Server rooms.

[Temprite]

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.

[NoNickName]

A speed reduction while ambient t is low will cause a further reduction in condensing pressure. Condensing fan speed must be reduced instead.
Also, this solution is pretty much energy-hungry. A Free Cooling (shelter or chilled water) would be much better.

Besides, a split unit will not control humidity, while a close control will.

[Below 0]

Hi
I currently work on computer server rooms that have inverter units in them and find they work very well.Obviously a specialist computer room a/c unit would be the best option but a lot of small companys dont have the funds to justify the expense.The inverter models tend to work well due to the fact that they hold the room at a consistent temp and and are cheap to run because they are variable speed.You will also find that the condenser fan cycles in low ambients and that they are less prone to outdoor icing because they are only just running, if you know what i mean.The other bonus we have found is that the building owner can buy two units for the price of a speacialist system and have 100% back up in the case of a unit failing.

Hope this helps.

[Abe]

Besides, a split unit will not control humidity, while a close control will.

No Nick

Please could you tell me what is a close control system
Thx

[NoNickName]

close control units, aka CCU, are upright standing cabinets, from 5 to 100kW of cooling capacity, having 1 or 2 dx circuits, either air cooled or water cooled, or with chilled water coil.
They monitor temperature and humidity, and are able to cool, heat, humidify and dehumidify.
Heating is done via electric heaters, hot gas injection or warm water.
Cooling plus heating performs dehumidification.
Humidification is done via an immersed electrodes boiler with steam distribution in the air flow, or by other means of water dispersion, either cool water or hot water. Hot water is preferred to avoid bacteria proliferation.

Eg of close control unit

http://www.montair.it/prodotti/3_interno.jpg

Air discharge can be from the top (aka as OVER when no false floor is available) with front air intake, or bottom (aka as UNDER) with top air intake. In the image an OVER unit is shown.
Few units are so called "displacement CCU", with top air intake and front air discharge.

Shelters units are not strictly CCU, but they have an air damper to provide free cooling.
Free cooling can also be achieved with water cooled dx units, and diverting cold water to a water coil instead than into the condenser in winter time.

[Peter_1]

We have some standard AC's running in server rooms in a hospital, in a big factory, in a telecoms company...and had never had problems with it.
One is even running in a company who's running the telecoms service in Brussels for the Belgium Parliament.

Nowadays computers can work within a wide range of humidity and the time that humidity had to be kept at a certain high level is almost nonexistent.

This was mainly a demand to prevent static electricity in the machines.

If you see in what a rough industrial environment some computers have to work these days.

[Renato RR]

No electronic cant work in all conditons.They can but they life is then much shorter becose electric condenser react very badly to dry envirement.They simply lose they capaciti.Also the circuit board reacts badly to dry air.Some versions of EPROM start to mulfunction on long period dry air condition.Belive i know we maintain sites for mobil phone company.

Renato

[Abe]

Thank you Nick for your posting
Its very informative

Best regards
Abe

[Abby Normal]

here is a redundant pair of 40 ton units,

http://i32.photobucket.com/albums/d41/a_bee_normal/Forums/Twin_Lieberts.jpg


they failed capitalize on the built in piping chase of one

http://i32.photobucket.com/albums/d41/a_bee_normal/Forums/PAC-1.jpg

[Peter_1]

These are installed in the VRT, the digital center of the Belgium television broadcating company.

[frank]

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 also heard of this but didn't get the full explanation. From memory it was due to a batch of problems associated with the control logic in the electronics and the high sensible loads associated with Server room applications.

I think Daikin had a lot of complaints about units failing to control properly in these environments.

[Ross]

G'day mate.

I'm not 100% sure about wall mounted Daikin's used for server/computer room application but it is possible to use Daikin FFB (600 by 600) R410A skyair cassettes for this application. It is however necessary to change a field code setting to alter the freeze prevention parameters due the low humidy of this appication. I guess this would apply for the wall mount FCU's as well.

