Advice on residential split system

[DistortedVision]

I am looking for a split system for a home office. Most contractors have quoted for a 2.5kW system like the Mitsubishi Ecolution eg SRK25-ZG but I feel this unit is underpowered for my requirements. I currently have a 10 000BTU/hr portable unit but it is only capable of reducing the temperature by 2-3C. The temperature in the room reaches 28-30C in summer. The SRK25-ZG has an equivalent 10 000 BTU/hr cooling but are the ratings of split systems and portable units directly comparable? I was therefore looking at a 5kW system such as the SRK50-ZG instead. The room size is 5x5m.

Would air conditioning engineers consider this to be overkill for this application? I would like to be able to reduce the room temperature from 28-30C to ~18C. Is this feasible?

Many thanks!

[mikeref]

D.V. I have a 3 by 2.5m office and only a 7,000 btu/hr window shaker for the hot days when i'm stuck here doing paperwork. Your portable a/c probably uses air from inside room to cool condenser therefore a high air change load and poor performance. 5KW is overkill and 18 degrees C is just too cold, for this part of the world anyways. I like 22 to 23C on the muggy 30+ degrees days.. Mike.

[install monkey]

3.5 kw
5*5=25 *150w/m"=3.75kw and thats being on the conservative side.

[DistortedVision]

Install Monkey are you a contractor in the North West area? Would you be interested in giving me a quotation.

[install monkey]

contractor yes, but due working unsociable hours on tracker for a penny pinching boss unfortunatly i do not have much spare time- got called out on sun 3pm got home monday 8pm!!! currently doing 85hr weeks

[DistortedVision]

Can you clarify on your calculation above. I want to know if a 3.75kW system would be capable of reducing the temperature in my office from 28-30C to 20C?

What brands of split system do you recommend. I was looking at Toshiba and Fujitsu.

Many thanks.

[DistortedVision]

...and Mitsubishi Ecolution.

[install monkey]

thats a basic heatload calculation. normally 110w/m2 is for an office enviroment,allowing for 150w/m2 compensates for expansion of equipment,big windows etc.
fujitsu- low end of the market but suprisingly not bad-i have an old r22 asy12 wall mount,been in for 10 yr,the fan bearing is squeeky and when i get a free 2 days of not being on call its getting replaced with a daikin 3.5kw wall mount inverter.(rom size is 6m*4.5m)
toshiba units have improved recently,mitsi are good but i think the indoors are bulky

[DistortedVision]

I've been quoted £1050 for a Mitsubishi SRK25-ZG. Is this reasonable? I'm going to ask for quotes for the SRK35-ZG and SRK50-ZG which are the 3.78kW an 5.14kW models respectively.

Going back to my original question would the 3.78kW and 5.14kW models be capable of reducing the room temperature from 28-30C to 20C?

Also are the 3 sound pressure level values for high / medium / low settings on the fan of the indoor unit?

http://imageshack.us/photo/my-images/17/77043473.jpg/

[DistortedVision]

http://img17.imageshack.us/img17/6721/77043473.jpg (http://imageshack.us/photo/my-images/17/77043473.jpg/)

[install monkey]

the 25 and 35 are the same indoor unit just more runs on the coil. extreme outdoor temperatures can reduce capacity, ie -10 and +30 ambients
http://www.mitsubishi-aircon.co.uk/default.asp?url=http%3A//www.mitsubishi-aircon.co.uk/mitsubishi_electric.asp%3Fid%3D119561

one thing to consider is a wall mount unit only gives 4mtr air throw so hopefully you have a wall full of cabinets

[DistortedVision]

What about the sound pressure levels? Is it as I assumed?

[install monkey]

26-32-38-43 /26-32-38-43db
for an m series 3.5kw wall mtd inverter-why the concern of noise,all wall mounts have similar wattage of fan motors so noise levels will be very similar.

