Problems running on a generator

[Anonymous user]

Last week we had the pleasure of the power company disconnecting power from 9am to 3pm.
During that time we ran our site on a 5600watt generator.

The one APC 2200XL with battery pack worked well. Only briefly at the start did it flick back and forth between "on battery" and "normal".
The other APC 2200XL and two APC 2200 and ten APC ES750VA all had problems living with the power from the generator. Every five to ten seconds they would switch between "on battery" and "normal".

I noted the voltage using the APC software was between 118 and 124 volts.

I tried connecting an APC Line conditioner LE1200 between the UPS and the power source. This made no difference.
Other equipment not connected to APC UPS's, like the Xerox 5655 Workstation Copier/FaxMachine/Printer had no problems with the power.

I need to solve this problem for next time the power goes out and we have to switch to the generator.
I could remove the UPS's but I fear damaging the equipment.

Any thoughts would be greatly appreciated.

ps
The generator is a Sears Craftsman 5600 watt
http://shopping.canoe.ca/shop/product--catId_1001973__locale_en__catCrumbIds_1001199-1001981-1001973...

[Anonymous user]

Slight mistake in this information. The APC 2200XL UPS is a 1.1KW, not 11KW, capacity. There is no problem since the actual rating is only 20% of the generator's capacity.

[upsguy_apc]

If you read the first post he had 14 UPS's on the generator.

[BillP]

have you tried lowering the sensitivity on these units? the UPSs have a sensitivity setting that can be adjusted.

[here is some info on what sensitivity is|http://nam-en.apc.com/cgi-bin/nam_en.cfg/php/enduser/std_adp.php?p_faqid=62]

to adjust it on a Smart UPS:

Press the voltage sensitivity button (rear panel). Use a pointed object (such as a pen) to do so. You can also change the sensitivity level through Powerchute software.

Notice the green sensitivity LED..

Brightly lit: UPS is set to high sensitivity (default).
Dimly lit: UPS is set to medium sensitivity.
Off: UPS is set to low sensitivity.

On the Back UPS ES 750 (if its a BE750BB), you will need to adjust this via powerchute personal edition. Once you configure that, you can adjust the setting. If its a BE750G, you can adjust it by doing the following:

1. Plug the Back-UPS into the utility power source. The Back-UPS will be in “Standby mode” (no indicators are lit).
2. Press the ON/OFF push button fully in for 10 seconds. The Online LED will begin glowing in a cyclical order: GREENAMBER-RED, indicating it is going into “Program mode”.
3. The Back-UPS will then indicate the current sensitivity, as shown in the Transfer Voltage and Sensitivity Adjustment table below.
4. To select the LOW sensitivity setting, press the ON/OFF push button until the LED begins flashing GREEN.
5. To select the MEDIUM sensitivity setting, press the ON/OFF push button until the LED begins flashing RED.
6. To select the HIGH sensitivity setting, press the ON/OFF push button until the LED begins flashing AMBER.
7. To exit Programming mode, once sensitivity is set, wait approximately 5 seconds, and all of the LED indicators will be
off (unlit).

if you have done this, and it still doesnt work, then the power is too dirty from the generator for the UPS and there isnt anything else to really try..you'd have to fix it on the generator end or get some UPSs that can accept a wider range of voltage (like a Double Online Conversion UPS depending on the severity of this issue)

[upsguy_apc]

The main problem I see is that you have 11kw of UPS on 5.6kw of generator. Even though you may no have the full load of 5.6kw on the UPS your may possibly be overdriving your generator and that could cause frequency and phase shift issues which could play all kinds of havoc on your UPS's.

UPS's use more current than they provide to your load so even though you may only see a sum of 5kw on all of your UPS's you could easily be putting 6-7kw of load of the generator.

my 2 cents. next time shed some load and see what happens. "shed load" aahhh screams the IT guy.

[Anonymous user]

Good information. Much appreciated. I will try lowering the sensitivity on the UPS's

[Anonymous user · Accepted solution]

A good thought but I am sure I was not overloading the generator. I measured the load on each UPS with a WattsUp PowerMeature (a real handy device) One of the APC 2200's has only 140 watts of power attached to it. I switched load to the generator in phases. On the first phase with only 1500 watts being used I noticed the UPS problems.

[RobRut]

Thank you so much! I had a similar issue and lowered the sensitivity (based on your suggestion and instructions); now, all four Smart UPSs work great! I can't thank you enough!