[quiksilva]

In my experience the last thing you would require in a dedicated data centre / comms room would be a potential source of water above servers which is exactly what a cassette is - be it failed lift up pump or coil icing over due to high heat loads especially with the new generation of 'blade ' servers which can go up to 7-9 kw per cabinet. Also bear in mind close control units generally offer a lot higher filtration qualities then a split (disposable EU spec box filters) and put the cooling where its required - say under the floor to be pulled through the cabinet via its own fan module. Im prepared to be convinced otherwise but horses for courses - 24/7 365 days a year operation in critical applications is not for split a/c but dedicated close control equipment.

Andy

[frank]

but it is possible to use Daikin FFB (600 by 600) R410A skyair cassettes for this application.

They are called FFQ cassettes in the UK.

You cannot alter the operating parameters on wall fan coils with infra red controllers, only on units with hard wired controllers and these start at size 7kw upwards

[Jase]

I encountered a problem with a wall mount FAYP100 (non-inverter) once. Unit was installed in a small server room. The unit kept frosting back to the compressor and at one polint had lost 2 compressors within 4 weeks.
I ended up sticking a couple of kettles into the room to increase the humidity and this seemed to do the trick.
In the end a remote sensor was fitted in another part of the room and a few jiggery pokery of the settings was carried out. I was told by Daikin that they sell units designated for server applications, but nothing was ever followed up. Anyone know of this?
BTW took the kettles out of room!

Regards
Jase

[puddleboy3]

The problem with using the split type units in a server room is that they are not designed to operate in low latent heat applications i.e server rooms. This was a problem with Daikin units and as already pointed out the units would go out on freeze protection and by the time it reset the server room would be over heating. Daikin started to change the control strategy of the B series 407c Sky air units, which entailed changing PCB's and field settings. The new Sky air range RZQ units offer what Daikin call EDP setting (Electronic Data Processing) Setting which alters freeze protection settings to prevent any problems.

[Makeit go Right]

The Daikin design change is very interesting. (Strange they did not start with the wall-mount, which is more appropriate in server rooms.)

Before reading Puddleboy’s post, I would have said that the reason one would not (ideally) select a split for a Server Room is that it will drag the RH right down, often below 50%. You can see this best on a psychometric chart.

And as stated above, electronic equipment does not like a very dry space, preferring 50-75% RH, as a generality.

The alternative is a more expensive chilled water system.

[Abby Normal]

Out of curiosity, server rooms are usually almost all sensible cooling. Maybe some latent load from ventialtion air.

So when you have a big sensible load, you need a very high air flow rate per unit cooling. In imperial units, it could be 600 to 700 CFM per ton and it works the best when it is a blow through process, allowing the cooling coil to remove the blower heat.

Something that does not move this amount of air and is draw through is forced to over 'dehumidify' the air in an attempt to control temperature.

Not always the best bang for the buck, although every leibert I have seen is draw through.

[Ross]

Hi guys.

What about the new Daikin Ururu / Sarara for computer room / server room applications? Should be now available from Daikin UK but not sure about Daikin Oz Temprite. A much cheaper alternative to other specialised systems. Should be a info on the Daikin UK website.

[Temprite]

Thanks for all the responses everyone.

The reason I started this thread was because someone I know was looking to put an inverter wall mount in a computer room and I mentioned to him that it was not satisfactory for that application, but could not remember exactly why.

Instead of a wall mount they put in a ceiling cassette inverter model.Have not spoken to him recently but I assume all was ok


Hi guys.

What about the new Daikin Ururu / Sarara for computer room / server room applications? Should be now available from Daikin UK but not sure about Daikin Oz Temprite.

I dont think this unit is available in oz.

[Makeit go Right]

Regarding the “Ururu Sarara”, the equipment has a design problem that needs sorting out yet. ie, these units will not cool below 21 degrees C (making them useless for Comms Room applications). However, there will be a revision to the outdoor unit in January that will enable the condenser to cool down to minus-10 degrees C, so that should resolve this issue.

Units only come in the following sizes 2.8kW (£732 trade), 4.2kW (£852 trade) and 5kW (£1133 trade).

