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Thread: Server rooms.

  1. #51
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    Re: Server rooms.



    we are about to change hiross ccu to airdales, anny advice???



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    Re: Server rooms.

    Quote Originally Posted by thebigcheese View Post
    we are about to change hiross ccu to airdales, anny advice???
    Bad move. Why?

  3. #53
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    Re: Server rooms.

    The airflow range of the equipment may be limited to normal ranges of cooling with dehumidification.

    When the load is virtually all sensible, the nominal CFM range of equipment is too low.

    So nominal airflow rates on sensible only loads, will be very similar result as a plugged filter and a coil freezing up.

    The SST will drop until it balances out with the compressor under the low load situation. Need high airflow when it is sensible only.

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    Re: Server rooms.

    Quote Originally Posted by richardc1983 View Post
    Okay im not an engineer but why would the indoor unit ice up if it was low humidity anyway?

    My a.c at home only freezes up if the room temperature is too low.
    Because the evaporating temperature will only stay above the zero when the heat removed is considering latent.
    Otherwise, if heat load is only sensible, because of the small coil surface, the evaporation temperature will drop below freezing.

  5. #55
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    Re: Server rooms.

    OK Richard, some very simple terms (don't flame me guys!!)

    The A/C coil can both cool the air and dehumidify it, it's doing two jobs...

    If it doesn't have to do any dehumidifying then cooling capacity of the whole system is now oversized.

    It can therefore cool the air without problem but is now capable of lowering the temperature below what is needed and so gets colder and colder. Being extra cold it can now freeze any moisture in the air stream which it does and causes ice to build up on the coil tubes.
    Brian - Newton Abbot, Devon, UK
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    Re: Server rooms.

    Quote Originally Posted by richardc1983 View Post
    Okay im not an engineer but why would the indoor unit ice up if it was low humidity anyway?

    My a.c at home only freezes up if the room temperature is too low.
    Hi richardc1983,

    The freezing (ice build up) of your aircon (evaporator coil) is due to the refrigerant (*****) inside the evaporator coil reaching temperature below freezing or below zero degree Celcius (0 deg C).

    The low humidity means that there is small quantity of water (moisture) in the air. But still, there is water in the air that passes your aircon (evaporator coil).

    This water in the air freezes whenever it touches the evaporator coil (below 0 deg C) thus, you will have frost and then ice, when a lot of frost or moisture (water) accumulates in the evaporator coil.

    I hope you can now understand the above explanation.
    It would have been easier if i can draw (in your presence) while i am doing the above explanation.

    Regards,
    winfredy

  7. #57
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    Re: Server rooms.

    Coils normally extract so much heat, by lowering the air temperature and by condensing moisture.

    When there is lots of potential heat to be removed in the incoming load, the suction pressure of a system will rise. You start up a new system and a building is hot and very humid; the pressures will be up.

    As you reduce the potential heat (entering dry bulb and humidity reduce) the suction pressures will fall. As that new house cools off and dries out the pressures fall to a normal range.


    A way of even causing the pressures to drop more is to further reduce the load. An easy way of reducing the heat load is by not changing the air filter to the point where it restricts the airflow.

    It reduces air flow and load on an evaporator coil. The suction pressures fall, and the saturated suction temperature gets below freezing and the condensate freezes up.

    A lot of mini-split coils are sized to cool the air so much, and to also remove moisture. Another way of reducing the potential heat going into that evaporator is to dry the air out first. So just like with a plugged filter the heat load entering the coil is low, the suction pressure will drop below freezing. When it is cold like this it will dehumidify some and the condensate will freeze.

    So when there is not much moisture to remove from the air, you need to be moving more air through the system, to keep the heat load up and the suction pressures up. You should also have a larger coil as well.
    Last edited by Abby Normal; 16-11-2006 at 06:04 PM.

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    Re: Server rooms.

    Well, here is the scoop on the new Daikin equipment. They've added some humidification to the unit. http://www.daikin.co.uk/aircondition...dification.jsp I guess the smaller CCU units will be under some pressure as this approach creates a good range of kit to compete for the smaller computer/comms rooms.

  9. #59
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    Re: Server rooms.

    Quote Originally Posted by Temprite View Post
    G'day all

    Was wondering if anyone can give me an explanation as to why you can not use Daikin inverter wall mounts in computer or server rooms, where there is going to be a call for cooling even if the outdoor ambient is low.
    Thanks in advance.


    I havn't read all the replies to this question so forgive me if I'm repeating what somebody else has already said. I think it's the cooling only units you are refering to as they will not run when outdoor amb. is below 15C I think. Becuase these units are primarily comfort cooling Daikin in their wisdom have decided that you not need cooling below this amb. If you use a heat pump system as I have done many times there is no such limit.

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    Re: Server rooms.

    Peter1 is a standard ac a split unit?

    Our company has recently had a lot of compressor faults on split units used in server rooms. We don't have any compressor faults on normal jobs. Maybe it is a maker problem. But the kit we use is supposed to be the best in europe.

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    Re: Server rooms.

    Quote Originally Posted by Temprite View Post
    G'day all

    Was wondering if anyone can give me an explanation as to why you can not use Daikin inverter wall mounts in computer or server rooms, where there is going to be a call for cooling even if the outdoor ambient is low.

    I remember reading or hearing somewhere that in low ambient conditions on cooling that the compressor speed is restricted, but can not think of why.I know that if the indoor thermistor senses a pending freeze up of the indoor unit that this will cause the compressor speed to drop in an attempt to combat it, but I am sure there is another reason.

    Thanks in advance.
    I have been using small server or lan room with Daikin VRV and it works fine here. Average room size about only 10ft x 10ft x 11ft. Using 2 units RSX5 condensing units running on 4 units indoor units. 2 indoor on each outdoor. Each system operating 12 hours alternately daily being monitor by a PLC controller. Installed a high temp alarm and fault controller to switch over system whenever a fault exist.

  12. #62
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    Re: Server rooms.

    Quote Originally Posted by woolyback View Post
    without doubt the correct unit for the job. but if it is a small customer without out that sort of money to spend what is the sales person going to sell?
    True words.

    Earlier this week, I went along to a potential customer to advise on problems they were having with their Server Room A/C.

    See pics....




    If you look closely (look twice, maybe) there is some rainwater guttering running beneath the Room Units. The IT Manager installed this when the Room Units started icing up, regularly. Naturally, with one of the Racks right underneath the Room Units he had to be smart, and so he installed the rainwater guttering. The guttering empties into a drain line which runs out nicely in a gravity fashion.

    Obviously, with the units icing up he needed some other handling.....Ah yes, there are those two time-switches. Yes, he plugged these two DIY Klunk-Klick things into a timer-plug adaptor. They were set for 3-hours on, then three hours off, with the two units leapfrogging. In other words, within 3 hours one would ice up, so the timer would switch that one off and the other unit would come on. Three hous later, when the #2 unit was icing up, all change again, when the time-switches shut off #2 and start up #1 unit(which would have thawed out by this time).

    So, there has been quite an education program involved with this (potential) customer.

    Just thought it might be of interest on this string about the problems of Server Rooms and the appropriate aircon solution.
    Last edited by Makeit go Right; 01-08-2007 at 08:16 PM. Reason: sort out pics

  13. #63
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    Wink Re: Server rooms.

    How did you manage to hold the camera still while laughing?!, the thread is great!, kept me amused for a while.

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