[DistortedVision]

Cheers install monkey. I'm just trying to determine if its quieter than my portable Amcor 10 000 BTU unit which is very noisy.

You never answered my question. Would it be capable of reducing the temperature from 28-30C to 20-22C.

[install monkey]

it will be quieter as the compressor will be outside. as for the latter question-more than likely 99% the best way to determine this is a heatload calculation with volume of all walls,inc construction and window sizes, lighting,people office equipment. just out of intrest how are u getting the room upto 30deg when its been max25 deg in the north west-have u got windows that open? are u growing any herbal substances or is someone not putting the photocopier in standby mode?

[DistortedVision]

I have alot of lighting in the room. The main lightbulb is 200W (incandescent) plus two floorstanding lights 50W each. High end PC with a 900W PSU plus photocopier/scanner. Windows always closed.

I don't like the quality of CFLs - I could replace it with a lower rated bulb.

I think I might go for a 5kW system. I assume I'm right that it will cool the room quicker? I don't think the price of difference between the SRK-35ZG and SRK-50ZG is that great?

Could you recommend any companies in the Warrington area. I've had quotes from Aircare Europe and Andrew Sykes in Manchester.

[Jeremy-ACE HVAC]

Yep, im having a problem just finding a basic place to ask a sizing question(opinion) on this site.

What is the min duct size for a 2 ton a/c system with a 2 ton drive blower??? Lets say it has 8 six inch round supply ducts coming off the ductwork. I guess im wondering the minimum size of capacity of ductwork. Like 24x8 or 2(12x8)?? Is it a total square inches im looking for as the minimum??

How bout for a 3 ton a/c with a 3 ton drive blower???? 2 (16x8) ducts with 12(6 inch runs)??? or 32x8 min??? with 12 (6inch runs)????

Where on this site can i go to just start a basic question or post????

[r.bartlett]

Yep, im having a problem just finding a basic place to ask a sizing question(opinion) on this site.

What is the min duct size for a 2 ton a/c system with a 2 ton drive blower??? Lets say it has 8 six inch round supply ducts coming off the ductwork. I guess im wondering the minimum size of capacity of ductwork. Like 24x8 or 2(12x8)?? Is it a total square inches im looking for as the minimum??

How bout for a 3 ton a/c with a 3 ton drive blower???? 2 (16x8) ducts with 12(6 inch runs)??? or 32x8 min??? with 12 (6inch runs)????

Where on this site can i go to just start a basic question or post????

It's very rude to just jump in and hijack a person's thread.

It's not that difficult to work out where to post and if it is then perhaps this isn't the right forum for you...?

[DistortedVision]

This is the best quote I've had:

3.5kw 5kw

Toshiba £ 1398.00 1507.00

Fujitsu 1378.00 1494.00

Daikin 1562.00 1815.00

Mitsubishi 1342.00 1471.00

Do these prices look reasonable to you? They are Ex. VAT. The sales manager tells me that he thinks that the order in wich he rates the manufacturers are:

1. Daikin
2. Toshiba
3. Mitsubishi
4. Fujitsu

Would you agree?

[install monkey]

daikin
mitsi
tosh
fujitsu
if ur in warringto nip to trebaron garden ctr,go outside to the conservatory section,i put in a 3.5kw floor stander,5 kw wall mtd and a 7kw wall mount-no comment on the 7kw location,it was where they requested it,check the size of the outdoor units round the back,check belfrygroup website-i work for the slave drivers,contact the helpdesk,and tell em granty recommended you.ps all mitsi kit-threw them in about 3yr ago

[Kev The Tool]

Mitsi Electric
Daikin
Toshiba
Fujitsu
Mitsi Heavy

I believe the quote you have is for Mitsi Heavy, do the quotes include installation, if not then they are a bit rich especially for mitsi heavy.
Kev

[Kev The Tool]

when i say a bit rich i mean for mitsi heavy, this leads me to suspect it is for system only, which IMO is a ridiculous price for wall mounts.

