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  1. #1
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    Jun 2018
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    Split A/C as air to water heat pump

    Hi!
    First sorry because my bad english.
    I am from Europe.
    I have one r22 outdoor unit with capacity of 18000 btu.
    I have a water tank.
    I have copper pipe with diameter of 8mm.
    I want to make a heat exchanger coil in tank and connect it to outdoor unit.
    I want to use it also for heating and cooling.
    My question is what length of copper pipe would be good for this project?
    I know that in old inside unit has copper pipe of 6mm diameter about 12 meters.
    But this heat exchanger is made for refrigerant/air. Not for refrigerant/water.
    Thank you!

  2. #2
    Join Date
    Sep 2002
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    Where are you in Europe?

    What kind of work are you involved with there?

    To use just bare 8mm copper tubing submerged in water as an evaporator will require about 100 meters length. As 8mm would have substantial pressure drop in a single length it would be better to parallel equal-length 8mm tubes. At least six and eight would be better.

    What is the metering device?

    PHM
    --------


    Quote Originally Posted by dark84 View Post
    Hi!
    First sorry because my bad english.
    I am from Europe.
    I have one r22 outdoor unit with capacity of 18000 btu.
    I have a water tank.
    I have copper pipe with diameter of 8mm.
    I want to make a heat exchanger coil in tank and connect it to outdoor unit.
    I want to use it also for heating and cooling.
    My question is what length of copper pipe would be good for this project?
    I know that in old inside unit has copper pipe of 6mm diameter about 12 meters.
    But this heat exchanger is made for refrigerant/air. Not for refrigerant/water.
    Thank you!
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  3. #3
    Join Date
    Jun 2018
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    Thread Starter
    I'm living in Serbia.
    I am an electrician in ceramic tiles factory.
    My friend is working as AC unit mounter and serviser. He has tools.
    Some time ago we try this thing with a 8mm copper tube with 30 meters length.
    The factory charging of outdoor unit is 1,3 kg R22 refrigerant.
    But for start we must put 3kg in this configuration and we not have the pressure what we need.
    After this try we stopped with project.
    We not have time.
    But now we want to finish this and i need a help from sizing the exchanger.
    The metering device is a capillary tube what the outdoor unit have originally.
    I want to use this machine for heating and for cooling.

  4. #4
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    Jun 2018
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    Thread Starter
    The tank is about 120 liters. In the colling/heating system i have around 100 liter water. I cooling/heating with 3 fan coils. When i cool, i need to cool down a water to 18 celsius. When i heat i need to heat up the water to 45 celsius. The pump witch circulate the water from tank is working with 50 liter/minute on the highest speed.

  5. #5
    Join Date
    Sep 2002
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    I have a friend in Serbia. His name is Nikola. He is married with a small son. He was a scooter/motorcycle mechanic but he became a soldier in the war. During the war I heard from him a few times but not since the war ended.

    30 meters in one length is too long for 8mm copper - there will be too much pressure drop. Also; you will need about 100 meters of 8mm copper for 18,000 BTU's. But the 100 meters will have to be divided into shorter lengths. Eight would be the best.

    I suggest a cap tube for each 12.5 meter length. Feed each 12.5 length of tubing with 228.5cm length of 0.049" internal diameter cap tube.

    PHM
    --------


    Quote Originally Posted by dark84 View Post
    I'm living in Serbia.
    I am an electrician in ceramic tiles factory.
    My friend is working as AC unit mounter and serviser. He has tools.
    Some time ago we try this thing with a 8mm copper tube with 30 meters length.
    The factory charging of outdoor unit is 1,3 kg R22 refrigerant.
    But for start we must put 3kg in this configuration and we not have the pressure what we need.
    After this try we stopped with project.
    We not have time.
    But now we want to finish this and i need a help from sizing the exchanger.
    The metering device is a capillary tube what the outdoor unit have originally.
    I want to use this machine for heating and for cooling.
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  6. #6
    Join Date
    Jun 2018
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    Thread Starter
    Quote Originally Posted by Poodle Head Mikey View Post
    I have a friend in Serbia. His name is Nikola. He is married with a small son. He was a scooter/motorcycle mechanic but he became a soldier in the war. During the war I heard from him a few times but not since the war ended.

