UPS Room Cooling with a rooftop unit
UPS Room Cooling with a rooftop unit
(OP)
I have been asked to provide a redundant cooling system for a UPS room. Actually, this new system would be the primary with the existing being a backup. Right now they have a Carrier split system with a 40RM012H air handler and a 38ARD014 condensing unit. The room has some envelop load so 12 tons is the design capacity, but 2nd stage cycles. This gives them some redundancy with the dual circuiting, but basically they are in trouble if this system fails.
I have always seen Liebert or other precise cooling units on these types of rooms, but in this case I don't see how to make it work. We have absolutely no floor, wall, or ceiling space to put another split system. The roof is my only option, and I will have to duct down outside the room and punch through in the only free wall space available.
Any recommendations on manufacturers or at least what to look out for? I don't want to put a standard HVAC unit for such a critical application. I would like something with more precise control. Also, what about outside air? There are no people in the room, so I am guessing I can get away with no OA, but an economizer sounds appealing for energy use. I don't know the humidity parameters, but will an economizer cause me any problems if I use enthalpy?
Any ideas are appreciated.
I have always seen Liebert or other precise cooling units on these types of rooms, but in this case I don't see how to make it work. We have absolutely no floor, wall, or ceiling space to put another split system. The roof is my only option, and I will have to duct down outside the room and punch through in the only free wall space available.
Any recommendations on manufacturers or at least what to look out for? I don't want to put a standard HVAC unit for such a critical application. I would like something with more precise control. Also, what about outside air? There are no people in the room, so I am guessing I can get away with no OA, but an economizer sounds appealing for energy use. I don't know the humidity parameters, but will an economizer cause me any problems if I use enthalpy?
Any ideas are appreciated.





RE: UPS Room Cooling with a rooftop unit
Standard roof-top HVAC stuff is not designed for computers and will not provide right dry bulb and wet bulb control.
RE: UPS Room Cooling with a rooftop unit
For some idea of what I am talking about, take a look at these APC tech specs, APC UPS and check out the environmental requirements at the bottom. I just finished a job with several of these APC UPSes and we stuck them in the main building electrical room along with several transformers. The only reason we cooled the space was because with the transformers located in the space, we would easily exceed the 104F max operating temperature. The additional cooling was with a standard split system. As a side note, the concern above the 104F temp wasn't for unit operation, but performance degradation of the batteries in the UPS.
RE: UPS Room Cooling with a rooftop unit
Some UPS have and in-built logging and I have seen warranty claims being rejected due to short periods of excessive temperature!
With some careful selection a rooftop unit could be used, but may need a non-standard unit, just need to talk to the supplier about coils selections.
RE: UPS Room Cooling with a rooftop unit
RE: UPS Room Cooling with a rooftop unit
This goes double when you lose normal power; your split system needs to be on its own UPS or you have no cooling just when it is needed the most! Without knowing your climate, most of the year (statistically) OSA is in the range to keep a room like this cool enough without a mechanical refrigeration unit (certain batteries de-rate at 77 degF, the electronics are good above that). With an OSA econ unit, you can likely get by with just the fan running on a UPS, unless you are in Phoenix or Las Vegas...
RE: UPS Room Cooling with a rooftop unit
RE: UPS Room Cooling with a rooftop unit
Mike