Sizing Air Conditioners

[Bob O]

I need to size an air conditioner for an enclosure that contains a number of large drives, a number of small drives and some motor starters. I have read the Hoffman sizing and they mention sizing the heat load of the internal components in Watts which I think they mean the operating Voltage *FLA of the device but the devices don’t give all this off in heat, I don’t think any ways. Is there a percentage that I should take from this calculation and sum all the components to get my total heat load? I have searched some of the manuals but didn’t see anything. Any help would be appreciated. Thanks

[Ken Moore]

I usually have the local dist. do the sizing for me. But, I would guess you could assume a certain efficiency, and then use that for your calculation. If you have a 1000 VA device and assume 75% efficiency, then the other 25% would be your heat load, so 250 VA of heat generation. So add up all the VoltAmps (VA or Watts) in the cabinet, and then take a percentage, might want to be a little conservative. Better to have a large unit that runs as needed, than a small unit that can't keep up. One thing to remember, there is going to be condensate coming out of the unit, do you have a plan for this? I have one large enclosure where piping the condensate wasn't an option, so we just ran a flexible hose to a 5 gallon bucket, the "roving" operator checks it on his rounds and dumps it as needed.

[Bob O]

Ken, I found an AB document on heat dissipation that gave me some information and what to search from in the manuals so I can attempt to size one up. Also, I hadn’t thought of condensation. Thank you