02-22-2005 06:11 AM
Solved! Go to Solution.
02-22-2005 06:40 AM
Off hand, we use temperature targets. The specifications for the machine note the operating temperature range and we get enough power to keep it comfortably within that range.
I don't think power supply watts to BTU is a good approach. You need to know how much heat every device in the room gives off at full capacity, disks included.
Owner of ISN Corporation
02-22-2005 06:51 AM
â ¢ A BTU = 3.412 * Watts
â ¢ A ton = BTUâ s / 12,000
â ¢ The 30 ton air units we use cost about $26,638.88 to operate, per year, at full load.
â ¢ To cool a ton of air costs $888.00 per year.
** Always use maximum wattage of a server
** Concern yourself with HOTSPOTS
Yes, it costs money to operate air conditioners. I used these numbers to justify the removal of all K-class equipment with virtually partitioned N-class servers.
live free or die
02-22-2005 07:10 AM
You have to realize that for all practical purposes (and to greater than 99.9% accuracy) computers are nothing but heaters -- expensive heaters but heaters nonetheless.
This means that if you have the input power, you have the output heat dissipation --- they are one and the same. As long as you use the maximum values listed on the power supply for your calculations then what that power is doing (running disk drives, memory, powering chipmunks) doesn't matter; it's all going to be converted to heat.
To approximate power dissipation, you can multiply rated input voltage by rated current to get Volt-Amps. Then multiply by a power factor (usually about 0.8 to get watts - remember this is AC 1VA is usually not 1WA because we have those pesky phase angles) If you want to be very conservative, use a pf of 1.0 and some HP computers run a pf of 0.99. If you use a power factor of 1.0 then you will always be safe. The one other formula I should throw at you is how to calculate 3-phase power. It's simply P = IV * 3 ^ 0.5 * pf where P = power in watts, I = current in Amperes, V = Voltage, 3 ^ 0.5 ==> square root of 3 (or the appropriate number of phases), and pf = power factor (again somewhere between 0.8 and 1.0). Power factor is actually the cosine of the between the phase angle of the current and voltage.
Suppose the power supply label indicates 10 A at 200V; what is the maximum thermal dissipation?
10A x 200V = 2000VA x 0.8 (pf) = 1600W.
1600W x 3.412 BTU/HR-W = 5460 BTU/HR.
The other conversion factor you need to know is that 12000 BTU/hr = 1Ton Cooling Capacity
02-22-2005 07:13 AM
live free or die
harry d brown jr
02-22-2005 08:15 AM
02-22-2005 10:35 AM
02-22-2005 10:20 PM
I expected to see you pop up here, but what confuses me is this:
"1600W x 3.412 BTU/HR-W = 5460 BTU/HR."
This seems to be converting watts to BTU. However, your second reply states:
"it is impossible to convert BTU's to Watts or vice-versa", yet you seem to be doing just that. Which is it? Vice? Or versa? What am I missing?
02-23-2005 02:08 AM
02-23-2005 04:50 AM
VA7410 (labeled on each of 2 power supplies)
3 of the 2405 enclosers (labeled to on each one)
1) These are plugged into a 110 power strip. So am I to read it as 8.2 amps max but if I had it plugged into 240 the amps would be 3.4 amps max?
2) This is probably a silly question. it seems low, so I guess I to add the hard drives on to this too? they are not visable so I guess I need to grab the white papters?
02-23-2005 08:04 AM
02-23-2005 08:07 AM
02-23-2005 08:40 AM
07-12-2005 12:06 AM
Equipment designed for computer rooms is designed with this in mind, but there is still latent work being performed.
It would be a good thing to consult with a HVAC professional or forum dedicated to HVAC to answer more questions.
And, no... you don't have to buy Liebert to make it work correctly.
07-12-2005 12:46 AM
05-16-2007 07:02 AM
I just read your blog about converting watts to BTU's/hr for sizing air conditioning needed for your computer room. As a Data Center Facilities Designer, I have been designing data centers for 7+ years.
Based on the method described (maximum input ratings of the power supplies), you would derive numbers which are way too high.
The numbers indicated on the power supplies are the maximum input power, assuming every available device option is installed, and all these devices are running 24 hours/day.
In my experience, typical computer systems draw less than half of the rated input power stamped on the power supply. As a result, using these numbers would derive a figure approximately tripple your actual loads. And you probably bought way too much air conditioning for your data center (don't worry about it. I once made the same mistake myself).
Just guessing, but I would bet that you still have plenty of cooling capacity in your data center, even after two years of adding equipment. Am I correct?..
05-16-2007 09:16 AM
06-01-2007 01:06 AM
07-05-2007 04:20 PM