power supplies and surge protection


Thread Starter

Zeljko Fucek

Hi All,

I was wondering what are the best practices when installing PCs where it is likely to expect "dirty" voltage and random power outages. Is small and properly sized UPS with surge
suppression and shutdown software enough to protect and serve well under these conditions?


Zeljko Fucek

Daniel Chartier

Hello Zeljko;
From the brief description of your situation, I would suggest a "full over the line" UPS system, which uses a charger to maintain the batteries and an inverter to generate from the batteries the AC power that will actually be used by the PC. This effectively isolates the PC from fluctuations of the network and protects your investment; shutdown software then can be useful to close applications in case of dangerous power outage.
Hope this helps,
Daniel Chartier

Bob Peterson

I am not a big fan of using UPS's in industrial environments. There are several problems associated with them.

1. They are generally not designed to take the conditions normally encountered (temperature, humidity, dust, etc) in the industrial environment.

2. The batteries require replacement on a periodic basis, and sadly tend to fail when most needed.

I suggest the following approach.

1. Clean up the power coming to the PC as best you can. Often a constant voltage transformer can do wonders.

2. Buy the largest power supply you can get for your PC. They seem to be more robust and forgiving then a smaller one.

3. If you have a problem with actual outages, install a UPS in a more suitable location and just run the wires out to the floor. This makes the communication between the UPS and PC a little more difficult but not a whole lot.

4. It might be practical to install a diskless workstation in the "dirty" environment and the server someplace less nasty. This way if power fails out on the floor it does not affect the server anyway.

The main idea is to avoid power outages if possible, rather then simply dealing with them. Regardless of how well you deal with power off and return its a nuisance. In fact some, PCs will not even come back on automatically on power up. Thye have to be manually restarted by someone actually depressing the power switch. This is not an ideal situation in an industrial environment.

Michael Griffin

Something which has a bearing on this is what operating system and application software you are using. If they can tolerate being shut down
without warning, then you may be better off without a UPS. If they cannot (e.g., Windows - according to the specs), then a UPS may be a necessary evil.

If you use a UPS, then you should configure it to maintain power to the PC for several minutes after loss of the normal supply. At that point, if main normal power is not present, have it force a controlled shut down on the PC. Once normal power has been restored for at least a minute (you may wish to cut this shorter, but not too much shorter), have it auto-start and re-start the PC. Alternatively, you may wish to make re-start a manual operation.

The objective of the above is to have the PC remain on during brief interruptions, but to shut it down if the power is going to remain off for
some time. Size the UPS to allow it to go through several shut-down cycles, as thunderstorms or ice storms may cause several interuptions before the
battery has re-charged.

Make sure the UPS is powering only the PC, and not any attached loads. Post prominent warning signs that a UPS is present (this is an electrical shock hazard). Put the UPS on your preventative maintenance schedule. Above all, if
you don't need a UPS, then don't use one.

Michael Griffin
London, Ont. Canada