HVAC on UPS

[bwyllie]

Can someone explain the reason why HVAC should not be powered from a UPS? I cannot seem to recall the exact theroy.

Thanks

 

[wanderer20001us]

HVAC systems are put on UPS systems all the time in critical Data Center applications. The key is designing a dedicated UPS system for the purpose of the HVAC loads. You would not want to put HVAC and data processing equipment on the same UPS system as the HVAC could create power quality issues (voltage sags, spikes, etc.) that would distrupt the data processing equipment. But HVAC connected to a dedicated mechanical UPS is fine. Design considerations for motor LR conditions must be addressed when sizing the system.

 

[dereckbc]

Ecconomics is the number one reason. UPS are used to power critical information technology systems, not lighting and HVAC. In a facility housing mission critical IT equipment will have generators to pick up the all the loads in the event of commercial power loss.

 

[wanderer20001us]

Tier 3 and 4 Data Centers, as a design, will put the mechical systems on UPS to minimize risks associated with equipment restart after the generators come on line. Ture, more expensive, but if you are a bank or a next day courier prossesing center, the extra cost is offset by the potential cost per minute of down time. Cheap insurance by comparision.

 

[ron]

I would suggest that Tier 3 and 4 do not always result in HVAC loads on UPS. 9 out of 10 designs that I review/design have no HVAC on UPS.
The biggest problem for HVAC not on UPS is to be sure you have either thermal storage to carry you through the restart of a chiller delay (pressure equalization) or a standby chiller that can start from the off position to carry you through the restart of the previously running unit (pressure equalization).