Question: I have several Dell PE2950 Servers and several 20A Powerstrips, my facility provides 120VAC. How many PE2950’s can I plug into the 20A Powerstrip without tripping the breaker?
Answer: The Dell PE2950 has a manufacturer’s rating of 750W, however this rating can vary by +/- 20% depending upon the operating efficiency of the primary power supply. The operating efficiency is mainly affected by temperature but there are a host of other things that can affect the operation as well.
Start by calculating an operational range for a single server:
750W + 20% = 900W
750W – 20% = 600W
The next step is to determine the Amperage: W/VAC=A
900W/120VAC = 7.5A (max)
750W/120VAC = 6.25A (spec)
600W/120VAC = 5A (min)
The operating load of the Powerstrips must be determined. This is where the 20% variation in operating efficiency is important. If you load the Powerstrips over 80% you can run the risk of overloading the breaker under a maximum load.
20A * 80% = 16A
20A * 85% = 17A
20A * 90% = 18A
Using these guidelines you can easily determine how many PE2950’s you can plug into your 20A Powerstrips:
7.5A * 2 = 15A (max load)
6.25A * 2 = 12.5A (spec)
5A * 3 = 15A (min load)