[Renato RR]

Emerson-Liebert Hiross SE+SC10 is best solution.Or TD10 there are some mount 1998 in my region.Carly compressors,alco TEV,realy good design.Controls humidity,fresh air and do everyting you want.I have 75 machines on maintance and replace 3 compressors in 4 years.

Best regrds,
Renato

[quiksilva]

So let get me this straight....

to cure your low humidity issues in a server room you ducted untreated / unfiltered air straight in?

What are we dealing with here? Cooling a small room with a couple of comms cabs via everyday split a/c or proper close control, there is a difference.. temp control / humidity control via hum/dehum
And also regarding the Liebert comment fine but you obviously havent worked on Isovel products - designed by an engineer for engineers - Airedale /denco etc etc all make or have made worthy products particulary when based round the maneurop MT/MTZ compressor which can take a huge amount of abuse when compared to copeland scrolls in the same application

[Jase]

So let get me this straight....

to cure your low humidity issues in a server room you ducted untreated / unfiltered air straight in?

What are we dealing with here? Cooling a small room with a couple of comms cabs via everyday split a/c or proper close control, there is a difference.. temp control / humidity control via hum/dehum
And also regarding the Liebert comment fine but you obviously havent worked on Isovel products - designed by an engineer for engineers - Airedale /denco etc etc all make or have made worthy products particulary when based round the maneurop MT/MTZ compressor which can take a huge amount of abuse when compared to copeland scrolls in the same application
You will probably find that Airedale are using copeland scrolls now! What advantages are there with the Isovel equipment?
Regards
Jase

[rbartlett]

We have just lost 2 out of 3 wall mount 10kw Daikin cooling only non inverter systems -compressor seized.

I have had a 1/2 hr chat with Daikin technical and the latest is the you should fit INVERTERS to server rooms but make sure you adjust the PCB for data room application.

The old 407a inverters were the ones which caused problems but these are obsolete so that 'no inverter' advice is out of date.

The problem of non inveters is exacerbated by the fact that on 410a units Daikin removed the accumulators and hence any prolonged low temperature running increases the risk of liq return back and washing out of the oil .

We are currently considering a swap out to RZQ inverters to get over this.

However some advice for those with non inverters

1. if pipe length is less than precharged max REMOVE a % to lower the risk of flooding
2 Ensure the controller cannot be set lower than 20 but ideally 21/22
3 fit a suction accumulator


Cheers

Richard

[NoNickName]

What about fitting real full-function close control units, instead than those low cost consumer wall mounts?

[rbartlett]

What about fitting real full-function close control units, instead than those low cost consumer wall mounts?

firstly you answered your own question but frankly 99% of rooms simply do not need anything like the old computers did. I can remember looking after a room with 6 big Lieberts cooling the air and the computer had a 15 stage water cooler for it's insides.

Frankly it's the air conditioning which seems to suffer not the servers now. The days of close control as a necessity has pretty much gone and only those old fashioned computer guys who think a room should be kept at 16 deg's C are left. The UK had a big market in the manufacturer of CC units -denco,Isovel etc and most have long gone.

Times have changed and kit moves on specialist computers like the Kray may need a proper climate but these rack server blades are pretty robust.

I think 22 c is more than adequate for most rooms with good air circulation and if we could only convince Mr IT man our a/c would prefer it too..!!

Cheers

Richard

[NoNickName]

That doesn't answer my question. Or, put it in other words: why should anybody bother intaking fresh air for preventing coil freezing, while more professional units will not suffer from absence of latent heat. CCU are already designed for all sensible. I'm afraid it is not Mr IT's fault, it is Mr RE who wants to simplify because lacking proper know how.

