Air-con Question

[Lazy Sod]

Our house has a 36,000 BTU floor standing (looks like a tall fridge) indoor air con unit downstairs for the open plan living/dining areas (about 50m2). Problem is that we've come to realise it's too powerful. It cools really quickly and then cycles on-off-on every 3-4 minutes, each time the compressor starts the lights dim so it's obviously using a lot of power. Aesthetically we like the floor standing indoor unit as it fits nicely into the room. I'm thinking we could keep the indoor unit and replace the outdoor unit with something less powerful.

So my question is this, is it possible to keep the 36,000 BTU indoor unit and buy a new smaller and more economical outdoor compressor unit (say 26,000 BTU instead of the current 36,000 BTU)? Or do the indoor and outdoor units have to be exactly the same BTU?

[londonthai]

air con should be by the ceiling, where air is the hottest (as heating radiators should be on the floor), to work the most efficient. So I would move it up (and eventually conceal).

of course air con uses a lot of power, reduce the temperature on the thermostat to save money.

somebody who installed your air con made it suitable for the hottest months of the year and probably took into consideration, that foreigners in thailand do prefer lower temperatures.

replacing the outside unit means it will run longer to make your room cool (not the best idea if you are coming back home all sweating and exhausted from heat) and have shorter brakes/no brakes, so in effect will use the same/more energy than your present one.

the rule of economy of scale (larger is more efficient)

[pampal]

The unit you have installed is entirely too powerfull, 50 m2 requires around 24000-26000 Btu. The stand up model you have is commonly used in restaurants and is meant to cool a room with many people inside eating hot foods. Every person that comes into the room consumes 1000 Btu on average not to mention all the hot food in the room, imagine 3 or 4 suki units working continuosly.

To answer your question, the Indoor unit does not contain a compressor, so there is no Btu rating for the indoor unit, the outdoor unit that contains the compressor is rated at 36000 Btu. The problem is the indoor unit is designed to deliver a certain volume of air to the outdoor unit which cools the air and returns it to the indoor unit so it can be delivered to the room being cooled, if the new proposed 26000 Btu unit that you want to install doesn't deliver the minimum volume of air required by the indoor unit and vice versa, you could have a problem on your hands.

As for the thermostat, try setting the air conditioner at a cooler setting to avoid the constant cycling of the compressor, if it gets too cold, crack open a window.

Can you tell me exactly what make and model you currently have?

Edited March 15, 2008 by pampal

[Naam]

Our house has a 36,000 BTU floor standing (looks like a tall fridge) indoor air con unit downstairs for the open plan living/dining areas (about 50m2). Problem is that we've come to realise it's too powerful. It cools really quickly and then cycles on-off-on every 3-4 minutes, each time the compressor starts the lights dim so it's obviously using a lot of power. Aesthetically we like the floor standing indoor unit as it fits nicely into the room. I'm thinking we could keep the indoor unit and replace the outdoor unit with something less powerful.

So my question is this, is it possible to keep the 36,000 BTU indoor unit and buy a new smaller and more economical outdoor compressor unit (say 26,000 BTU instead of the current 36,000 BTU)? Or do the indoor and outdoor units have to be exactly the same BTU?

the compressor/condenser (outside) unit can be smaller than the inside unit but not the other way round. replacing the 36k unit with a 24k will indeed help to solve the on/off cycling problem but the total capacity is still a bit too high for 50m² except for the really hot months of the year.a lot depends of course what heat load the area receives through windows or sun radiation on walls.

[Naam]

As for the thermostat, try setting the air conditioner at a cooler setting to avoid the constant cycling of the compressor, if it gets too cold, crack open a window.

[Naam]

air con should be by the ceiling, where air is the hottest (as heating radiators should be on the floor), to work the most efficient. So I would move it up (and eventually conceal).

replacing the outside unit means it will run longer to make your room cool (not the best idea if you are coming back home all sweating and exhausted from heat) and have shorter brakes/no brakes, so in effect will use the same/more energy than your present one.

the rule of economy of scale (larger is more efficient)

:D

[pampal]

As for the thermostat, try setting the air conditioner at a cooler setting to avoid the constant cycling of the compressor, if it gets too cold, crack open a window.

