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KE2KB 11-15-2012 09:07 AM

Generator power for PC?
 
Hi;
I'm not sure if this post belongs here, or in the PC forum, but I figure you guys know more about generators than they do;

I just got through a 7 day outage here in NJ. We were running our refrigeration, the gas fired hot water furnace, lights, and several computers from a 10yr old Craftsman 3600W/5300W surge gasoline powered generator.

I have read a lot about using (portable) generator power for running PC's, but after the Oct 2011 snowstorm when we had a 3 day outage, and this 7 day outage, we have not had any problems with the PC's. All were connected through good quality surge protection.
Interestingly, when I tried to connect my APC back-up supply to the generator power, it kept beeping and switching back and forth between AC and battery, so I disconnected it and used only the surge protection.

I understand that the inverter type of generator produces a much cleaner power, but these are a lot more expensive than the standard ones.

Any thoughts on this?

Thanks

FW

tylernt 11-15-2012 10:21 AM

Your generator is either producing the wrong voltage (over or under), or isn't producing an accurate 60Hz. Your UPS is trying to protect your PC from this out-of-specification power.

A new inverter generator uses electronics to regulate the frequency to a perfect 60Hz, whereas your old generator simply has a governor on the carburetor to regulate engine speed to 3,600RPM (typically). As long as the engine is running at the right RPM, output power is 60Hz. If your governor isn't working right or you're overloading the generator, the engine will run too fast or too slow which gives you something over or under 60Hz.

It's easy enough to test the voltage from the generator, not sure how you can test the frequency though?

av-geek 11-15-2012 10:43 AM

The speed your generator operates at, and thus the frequency and voltage produced, can vary depending on the load. Like KE2KB stated, most older generators simply use a mechanical governor to regulate the speed to 3600RPM (3600RPM / 60 minutes in a second = 60 cycles a second)

If a device connected to your generator starts or stops, it can affect the speed of the generator. You stated this is a 3600 watt generator. Do you have a refrigerator or other motor load connected to it? If so, these devices can pull large amounts of current momentarily. While your fridge doesn't pull but probably 200 watts while running, it may pull up to 2000 watts when starting the motor. This will make your generator slow down and produce a much lower voltage and frequency before the governor detects the extra load and cracks open the throttle. By that time, the demand is gone, and the generator over-speeds, producing a higher voltage and frequency than needed, thus the governor closes the throttle...this may set up an oscillation for a few moments until the govenor stabilizes. Your computer's UPS is sensitive to these voltage fluctuations and will switch off to battery whenever voltage and frequency are not to spec. A surge protector will NOT protect your computers from this abnormal power!

If you ever notice your generator revving up, producing sort of a "runnna, runna, runna" kind of sound, IMMEDITELY disconnect anything plugged in. This sound means your generator is oscillating between fast and slow and is throwing out really BAD power!

obadran 11-15-2012 12:41 PM

You might want to consider a line conditioner.

For example http://www.tripplite.com/en/products...xtModelID=4301

There have been a lot of posts where generators don't quite spit out 120V @60Hz and a line conditioner will smooth this out and maintain a constant 120V @60Hz.

Not all UPS's will do line conditioning. If the input voltage is crap, the UPS will just switch over to battery.

Fairview 11-15-2012 01:09 PM

Until you can feel comfortable spending your hard earned money on an inverter generator check into purchasing the measuring device Kill-A-Watt to see where your genny stands on volts, Hz etc.

I had one until I loaned it and I guess the borrower thought it was great.

HVAC_NW 11-15-2012 01:31 PM

Switching power supply is fairly resilient, but generator is small, so its susceptible to excess voltage dip and cause the computer to drop. You'd need a UPS to get around this... but the thing is, UPSs are pickier than necessary, so the excess THD and frequency swing will never allow the load to remain on generator power. To get around it, you'll need an online double conversion UPS, which is expensive. Computers are not picky about frequency at all and many newer power supplies are rated for 100 to 240v without the need for switch setting.

Only issue is that when your power dips below 96v for more than the hold up time the power supply is capable of, the computer will either shut off, or reboot.

If you use a laptop with a functioning battery, you're all immune from these issues though. Just run it on generator and if it dips, battery in the laptop picks up.

KE2KB 11-15-2012 01:42 PM

Thanks for the info/advice.
I never heard any significant speed fluctuations from the generator. We weren't running anywhere near its rated load, but did have two refrigeration units (a freezer and a fridge) connected, so these were starting and stopping. There was an occasional change in pitch from the generator, but it did not seem to be oscillating.

