Take the 2-minute tour ×
Server Fault is a question and answer site for professional system and network administrators. It's 100% free, no registration required.

I have a number of dell servers and two UPS. I plan to give two different input to servers from two different UPS, my question is:

A short circuit of redundant powersupply unit (PSU1) will trip one UPS(1) section. Will the fault with PSU1's return power supply will affect another psu (2) and will this trip the UPS(2)?

share|improve this question
add comment

5 Answers 5

This is exactly why you have redundant power supplies and dual UPS’s. If power supply A fails instead of the load being spread over A/B it is transferred to power supply B.

Also most UPS’s can isolate each output so if there is a problem only that output is affected. Without knowing what UPS you have I couldn’t say yes or no if it has isolated outputs.

As for UPS configuration you have got it spot on. No point in having 2 power supplies going into the same UPS as then the UPS becomes a SPOF (or single point of failure) so many times I have seen people attached 2 power supplies to a single UPS. If you don’t have 2 UPS’s the best thing to do is put one power supply into the UPS and another into the mails via a surge protected power cord.

share|improve this answer
add comment

Not sure if I correctly understood the question.

A short circuit in one power supply should under normal circumstances have no effect on the other power supply.

Of course, your second UPS will need to be powerful enough to hold the increased load. When one UPS fails, the load on the other one will double instantly. So if either of your UPS is already running at >=50%, it will almost certainly overload when the other UPS fails.

share|improve this answer
add comment

Theoretically they protect them selves from power surges . Depending on the manufacturer it should block the power at input , and not distribute it at exit (because they usually regulate external power.

share|improve this answer
add comment

Also, be careful if both UPS feed from the same mains fuse. I have seen offline UPS pass dead shorts straight through and blow upstream fuses. Even worse if ampacity of the mains line is overcommitted (eg two 3000VA capable units from a 230V 16A line ... do not do that!*). Luckily, it seems that server PSU makers have by now gotten wise, it has been a long time since I have seen a server grade PSU short out its source (have seen so in the past esp with 3U/4U servers using commodity ATX PSUs).

*EE basics for server people: Volts times Amperes gives you VA. Which is close to Watts but not exactly on an AC system (pretty close if everything has good PFC). If you have to care about the difference you are operating too close to the limits anyway. Also, loading a UPS to a significant percentage of its rated output gives you short runtime.

share|improve this answer
add comment

is there any document for DELL power edge R710's PSU (E02S001) or circuit diagram for how it will protect from short-circuit from other psu.

share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.