Electrical/Electronic Heat Dissipation
Electrical/Electronic Heat Dissipation
(OP)
Hi guys and gals,
I have done alot of analysis at the CCA level and have always used the "power" that was being used by the device as the heat dissipated. Well these days Im doing work with racks of equipment in a room. My logic is that the power the equipment is using is also the heat dissipated. If the deivce is using 500W it will dissipate 500W to the air thru convetion and conduction (thru the chassis to the rack to the air at steady state). At a meeting another Engineer said that I was being way over conservitive by four times.
Part of my goal is to size the AC for the room. If I used all of the power being used I will have a good size AC, but if my coworker is correct, the AC will be way over kill.
I know for mechanical equipment there is a power factor that you have to consider to get the heat dissipated, but is that the same for electronic equipment? I know there are fans, but I would think that they would be neglectable.
I guess my question is "if the router is using 100W, is it dissipating 100W to the air both thru conduction and convection at steady state'?
Thanks in advance for your time and knowledge
I have done alot of analysis at the CCA level and have always used the "power" that was being used by the device as the heat dissipated. Well these days Im doing work with racks of equipment in a room. My logic is that the power the equipment is using is also the heat dissipated. If the deivce is using 500W it will dissipate 500W to the air thru convetion and conduction (thru the chassis to the rack to the air at steady state). At a meeting another Engineer said that I was being way over conservitive by four times.
Part of my goal is to size the AC for the room. If I used all of the power being used I will have a good size AC, but if my coworker is correct, the AC will be way over kill.
I know for mechanical equipment there is a power factor that you have to consider to get the heat dissipated, but is that the same for electronic equipment? I know there are fans, but I would think that they would be neglectable.
I guess my question is "if the router is using 100W, is it dissipating 100W to the air both thru conduction and convection at steady state'?
Thanks in advance for your time and knowledge
Tobalcane
"If you avoid failure, you also avoid success."





RE: Electrical/Electronic Heat Dissipation
You might wish to chart the spec'd power requirements versus some measurements of the equipment. You'd want to see the VA and watts.
RE: Electrical/Electronic Heat Dissipation
Where else would the power go?
RE: Electrical/Electronic Heat Dissipation
Your friend is correct that nameplate can be 4x steady-state loads, but you have no control over how the equipment is used.
RE: Electrical/Electronic Heat Dissipation
Keeping it cool,
At this point I have nothing to measure, I just have spec sheets. I checked a few and found that they only report the power in watts. Nothing on power factors or apparent power (V-Amp). However, real power (watts) is what I am assuming to be the heat dissipated and not the apparnet power (V-Amps). Apparent power would be a bigger number. In the past I have always associated the power factor with big pumps and big fans, but not with electrical equipment. Is this typical that electronic equpment like routers and computers have a power factor?
MintJulep,
I agree with you ... conservation of energy right? Energy in and then the energy has to go some where. If there are no big gears or mechanical parts to move then it most like dissipate as heat. That is my rational electronic equipment. Except for the small muffin fan, everyting else is CCAs.
RossABQ,
Oh Yeah, I agree with you. However, the first AC just marginaly will accomdate the heat load, I'm recomending to go to the next higher size which is twice as big. I need some good evidence to convince my self and then them.
Thanks
Tobalcane
"If you avoid failure, you also avoid success."
RE: Electrical/Electronic Heat Dissipation
For example, a 500W computer power supply could have as much as 1000W of input power to generate the 500W output. Even the most efficient single-phase power supplies are very inefficient. In this case, there would be an extra 500W of "ghost" heat to remove.
RE: Electrical/Electronic Heat Dissipation
I agree with you there, however, the other 500w that goes to the electronic equipment, in my opinion since there are no moving parts, a small portion of it will do its job in the circuit and the rest (maybe 499w) will dissipate as heat. That is my rational.
Thanks =)
Tobalcane
"If you avoid failure, you also avoid success."
RE: Electrical/Electronic Heat Dissipation
RE: Electrical/Electronic Heat Dissipation
So is that 500w of dissipated heat to the air?
Tobalcane
"If you avoid failure, you also avoid success."
RE: Electrical/Electronic Heat Dissipation
In other words, in this case:
999 W goes into the UPS; it dissipates 499W. 500W goes to the servers and is didipated by them. Total cooling load is 999W, not 1499.
RE: Electrical/Electronic Heat Dissipation
I agree with you on that. If you ever had to size an AC would you use the 999W (3,409 btu/hr, AC use these units)?
I would, but other engineers are telling me that this is not the case. These same people do not know why. I'm thinking of thermal mass, but that is in transient cases.
Thanks
Tobalcane
"If you avoid failure, you also avoid success."
RE: Electrical/Electronic Heat Dissipation
RE: Electrical/Electronic Heat Dissipation
It's also a bitch to debug electronics in a hot room.
TTFN