Small Server Cupboard Cooling

[HilcrRWise]

I am currently planning to install an A/C unit for our small server cupboard (dimensions: 3.6m x 1.5m x 3.1m) containing 3 main servers, 2 desktop computers, 1 monitor, 2 UPS, a rack unit containing 15 switches. The unit will need to run 24/7.


We have received quotes from several companies and have shortlisted 2:

Company 1
Daikin FTKS35/RKS35 - 3.5 kW
5 year warranty
Installation cost = £1,595
Service cost = £50/year (2 visits/year)

Company 2
Hitachi 6.5W (model name unknown)
1 year warranty
Installation cost = £1,472
Service cost = £240/year (4 visits/year)

I would be grateful for any comments you can provide concerning these two quotes that will help me make a decision.

Thanks

[The Viking]

Two main differences here....

First, and most important,
TOTAL CAPACITY,
One of these are incorrectly designed.:eek:

If the true heatload is 3.5kW then the 6.5kW unit will be well over sized with possible temperature hunting and high running costs as a result.
If the true heatload is 6.5kW then a 3.5kW unit will never be able to cope.

If it's existing kit you are going to move in to this room, ask either one of the quoting companies or a sparkie to measure how many amps the kit is pulling (from this the heatload can be calculated. If it's new kit, check on the manufacturer's website, quite often you will find the heatload hidden amongst all the Mb/Gb/IO-IU data..

It is important to get this right.



Then you got the maintenance costs.....
No proper engineer would service a unit for £50/annum. Sorry, it's not possible.(I would have to travel to your site, park my van, sign in, sign out and leave. And I would still make a loss)



You also have to decide how important this kit will be for your company, ideally you would fit 2 independent systems in there.

A TIP:
Go to my website; www.the-viking.eu , there you will find a page dedicated to people in your situation.
;)

[The Viking]

3 main servers ------ 500W (assuming they are NOT blades) X 3 = 1500W
2 desktop computers ----------------------------------------- = 500W
1 monitor ---------------------------------------------------- = 200W
2 UPS ----Ask UPS manufacturer but say----------------------- = 1000W for now
A rack unit containing 15 switches------------------------------= 200W

So we're up to 3.4kW without building gains:rolleyes:

If we instead look at a very rough rule of thumb of 400W/m2 in IT rooms (But this is an old figure, goes back well before anybody had even thought about blade servers).

Dimensions: 3.6m x 1.5m x 3.1m
3.6 X 1.5 = 5.4m2
5.4 X 400 = 2160 W:rolleyes:

(PLEASE NOTE: THE ABOVE ARE EXAMPLES, NOT FACTS)


The unit will need to run 24/7.
And can one assume that the IT kit will be mission critical for your company?
If so, You do need more than one unit.
(Not for the load but for backup)

[eggs]

Two main differences here....

First, and most important,
TOTAL CAPACITY,
One of these are incorrectly designed.:eek:

If the true heatload is 3.5kW then the 6.5kW unit will be well over sized

Viking, a 6.5 kw inverter will happily bumble along all day, all week and all year with a 3.5kw heatload. Agree?

Have you never sized a server room correctly, then returned for a service and found twice the IT tackle in there?

HilcrRWise, go with the Hitachi option. Better still, spend another grand and get two 3.5kw Hitachi units installed insted set up for run and standby.

cheers

eggs

[Thermatech]

Both install companies know that standard split systems are not designed for this application & will most likely have premature failure within warrantee period.
One company has loaded the cost of emergency return visits within 5 years into initial cost of the system, the other company has only given 1 year warrantee & has loaded the risk into the maintenance charge.

Both companies know that standard split systems are designed for comfort cooling & will not cope well with the this high sensible heat load application.

The end user will never get good value for £ spent unless correct high sensible cooling system is installed.
It will cost more but it will last longer & maintain better room temperature & humidity conditions.

