank: Contributor
timestamp: September 23, 2020, 11:55:55 pm
content: Extra resistance might allow the generator to handle the excess load as well. I bought a homemade setup years back, a Honda 4 stroke motor coupled to a Davey 1KVA alternator. Very nicely built from inch square tubing by an electrician friend. On wheels. The reason he replaced it was that it wouldn't start a fridge, you need a much higher rating for starting an electric motor under load. Could be that there's a ferrite core in there somewhere that overheating has cracked, might explain the harmonics. The larger plants are everywhere now at reasonable prices, Go bigger !

author: james_s
author_rank: Super Contributor
timestamp: September 24, 2020, 04:26:12 am
content: That looks about like what I've seen from cheap conventional generators. How does the generator behave when the fridge tries to start? Does the engine bog down? My generator is the inverter type but I had an issue with the voltage sagging under heavy load and the engine failing to rev up sufficiently, I discovered that mud daubers had nested in the exhaust and packed it with mud which was hard like cement and was restricting the flow. I have also seen stale gas and gummed up carburetor jets result in reduced power. The ethanol put into most US gasoline these days is awful stuff for small engines, especially those that may sit for extended periods. Ethanol gas only lasts a few months before it goes bad, even with stabilizer. Worse, it sucks water out of the air forming a layer under the fuel that is very corrosive. I have seen carburetors completely destroyed by ethanol fuel, the old pure gas would gum up but even after sitting for 20 years you could still clean out the carburetor and be good to go, now after a few years it will be so badly corroded that it crumbles.

author: Dundarave
author_rank: Regular Contributor
timestamp: September 24, 2020, 05:15:50 am
content: You might want to check to be sure the refrigerator isn’t/wasn’t in the middle of a defrost cycle when you tried to get the compressor to fire up. The defrost timer mechanism shuts off the compressor & turns on a heater coil for a non-trivial amount of time.Just a thought.Btw, running some brands of furnaces on a generator could be problematic, because the flame detector requires a tiny leakage to earth ground to function, otherwise the microprocessor will shut the furnace down. Thus the generator would likewise need be be earth-grounded, but I don’t know about the safety of doing that...

author: mjk.kirschner
author_rank: Newbie
timestamp: September 24, 2020, 05:31:42 pm
content: thanks for all the responses!We used 12 gauge 25ft extension cords both times, copper conductors.Only used propane.The furnace actually started but as @Dundarave mentioned, it turned off after a few minutes, we think because it did not detect the leakage to earth ground.We'll double check it for bugs or rodents nesting, it was stored outside, but in a "waterproof" container.

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 24, 2020, 10:30:35 pm
content: Check the start and run caps in the refrigerator. Might need to add a hard start kit if there isn't already a start cap.

author: bob91343
author_rank: Super Contributor
timestamp: September 24, 2020, 10:49:44 pm
content: If a refrigerator is switched on right after it was running, the motor usually won't start due to the extra load of high pressure. It needs to rest for a while, typically an hour or three.I doubt that's your problem because you have given it plenty of rest. So the problem is either the refrigerator or the generator. Plug the refrigerator into the mains and measure the startup current. Then check specs on the generator to see if it's designed to handle that.Do you have the generator running at speed before connecting the load? Expecting it to start under load may be asking too much.

author: james_s
author_rank: Super Contributor
timestamp: September 25, 2020, 02:22:19 am
content: The critical part of the diagnosis is whether the engine holds RPM or bogs down. If it holds RPM then the engine is not overloaded and the problem is electrical. If the engine bogs then it is being overloaded and the problem could be either electrical (too much load) or mechanical (engine not developing rated horsepower). If it is the engine, some other things I forgot to mention. Check the air cleaner, a clogged air cleaner will have a similar effect to restricted exhaust. If it's the newer OHV type in particular (looks like it) check the valve clearance, there will be an adjuster nut on the rocker arms, specifications vary but they should be available, both should be just a tad loose on the compression stroke when both valves are fully closed. Next thing I'd try is a compression check, it's possible the rings are worn or even just stuck. How has the maintenance been? These small splash lubricated engines have no oil filter and should have the oil changed every 50 hours of operation or once a year, whichever comes first. People who experience lengthy power outages often forget that this means the oil should be changed every 2 days if you're running the thing continuously.There's a guy named James Condon on youtube who fixes a lot of generators and other small engines, it's a decent channel if you tinker with this sort of stuff, he's solved a few tricky ones.Oh and one other thing, pick up one of those Kill A Watt gadgets and use it to measure the power drawn by various things you want to run off the generator. It won't give you the startup surge but it can tell you the running watts, VA, power factor and other important bits. Keep in mind that generators are typically rated in "watts" but it's actually VA. You can burn up the windings by loading them up with low power factor loads.