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Generator question: Is flickering power bad for a fridge? - Page 2 — Parallax Forums

Generator question: Is flickering power bad for a fridge?

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  • GordonMcCombGordonMcComb Posts: 3,366
    edited 2013-12-11 13:14
    And it was already old when I moved here. So more like 45-50 years old, I'm thinking. Hmm. Maybe that explains my rather high electric bills...

    You can pick up a Kill-a-Watt at Harbor Freight for $20, and see what it pulls over a day's period. Handy little thing. Using one now to help us decide which of two fridges to keep using, and which to Craigslist.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2013-12-11 13:31
    You can pick up a Kill-a-Watt at Harbor Freight for $20, and see what it pulls over a day's period.
    That would entail pulling the fridge out from the wall to plug it into the little gizmo. 'Not sure I really want to see what's back there after all these years! :)

    Seriously, though, thanks for the tip. I plan to order one as it sounds pretty handy.

    -Phil
  • RforbesRforbes Posts: 281
    edited 2013-12-11 17:17
    In regards to the initial question: YES you can, and WILL, damage your fridge. If the lights are flickering while powered by a generator, then that generator is:

    1-under-sized for the load it's connected to. (most likely)
    2-Has a static voltage regulator which isn't capable of maintaining the appropriate voltage under the connected load. (common, but not as likely as #1)
    3-If it actually has an automatic voltage regulator (extremely unlikely) it's faulty and isn't adjusting the voltage properly. (avr's are almost non-existent in small
    generator sets)

    The most probable cause of the lights flickering is an under-sized generator set. Many professional electricians don't understand how to properly calculate loads and and even more commonly, customers don't understand the limitations of the generator set after it's installed and they overload them.

    The reason this can, and WILL damage your fridge is because any time you see your lights flickering, you're either consuming power at about 42 hertz (or less) or your voltage has dropped to around 80 volts or less (assuming a single phase 120VAC circuit.) Or both. And either of these conditions is immediately causing a mild-to-severe overcurrent condition on your compressor motor. Sure, it might run a couple years with the occasional brown out or automatic re-try (which are common utility-side power problems) but you're definitely doing it no favors by running it in conditions like what was described originally.

    Concerning restarting the compressor too quickly after it's been shut off: yep, it's bad. Most refrigerant systems nowadays have lockout timers. It's bad for several reasons, and those reasons have more or less drastic effects depending on the type and design of the refrigerant circuit.

    Also- attempting to "hook up a capacitor" to a generator set is very doable- it's called power factor correction. If you have the requisite knowledge to do so, you'll also have the knowledge to realize it's not worth doing on an isolated bus (which is what you'd call a generator set powering your home, because it's the sole source of energy when it's connected to the load.) Since the load changes every time something turns on or off, so does the power factor of that load. So one set of capacitors will only help significantly under a specific load condition. Generally, the only thing you'll get is a more leading power factor (towards unity from the lagging side) or potentially a leading power factor (past unity, into the leading side) on the generator. This condition will overheat your windings, stator and rotor, and will most likely damage the voltage regulator. And lastly, if you were able to use capacitors to create a unity power factor (again- doable but bad practice) you'd be creating so many harmonics on your system that you'd start damaging other electronics the generator is connected to.

    A properly sized, good quality genset for the location in question is the right way to go. At very least, a load that is well within the capabilities of the generator set (rms wattage, power factor, starting va, etc)
  • Peter KG6LSEPeter KG6LSE Posts: 1,383
    edited 2013-12-11 17:20
    Rforbes wrote: »
    Also- attempting to "hook up a capacitor" to a generator set is very doable- it's called power factor correction. If you have the requisite knowledge to do so, you'll also have the knowledge to realize it's not worth doing on an isolated bus (which is what you'd call a generator set powering your home, because it's the sole source of energy when it's connected to the load.)

    Exactly what I was trying to say.!

    @ all

    The Kill O watt is one tool no geek should be with out ...... VA ( KVA ) PF Watts and amps and Hz and Volts .

    I have 2 . one is the EZ verison for my segway and one is just in my tool bin that I added a cord too so that it can be used Off the wall ( bettter to view the screen with )

    I have compared them to the Fluke Over priced clamp on gizmos and the 19 buck meter is Spot on ! .

    Its a very good limited voltage and current poor mans AC power meter and analyzer. ( sans fancy screen )
  • RforbesRforbes Posts: 281
    edited 2013-12-11 18:11
    Haha!! Just looked up the Kill O watt gizmo. Neat. :)
  • mayanktanwarmayanktanwar Banned Posts: 1
    edited 2015-06-03 21:52
    Yes, Flickering of power is not good for any electric home appliances like AC, Fridge, Heater, Mixture Juicer, Fans and more. By Fluctuation of power continuously harms Fridge Its stop cooling and wired get damages. To stop this power fluctuation put voltage stabilizer on fridge and other appliances. A voltage stabilizer is a device that produces stable voltage to electric appliances. Voltage stabilizer is a line filter. It is mainly used to protect appliances from high or low voltage damages. Voltage stabilizers are cheap in prices and best equipment for electronic devices for protection.
  • frank freedmanfrank freedman Posts: 1,983
    edited 2015-06-06 20:11
    Mark_T wrote: »
    Also generators are not usually rated for a varying load, so a 2kW generator which can run 2kW of lighting won't cope well with 2kW of _theatre_ lighting which needs to change frequently. You would typically want to derate a generate for a varying load.