However a/c installers also know this & make more profit from emergency repaires following multiple failures & then installing another standard split system which will also suffer from multiple failures & more repaire costs.

Suggest request the exact specification of the operating temperature limits of the systems & details of the sensible heat ratio. Also request details of how the equipment will maintain 50% humidity in the room when this type of system will be constantly removing moisture from the room.

You might find that the units only have about 0.75 sensible heat ratio which means that they need some latent heat or moisture to work correctly. For high sensible heat applications 0.95 or better is required.
Without humidification in the room the relative humidity will fall to less than 30% which can cause static problems. At 30% the wet bulb temperature will be arround 12 - 13 deg C , but you might find that the lowest allowable web bulb operating temperature for standard splits like these will be about 14 - 15 deg C.

You could always specify to the contractors that you will monitor the temperature & humidity in the room & will only make final payment if the record proves that the system has maintained the temperature & 50% humidity for one month.

[eggs]

Thermatech, thanks for this reply.
I also enjoyed reading your reply to a post of mine a while ago regarding server rooms on VRF's. You make the complicated straight forward.

Cheers

Eggs

[The Viking]

Viking, a 6.5 kw inverter will happily bumble along all day, all week and all year with a 3.5kw heatload. Agree?

Have you never sized a server room correctly, then returned for a service and found twice the IT tackle in there?

HilcrRWise, go with the Hitachi option. Better still, spend another grand and get two 3.5kw Hitachi units installed insted set up for run and standby.

cheers

eggs

Maybe, but the only 6.5kW Hitachi I could find is a DOL one.

Even if I fully agree with Thermatech, from an engineers point of view, I (unfortunately) lives in UK.
Here all IT people are willing to spend tens of thousands of pound Stirling on the latest server but when they are told that the proper system to cool it will cost ~£8000, they get hiccups and blame the A/C contractor for overcharging:mad: then get something designed for comfort cooling installed because it's cheaper.

HilcrRWise (and all other end-users),
Unless you are willing to pay for a proper close control system, you will have to be prepared to suffer the inconveniences as described by the esteemed Mr Thermatech.
;)

[Danny11]

Sorry frank

[monkey spanners]

IMI/Marstair used to do high sensible heat systems for coms rooms. You'd get a '60' outdoor unit with a '80' indoor unit for example, as opposed to a '60'/'60' system for comfort cooling. Non inverter though and a bit noisey. Put a few in for BT years ago. Nice easy fit condesate pumps that shut the unit down if they had a fault. Top air discharge. Getting all nostalgic now:p

[HilcrRWise]

Thanks for the comments.

The kit is not majorly mission critical, they are for a school so cost is more an issue than quality. For the past 5 years or so they have been sitting in a small room with only a small extractor fan for ventilation which keeps the room at around 40+ degrees C, the only reason I am being given this opportunity is that the local proxy server computer that connects the school to the internet died the other week (god forbid if they have to go without access to emails for more than 10 minutes:)

Something Company 1 mentioned to me, when I queried them on the lower capacity of their unit compared to others, is that the higher capacity inverters are likely to run at lower speeds for our requirements so has a higher chance for its evaporator coil to ice up risking leaks inside the server cupboard, whereas their lower capacity unit (which will still be good enough to acomplish the task) will run faster negating this risk. The other company responded that this statement was put out by Daikin several years back, due to issues with their own systems, which is no longer valid. How would you respond to these statements?

[paul_h]

Thanks for the comments.