I do have a DMM that can read frequency, so I can check it.
My APC UPS does not have line conditioning. I am familiar with that type, and it is a lot more expensive than the one I use.
My thinking on using the surge protectors is that at least I will prevent the spikes and high frequency noise from getting to the computer.

FW

Dave632 11-15-2012 02:06 PM

Quote:

Originally Posted by KE2KB (Post 1052876)
...
There was an occasional change in pitch from the generator, but it did not seem to be oscillating.

...

That change in pitch indicates a change in line frequency.

What DC voltage does your laptop require? You might be better off getting some of the new hi-tech batteries, charge them off the generator, then hook them up to your PC.

KE2KB 11-16-2012 08:17 AM

Quote:

Originally Posted by Dave632 (Post 1052896)
That change in pitch indicates a change in line frequency.

What DC voltage does your laptop require? You might be better off getting some of the new hi-tech batteries, charge them off the generator, then hook them up to your PC.

I don't have a laptop. The iMac I referred to is a desktop machine.
I checked out some of the line conditioners on Amazon.com. I guess when I'm ready to replace my current APC UPS, I'll get one that also has line conditioning.

FW

jagans 11-16-2012 09:41 AM

Gen
 
The output from your Genny is probably falling below the threshold of acceptance to your APCUPS. The output from generators can vary widely. OK with most stuff, not with a UPS.

raylo32 11-16-2012 10:07 AM

This is another good argument for having an inverter generator or a good power conditioner. Having a generator that will charge the UPSs allows one to run the generator intermittently to warm the house and cool the fridge and still keep the PC and network gear up and running during some or all of the times the generator is off.

frenchelectrican 11-17-2012 12:06 AM

Quote:

Originally Posted by raylo32 (Post 1053484)
This is another good argument for having an inverter generator or a good power conditioner. Having a generator that will charge the UPSs allows one to run the generator intermittently to warm the house and cool the fridge and still keep the PC and network gear up and running during some or all of the times the generator is off.

There one thing about the UPS the crictal item most peoples are not aware is the battery capicity rating.

Most common resdentail UPS can run about 20 to 30 minuites at rated load unless you have larger battery supply then it can extened the run time but at low load demand it will last much longer.

Myself I do have UPS but that is used for limited time to let me start up the diesel unit but once I have it running the diesel unit will take over until the uility source is back on steady ( I useally wait about 15 min to half hours before I switch over due the first few miniutes is not really stable due it can flicker back off and on couple time until the sytsem stablized )

Now for the readers for the gaz driven generatours the sound like what runna, runna, which we call them hunting or surgeing due on low load mode the governer is not really holding back the speed correct due there are few possible issue.

Most common curpit useally are.

A) weak goveroner spring.

B) too wide a margin on goveroner setting.

C) idle screw is not set up correct useally either too rich or too lean ( lean is more common curpit )

D) Idle jet port is partall clogged.

E) This part if running near full load and do surge a bit then the carbuatour is either set wrong or have main jet clogged.

Those item is pretty common on gazoline carbed engine for dry fuel gaz like GLP ( Propane ) or Naturel ( Natural ) gaz the A, B ,E will be most common cuirpit beside the GLP supply if the supply line is too small the situation E as I posted will result like that when you run in full load and sound like you are running out of gaz actually you are running too lean.
( this part if you run lean too long it can overheat the engine or do some damage )

And make sure you have clean gazoline with fuel stabilzer in there that useally take care most of the situation unless you plan to keep the unit off the line like storage then try to drain the carbuatioer or run it out of gazoline so keep the fuel bowl empty.

Merci,
Marc

raylo32 11-17-2012 05:43 AM

I don't try to run a desktop PC during outages, I use my laptop and smartphone. I have a big PC-sized UPS hooked up to my network router and cable modem. It will run those for several hours. Yes, the cable company here has backup on their system that will keep connectivity up for a good while during many outages. So charge all the batteries on the generator every few hours whilst running the fridge and furnace. Then shutdown for awhile. Anyway, that's the plan.

Quote:

Originally Posted by frenchelectrican (Post 1053989)
There one thing about the UPS the crictal item most peoples are not aware is the battery capicity rating.

Most common resdentail UPS can run about 20 to 30 minuites at rated load unless you have larger battery supply then it can extened the run time but at low load demand it will last much longer.


Merci,
Marc



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