Will a 1kw genny start my fridge *update*

[Toller]

A month or two go I asked here if a Yamaha EF1000, which will produce 8a, will start my refrigerator that draws 13a at startup. The majority opinion was probably; the fridge probably doesn't need 13a to start and the genny will probably produce more than 8a for a short time; so between the two...

As it happens, one retailer claimed that Yamaha told them the EF1000 will produce 3500w for 3 seconds, which is not supported on the Yamaha website. I called Yamaha and was told that their website says it will produce 1000w, so that is all it will produce. Eventually I got to the supervisor's supervisor, who said that it will do 3500w, but they are not making that claim anymore. (presumably they got complaints from people who didn't understand what "3 seconds" meant.)

So I bought the EF1000. It will actually start my shopvac, which draws 16a at startup. I haven't pushed it any harder, so I can't actually verify the

3500w, but it is good enough. Alls well that ends well.

Incidentally, Honda told me the absolute max on their EU1000 is 1000w and it will not start my fridge; I don't know if someone higher up would say otherwise.

[Tony Hwang]

Hi, If you think in terms of peak to peak rating. But that is measured is fractional seconds.

[Smarty]

There is no such thing as "peak-to-peak" ratings for a generator measured in "fractional seconds".

You might be thinking of "peak", "surge", "maximum inrush" or other such terms which describe the brief maximum current which the generator (and its' associated fuse/breaker) can deliver.

"Peak-to-peak" is used in electrical engineering to describe the amplitude / height of an analog waveform when measuring from the maximum negative to positive swing. For a sine wave (the most common form of alternating current), it represents a value which is about 2.8 times the average / RMS value.

Smarty

[Mark]

Does this generator use a DC generator with an inverter?

I think that in the case of a generator with an inverter, the surge rating is limted by the electronics in the inverter.

With the old fashioned mecahnical AC generators, the surge rating is much higher and is limited by the resistance of the windings...

Mark

[ransley]

pushing a unit is the way to break it, sure it will work but for how long.

[Big Al]

The shop vac has a universal motor, one with brushes and a wound armature, like in a power saw. The refrigerator uses a different type motor, it may not start even if the shop vac does. Why not just try it?

Al

[Toller]

Because I drained the carburator already. But if it draws 16a and the fridge only draws 13a, it ought to be okay. True, the power factors could be completely different, and that might change things.

[zxcvbob]

The shopvac has a universal motor and the fridge has a capacitor-start induction motor. They are not equivalent loads. Your test is invalid; sorry. (and I'm not sure which is the harder one to start)

Bob

[Toller]

Well, Yamaha says it will produce 3500w for 3 seconds. In the manual they say it will simply shut off in event of an overload, and they don't warn about overload breaking it. So, it seems likely that 2000w for 2 seconds, without the genny shutting down, won't damage it

[Stormin Mormon]

Well, gas it up and try it. Don't keep us all in suspense.

[Don Young]

As others have said, you have not in any way verified that your generator will start your refrigerator. You have only verified that it will start your shop-vac. These are the kinds of tests that marketers like to demonstrate, to make people think they have proven something they haven't. If it is important that the generator start the refrigerator, try it several times. I suspect the 13A refrigerator will be harder for the generator to start than the 16A shop-vac but since there are several unknown variables it cannot be determined except by testing. I believe it will be okay.

Don Young

[Dave Martindale]

What matters is how the different appliances react to low voltage.

The shop vac has a universal motor, which will draw less current on lower voltage and run slower. It's driving a fan, which is almost zero load at startup from zero speed. So if the generator's voltage droops under load, the shop vac will just take a while longer to get up to speed.

The refrigerator uses an induction motor, which draws more current when voltage drops. It's probably driving a piston pump, which should be easy to start if the fridge has been off for a while and pressures have equalized, but not as easy as a fan. So you may find that drooping voltage under overload means the refrigerator won't start at all, and either the motor or the generator will eventually trip on overload.

