By Don Benton
Late last year I upgraded my 10 operator positions to PC’s. The PC’s consume more power than the terminals I was using and my UPS could no longer handle the additional load. It had to be replaced. I chose an APC Matrix 5000.
After the choice of which UPS to use, the next major decision is, “How may batteries should I buy?” The system comes with two batteries, which would power the system for approximately 30 minutes. Each additional battery will add 15 minutes to the time at a cost of about $500.00 per battery. The difficult question is “How long will the UPS need to power the system?” Since I live in California it appears that I can expect a number of outages and they may last for a while. Add to this the fact that the batteries will last from “3 to 5 years” at which time there will be another considerable expense of replacing batteries. I decided I should look for a generator that would supply the needed power when I am unable to use utility power.
There is a generator on the market that appeared to be an excellent solution to the problem. The Guardian generator made by Generac comes in 6, 8 and 10 kW size. It is a standby generator built to be permanently installed outside. It has a battery starter and all the electronics to sense a power outage, start itself and switch power to the load through a transfer switch which is also supplied. The system comes with all of the hardware and pre-wired cables. It runs on either natural gas or propane. I prefer propane to gas because propane will not get “old” when it is stored. I purchased the 8 kW generator from Northern Tool and Equipment for $3,500.00, which I thought was a good price. Since my purchase the price has been reduced to $2,500.00.
There are some factors which should be considered when selecting a generator. The UPS may have a problem “synchronizing” to the generator. The generator needs to be 2 to 3 times the kVA load drawn from the UPS. This problem can also be relieved by placing a small load on the generator, such as a couple of 100W incandescent light bulbs on a separate circuit to the generator. This load will help the generator to regulate its voltage and frequency before the UPS load is applied.
The use of this generator with a UPS gives you the best of both worlds. The UPS provides power immediately when the utility power fails. The generator senses the loss of power, starts itself and after it gets up to speed the transfer switch is activated and the UPS gets its power from the generator.
For my load the generator will run for about five hours on one 5 gallon propane bottle. The generator has been installed and tested. We have not yet had a rolling blackout, but I now feel like I can leave town without worrying about my system if there is a loss of power.
Don Benton of Custom Communications, Inc. can be reached at 925-373-7482.
[From Connection Magazine – September 2001]