    The dangerous failure mode for a fridge is when the mains supply goes too low for a long time - the motor stalls and then overheats, potentially then bursting and catching fire. Since it is immersed in an oil bath so it is an effective incendiary device (note that the refrigerant under pressure is not the issue). However power generating companies are well aware of the dangers of such brown-outs and the network should automatically trip out if this happens. With your own generator this is your own responsibility (a good generator control circuit will do the right thing and protect against under and over-voltage.)

    I suspect modern efficient fridges have much less powerful motors than in the past and are less likely to be able to overheat to the point of failure. Googling suggests fridge-related fires are rare.

    Actually this should never present a hazard in any refrigerator less than say 50Years old of the hermetically sealed variety. They are protected by thermal overload devices that should open the compressor circuit long before any dangerous situation could occur.

    As mentioned earlier, starting up too frequently can cause problems over time because trying to start the compressor when the cylinder is under high pressure puts a heavy load on the motor and they will heat up.

    Same thing applies but more so to your house A/C. As to the cap across the line, yep boom! Someone may have been thinking of the caps some people (and quick fix HVAC types) use to fix an aging A/C system. Some times referred to as a hard start cap, it gives the motor a bit of a boost on starting in older units. Probably helps in older units whose bearings and shafts are worn and sticking on startup. The gas pressures probably haven't changed that much since it was new. It goes in the start winding circuit and gets cut out when the motor rpm reaches a certain point. No boom. Well at least not until you get handed the bill by the AC&R guy who came out to do a "tune up" and wants to charge you $150.00 for a hard start kit. Opinions are all over the place on this topic, but if it worked right out of the install, then likely if you need a hard start kit, you may be looking at a new compressor sooner than you would like. How much time it buys you is anyone's guess.


    Y'know, there is one other thing that could kill the fridge if it is a newer one, say less than ten years or so. Nearly everyone I have seen or checked out when getting ready to repair or replace the last one I had, all were loaded up with electronics to control various parts or all of the functions of the unit. If you kill the board that controls the frost free, you may still have a fridge, but you will be back to the 50's and regularly defrosting your fridge and god help you if you live in a rather humid part of the country. We now have a 2013 unit and everything is controlled by a little computer board and SSRs, and stuff. Even the little door that opens when you get ice is moved by a stepper motor circuit. So a crappy generator with poorly shaped output or spikey voltages may not always harm the compressor, but those little electronic boards are expensive. This fridges predecessor had a failure on the board for defrost. 2 inch square not many components, $35.00!!!! And that was cheap at discount.....
  • frank freedmanfrank freedman Posts: 1,983
    edited 2015-06-06 20:33
    @ potatohead,

    Like you I prefer to oversize rather than undersize wiring. for anyone wondering just what to use, go to your friendly Home Despot and look above the bulk wiring rack. There in black and white (and in line with the current (pun alert) NEC specifications) will be the current carrying capacity "ampacity" of all the gages and types they sell and the temp ratings at which the values are valid. You will never go wrong if you exceed the NEC unless your municipality went even stricter. If you have an electrician do a project for you, don't be afraid to question him. We had one that wanted to do a hot tub for us which required a 50A service. He wanted to do 110' / #8 wires. That would have been a red tag for sure. City inspectors are > $100.00 per hour on a re-inspections. Code now for a run containing 2 hot, 1 neutral, 1 ground 50A means #6 for all, and for the outside run, 3/4" conduit. How do I know this? Was told cost would be less if he did not have to pull the permits. So I pulled them. He was right, cheaper if not following code. So now I will be doing it with the assistance of another electrician who is willing to work with me on the install.
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2015-06-06 22:51
    If one really is considering a generator as backup for a refrigerator due to frequent power outages, why bother with electricity at all?

    There are propane refrigerators that actually work very well with no mechanical parts to wear out. The pump works like a coffee perculator heated by a tiny flame.

    Here is one that is both 120VAC and propane.
    http://www.bensdiscountsupply.com/dometic-servel-rge400-propane-gas-refrigerator.aspx

    I'd rather have quiet propane as an off-the-grid backup than running a gasoline generator that is mostly intended for temporary lighting and construction use. One can also have a propane hotplate for cooking when electricity is not available.
  • potatoheadpotatohead Posts: 10,261
    edited 2015-06-07 08:04
    Old thread, but I just got one of those type of fridge. It came in my Grandparents old trailer from the 70's, which I'm restoring and camping in now. :)

    I was kind of stunned at how little gas it uses. Ramp up is slow. Takes about a day to really reach optimal temperature. If one isn't in and out of these things all the time, they work well. Interestingly, the one I have has a simple bulb / wire type thermometer taped in there to monitor ambient temperature inside from the outside. It's about a half degree to degree of loss each time it's gotten into, unless one is very quick. Recovery on that is roughly half an hour to an hour, depending on outside temp. Right now, I'm toying with the idea of a little fan to improve airflow in the back where it's heat exchanger is.

    When left closed for a day, it hits about 20 degrees F in the freezer section, and will freeze everything in there on the max cool setting. Perfect for active use, as the food access losses prevent freezing in the main compartment. So, I fire it up just prior to a trip, right along with the heater set to low as both a "is it all still working OK?" test, and ramp up for the fridge.

    Haven't tried AC operation yet.
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