[woolyback]

A Server room with any ac unit in with no fresh air or humidification will have a low humidity level and if you look at the design spec most ac units these will not work well under 35-40% RH. If you look at the Daikin non inverter equipment depending on the gas will have freeze up problems under these humidity levels as it floods the evaporator sending the unit into a frost protection and the possibility of liquid flooding back to the compressor. If you use an inverter type unit (R410A) this will help by reducing compressor and fan frequency in doing so reducing capacity to reduce the last two problems but where you might have a 7kw unit it is more likely to work as a 5kw unit.
Solutions don’t use ac units in comms rooms, make sure fresh air is supplied to increase humidity, increase the humidity, and tell the end-user not to run ac units below 22C.
There is a code for Daikin to stop the end user turning the controller below 20C on new kit setting 14-7-02.
I hope this helps.

[quiksilva]

In all the posts so far regarding splits dont tell me they can approach the filtration levels dedicated CCU with disposable EU spec filters achieve. To be honest i havent noticed data centres ripping out ccus to go down the inverter split route - as mentioned in one of the above posts no accumulators on the latest 410 units etc do this and they will work sort of... sorry i dont buy into it, yes a split will cool a room down and with some fancy programming may manage humidity to some extent but a full house CCu with dx/chilled water/water cooled/ free cooling options is a damn site safer bet, reports of their demise may be premature :)

[woolyback]

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?

[NoNickName]

Well, I've been reading threads complaining about customers not buying the appropriate equipment for their needs. What about starting advising the CCU to be the right solution for their problem? Then, he will be the only to blame whether will opt out for anything inappropriate...
A DX CCU of 5kW or 7kW will cost approx 2000 euro more than a consumer split. What about teaching the sales person what ROE is?

[Peter_1]

Nobody mentioned - as far as I have read this thread - the selection of a one size bigger indoor unit then the outdoor unit.

Had a similar experience in the past like Richard with 5 Lieberts in a big computer room of a company almost in my backyard (+/- 2500 peoples working there, a subsidary of Fiat)

Most of the units are replaced with conventional splits and this works very well.

Like said in the beginning of this thread: we installed the cooling (Mitsubishi splits) in one of the communication centers (stacked full of computers, huge UPS, srvers, switchers,...) of the Belgium Parliament, years ago and all the units are still running and it works fine.

In the past, a too low humidity was a problem due to static electricty but all these problems are gone now.
Look how many standard computers you see in very greasy, dirty environments and they're still working.

[frank]

Of course, you should always select the 'split' type conditioner based on the Sensible load only from manufacturers tables. Problems seem to appear when the 'Total' cooling load is selected.

[woolyback]

if you were to use a size up indoor unit this would probably solve the problems. but when you tell the customer they wont get any warranty on the unit see what they say?

[malik55]

Okay question for those who are in favour of a commercial split installation in data rooms,
If humidity decrease up to low levels, How a commercial split can increase it if mean time there is also a cooling demand, and if required an under floor air flow directly enters in the cabinets from bottom then which type of unit will be fixed,
Actually this is same as to take a common pain killer for all types of body pains,
A one type of unit fix it every where for just for sake of a CLIENT because he can invest in computers data system a huge amount but for a proper A.C CCU system he is going for cheaper solutions'
Have very bad experience with commercial splits used in Data rooms,
malik55

[rbartlett]

In all the posts so far regarding splits dont tell me they can approach the filtration levels dedicated CCU with disposable EU spec filters achieve. To be honest i havent noticed data centres ripping out ccus to go down the inverter split route - as mentioned in one of the above posts no accumulators on the latest 410 units etc do this and they will work sort of... sorry i dont buy into it, yes a split will cool a room down and with some fancy programming may manage humidity to some extent but a full house CCu with dx/chilled water/water cooled/ free cooling options is a damn site safer bet, reports of their demise may be premature :)


Assuming you mean me..

You're splitting what I said but the rise of computers have been iinversely preportional to the demise of specialist computer room air conditioner manufacturers.

Whatever you feel about them splits are the way forward for most applications and the few left will have 'proper' a.c.

These are the data rooms with big servers etc which may -or may not- need specialist a/c. I remember speaking to a HP eng who said their kit runs happily at 30 deg C but he couldn't convince the resi IT guy!!.

