UPS on generator power

ochadd

[H]ard|Gawd
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May 9, 2008
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A couple years ago I bought a Westinghouse 9500DF generator as a whole home emergency backup and for portable welding. Works fine other than my battery backups will not charge with the power it provides.

Chatted with CyberPower and APC and the recommendation is a double-conversion online UPS like you might use in a server rack. Even if I wanted to spend the $ I'd also have to have an electrician do something to bring several outlets from different rooms together to make it work on a single unit. Is there anything I could do other than a much nicer UPS or generator?

I've set the UPS voltage range as loose as I can. Something like 90 volts to 140 volts plus the lowest sensitivity setting they have. They cycle on and off every few seconds until the battery is drained and the machine shuts down. The UPS units with an LCD read input voltage at a solid 120v. Have two CyberPower CP685AVRG and one APC BR1000G Back-UPS Pro, all line interactive units. Total power consumption is around 900 watts peak, 500 watts idle. Three computers and required network gear. The generator is connected with a 50 amp plug to a manual transfer switch that powers the main panel of my house.
 
Problem isn't the voltage, it's the ugly as sin harmonics coming out of it that the UPS doesn't like. Most home generators put out extremely dirty AC, which makes them not at all compatible with sensitive electronics.

You'll need a fairly beefy line conditioner between the generator and any electronics, but that may not even be enough, depending on how ugly the sine wave gets. The harmonic distortion isn't constant on a generator, and tends to get worse the higher the load is.

Maybe try something like this:
https://www.amazon.com/Tripp-Lite-L...171&s=electronics&sr=1-13&ts_id=10967061&th=1

I would also couple it with a double conversion UPS so that anything on the UPS side doesn't see a hint of what's on the AC side.
 
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The double conversion UPS might make sense but the price makes an inverter generator an option. For sure if I need an electrician involved or buy multiple double-conversion units. Not sure what I'm going to do yet. Might just throw caution to the wind and plug equipment into power strips during the next outage. We can do without computers for a short outage but I have to be able to work remote during a long one.
 
I would go with multiple units. It's more expensive, but rules out a single point of failure and distributes the load to get more uptime until your generator can kick in.
 
Hi,
Had a power outage and when generator kicked in, all of my APC BACK-UPS NS 600 continued to run on battery. Outlets all had power, but the UPS' beepings indicated that they were not getting power.

Also, have some Tripp-Lites. Their indicators said they were getting power but they all eventually consumed their battery and shut off.

Once we came off generator everything started working again. I should think this has something to do with the power generated by my generator. Anyone know what the problem could be?

High THD (Total Harmonic Distortion) coming from the generator combined with the type of UPS you're using. What you describe is what I experience as well. The power isn't "clean" enough and the UPS detects it, runs the devices off battery power. I've heard an online, double conversion, UP{S may work with high THD generators but I haven't tried it. They are expensive. Many years ago a neighbor loaned me a small inverter generator and that powered an ultra cheap UPS just fine. Before I bought my big portable generator.

Options as I understand them are:
1. Use a low THD generator. Such as a small inverter or a big permanent diesel unit.
2. Use an online, double conversion, UPS.
3. Find some way to cleanup the power. I've done allot of hunting for this online and haven't found anything easy or cheap.
Edit 4. Run your computer and networking gear straight off the generator power and ditch the UPS. I personally haven't had the need to do it but that's my plan for a long outage in the future. I bought a cheap laptop just for this as a sacrifice.

https://wenproducts.com/blogs/resou...-distortion-thd-in-generators-an-introduction
 
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1. Use a low THD generator. Such as a small inverter or a big permanent diesel unit.

Big is usually good, doesn't need to be diesel. My 35kW cummings makes my UPSes happy, and runs on propane, but it's really a Ford gasoline engine in there. Could run on natgas, too and probably gasoline as factory options. Not sure what the THD spec is on mine, but it's big enough that it's probably fine.
 
Big is usually good, doesn't need to be diesel. My 35kW cummings makes my UPSes happy, and runs on propane, but it's really a Ford gasoline engine in there. Could run on natgas, too and probably gasoline as factory options. Not sure what the THD spec is on mine, but it's big enough that it's probably fine.
At work I use both diesel and natural gas units between 17KW and 21KW. Kohler branded. They power two rack datacenters + AC and the UPS work fine. However I use online UPS there to. So it's good power and good UPS units.
 
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