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Old 08-02-2013, 03:28 PM   #1
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Would this work for computer on generator


Hi;
I want to be able to run my PC on generator power (5500 watt gasoline powered, just standard genset, no inverter).
I have been reading up on the fact that most portable generators produce power that is too unstable for sensitive electronics.

I already own an APC UPS, so all I need is the power conditioner, not a battery back-ups.
I found this APC model on Amazon. Seems like a good price for the 1200VA that it is rated for.
I calculate 1200VA would handle about 10A @ 120V. Am I correct in this calculation, or is it not so simple as that?
Here is the link to the unit I want to buy:
http://www.amazon.com/APC-LE1200-Aut...er+conditioner

When our power was out for 7 days after Sandy, I did not run my PC (I had just replaced the mobo 6mos earlier and didn't want to chance it), but my sister's Apple iMac was plugged in through a good quality surge protector and ran fine. I didn't like the idea of her running her pretty new IMac on the genny, but she was more than willing to take the chance. So far there have not been any problems with the Mac, or with an older Dell and the TV and FIOS STB that were running off the genny (all through surge protection). Perhaps the generator (a 10+yr old Craftsman) had a cleaner output than some.

I'm also thinking of the treadmill. It has electronics that seem to be even more sensitive than the computers, with the motor drive circuit having to be replaced once already. So I probably wouldn't run the TM off the generator, surge protection or not. I cannot afford a conditioner that would be able to power it.

Thanks for your advice

FW

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Old 08-02-2013, 04:07 PM   #2
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Would this work for computer on generator


Quote:
Originally Posted by KE2KB View Post
Hi;
I want to be able to run my PC on generator power
(5500 watt gasoline powered, just standard genset, no inverter).
5500watts is a LOT of power just for a computer.

Quote:
I have been reading up on the fact that most portable generators produce power that is too unstable for sensitive electronics.
That's where the battery and INVERTER come into play

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Old 08-02-2013, 06:41 PM   #3
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Would this work for computer on generator


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Originally Posted by TarheelTerp View Post
5500watts is a LOT of power just for a computer.


That's where the battery and INVERTER come into play
The generator wasn't purchased primarily to run the computer. It was purchased after Sandy knocked out our power for 7 days and we were so lucky that my brother has a generator and didn't need it.

The APC UPS (model BR800) will not switch to mains power when it is plugged into the generator directly. I want to try it when I use a good surge protector in line between it and the genny, but I don't think that is any sort of solution.
From what I have read, the conditioner should go between the generator and the UPS (if the UPS doesn't already have power conditioning) so that it can work properly.

FW
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Old 08-03-2013, 05:08 AM   #4
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Would this work for computer on generator


I would not be using a standard type genny on a computor,
A invertor style is more stable so would be ok.
But not an stardard style genny as the output is not stable enough.

To stabilise the genny,
You will need a decent stable load on the genny,
At least 50% of its capacity, and it must be stable.
I.E. something that doesn't cycle on and off !

With a stable load, the output of the genny would be stable.

Last edited by dmxtothemax; 08-05-2013 at 07:09 PM.
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Old 08-03-2013, 09:53 AM   #5
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Would this work for computer on generator


I use that same APC unit and a Tripplite Isobar with ham radio equipment and computers in my motor home for cleaning up the often questionable power available wherever we are, when running on our generator or inverter. Works well, reasonably priced.
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Old 08-04-2013, 02:36 PM   #6
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Would this work for computer on generator


Most computers and other electronics these days are not sensitive to power quality issues. That was much more of a problem in the past, when switching power supplies were new technology and kind of finicky. Today, many electronic devices are designed to run on any standard utility source worldwide - that's roughly 90 to 250 volts, 47 to 63 Hz, with no adjustments or settings to change. Any generator will work fine with that. It is pretty unlikely that a modern computer would have any problem at all running on your generator, with no filtering, surge protector, or UPS. Note that the power quality coming out of a UPS running on battery is usually TERRIBLE. They contain super cheap inverter circuits that produce square waves. That's much harder on an electronic power supply than any generator's output.
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Old 08-05-2013, 07:15 PM   #7
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Would this work for computer on generator


Quote:
Originally Posted by mpoulton View Post
- that's roughly 90 to 250 volts,
Trouble is !
The output of a 240v genny will easily exceed 250v on occasions,
I have seen voltages in excess of 300v for a short time,
before the regulators can kick in.

Modern invertors are much quicker,
but the standard type gennys,
some can be very slow to react.

Especially if a big load has just kicked out.
Wham !
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Old 08-05-2013, 10:09 PM   #8
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Would this work for computer on generator


Quote:
Originally Posted by dmxtothemax View Post
Trouble is !
The output of a 240v genny will easily exceed 250v on occasions,
I have seen voltages in excess of 300v for a short time,
before the regulators can kick in.

Modern invertors are much quicker,
but the standard type gennys,
some can be very slow to react.

