UPS testing at full load
UPS testing at full load
(OP)
Hi all!
We're purchasing a new 16kVA UPS and want to test it before signing off any acceptance documents.
We usually simulate full load by using a dummy load consisting of electrodes immersed in a tank of water. Salt is added to the water until the UPS is at full load.
I'd like your comments:
1. Does anyone here use the same method to test your UPSs?
2. Up to how high a load should I test? I'm contemplating testing up to 110% load for up to 3 hours.
3. What other stuff should I test? I will probably hook up a digital oscilloscope to capture the waveform.
Thanks,
Jan






RE: UPS testing at full load
RE: UPS testing at full load
What was that, $8,000 worth of heaters?
jlchaves; That load of yours is purely resistive you might want to add some sort of inductive loading. Drag in a 3HP motor and toss it on too. Maybe a wheel around air compressor. Let it run thru an open valve.
RE: UPS testing at full load
Most UPS systems designed for computer system use don't like motor loads much, I'd be careful about using motors as a test load.
RE: UPS testing at full load
You're thinking, 'Duh'. I did, too. But my two small UPS units would not allow their respective computers to start while the AC power was coming from a generator. Both computers started and ran just fine from the generator without the UPS.
I was too busy patching the roof to figure out why the UPSes did not care for generator power. It was clearly not undervoltage.
Mike Halloran
Pembroke Pines, FL, USA
RE: UPS testing at full load
Rather a lot depends on if the UPS is the only generator load, or just a small part of a much larger fairly constant resistive load.
The worst type of UPS to drive with any sort of generator, is the ferro-resonant type. As input voltage falls, current rises so it looks like a negative resistance load to the poor generator. Also, small generator speed and frequency changes can cause fairly drastic voltage and current changes at the load, because the ferro is "tuned".
All this can create some horrible stability problems that can be difficult if not impossible to cure. It may all work perfectly, or it could turn out to be quite an "interesting" day.
RE: UPS testing at full load
Thanks for the ideas, guys. I rely on building gensets to provide auxilliary power in the event of a blackout.
Here's another challenge: I've been wanting to install a small genset for years, but we are located high in a commercial building. Short of punching intake and exhaust ports in the walls, I don't have a clear-cut way of installing a genset. Fuel cells cost too much, too.
Jan
RE: UPS testing at full load
Jan, disguising the gas ports is probably achievable, but concealing the presence of a generator from your landlord and/or insurance company carries some obvious risk. Safely storing fuel near the generator, and replenishing it when the elevators don't work, are bigger challenges.
Scattered through this blog:
http://nola.us/frame.html
you will find references to buying, storing, guarding, hauling, transferring, filtering, and reeking of, Diesel fuel.
Mike Halloran
Pembroke Pines, FL, USA
RE: UPS testing at full load
The worst part is the building engineers normally cut ALL power to perform maintenance during certain holidays here in the Philippines. I have to shut everything down for 3 days. Even the chilled water supply is shut off, so my cooling system dies, too.
Bummer :(
Jan
RE: UPS testing at full load
RE: UPS testing at full load
Anyway, we're pushing through with the UPS purchase soon. We're just finalizing the designs.
If the budget fits, we're going for a 20kVA unit that runs on 3-phase power.
Jan
RE: UPS testing at full load
You could lower a heavy weight, braking it with a generator, and hoisting it up again when power is restored. Just like winding a cuckoo clock. Depending on the building, you might be able to drop the weight on the outside, increasing your energy storage capacity.
A gargoyle that very slowly changed floors when the building was unoccupied might go unnoticed for a long time...
</fart>
Mike Halloran
Pembroke Pines, FL, USA
RE: UPS testing at full load
I also commission UPS's with heaters in the room (to test the HVAC) or load banks outside (on ground/roof). With many new computer power supplies compliant with the IEC regulations, power factor is relatively high and harmonics is relatively low when the computers are connected.
You can also rent a resistive/reactive load bank for hours of testing fun. :)
RE: UPS testing at full load
I haven't used water with salt.
How do you know how much salt you need to add to measure the full load and what should be the increment?
RE: UPS testing at full load
Salt water rheostats work well (if not great). They will get hot. You can end up with lots of steam. They are sort of self regulating since if things get too wild they self increase in resistance.
Do be careful you don't melt your plastic container..
RE: UPS testing at full load
Mike
RE: UPS testing at full load
Now its a functioning data hall and we cant do what we did back then but it sure as heck kept its end of the deal.
Rugged
RE: UPS testing at full load
RE: UPS testing at full load
You can rent water-cooled load banks.
I have worked in many high-rise buildings that had a common diesel generator either on the roof or in the basement for several tenants. I wondered how the building manager decided who was overloading the unit when problems occurred?
RE: UPS testing at full load
Haha, nice brain fart, Mike. Perhaps a windmill might work, too.
About our dummy load, we just get the largest nonmetallic tank we can find. I think the last time we used a 50 gallon plastic barrel, the kind used for fruit juice concentrates. It did get pretty warm, but not too hot to melt. The water was hot but not boiling. Wooden spacers kept the electrodes apart.
We met with the UPS vendor yesterday. We finalized the design at 20kVA, N+1. Which means three 10kVA power modules. Input is 3ph.
I'll probably need three 50-gallon barrels and a lot of cable for this. Breakers everywhere too.
Jan
RE: UPS testing at full load
Have you had a look at the GE Digital Energy 'Signature' range? GE bought out the European manufacturer IMV who always had a pretty good reputation and painted the IMV product in GE's colours. We got a cracking deal a couple of years ago on an 80kVA redundant pair.
Those who use heaters as loads: if you have the time, adding a rectifer and a small smoothing cap to the element connections makes it behave like a more typical load. Obviously don't rectify the supply to the fan motor, and beware that the elements will dissipate more power than they otherwise would. I've done this a few times when I've needed a non-linear test load - not 608 times over though!
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One day my ship will come in.
But with my luck, I'll be at the airport!
RE: UPS testing at full load
rugged
RE: UPS testing at full load
RE: UPS testing at full load
1. It loaded up the electrical system - the hall distribution network and switchgear, allowed us to undertake heat soak testing of the kit ensuring that there was no localised hotspots.
2. it allowed us to distribute a source of heat in a regular manner through out the hall so we could check the enviromental operation and prove that, again looking for any issues.
It did look rough and ready and a little heath robinson but it did do what it said on the tin and allowed us to test check a lot of the operation.
As you can imagine the infrastructure under went a lot of intensive testing, one of the tests involved a bolted short - this comprised of a contactor in a box and connected to a very long lead. The box was connected upto a distribution board and then activated while lots of equipment monitored the supply to check the effect and ensure that the supply was able to cope with the fault clear it and not impact any other area of the network.
Rugged
RE: UPS testing at full load
RE: UPS testing at full load
RE: UPS testing at full load
http://www.avtron.com/portable_load_banks.htm