| I thought that the biggest problem was the conditioning system working
| less efficiently if they have to draw heat from a room which is already
| cold to bring it to a place which is already hot.
| Is this factor irrelevant?
It's what A/C systems are designed to do. They "compress" heat so it is
actually coming out of the precipitator at a higher temperature than it
entered the evaporator. Stick your hand in the air flow out from the A/C
outside and you will see it is hot.
| It seems relevant to me:
| I have tried to put plastic sheets so to drive hot air from the servers
| to the input of the conditioners, preventing it to mix to the cold air
| output from the conditioners. This gave hotter air to the conditioners
| (might have been about 10 celsius hotter, I am not sure). They appeared
| to work much more efficiently, like 50% more efficiently, but I have not
| tested this really well to be so sure.
That would help if you don't mind the rest of the room operating at a
|> This depends on so many factors that you pretty much just have to test it
|> and see. It's hard to test this with everything running, which you most
|> likely must do. One reason is the test varies depending on what the
|> outside temperature is.
| If everything was not running, how would you test this?
| Like bringing the temperature down then looking at the speed at which
| the temperature increases?
The timing of temperature rise under varying external conditions would give
some clue as to the rate the heat comes into the building from outside. If
you can do it with all computers off, that's more accurate. But I guess
you don't have that option.
|> Do the existing A/C systems run continuously or do they cycle on and off
|> in a normal manner? Is the temperature stable now, or does it go up and
|> down rather extreme? Is it just too hot in there and the A/C you have now
|> just can't cool it any better?
| It seems like the current conditioners cannot keep the temperature
| stable to the temperature which has been preset to them. But I haven't
| really tested well.
| Yes they are working full time, no cycle.
You should also look at whether they have the correct blower sizing, and
that they are operating with all other conditions in good shape. Make sure
the precipitator baffles are clear. Make sure the freon is in good state.
If you have air in the freon line, that can reduce efficiency. If you hear
the compressor working really hard right when it kicks on, there may be air
in there (which cannot be compressed to a liquid).
| It might be possible for us to stop all equipment for a while.
Good thermal testing might take a couple days. I doubt you can do this
with things turned off.
Someone with experience in A/C systems and building insulation might be
able to give you a good estimate of your building efficiency, and adjust
your new A/C sizing appropriately. But my guess is you will need 50% to
100% more than what you have now.
I would also figure in redundancy at this time, too. In one place I used
to work, we made a conservative heating estimate and figured 2 units to
cool it, but installed 3 units anyway for backup purpose so we could take
one unit out of service at any time. I've heard of some places going to
250% to 300% for high redundancy (they were uptime critical).
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
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