The kit is not majorly mission critical, they are for a school so cost is more an issue than quality. For the past 5 years or so they have been sitting in a small room with only a small extractor fan for ventilation which keeps the room at around 40+ degrees C, the only reason I am being given this opportunity is that the local proxy server computer that connects the school to the internet died the other week (god forbid if they have to go without access to emails for more than 10 minutes:)

Something Company 1 mentioned to me, when I queried them on the lower capacity of their unit compared to others, is that the higher capacity inverters are likely to run at lower speeds for our requirements so has a higher chance for its evaporator coil to ice up risking leaks inside the server cupboard, whereas their lower capacity unit (which will still be good enough to acomplish the task) will run faster negating this risk. The other company responded that this statement was put out by Daikin several years back, due to issues with their own systems, which is no longer valid. How would you respond to these statements?
An inverter running slower would have a higher SST, therefore less chance of icing up, the first company doesn't know what they're talking about.
On the downside, an inverter running slower has lower flow velocities, meaning more risk of oil not being returned to the compressor.
Also a smal inverter running flat out has a greater power consumption than a larger inverter (or even a conventional) running at a lower capacity

[Thermatech]

Very common to see contractors have resorted to retro fit a large drip tray underneath split system indoor units when installed in computer rooms.
This is because at low humidity conditions the indoor coil will tend to freeze up on standard comfort cooling split systems.
Most qaulity products will have some sort of coil freeze or coil frost protection to prevent the coil from becoming a block of ice. Typically the unit will cool for a short while & then stop on coil frost prevention, the frost or ice melts & the unit starts to cool again.
If the compressor is restarting every few mins 24/7 it will not last so long.
The size of the indoor coil, the air volume & target refrigerant evaporating / super heat are designed for much higher humidity conditions so coil frost prevention is not a problem at normal comfort cooling aplication conditions of arround 50% or higher.

In small computer rooms the standard split system is constanly removing moisture from the air & the humidity becomes very low typically 30% or less.
This operating condition is completely outside the manufacturers allowed operating conditions envelope & the units will tend to cycle on coil frost prevention.

The Daikin Sky Air inverter systems did at one stage have an option for high sensible application. A high sensible setting could be made which adjusted the target super heat. If the evaporating temperature can be maintained at a higher temperature then coil frost prevention is not such a problem. But the max cooling capacity of the system will be reduced.

Some contractors deploy a number of head pressure control tricks to force the system to run at higher than normal discharge pressure which helps ceep the refrigerant evaporating temperature at the indoor coil slightly higher & reduce coil frost prevention problems but this will void any warrantee.

The other option which some contractors use is to install a Vapac type humidifier in the room. This helps maintain 50% humidity which is what standard split systems need to work correctly.

At the end of the day a computer room is the most demanding place to install a standard split system because it has to operate 24/7 in extreem conditions & operating cost will be high due to emergency call out repairs.

[Makeit go Right]

If calculating the heat load from the computers by checking website info, the manufacturers normally give the maximum load the computer can draw, implying maximum electricity-using components are fitted. That's not normally the case, of course.

I used to have a web-link to an American site where the techies had taken the trouble to note down their impirical loads from a whole range of computers they had worked on/with. Surprisingly low figures.

SO, the best way to assess the equipment cooling load, as stated earlier, is to get impirical Amp readings from the computer equipment installed, which would all add up to total AMPS drawn. Divide that by 4 and you have your sensible heat load.

Then add in the Room cooling load (fabric, lights, etc).

When selecting equipment (yes, you all know this), seek out the separate sensible and latent cooling figures and make adjustmemts for UK conditions (if the location is in UK). The manufacturers talk in terms of TOTAL NOMINAL cooling load....Total is Sensible+Latent cooling, and Nominal figures are based on Not-UK conditions, and are way off.

So, even if the equipment sensible load is say 3kW, there is some more work to do before selecting the kw-size of kit.
Then you can step into the heated debate on whether you want to spend out £5k+ on a Close Control System, or the £1500-odd quoted already. There is at least 2 strings of discussion elsewhere on these boards about the subject.

Considering the splits, which seems to be where your customer budget is focused: An inverter-type unit would work better to match the room load accurately, with little changes in the room temperatures. The non-inverter (on-off) models give changes in the room temperature, and lots of on-offs that compressors disslike. The aircon equipment must be able to operate at low outside ambiants - some need a 'low abiant kit' (aka Fan Speed Controller) fitted to achieve the desired results.

