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  1. #1

    Using a second hand Heat Pump

    Hi All

    I picked up a heat pump locally VERY cheap and the cop curve shows it should provide me with decent output down to approx -5 degrees which should be fine so i'm going to plumb it in and try it out this winter with my electric heater on standby. I was going to plug it into a temperature controller plug so I can control the temp fluctuation.

    Before I do so, I wondered if there were any risk to my fish if I plumb in a heat pump which has had 5 years of use heating a swimming pool, exposed to chlorine and chemicals etc? Any risks here? I will rinse it out thoroughly of course

    Thanks!



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  3. #2
    Senior Member Rank = Mature Champion Ajm's Avatar
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    Could you make a short closed circuit ie a water tank with a pp mix in pumped though heater and back to tank . Could be talking out me back end like

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    Johnathan

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    Senior Member Rank = Grand Champion RS2OOO's Avatar
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    Quote Originally Posted by Ajm View Post
    Could you make a short closed circuit ie a water tank with a pp mix in pumped though heater and back to tank . Could be talking out me back end like

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    Sounds a good idea to me mate.

    Sent from my Pixel 2 using Tapatalk

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    Senior Member Rank = Rokusai Handy Kenny's Avatar
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    Willshill,

    I would definitely think of a closed system with a submersible stainless steel heating coil, Absolute Koi sell them. I heat my pond from the house gas heating system and use a submersible coil as the radiator. Unless your water is super clean there is a good chance that the pipes would be affected by algae (making your heating less efficient) or even the chemicals in the pond water.

    Kenny

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  9. #5
    Thanks all for the responses. I hadn't thought of this...great idea! Question, What is pp mix? some sort of additive to help with heat transfer? Also, would this be less efficient if a heat exchanger is required rather than heating the pond water directly? My water quality is crystal clear, almost no algae at all. So i'm not worried about algae built up, more chemical exposure and fish health.

    Thanks

  10. #6
    Senior Member Rank = Mature Champion Ajm's Avatar
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    As I said my thinking could be wrong but my ideal was just to set up a closed circuit and run a pp mix which is just a disinfectant used in ponds to make safe then set up running the pond directly as you say

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    Johnathan

  11. #7
    Quote Originally Posted by Ajm View Post
    As I said my thinking could be wrong but my ideal was just to set up a closed circuit and run a pp mix which is just a disinfectant used in ponds to make safe then set up running the pond directly as you say

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    Sorry I misunderstood you. Yes this is a good idea. Is there a way of testing the water for unwanted chemicals apart from the normal dpd chlorine testing tablets?

    Cheers

  12. #8
    Senior Member Rank = Mature Champion Ajm's Avatar
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    With water the best ever person to speak to would be manky sanke Home
    He is on here and could be worth PM him if you type his name in the top
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    Johnathan

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  14. #9
    The heat exchanger circuit in a heat pump is very simple and won't hold any swimming pool chemicals from its previous use. I would just connect the heat pump input to the pond pump circuit but leave the output unconnected then run it for literally a few seconds with the output running to waste or directed onto the floor. That will be all the rinsing out that it will need.

    Below is a block schematic of a typical heat pump that I drew for an article in Koi Carp magazine. It shows the simplicity of the internal plumbing for the heating circuit. Real life heat pumps are no more complicated.

    This is a link the article:
    Good water guide: pt 8


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  16. #10
    Senior Member Rank = Mature Champion Ajm's Avatar
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    Cheers manky mate thought you would have the best answer.

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    Johnathan

  17. #11
    Fantastic ! Thanks very much

  18. #12
    Senior Member Rank = Nanasai Tom Koi's Avatar
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    Quote Originally Posted by Manky Sanke View Post
    The heat exchanger circuit in a heat pump is very simple and won't hold any swimming pool chemicals from its previous use. I would just connect the heat pump input to the pond pump circuit but leave the output unconnected then run it for literally a few seconds with the output running to waste or directed onto the floor. That will be all the rinsing out that it will need.

    Below is a block schematic of a typical heat pump that I drew for an article in Koi Carp magazine. It shows the simplicity of the internal plumbing for the heating circuit. Real life heat pumps are no more complicated.

