Server Room AC Sizing Questions
Server Room AC Sizing Questions
(OP)
Looking for advice on server room cooling sizing. I'm hoping to get some unbiased opinions from other pros who aren't trying to sell me something.
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Part A:
We are moving 129 servers (4 racks), each with a nameplate rating of 350W, into a small room. Based on our measurements, each server is pulling 200W at peak load -- or a total of 26kW for all systems. There are no windows, and no one will be permanently stationed in the room (only in there to service the equipment). I would like to have some room for expansion. According to my calculations, I would require around 8 tons of cooling. However, I'm getting wildly differing opinions from the pros about the size:-
1. Previous owner of equipment is specifying that he was using 4 tons.
2. HVAC Engineer is specifying - a 5 or 6 ton "Liebert" Unit
3. Data Aire Rep is specifying - a 8 ton air-cooled ceiling mount unit
4. Liebert Rep is specifying - 10 tons (possibly 2 - 5 ton units)
Any contractors/engineers out there agree with any of these numbers?
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Part B:
The room is only 124 sq ft. It is a bit small, so I'm worried that the system might short cycle. There will be a LOT of air moving around in this room. I had a few contractors in yesterday, and one of them jokingly said I might have problems opening the door.
Any advice about this? I might be able to convince management to make the room bigger (knock down a few walls around it), but I need some compelling opinions. However, I'd rather not make the room any bigger.
Thanks!
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Part A:
We are moving 129 servers (4 racks), each with a nameplate rating of 350W, into a small room. Based on our measurements, each server is pulling 200W at peak load -- or a total of 26kW for all systems. There are no windows, and no one will be permanently stationed in the room (only in there to service the equipment). I would like to have some room for expansion. According to my calculations, I would require around 8 tons of cooling. However, I'm getting wildly differing opinions from the pros about the size:-
1. Previous owner of equipment is specifying that he was using 4 tons.
2. HVAC Engineer is specifying - a 5 or 6 ton "Liebert" Unit
3. Data Aire Rep is specifying - a 8 ton air-cooled ceiling mount unit
4. Liebert Rep is specifying - 10 tons (possibly 2 - 5 ton units)
Any contractors/engineers out there agree with any of these numbers?
---
Part B:
The room is only 124 sq ft. It is a bit small, so I'm worried that the system might short cycle. There will be a LOT of air moving around in this room. I had a few contractors in yesterday, and one of them jokingly said I might have problems opening the door.
Any advice about this? I might be able to convince management to make the room bigger (knock down a few walls around it), but I need some compelling opinions. However, I'd rather not make the room any bigger.
Thanks!





RE: Server Room AC Sizing Questions
If the server-equipment is using 26kW then that is the minimum cooling-power that is required from the cooling-unit. (I think the power that goes outside the room via the wires is quite neglible)
Why you Imperial folk like to use "tons" (whatever that is) when you are talking about cooling-power is beyond me...
Just convert "tons" to "kW" and you will know what unit you need.
However:
30kW , dT=10K --> 9000 m3/h
room 11 m2 , height 2,5m = 28 m3
That is over 300 airchanges per hour...
RE: Server Room AC Sizing Questions
Part B: The precision cooling units should be able to control the space temperature without short cycling. If you need future capacity you may be tight for space to install a second unit. (The Liebert rep may have suggested 2 five ton units for some redundancy and some future capacity)
RE: Server Room AC Sizing Questions
Total Watts 28,024
Total BTUs 95,562
Total Sensible Tons of Air 7.96
Total BTUs Per Square Foot 770.66
Total Square Feet Per Ton of Air 15.57
Does the calculations include lights, shell load, UPS loss and HVAC Equipment itself. However, it is quite satisfactory for electrical and mechanical program requirements. If it was me I would go for 2-5ton units because of mayainance and repair issues from time to time
RE: Server Room AC Sizing Questions
The Liebert rep is telling me I need a total of 10 Tons...because I am only considering sensible heat...not latent heat. Does this make sense to anyone?
I didn't consider the room/shell load..it seems to be about .25 ton. If we expand the room, the total size will be 240 sq ft. Will it change the size of my unit significantly? I know it will help with airflow. Is 300 ACH an issue?
RE: Server Room AC Sizing Questions
RE: Server Room AC Sizing Questions
RE: Server Room AC Sizing Questions
Data centers use, at most, 50 W/sq ft, says the report, including energy needed for cooling.
RE: Server Room AC Sizing Questions
This case is more of a closet, not a server farm. Within data centers, there are at least 4 different types, based on the data being processed which affects the load characteristics.
For this load and this size room, air management could well be an issue. Note that 4 standard cabinets and a floor-mounted CRAC unit will take up nearly half of the floor space. Is this on a raised floor with underfloor air distribution, or hard floor with overhead air distribution?