Dave

[Smarty]

Most likely neither the windings nor the inverter electronics will actually be the limiting factor. All generators use some form of circuit breakers and/or fuses to limit both the continuous current delivered as well as the transient surge demand which is imposed by big inductive loads like motors, etc. The breaker / fuse is deliberately chosen to protect the inverter / windings / etc.

Unless somebody is deliberately trying to circumvent this design by either putting a jumper across the breaker/fuse or repeatedly overloading the circuit and flipping the breaker on manually, the generator should know how to protect itself against the common start-up demands which typical appliances demand.

It is entirely possible though that the generator is designed and fused to only deliver a very small amount of extra transient surge current above its' normal steady state continuous rating. In this case, the 'fridge' could blow the breaker every time it cycles on its' compressor, if the generator is undersized.

[Toller]

Since people were actually interested, I tried it; leaving 5 minutes between trys. (Yamaha claims 3500w for 3 seconds, and then 1000w for 20 minutes, finally

900w indefinitely) Wattages are per the meter on the transfer switch, so they are approximate. When I tested on commercial power the refrigerator drew 13a for about a second, and then 1a to run.

The first time it went to 1500w for about 5 seconds and the generator tripped out. I reset the generator. The second time it went to 1500w for a second and then dropped to 100w. Normal operation. The third time it went to 1500w for 3 seconds and I flipped the transfer switch off, since it seemed to be like the first time and I didn't want to go upstairs to reset the generator. The fourth time was like the second; all normal.

I have have tried it maybe 3 times on commerical power and it has never held at 13a like 1 & 3. So the question is: Does the generator somehow cause it to sometimes take longer to start up, or is that a refrigerator issue that I just never happened to see before. I don't know enough about refrigerators to know. But, as I understand it, inverter generators hold the 120v; when they can't do it, they trip out. So, they only give 120v or 0v, never low voltage.

I hope never to use this on the refrigerator; I have a Honda EU2000 that I have used in 3 power outages. I bought this for another purpose where the EU2000 was too heavy, but liked the idea of having it as a backup for the backup. Hey, I hope never to use the EU2000 either; in the 2 years since I put a transfer switch in we haven't had an outage.

[Tony Hwang]

Hi, You just explained what I said in plain language. Yup, peak to peak, average, rms three terms commonly used. Remember stereo salesman used to use peak music power to sell El Cheapo amps? Kikewise! Marketing gimmicks are many and confusing to gemeral consumers.

[Smarty]

Tony,

Peak to peak means one thing and "peak" means another. "Peak" music power as mis-used by stereo salesmen (until the FTC forced the industry to adopt correct and standardized terms) was a term used to exaggerate the true average/RMS power which an amplifier could deliver. This has absolutely nothing whatsoever to do with "peak to peak", the term you originally mis-used.

Peak-to-peak, as the reference in Wikipedia correct states, merely indicates the size of a waveform from its lowest (negative) peak to its highest (positive) peak. If you have a scope in front of you, looking at a waveform, the peak to peak voltage is nothing more than the height of the signal in volts.

Generators make electricity, and one could describe the waveform they produce by saying it has a peak to peak voltage of 336 volts (assuming a sine wave and 120 volt RMS generator) but this is not a description of the surge capacity of the generator.

When specifying / characterizing the ability of a generator to provide transient, brief additional power, the term which electricians and electrical engineers use is "peak" or "surge" or "transient", but never "peak to peak". It may seem or sound similar, but is not the same thing.

Smarty

[Dave Martindale]

The induction motor in the refrigerator will take longer to start if the voltage is low.

That's probably true over a long time, but not necessarily true for short periods. If you overload the generator, the voltage almost certainly *will* drop somewhat. This may cause the generator to trip in a short period (and it did on a couple of your tests), but if the refrigerator comes up near operating speed before that the overload will be gone, the voltage will recover, and the generator will decide not to trip after all.

To be sure of what's going on, monitor the generator output waveform with an oscilloscope. Then you'll know. A meter may not respond fast enough to tell you anything about a transient voltage drop.

Dave