    30 meters in one length is too long for 8mm copper - there will be too much pressure drop. Also; you will need about 100 meters of 8mm copper for 18,000 BTU's. But the 100 meters will have to be divided into shorter lengths. Eight would be the best.

    I suggest a cap tube for each 12.5 meter length. Feed each 12.5 length of tubing with 228.5cm length of 0.049" internal diameter cap tube.

    PHM
    --------

    I know peoples from my town who going down in Kosovo and never came back... :-(

    Back to the project.
    If i need 100meters of tube, than better to buy a brazed heat exchanger and install it.
    Just carried to use this kind of exchanger because freezing...
    But to buy a tube is lot of money and lot of time to create a spiral and put into tank.
    Thanks for the answers.
    What kind and size of brazed heat exchanger i need to buy?

  7. #7
    Join Date
    May 2014
    Location
    Bay Area California
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    Now there is a damn good reply.


    Quote Originally Posted by Poodle Head Mikey View Post
    I have a friend in Serbia. His name is Nikola. He is married with a small son. He was a scooter/motorcycle mechanic but he became a soldier in the war. During the war I heard from him a few times but not since the war ended.

    30 meters in one length is too long for 8mm copper - there will be too much pressure drop. Also; you will need about 100 meters of 8mm copper for 18,000 BTU's. But the 100 meters will have to be divided into shorter lengths. Eight would be the best.

    I suggest a cap tube for each 12.5 meter length. Feed each 12.5 length of tubing with 228.5cm length of 0.049" internal diameter cap tube.

    PHM
    --------
    If you were a real tech, you'd solder a relay on that board and call it good to go.

    I do a triple evac with nitro to remove non condensables.

    I use 56% silver on everything except steel.

    Did you really need the " If you were a real tech " ??

  8. #8
    Join Date
    Sep 2013
    Location
    Atlanta, GA
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    PHM gave good advice for your situation, but I just thought I would mention that R22 is not a good refrigerant for this. If you are simply trying to use a condenser you no longer have use for... go for it. However, if you are looking to design something from scratch R744 is the way to go.

  9. #9
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    Jul 2013
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    Israel
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    i know this thread is 5 months old, but i just saw it now, im curious to know what you've done in the end (dark84)
    I've done this several different ways with varying levels of success, (its currently my only means of heating water in my house) if you're interested in more details, I'm happy to share.

  10. #10
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    Sep 2002
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    I must have missed this before.

    How would these guys go about cobbling together a safe working version of a heat pump using R-744 in their garage or basement?

    PHM
    ---------

    Quote Originally Posted by davidadavis View Post
    PHM gave good advice for your situation, but I just thought I would mention that R22 is not a good refrigerant for this. If you are simply trying to use a condenser you no longer have use for... go for it. However, if you are looking to design something from scratch R744 is the way to go.
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  11. #11
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    Jul 2013
    Location
    Israel
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    i didn't mean r744, i used a 12000 btu r410 unit mated to 15 meters 3/8" coiled in a 200 liter water tank

  12. #12
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    Jul 2013
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    actually i don't know why davidadavis was discouraging of using an r22 unit, i have, and it worked quite well, in fact, it gets the water hotter at safe pressures, than r410.

  13. #13
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    Sep 2002
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    Did you track the head pressure versus the heated water temperatures?

    How hot does the heated water get?

    How high does the head pressure get?

    PHM
    --------



    Quote Originally Posted by Natmat View Post
    actually i don't know why davidadavis was discouraging of using an r22 unit, i have, and it worked quite well, in fact, it gets the water hotter at safe pressures, than r410.
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

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