[install monkey]

nah thats got to be fitted-its only about 500 quid for a 3.5mitsi wall mtd inverter-m series

[DistortedVision]

Prices are supply and installation. I'm tempted to go for the Mitsubishi 5kW over the 3.5kW. The price difference is only £129. The model no. are: SRK-50ZG and SRK-35ZG respectively.

Are these prices reasonable or not?

[install monkey]

our gaff used to charge £1200 for a 3.5kw wall mount that was fitted during conservatory installation-2yr ago.
price depends on length of run,access,location of equipment,spare way on fuseboard and ease of run.
brackets,condensate pumps,normal working hrs,additional charge of refrigerant,many factors contribute to the cost.its a dog eat dog world,at least by getting a legitimate company you are ensuring ur warranty,and u can claim the vat back and use the invoice as office overheads.

[Kev The Tool]

personally for that money i would ditch mitsi heavy and go with hitachi at least you get 5 years warranty, and i have never had any probs with hitachi kit.

[DistortedVision]

Had another quote from Cornwells Air Conditioning Ltd and it appears to be a one man operation. His quote was for £700 Ex.VAT for a Mitsubishi Heavy Industries SRK40HG-S.

Seems too good to be true? He said he gets the unit for around £300 and the labour is £400.

What do you all think?

[r.bartlett]

Had another quote from Cornwells Air Conditioning Ltd and it appears to be a one man operation. His quote was for £700 Ex.VAT for a Mitsubishi Heavy Industries SRK40HG-S.

Seems too good to be true? He said he gets the unit for around £300 and the labour is £400.

What do you all think?

We're on a race to the bottom and it's great to see some here helping that along :confused:

[install monkey]

is he powering it as well or do you get a plugtop??

[r.bartlett]

Is he F-Gas

[monkey spanners]

Seems a bit cheap, if this was coffee it wouldn't be Fairtrade....

Jon :confused:

[sinewave]

An SRK40HG-S is an older fixed speed unit, I'd be looking at an Inverter unit minimum from a manufacturere of your choice.

[back2space]

Personally in your situation I would oversize just slightly - 3.5kw will be more than adequate for your needs I should think.

A point to bear in mind that the max out put from the unit be it 2.5kw, 3.5kw or 5kw you only reach this output when the fan speed is set to high. At lower fan speeds you will get a lower output of cooling/heating. So going for the 2.5kw you will only get 2.5kw at max fan speed = more noise. Going for the 3.5kw you will prob be getting 2.5kw out of it at low fan speed and will only need to run it at high fan speed at start up for a short time before returning it to low fan speed.

5kw is over kill in my opinion as others have said - I have a 3.5kw in a south facing bedroom with large bay windows and it is run in low fan speed even at 25C outside temperature and full sun and it manages to keep the room at around 21-22C easily removing humidity and the room feels lovely.

When I first turn the unit on I run it in high fan speed for half an hour. The problem with the 5kw unit is even at low fan speeds you will have a lot of air movement = draughts which become unpleasant if your sat working at a desk/computer. It will also be outputting far more cooling than you require even at the lowest fan speed so you will find the unit short cycles at it reaches the room temperature too quickly. It will also not have time to remove enough moisture from the air as it reaches temperature too quickly.

Bigger is not always better but slightly oversized by 1.5kw is not a problem as it enables you to run in low fan speed yet you have the extra capacity available at start up or in very cold winter. Go with the 3.5kw.

Regards
Richard.

[our v]

Hi i am a contractor from bolton i could fit you a 3.5kw daikin for 1200+vat without electrics with would be 1350+vat.

[chillerman2006]

We're on a race to the bottom and it's great to see some here helping that along :confused:

Agreed...Not done installs for a while, but I would suggest to safe guard a fair price for installers

when joe public comes on here with price queries...nip it in the bud with a 10%-20% increase in the going rate

let them know the prices quoted are good..as long as they are not silly