Edited March 16, 2008 by pampal

[Lazy Sod]

Thanks everyone for your comments so far. To answer pampal's question the unit I have is Carrier brand floor standing, the dimensions are perfect for the area downstairs, hence my desire just to change the outdoor unit. Details as follows;

Carrier 40QB/QD SERIES

TYPE : FAN COIL UNIT

NOMINAL CAPACITY : 36,000 BTUH

FEATURES :

- FLOOR STANDING SPLIT

- DIRECT EXPANSION COIL ONLY

Edited March 16, 2008 by Lazy Sod

[elkangorito]

Wow! Lots of air cond "specialists" here. Even though I'm not a qualified air conditioning/refrigeration mechanic, I did start (but not complete) a Journeymans Certificate in Refrigeration & as such, I would only listen to the responses of one person. That person is Dr Naam.

Strangely, there seem to be as many electrical "specialists" too.

[ClaudeFeller]

Here for the specialist:

Living area 50 m² and incredible 5,50 m high, large window front with sunprotection glasses to the west.

Is an air-con with 36.000 BTU powerful enough? Is a floor standing unit a better choice? Should prevent to cool the upper 2 m under the ceiling...

[Naam]

Here for the specialist:

Living area 50 m² and incredible 5,50 m high, large window front with sunprotection glasses to the west.

Is an air-con with 36.000 BTU powerful enough? Is a floor standing unit a better choice? Should prevent to cool the upper 2 m under the ceiling...

Claude, in this case a floor unit has the advantage of leaving the upper and warmer air undisturbed without cooling thus saving energy. but no matter what heat load an area to be cooled has, as far as energy savings and cool air distribution is concerned it is always better to go for for two or even three smaller units which i would mount at a height of 2.50m if the total room height is 5.50m.

"living area in m² and large window front to the west" is not specified enough to calculate the necessary cooling capacity.

disclaimer: i just had a 36,000 btu/h ceiling unit in my (enclosed) pool area installed although the ceiling height is 4.00m. the main reason for the "unprofessional" setup was that i use the compressor/condenser heat to heat up my pool water. top quality heat exchangers (with Titanium coils) are bloody expensive. therefore splitting the cooling/heating capacity in smaller units would have cost a fortune... not to talk about triple the piping work and electronic triggering for three individual pumps.

p.s. my pool area is around 135m² and has a full mirror glass front to the west. but the main objective is heating the pool, cooling down the area a few degrees comes for free.

[ClaudeFeller]

disclaimer: i just had a 36,000 btu/h ceiling unit in my (enclosed) pool area installed although the ceiling height is 4.00m. the main reason for the "unprofessional" setup was that i use the compressor/condenser heat to heat up my pool water. top quality heat exchangers (with Titanium coils) are bloody expensive. therefore splitting the cooling/heating capacity in smaller units would have cost a fortune... not to talk about triple the piping work and electronic triggering for three individual pumps.

p.s. my pool area is around 135m² and has a full mirror glass front to the west. but the main objective is heating the pool, cooling down the area a few degrees comes for free.

Hmmm.. compressor heat to heat a pool. Does this heat pump affect the warranty of your A/C? Personally I dont like this heat pumps because you need to open the A/C to get warm water...

[Naam]

disclaimer: i just had a 36,000 btu/h ceiling unit in my (enclosed) pool area installed although the ceiling height is 4.00m. the main reason for the "unprofessional" setup was that i use the compressor/condenser heat to heat up my pool water. top quality heat exchangers (with Titanium coils) are bloody expensive. therefore splitting the cooling/heating capacity in smaller units would have cost a fortune... not to talk about triple the piping work and electronic triggering for three individual pumps.

p.s. my pool area is around 135m² and has a full mirror glass front to the west. but the main objective is heating the pool, cooling down the area a few degrees comes for free.

Hmmm.. compressor heat to heat a pool. Does this heat pump affect the warranty of your A/C? Personally I dont like this heat pumps because you need to open the A/C to get warm water...

it does not affect the warranty as the Daikin general distributor for our area built the system for me. in fact i am getting smoother and lower condensation temperatures with my setup, i.e. the compressor does not have to work as hard as with air cooling only and draws 15-20% less amps when switched to water cooling (measured various times during test runs). that i have to run the a/c to heat my water goes without saying but that was intended. the pool area is now part of the living area and will be used as living area, therefore it was mandatory to have it airconditioned. i would have preferred separate systems but nobody in SouthEast Asia can deliver and install the mats for solar heating to which i was used for nearly 20 years. the set-up would have been cheaper

bottom line: i killed two birds with one stone because i had no alternative.

p.s. i expect to be crucified by some 'good-hearted' environmentalists because of my carbon footprint

[Naam]

Hmmm.. compressor heat to heat a pool

addendum: i lived for 15 years in Florida where it was quite common that the hotwater supply of a home during cooling season was generated by means of a heat-exchanger hooked up to the compressor/condenser unit. if the generated heat was not enough an electric resistance heater kicked in.