It has always been that the major problem is not the heat/humidity that kills comuters it's the rate of rise. This is why the stuff hits the fan when the a/c goes down as a 10 deg rise over 10 days will have not effect on the computers but a 10 deg rise in 2 hours causes the c.b's to flex and expand and this is why joint failure occurs.

Filtration is another red herring as these rooms are naturally very clean so why the need to be extra clean/?Again it all harks back to the olden times when computers were so unreliable that they over spec'ed everything as a 'just in case' get out. This is akin to the romans building bridges which which will stand for 1000's+ of years
Why?? well because they did not have the skills to engineer it down enough so just kept doubling and doubling the thickness for the 'feel good' factor.

As the late Colin Chapman said
"any one can build a bridge which stands up :only an engineer can build a bridge which stands up -just"

Cheers

Richard

[NoNickName]

It goes by itself, I don't agree with the latest comments. Of course a Mitsi split goes well. I'm not implying splits are rubbish and CCU's are golden. I just would like to stress the fact the using splits in a server room is an improper usage of a comfort air conditioner.
There was a time back in 2000, prior to .com explosion, when consultants were advising that in the short time, based on Moore's law principle, computers will be doubling their computing capability in half the space, and this would end up in quadriplying the cooling demand per square meter.
At that time we were around 1.5-2kW/m2.
How would you guys cope with a 8kW/m2 heating, on a 50m2 server room?
With splits?
And what about a backbone landing in Amsterdam, with 10000m2 filled up with optic fibers interfaces, amplifiers, modems, switches, etc?

Not mentioning the newest water cooled blade server racks... it seems to me that RE are taking advantage of big supplies of chinese low-cost splits, and whatever happens either install them in houses, offices, or server rooms.
If it breaks, replace it.

This is not the road to go.

[NoNickName]

Oh, and I forgot to add: no, HP servers will not run happily at 30°C, assuming that 30°C in the room will correspond to 60°C in the rack.
Here I'm writing this email at 21°C temperature, and the CPU is 48°C thanks to a bigger fan by Arctic. It was 66°C with OEM Intel fan.
HP engineers do not know what they are talking about when speaking about air circulation, local pockets of warmer air, pressure drops across false floors and the like.
Real applications are different than testing a single 4U in a controlled environment.
Infact, manuals of servers read: "operating temperature -15 to +40°C". Then, why not keeping the window open or just filtering ambient air through an inlet louver?

[Peter_1]

There was a time back in 2000, prior to .com explosion, when consultants were advising that in the short time, based on Moore's law principle, computers will be doubling their computing capability in half the space, and this would end up in quadriplying the cooling demand per square meter.
At that time we were around 1.5-2kW/m2.
How would you guys cope with a 8kW/m2 heating, on a 50m2 server room?

But has Moore taken in account that computers nowadays uses less energy for a lot more tasks?

[quiksilva]

As the late Colin Chapman said
"any one can build a bridge which stands up nly an engineer can build a bridge which stands up -just"

As an owner of one of his cars aint that the truth!
Back to thread though generally if you lose a fridge circuit on a DX CCu you normally would have between 1 to 3 remaining circuits still operating which when correctly sized will keep the equipment running happily. Now take a split a/c - single point of failure when compressor goes t*ts up and you lose the room, Generally most of the SUN/Compaq/HP gear will automatically start winding down at anything over 37 degrees. Belts and braces i know but also with the added benefit of additional capacity which can in a lot of cases take the strain of switching from standard racks to next generation blades with no upgrade of existing a/c equipment.

[Peter_1]

generally if you lose a fridge circuit on a DX CCu you normally would have between 1 to 3 remaining circuits still operating which when correctly sized will keep the equipment running happily. Now take a split a/c - single point of failure when compressor goes t*ts up and you lose the room,

Explain why you still have 1 to 3 remaining circuits in a DC CCU when one fails? Only if this unit is fitted with 3 independant circuits of course.
Well, then you have to compare it the same way for splits: you need to install for 50 kW heatload, 3 independant units of 25 kW of course.
This is how we do it for a nearly fail-safe operation.