The £1500-od split solution seems to be to leave the existing wall opening you have for the extractor fan, so the room can draw in some moist air from the other area to create some latent heat load for the aircon kit to perform happily.

On the two quotes, the one offering cheap maintenance seems to have very little overheads. I would ask to see his insurance certificates and aircon training certificates. Of course, he could just be a very busy chap who has other maint in the area and can add this one in easily/cheaply.

As for the selection kw-sizes, the 3.5kW chap may have just wet his finger and decided on the selection that way - ask them both how they worked out the equipment Kw-size. I suspect one will no-answer you, and the other will talk about fabric loads and computer calculations etc. (Also bear in mind, a computer only works out answers based on what info is fed into it - one also needs the right data for your electrical/computer equipment fed into the calculation to get the right/accurate answers.)

Could be the calculations have excessively high figures for the computer kit and the guess-chap is spot on. :-)

[frank]

Thanks for the comments.

The kit is not majorly mission critical, they are for a school so cost is more an issue than quality.

The saying, penny wise, pound foolish comes to mind here.

I can't see the point of spending any money on this project unless you are going to get a system that works for more than just a few months and comes without the prospect of additional on costs.

There's some good advice given here.

[al]

HilcrRWise

We've installed a number of Hitachi high wall units in simialr situations with no hassles, we personnally always oversize by at least one to two Kw to allow for additional equipment. All current hitachis are inverter, i didn't know they still did the DOL type, Viking?

if you can give the model number this could easily be confirmed, i'd be more worried if they can't provide it as they may be offering an older unit?

Regards

Alec

[The Viking]

Al,

The only 6.5kW (well...6.4kW but anyway) unit that I found on their website was the [RAS-24G4/RAC-24G4] and in the technical burf, that's listed as direct on line.

But I might be wrong, I rarely work on them and just went with the info on their website...

[The Viking]

HilcrRWise,

Now I'm about to swear in the church, but here it goes...

Most IT equipment manufacturers are giving a higher temp limit for their equipment of about 30C, as long as it is constant. (Most IT guys insist on having it below 20C, but that's another matter).

You said that the old cupboard only had an extract fan...
Is it possible to have 2 ducts in to the room? (Is there an outside wall?)
If you are able to get a high and a low level vent in to the room, the high level one extracting on the side of the kit where the heat is coming out. The low level one supplying fresh air where the kit is taking air in..

This, together with a thermostat controlled fan in the supply air, would most likely be enough to keep your equipment happy.
And all this discussion would be unnecessary, the maintenance costs would be almost zero and the running costs a fraction of what it would cost to run an A/C....


(I'll get my coat)

[declan simmonds]

Hello everybody i have worked on many small severooms with of cables everywhere no access to the unit and also i find that small wall units are not up to the job in keeping the room temprature stable within the specified specs IE you tend to get hot spot within the sever room sometimes i fit a remote stat where the hot spots are and i think that the fitting two small 3.5 splits with a control panel to change over in 12 hour periods and if the other unit breaks down the other unit comes on it depends on what the customer is will to pay, but best of all is a underfloor cooing system making the cold air flow through the racks.

[Thermatech]

Follow on from Viking with the free cooling principle.

For instance
Airedale make specialist cooling systems for the telecoms industries.
These are for mast cabins & base stations.
The smallest unit is 5kw Ecotel.
Free cooling as standard.

As this application is for a very small room with the possibility of an outside wall this would seem to be worth investigation.

Do any engineers here have experiance of this type of kit & can comment ?

[The Viking]

Airedale make specialist cooling systems for the telecoms industries.
These are for mast cabins & base stations.
The smallest unit is 5kw Ecotel.
Free cooling as standard.


