Heat Transfer Unit

[quiksilva]

I read a story in the Bangkok Post that intrigued me

....The company [Property Perfect] will also adapt the heat transfer idea, which many large hotels currently use, to its future housing units as well. The heat transfer system recycles heat from the condensing units of air-conditioners for use by water heaters.

The system, including a boiler and pipes linking an air-conditioning system with a water heater, costs around 5,000 baht, the same as a water heater. But after testing the system at his own house, Mr Teerachon found he could save 1,000 baht in electricity bills a month.

Has anyone has any experience of these domestic systems? If so do they work as suggested and where are they sold?

[Naam]

I read a story in the Bangkok Post that intrigued me

....The company [Property Perfect] will also adapt the heat transfer idea, which many large hotels currently use, to its future housing units as well. The heat transfer system recycles heat from the condensing units of air-conditioners for use by water heaters.

The system, including a boiler and pipes linking an air-conditioning system with a water heater, costs around 5,000 baht, the same as a water heater. But after testing the system at his own house, Mr Teerachon found he could save 1,000 baht in electricity bills a month.

Has anyone has any experience of these domestic systems? If so do they work as suggested and where are they sold?

they do work. i am using one to heat my pool and cool my pool area. system was built according to my design.

problems: home has to be piped with separate feeds for hot and cold water, combination not possible with instant water heater. water heating only when a/c in cooling mode.

price 5,000 Baht? no way!

[quiksilva]

Yes I must admit I thought a system which is purported to save 1000 Baht a month in electricity bills that cost only 5,000 Baht sounded too good to be true too.

[tjo o tjim]

Mitsubishi is pushing this type of system for residential applications as well. There is talk of putting the refrigerator into the coolant circuit as well. Not sure if it would work in LOS, but some climates it makes sense to use some of the waste heat to warm your closet to prevent mildew. (Curious if 'critters would like it too much.) Any excess heat is rejected via the condenser.

For heating water, it is more effective than electric heat but less efficient than just using solar.

[Naam]

Mitsubishi is pushing this type of system for residential applications as well. There is talk of putting the refrigerator into the coolant circuit as well. Not sure if it would work in LOS, but some climates it makes sense to use some of the waste heat to warm your closet to prevent mildew. (Curious if 'critters would like it too much.) Any excess heat is rejected via the condenser.

For heating water, it is more effective than electric heat but less efficient than just using solar.

i measured digitally the temperature from compressor out to heat exchanger in which is a continous 88ºC (190ºF) and i doubt a solar panel achieves this output. usable heat recovery in degrees depends of course on applied flow of medium to be heated up.

in comparison with solar panels one must not forget that the available heat from aircon systems is "free of charge", i.e. a byproduct when cooling. in other words "killing two birds with one stone".

Edited July 19, 2008 by Naam

[tjo o tjim]

i measured digitally the temperature from compressor out to heat exchanger in which is a continous 88ºC (190ºF) and i doubt a solar panel achieves this output. usable heat recovery in degrees depends of course on applied flow of medium to be heated up.

88C out of the compressor! Wow... Do you know what your SEER is?

I would have expected a hot gas temperature around 135F/57C, which I guess is still enough to be effective with the heat exchanger.

[beechstreet]

they do work. i am using one...

Naam,

You may have already cover this elsewhere...but do you have any other details you can share about your set up?

David

[VocalNeal]

Very popular in Indonesia with expats who use aircon a lot and where most use hot water tanks instead of shower heaters. You put a seperate tank before your water heater put a coil inside in the A/C circuit. The heat from the A/C goes into the water and bingo. If water gets up to maximum available temp because of low usage the A/C simply dumps the heat into atmosphere in the normal way with the fan.

Don't have a pool otherwise I would do that to. Hate cold pools.

[Gary A]

You save in two ways. A water cooled condenser is more efficient that an air cooled unit and using the heat from the cooling water is free.

[Naam]

i measured digitally the temperature from compressor out to heat exchanger in which is a continous 88ºC (190ºF) and i doubt a solar panel achieves this output. usable heat recovery in degrees depends of course on applied flow of medium to be heated up.

88C out of the compressor! Wow... Do you know what your SEER is?

I would have expected a hot gas temperature around 135F/57C, which I guess is still enough to be effective with the heat exchanger.

i have no idea about the SEER of the unit. the hot gas temp varies of course as it depends on the ambient, respectively return air temp in my pool area. when i measured 88ºC return air was 29ºC. according to my calculation the heating capacity is ~11kW (input including circulation pump is ~4kW). efficiency is hampered by total pool pipe length (not insulated) about 60cm underground.

[Naam]

they do work. i am using one...

Naam,

You may have already cover this elsewhere...but do you have any other details you can share about your set up?

David

i have covered it David but don't know where. anyway, setup is simple. compressor pressure side is connected to heat exchanger before returning to condenser. a pump recirculates water from overflow tank to heat exchanger and back. pool pump recirculates pool water via the overflow tank. the fan of the condenser unit has a sensor which switches the fan on if return gas is too hot or if aircon unit is used for cooling pool area only ifs water temperature is comfortable. in this case i switch off the circulation pump manually. not a problem as in present season i don't need more water heating than 5-6 hours twice a month. don't have any experience what the run time will be in the "cool" season november till february. in my case most probably october till march as my pool never gets any sun.

here's a self explanatory picture. if you have any additional questions please ask.

[tjo o tjim]

i have no idea about the SEER of the unit. the hot gas temp varies of course as it depends on the ambient, respectively return air temp in my pool area. when i measured 88ºC return air was 29ºC. according to my calculation the heating capacity is ~11kW (input including circulation pump is ~4kW). efficiency is hampered by total pool pipe length (not insulated) about 60cm underground.

Interesting setup. You might be able to gain some efficiency with a few more controls; by your description the compressor is still working based on internal load and outside air temperature and not return gas temperature. If you really wanted to be fancy, you could push up the temperature when you want additional pool heating...

[Naam]

i have no idea about the SEER of the unit. the hot gas temp varies of course as it depends on the ambient, respectively return air temp in my pool area. when i measured 88ºC return air was 29ºC. according to my calculation the heating capacity is ~11kW (input including circulation pump is ~4kW). efficiency is hampered by total pool pipe length (not insulated) about 60cm underground.

Interesting setup. You might be able to gain some efficiency with a few more controls; by your description the compressor is still working based on internal load and outside air temperature and not return gas temperature. If you really wanted to be fancy, you could push up the temperature when you want additional pool heating...

i'm not sure i understand what you mean. the compressor is running based on internal load only, not based on outside temperature or return gas temperature but the inside temperature of my pool area. it will (if water heating is required) most probably always run on internal load as i set the thermostat to 16ºC which i will never achieve in an area of 140m²/500m³ and 40m² glass to the west. what "few more controls" are you thinking of? are you talking about enhancing "actual" efficiency meaning more heat recovery at same energy input or just "timely" efficiency"? if "actual" is meant i'd be open to any suggestions.

presently i have no problems to maintain my pool temperature at 28.5ºC by running the unit ~10-12 hours a month in water cooled mode. but i have no idea how many hours i will need in the "cool" season from end nov till early march.