Aircon strategy for a school hall with short lease?

[mamborambo]

Sorry I am not an aircon engineer, but I am doing this conversion project as a volunteer and I would like some help from the experts.

We are planning to convert a school auditorium to an arts studio, and I would like to work out the budget of airconditioning this space.

The location is in Singapore and the lease is only for three to five years, so we want to explore the most cheapo solution which can still work.

The dimensions are 15m wide x 24m long x 5m high. The hall will hold around 80 people seated, with a stage in the front.

Any suggestion of what is the best products for the job, their ballpark cost figures would be, and estimate of installation and operating costs. I need these figures for the purpose of presenting a budget to the committee.

[Lc_shi]

Use air cooled chiller + fan coil unit termianl. It's cheap and easy to install. Suggest to check with the local AC company to confirm the price.

rgds
LC

[mamborambo]

I got a quotation for 12 sets of Daikin ceiling suspended unit, model R125/FHY125 44,500 btu/hr each set c/w wired remote controller, pipework for refrigerant and drainage system, control wirings, testing and commissioning the system to normal running condition, our unit price is S$2,600.00, totalling S$31,200.00.

Is this proposal correct in (1) cooling capacity and (2) market prices?

Since the lease on this space is only for 3 years, do you think I can easily remove the AC to another space later?

[Lc_shi]

Daikin's VRV product. Daikin's price is higher than others in my place. Quality is very good. cooling capacity is enough on my rough estimation.You can check the load calculation report. These unit can be removed easily and many company's offer one time free move service included in the contract.
You'd better ask quotation for other suppliers and make the comparison.You'll know much more. wish you lucky.

regards
LC

[frank]

The dimensions are 15m wide x 24m long x 5m high.

Using rule of thumb calculations (UK Conditions) of 125w/m2 this room requires 45kw of cooling. Obviously a full heat gain calc should be carried out before selecting any equipment, but we have limited details here so some assumptions must be made. With 80 persons you must also consider fresh air ventilation which will add to the load. Assuming 8 l/s/person you would need another 10kw of cooling (dt = 13K)

12 Daikin ceiling suspended units @ 12.5kw cooling capacity equates to a total cooling duty of 150kw (this will vary slightly dependant on ambient operating conditions).

At first view it would seem that 5 Daikin FTY125 units would satisfy your heat gain.

UK install costs for 5 x 12.5kw split systems circa £12 - 15k (34000SD - 43000SD)

Be aware that you will lose the effeciency of the cooling if you install the indoor units higher than 3.5m

[Abe]

Frank, would you mind putting down the maths how you arrive at your calculation

Im not testing you, I want to learn, thats all.

Thx

[frank]

Hi Abe

The maths are quite easy. Do you use rule of thumb? It's very useful for a quick calculation and check against your definative calcs.

CIBSE give heat gain Rule of Thumb figures for office type areas as 125w/m2. So, for every sq m of floor space you would multiply bt 125 to give a total cooling load.
One word of warning - only use rule of thumb as a check method. 125w/m2 is on the high side so you run the risk of oversizing which means over pricing and shortened equipment life.

Back to the problem. The room is given as 15m x 24m which equates to a floor area of 360m2. Multiply this by 125w/m2 and this gives 45000w (45kw)

Now 80 people occupancy each person requires 8 l/s of fresh air. This gives a total air input of 0.640m3/s. (8 l/s/person x 80 persons = 640 litres/second. 640/1000 = 0.640m3/s)

The cooling load to bring 0.64m3/s down from 30C ambient to 17C delivery temperature (30 - 17 = 13K dt) is given as Q =m x c x dt so Q = 0.64 x 1.22 x 13 = 10.15kw.

Total estimated cooling load now, excluding infiltration, lighting, solar gain, fabric gain, equipment gain is 45 + 10 =55kw.

The Daikin FHY125 indoor unit is rated at 12.5kw total cooling duty @ 21C indoor 27C ambient. So, 12 sets of indoor units as per the second post would give a total cooling duty of 12 x 12.5 = 150kw. Much too much.

5 x 12.5kw indoor units would give a total cooling duty of 62.5kw - much closer to the required duty of 55kw.

Obviously there are lots of assumptions here so it is vital that a proper survey is carried out and the correct heat gain determined before selecting any kit.

Mind you, there are loads of firms here in the UK who use nothing but Rule of Thumb as the only means of selecting kit

[eggs]

Frank, i'm more interested in your calculation on how you can install 5, 12.5kw Daikin cassettes for £12K

If my calcs are correct, that means you get them for less than £1k each

I gonna see my rep about my discount


cheers

eggs

[Lc_shi]

I think Frank's calculation is effective. But Singapore is in tropical area, the design parameters should be much different with UK.
The price seems not too high in UK It's equal to the price in China.

Be aware that you will lose the effeciency of the cooling if you install the indoor units higher than 3.5m

I agree. Maybe displacement ventilation is fit for it.

rgds
LC

[arkay]

Hi Mamborambo!

For our island here, which is a tropical region with temperatures up to 35 deg.C in summer, the cheapest solution often works our to be split units.
Nowadays split units from China are very cheap or even McQuay splits from Malaysia are quite cheap. Their lifetime is usually 7-8 years, which will suit your needs.
I would suggest 5 split units of 50,000 Btu/hr for the hall and 2 splits of 24000 BTU/Hr for the stage - a rough estimate for our climate here would be 80 KW cooling.
But you have to be careful about the high running cost which can be up to 30% higher.
Still, you have the advantage of switching them off one by one off as you move to winter. And all will not breakdown together...
Hope this helps.

[frank]

Frank, i'm more interested in your calculation on how you can install 5, 12.5kw Daikin cassettes for £12K

If my calcs are correct, that means you get them for less than £1k each

I gonna see my rep about my discount


cheers

eggs

Hi Eggs

I wasn't specifically talking about my rates but, as you know, you put something on here and 9 times out of 10 someone will come and say - we do it different or cheaper.
If you were installing say 5 x Fujitsu cassettes (or other cheaper brands) then I would think it would be closer to the £12k. Obviously quality kit costs more.

I've recently quoted to install 3 Fuji cassettes (2 x AUY12FBAB and 1 x AUY14FBAB) with a total equipment cost of £2092.57. Add to that a mark up, pipework, insulation, pumps, ancillaries, labour + profit.

Well, the client wrote back and told me I had lost the job because his regular guy had come in with a price of £4400.00

Is it me?

[eggs]

Well, the client wrote back and told me I had lost the job because his regular guy had come in with a price of £4400.00

Is it me?

No it's not you Frank, using my rule of thumb pricing this fella is short of work and is working for just his wages. Without seing the job, I would say i would open the bidding at £6.6k for this.

It's a black art isn't it.

cheers

eggs

[Abe]

Thx Frank, I really appreciate your time spent and explanations.

Ive learnt something very useful.

Thank You

Abe

[Peter_1]

Don't forget that it can be extremely humid in Singapore.
Was once there when visiting Mitusbishi Thailand and never was in a country where it was that humid.
So, a lot of latent heat is lost there.