Determining UPS requirements

[Anonymous user]

I'm having a little bit of trouble figuring out exactly what I need in the way of UPS.
It's going to be supporting a Single desktop computer and Monitor. It's going to be in an automotive workshop with a large air compressor and welding equipment, so I need it to be able to provide clean filtered power (not just surge protected) there is going to be a lot of spikes, sags, brownouts etc around this machine. ONe computer has already been sent to the funny farm because of the dirty power... Backup time isn't real critical.. 5-10 minutes is plenty as a minimum.. just long enough to survive the compressor starting, or allowing a clean shutdown if power is lost completely..

[Anonymous user]

I agree with the other comments, and would suggest an additional consideration: Bring a line from the electrical panel that will be on a cleaner phase; as most 3-phase services are seldom well balanced, and/or re-worked after initial installation, it's possible that too much noise/spike/inrush-drop/phase corrupting junk gets piled up on one side or another. It's the same nonsense as having part of a network running on one clean phase and another parts running on phase sides with a mother-of-all-xerox, the uber-shredder, and nearby bathroom fluo-lights on auto-switching.
Over the years, I've been lucky enough to clear up all sorts of "cosmic-events" by taking a survey of the power distribution and loads, and then recommending improvements.
This common oversight has probably damaged more good equipment than all the lightning, fire, acts-of-God, and dumb users put together.

[Anonymous user]

wow.. i guess this question is a lot tougher than i thought!

[Anonymous user]

kc8oye,

Well the question does have alot of angles to it.

You probably want to look at either a SmartUPS or SmartUPS RT UPS. The difference is the topology used by the two. The regular SmartUPS line is Line-Interactive, which filters the AC power, suppresses voltage spikes, and provides sufficient voltage regulation during normal, non battery operation.

The SmartUPS RT line is Double Conversion Online, which means it is basically always converting power through the batteries from AC --> DC -->AC. This can be nice because it's completely recreating the sin wave, which should lead to very steady clean output regardless of the input characteristics.

APC has a white paper that discusses the pros and cons of these two topologies here.

-Mike

[BillP]

Well for a real answer we would need to find out all of the amp and watt draws that your equipment could potentially reach. Motors and other mechanical items normally have a large current inrush when starting up. As a result if you dont size the UPS properly it will overload and drop load. APC ups's are normally billed for IT equipment in general and not mechanical. Another issue may be that the EMI or distortion from the mechanical equipment itself could be to great for the unit to contend with and cause it to go on battery when they are used.

Any ideas on what your watt/amp draws are? What voltage does the equipment require?

Ah Mtroha got there before I did 😛

Message was edited by: syn2083

[Anonymous user · Accepted solution]

syn2083: It didn't sound like he was going to connect air compressors, etc to the UPS, only that they were going to be a cause of fluctuating line voltage.

Smart-UPS sounds like your best bet, as Mtroha suggested.

Stew