Especially if a big load has just kicked out.
Wham !
Still probably OK. for 240V input. the lowest rated filter capacitors typically used are 350V, and 400V diodes. The switching devices are almost always 400V or higher. I just don't see it being a problem with modern equipment.
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Old 08-05-2013, 10:36 PM   #9
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Would this work for computer on generator


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Originally Posted by mpoulton View Post
Still probably OK. for 240V input. the lowest rated filter capacitors typically used are 350V, and 400V diodes. The switching devices are almost always 400V or higher. I just don't see it being a problem with modern equipment.
Most modern electronic appliances have over voltage protection devices
in them, this is usually just a "VARISTOR" which is just a large zener diode,
it sits across 240v mains input after the fuse, should the mains rise above
275v ac, then this little device goes short circuit, places a short across the mains supply, this usually blows the fuse.
These little devices usually leave a big mess.
And usually scares the crap out of the owners,
should they be lucky enough to hear it !

Most of the time the damage to other area's is minimal.
But a fix requires a electronics engineer usually.
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Old 08-06-2013, 12:18 PM   #10
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Would this work for computer on generator


Quote:
Originally Posted by dmxtothemax View Post
Most modern electronic appliances have over voltage protection devices
in them, this is usually just a "VARISTOR" which is just a large zener diode,
it sits across 240v mains input after the fuse, should the mains rise above
275v ac, then this little device goes short circuit, places a short across the mains supply, this usually blows the fuse.
These little devices usually leave a big mess.
And usually scares the crap out of the owners,
should they be lucky enough to hear it !

Most of the time the damage to other area's is minimal.
But a fix requires a electronics engineer usually.
I've had experience with varistors. Once I was testing a unit on 240V when suddenly there was a loud crack and a puff of smoke from inside. Before opening it up I already knew that someone had installed a 150V varistor instead of the required 275V one. I simply replaced it and the fuse, and everything was fine. The others who saw the incident couldn't believe I was so calm about the 'explosion'.

Considering that the inexpensive APC UPS I own puts out a lousy wavefore, I would hope that at least the output of that inverter is routed through the surge protection where perhaps the worst spikes get clipped.

The genny I own (my dad owns it actually) is a Westinghouse WH5500. In the specs the following line appears:
"Features our exclusive VR System-Voltage regulated power for all your electronics".
I would hope that they can back up that claim if someone has an issue with their electronics.
Still, I don't know whether I would connect an expensive TV to the generator output without line conditioning. Of course the point is moot is the power is out, and the TV is out as well...

FW
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Old 08-06-2013, 05:26 PM   #11
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Would this work for computer on generator


If a substancial portion of the genys load is stable, i.e 50%.
The the output voltage of the genny would be reasonably stable,
And safe to use a television.
The only time to worry is if you have large loads on the genny,
like an A/C unit, that is constantly kicking in and out,
This is where the problem lies.
Cause if a a/c kicks out, the load on the genny is suddenly much lighter,
the output voltage will usually rise,
usually only for a short period,
till the regulators can compensate.
I have seen some gennys very slow to respond,
And sensitive electronics don't like this at all.
Other loads don't seem to mind as it is usually only brief.
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Old 08-07-2013, 01:18 PM   #12
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Would this work for computer on generator


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Originally Posted by dmxtothemax View Post
If a substancial portion of the genys load is stable, i.e 50%.
The the output voltage of the genny would be reasonably stable,
And safe to use a television.
The only time to worry is if you have large loads on the genny,
like an A/C unit, that is constantly kicking in and out,
This is where the problem lies.
Cause if a a/c kicks out, the load on the genny is suddenly much lighter,
the output voltage will usually rise,
usually only for a short period,
till the regulators can compensate.
I have seen some gennys very slow to respond,
And sensitive electronics don't like this at all.
Other loads don't seem to mind as it is usually only brief.
So an AVR like the APC unit I posted the link to should stabilize the voltage more quickly, right?

In the end, I think I can do without my PC during an emergency, more so if the Internet is out as well. I cannot speak for other members of my family though.
I will be checking the generator's performance under varied load conditions over the next few weeks.

FW
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Old 12-30-2013, 03:48 PM   #13
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Would this work for computer on generator


I have updated info for this thread which may be useful to others:

When I first posted, I had tried to run my APC BR800 battery back-up on the generator, but it would not accept power from the generator. I had measured the generator output with a good quality DMM and it was very close to 120VAC. The APC unit continued to run on battery - its green line power indicator never came on. It did not matter whether the generator was loaded or not.

About a month later, this same APC BR800 stopped accepting AC power from the mains in the house. There was absolutely nothing wrong with the power from POCO.
I found that the battery in the APC unit was bad, so I replaced them (it takes 2 batteries). Now, not only does the APC unit function properly on the AC mains in the house, but it functions properly when connected to the generator as well.
I ran it both with and without a load, and the APC unit was accepting power from the genny. The only time the unit switched to battery was briefly when the load was added or removed from the generator. This test, and what has been said in this thread leads me to conclude that generator power is OK for electronics, so long as a good surge protector or UPS (like the APC BR800) is used - and that there aren't any heavy load changes occurring (as with AC units or a refrigerator). That said, I believe that using a power conditioner ahead of the battery back-up would help in those situations where the load is changing.

The APC BR800 does not have power conditioning, but since it will disconnect from the AC mains when under or over-voltage is detected, might it not be as good as using a power conditioner, so long as the heavy load changes are not causing excessive change in generator output voltage?
I haven't measured the generator output during load changes yet. I think I need to do this, as it will help the next time I am running electronics on the generator.

FW

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