[Gary A]

Unfortunately it is very common practice to install air con units that are WAY to large for the area. When you walk into a place that has a TOO large unit the air will feel cold and damp. The air con does not cycle long enough to remove the moisture from the air. My master bedroom is about 18 square meters with poor fitting windows and no insulation. A 9,000 BTU unit does a great job.

[PhilHarries]

Naam, that sounds a real neat system. Maybe not ideal but, as with most things in life, a dam_n good compromise and to hel_l with the tree huggers.

[Naam]

Naam, that sounds a real neat system. Maybe not ideal but, as with most things in life, a dam_n good compromise and to hel_l with the tree huggers.

but it is ideal Phil! i am not spending a single Satang on my considerably high electricity bill because all is paid for by the money... which my heirs won't inherit.

[Naam]

Unfortunately it is very common practice to install air con units that are WAY to large for the area. When you walk into a place that has a TOO large unit the air will feel cold and damp. The air con does not cycle long enough to remove the moisture from the air.

TRUE!

[ClaudeFeller]

..in fact i am getting smoother and lower condensation temperatures with my setup, i.e. the compressor does not have to work as hard as with air cooling only and draws 15-20% less amps when switched to water cooling

Can you explain this? As you keep the pool water warm the room temp is up compared to "No water heating" - thus you should need more energy to cool the room down... or you mean while the heat pump is running your compressor needs less energy?

i would have preferred separate systems but nobody in SouthEast Asia can deliver and install the mats for solar heating to which i was used for nearly 20 years. the set-up would have been cheaper

(..and running costs also). Yes, there is still no market for solar pool heating in SEA, otherwise the chinese copy masters would have produced already. Shipping for australian products is too expensive.

p.s. i expect to be crucified by some 'good-hearted' environmentalists because of my carbon footprint

C'mon, you have about 10 A/C in your villa, you must have been crucified before this statement.

[Naam]

..in fact i am getting smoother and lower condensation temperatures with my setup, i.e. the compressor does not have to work as hard as with air cooling only and draws 15-20% less amps when switched to water cooling

1) Can you explain this? As you keep the pool water warm the room temp is up compared to "No water heating" - thus you should need more energy to cool the room down...

2) or you mean while the heat pump is running your compressor needs less energy?

i would have preferred separate systems but nobody in SouthEast Asia can deliver and install the mats for solar heating to which i was used for nearly 20 years. the set-up would have been cheaper

3) (..and running costs also). Yes, there is still no market for solar pool heating in SEA, otherwise the chinese copy masters would have produced already. Shipping for australian products is too expensive.

4) p.s. i expect to be crucified by some 'good-hearted' environmentalists because of my carbon footprint

C'mon, you have about 10 A/C in your villa, you must have been crucified before this statement.

1) higher room temperature due to warmer pool water will be minimal and therefore negligible as temperature difference won't be more than 2ºC (maximum water temperature 28.5ºC / minimum air temperature 26.5ºC).

2) there is no "heat pump" running. the A/C is doing it's normal job cooling the area. the only difference is that for cooling the hot refrigerant gas my pool water is used instead of the (in most cases) higher ambient air. lower cooling medium to condense the hot gas means slightly lower amps drawn by the compressor but higher cooling capacity/efficiency. this of course does not apply during the "cool" season in Pattaya when the ambient temperature is lower than the pool water.

3) actually the energy consumption would be higher with solar mats. reason: the fully enclosed pool area has to be airconditioned in any case but for the solar mats the pump size would have been considerably bigger (approximately three times the size i am using now, i.e. 1.5kW instead of 0.5kW) to match the flow resistance of solar mats.

4) 15 till 3 weeks ago, now 16

edited for addendum: i am not a complete freak only a partly one heating up the pool is required that i (we) can use it year round. my water temperature was in december 25, in january 23 and in february 22ºC as i get only an hour or so evening sun on the pool surface.

Edited March 22, 2008 by Naam