These units are also known as clingons.
There is a large cupboard like thingie to be bolted on to the outside of the cabin and 2 vents will allow airflow inside.
They are reliable and robust but they are also more expensive than a close control unit.
Their free-cooling function is very limited but this is a control issue that can be overcome with some "on site engineering".

[Andy W]

I have faced the dilemma many times on what to fit, once you start talking close control, the school budget cannot stretch to that, I myself have fitted Fujitsu wall mount inverters in small server cupboards and never had a problem (touch wood), one I fitted over 2 years ago and it has never been serviced, I spoke to the guy about it 2 weeks ago! How many of us have been asked to quote for jobs but the customer cannot give you the heat loads of all the equipment, up to a point there is always a risk in installing anything in a server room working to a budget.


Oh, some great posts on this thread, very enlightening.

[Electrocoolman]

Whilst on a recent SANYO course, this subject came up, and the solution (as mentioned elsewhere) is to oversize the evaporator but to then alter the system setup parameters (on an SPW system), as though it had a smaller evaporator which I believe gives you a high sensible cooling.

[HilcrRWise]

It took a while for them to get back to me, but the Hitachi model they have quoted me for is the RAK-60NH4 (I have attached a datasheet if anyone is interested). It looks as though this will be the solution I will be going for.

Thanks for all the comments.

[eggs]

Company 2
Hitachi 6.5W (model name unknown)
1 year warranty
Installation cost = £1,472
Service cost = £240/year (4 visits/year)




It took a while for them to get back to me, but the Hitachi model they have quoted me for is the RAK-60NH4 (I have attached a datasheet if anyone is interested). It looks as though this will be the solution I will be going for.

Thanks for all the comments.

I'll do it for £1471 and £239/year.;)

eggs

[HilcrRWise]

I am still fairly concerned about the Hitachi unit only having a 1 year warranty. Considering the unit will be running 24/7 what are the likely components that could break, in what time period and what would they cost to replace? Also as the unit will be running 24/7 would these components still be covered if they go during the warranty period or do the manufacturers have a maximum hours used clause?

I have been offered a Fujitsu ASYA18LC unit for £1745, while it is more expensive it does have a 3 year warranty.

Would I be better off getting the 3 year warranty unit or gamble on the Hitach unit lasting more than 3 years without needing a major component replaced.

Thanks

[nike123]

Both of units will work in conditions for which they are not designed and I will go with longer warranty.

[Thermatech]

Any manufacturer can choose to refuse warrantee claim for equipment which is operating outside the specified min/max operating range.

However in practice they often never find out unless they send an engineer to site to investigate.

[Makeit go Right]

Warranty is often a little unclear.

The installer will mention a warranty for the whole system of 12 months, when quoting.

Meanwhile (separately) the equipment manufacturer normally offers a 3-year warranty on the equipment. This is true for Fujitsu and also true for Hitachi.

This means that if a warranty issue crops up after 14 months, the replacement part comes free from the manufacturer, but the labour element is not covered, and the customer would have to pay for the whole repair, less the cost of the new parts.

If nothing has been hitherto discussed, an installer might forget to mention the manufacturer's free replacement and include a sum in his bill for the replacement part. Not honest, but it can happen.

When quoting, a clever salesman will talk about a 3-year warranty but in their small print this refers to the equipment only.

In your case, you have the Fujitsu looking better because there is mention of "a 3 year (parts) warranty," yet the Hitachi offer a similar 3-year parts warranty.

I will bet the Fujitsu warranty is Parts Only, as discussed above.

So, you will be back to the basic question, which kit is the best for your application?

I would like to step aside now, as those who favour one of these manufacturer's kit will offer their experience and recommendations.

[HilcrRWise]

Change of plans, I've been provided a quote for a Daikin 6Kw unit for £1600 and as the company is a Daikin D1 Partner it comes with a 5 year warranty, so we will be going with this one.

[Makeit go Right]

Sounds good. Now would be a good time to get his price for annual maintenance (before you place the order).