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Thread: AC Split unit working under 16ºC
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25-12-2010, 09:41 AM #1
AC Split unit working under 16ºC
Hi and Merry Christmas to all
I work for a company in Mozambique that does air conditioning work.
At 2 diferent sites we are facing the same problem:
in the server rooms, normal wall split units were installed and the users run them all the time at 16ºC. The sution line, although well insulated with armaflex is always condensating, creating drops on ceiling. We replaced the inslation but it is still doing the same thing.
Is this a insulation problem of the piping or can be related with the fact that the ac split units are runing at 16ºC?
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25-12-2010, 11:38 AM #2
Re: AC Split unit working under 16ºC
Running the splits at 16c is defiantly not a good idea.I doubt there is anything in the server room that requires such a low ambient to operate,The splits probably never achieve set point and run continuously .And if you have any air breaks in the insulation this will cause the suction pipe to sweat profusely,if ice then starts to form on the evap coil this will only start to compound the problem as the back pressure starts to drop off
May be an idea to use thicker walled armaflex if the humidity is high
Try operate the splits a few degrees higher about 20-21c ,if they can maintain temp shouldn't have any issues
Cheers
StuLast edited by stufus; 25-12-2010 at 11:41 AM.
Tool's ? check ! Condom's ? check !
If you can't fix it , f*ck it !!!
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25-12-2010, 11:54 AM #3
Re: AC Split unit working under 16ºC
As Stufus said, raise the temperature set point.
Also make sure that the insulation is vapour sealed at all joints and ends; don't not squeeze it with tie-wraps.Brian - Newton Abbot, Devon, UK
Retired March 2015
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27-12-2010, 11:49 PM #4
Re: AC Split unit working under 16ºC
Maybe you have a humidity problem inside your server room beacause I have been to many server rooms and temperatures reaches up to 18 below deg C. As far as i know normal splits are for comfort cooling only and are not design for server rooms application instead try using presicion aircon that controls humidity and temperature. And for installation of refrigerant pipes do not install it above your server rooms or water drops pouring on your computers and servers will be your next problems.
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28-12-2010, 11:07 PM #5
Re: AC Split unit working under 16ºC
Install outdoor fan speed regulation to stop over condensing and system over performance, and condensation problem.
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29-12-2010, 04:41 AM #6
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29-12-2010, 10:11 AM #7
Re: AC Split unit working under 16ºC
Yes, you mean too low a head pressure
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29-12-2010, 07:10 PM #8
Re: AC Split unit working under 16ºC
The problem here is the user, and you need to advise them. If you can obtain the specs for one of the servers, you will be able to show them that the units are rated for temperatures up to 40C with a rh range of 20 - 80%. IBM recommends a data center temperature of 22C.
http://publib.boulder.ibm.com/infoce...ditydesign.htm
Server rooms are generally not as controlled as data centers, and are usually contiguous with office space, where the dew point could occasionally rise above 16C, causing condensation on server cabinets. So 16C is definitely not a good idea.
However, the suction line condensation may still occur, even at reasonable space temperatures, so the insulation needs to cover all of the exposed suction-side components, have all of the joints sealed, and be finished with a tight vapor barrier.
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29-12-2010, 10:29 PM #9
Re: AC Split unit working under 16ºC
Along with the other posts, there is also likely chance the systems were sized incorrectly. Their total duty being used without consideration for the sensible load and shr of the indoor units.
Typical indoor AHU's have only 0.7 shr in which case they could be undersized by 30% and the user sees a low performance, hence turning down the stat to 16CReality is an elusion created by alcohol deficiency. Quaff and enjoy. [Yorkshire, UK]
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30-12-2010, 03:40 AM #10
Re: AC Split unit working under 16ºC
Hi Mikeref and Paul.
I will wash my mouth out with salt.
magoo
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30-12-2010, 07:34 AM #11
Re: AC Split unit working under 16ºC
Only the dogmatist says he will never change his mind. We all know that some of our opinions are wrong but none of us know which they are for if we did then they just wouldn't be our opinions. - JS Mill.
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30-12-2010, 02:31 PM #12
Re: AC Split unit working under 16ºC
A differrent balance point will be achieved, with a lower suction pressure, and lower duty from the compressor.
Reality is an elusion created by alcohol deficiency. Quaff and enjoy. [Yorkshire, UK]
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30-12-2010, 10:16 PM #13
Re: AC Split unit working under 16ºC
To the optimist, the glass is half full. To the pessimist, the glass is half empty.
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03-01-2011, 02:25 PM #14
Re: AC Split unit working under 16ºC
Thank you very much for your coments.
We already advise teh user to set the temperature at 20 ºC, it is more than enough, but with no results.
We have insulated the pipes again and sealed the joints, but it is still droping.
We will take in consideration your comenmts.
Thanks again
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04-01-2011, 10:18 PM #15
Re: AC Split unit working under 16ºC
This condensation problem, is it moisture forming on the outside of insulation only? Is there condensation in other areas like under the evaporator? Assuming this a/c has refrigerant expansion at condensing unit, then both lines are independantly insulated right?
To the optimist, the glass is half full. To the pessimist, the glass is half empty.
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05-01-2011, 07:22 AM #16
Re: AC Split unit working under 16ºC
If you still have condensation, then you've used too thin isolation or low quality isolation or gaps.
If condensation comes on your isolation, then the isolation is faulty, not the split.
What band and thickness have you used? What thickness of isolation are you using, what brand of isolation, what type of that band. What's your SH and TEIt's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.
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