[rbartlett]

As the late Colin Chapman said
"any one can build a bridge which stands up nly an engineer can build a bridge which stands up -just"

As an owner of one of his cars aint that the truth!
Back to thread though generally if you lose a fridge circuit on a DX CCu you normally would have between 1 to 3 remaining circuits still operating which when correctly sized will keep the equipment running happily. Now take a split a/c - single point of failure when compressor goes t*ts up and you lose the room, Generally most of the SUN/Compaq/HP gear will automatically start winding down at anything over 37 degrees. Belts and braces i know but also with the added benefit of additional capacity which can in a lot of cases take the strain of switching from standard racks to next generation blades with no upgrade of existing a/c equipment.


Ah but you're being disingenious. You state a multi CCu system but a single split.why not compare a single stage CCu and a room with two splits??

Cheers

Richard

P.S I must admit CC comment is laughable given the heaps of rubbish that came out of East Anglia!!

[NoNickName]

2 splits do not match with 2 circuits CCU, in terms of efficiency, proportional band sharing, rotation and back up. They simply start and stop following a thermostat, even uselessly at the same time.

[NoNickName]

But has Moore taken in account that computers nowadays uses less energy for a lot more tasks?

No, but in fact there no 8kW/sqm yet.

[woolyback]

I know Daikin have allowed the use of DX coils on there skyair range. and I've seen a system designed with two Denco down flow units with close control and humidification 2 stage on 4 RZQ250 With M pipe run witch kept the room a + - 2C 50% RH system worked treat. but still considering cost what can do a job and is cheaper? that system I've just said or a system with the equivalent duty of fresh air (to help keep the space a moderate temperature) and Splits to cool the racks you could even double up the splits for a cheaper price! but lets face it IT people always want the room to cold, I'm also an electronics engineer and i know for a fact most CPU's we'll happily run into C with no affect the problem is getting the cooling where it is required, with the new racks this has helped us use splits preferable a cassette above the racks.
oh by the way I've also so seen VRV VRF equipment in Com's rooms OH NO! but had no problems.

[Leo1967]

there's no way you can compare porpouse built industrial units with silly split units builtfor comfort.Without mentioning better performance(i totally agree with no nick)
on industrial units you can wire all sorts of optionals like water leak detectors,fire detectors,you can put many units on a net system with cascade,stand by and so on.
Not to mention the air speed....a wall mount is designed for cooling mrs Smith's bedroom while she's asleep not for a 30 metres wide room,in the middle you would cook an egg!

[Double bubble]

Both Daikin and Mitsubishi Electric are nervous about their inverter systems being used in computer rooms. Ideally, they'd tell you why themselves of course but i believe that the low load of a computer room (low latent anyway), means that the compressor can be slowed down to compensate - particularly in low ambient conditions. This conflicts with their required refrigerant flow to keep the indoor heat exchanger free of oil - the alternative is to risk an indoor coil freeze-up.

That's my understanding anyway. As i said, the real answer should be coming from them.


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.

[Obi Wan]

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.
What is the model number? is it R407C or R410A?

Regards
Obi Wan

[Temprite]

G'day Obi Wan.

No particular model number, I was just refering to wall mounts.

[thebigcheese]

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

[NoNickName]

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

Bad move. Why?

[Abby Normal]

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.

[NoNickName]

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.

[Brian_UK]

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.

[winfred.dela]

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 :)

[Abby Normal]

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.

[Makeit go Right]

Well, here is the scoop on the new Daikin equipment. They've added some humidification to the unit. http://www.daikin.co.uk/airconditioning-products/for_your_home/ururusarara/ururuhumidification.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.

[renny_no1]

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.

[Tomking]

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.

[Cofreth]

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.

[Makeit go Right]

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....

http://i146.photobucket.com/albums/r260/MakeITgoRIGHT/310720071481-1.jpg
http://i146.photobucket.com/albums/r260/MakeITgoRIGHT/310720071482-1.jpg

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.

[stuartwking]

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