    This is a link the article:
    Good water guide: pt 8

    Thanks Manky, how often would you have a heat pump serviced, I know engineers who are F gas qualified who could service it for me,

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  20. #13
    Junior Member Rank = Fry Mpathe's Avatar
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    There isnt much to service on them as long as it is working ok, the only thing that really wants checking now and then is that the coil is clean, if not give it a brush downwards and not across.

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  22. #14
    Senior Member Rank = Nanasai Tom Koi's Avatar
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    Quote Originally Posted by Mpathe View Post
    There isnt much to service on them as long as it is working ok, the only thing that really wants checking now and then is that the coil is clean, if not give it a brush downwards and not across.
    Has the gas got to be changed topped up at all?

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  24. #15
    Junior Member Rank = Fry Mpathe's Avatar
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    The refrigerant doesn't need changing and is a sealed system so shouldn't leak, if it did leak you would notice a drop in performance and you would have to get an f-gas engineer to look at it then.

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  26. #16
    Senior Member Rank = Nanasai Tom Koi's Avatar
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    Quote Originally Posted by Mpathe View Post
    The refrigerant doesn't need changing and is a sealed system so shouldn't leak, if it did leak you would notice a drop in performance and you would have to get an f-gas engineer to look at it then.
    Cheers for that.

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  28. #17
    Few practical comments on ASHP use and plumbing:

    1. As Syd said - it can be plumbed directly into the pumped circuit

    2. In many models, there is flow sensor inside the ASHP heat exchanger monitoring water flow to shut the ASHP down in the case if there is no water flowing in - to prevent any permanent damage to the ASHP - this is the only part which might get fouled / blocked for example by bits of string algae - unless you pump your water after mechanical filter - in my case I have it plumbed in as direct separate loop - pumped from mid water pump pick up and returning via shower filter into the pond - all what is needed in my case it is at the end of the season, when I am switching ASHP loop off for winter - I just plumb temporarily exit to intake and in reverse mode flush out any debris which might get trapped inside / around the flow sensor.

    3. It is important to have each ASHP serviced - checked for internal pressure of the media inside - as it can leak out after some time - not sufficient internal media pressure equals damaged compressor unit - the most expensive part of ASHP for replacement - also not sufficient content of internal media equals lower heating output of the ASHP. So I suggest - especially as you picked up previously used ASHP unit, to have local refrigeration repair shop to come and check it for you - it is not expensive - and worth every penny as preventative care - as replacing the compressor unit can be very expensive - some times more than new unit (parts and labor combined).

    4. It is a good idea to find alternative heating solution in sub-zero temperatures - as only very few expensive ASHP models can really produce any heat efficiently under zero dC temperatures - and even if they do, COP factor is closer to 1 rather to 3 - in real life. Most cost efficient heating setup is for sub zero temperatures - as Kenny pointed out - to plumb in heating coil run from house central heating system.

    Just my five cents I guess....
    Last edited by milaz; 18-07-2019 at 01:44 PM.
    You get what you pay for - or better - what you make yourself.

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  30. #18
    Quote Originally Posted by milaz View Post
    Few practical comments on ASHP use and plumbing:

    1. As Syd said - it can be plumbed directly into the pumped circuit

    2. In many models, there is flow sensor inside the ASHP heat exchanger monitoring water flow to shut the ASHP down in the case if there is no water flowing in - to prevent any permanent damage to the ASHP - this is the only part which might get fouled / blocked for example by bits of string algae - unless you pump your water after mechanical filter - in my case I have it plumbed in as direct separate loop - pumped from mid water pump pick up and returning via shower filter into the pond - all what is needed in my case it is at the end of the season, when I am switching ASHP loop off for winter - I just plumb temporarily exit to intake and in reverse mode flush out any debris which might get trapped inside / around the flow sensor.

    3. It is important to have each ASHP serviced - checked for internal pressure of the media inside - as it can leak out after some time - not sufficient internal media pressure equals damaged compressor unit - the most expensive part of ASHP for replacement - also not sufficient content of internal media equals lower heating output of the ASHP. So I suggest - especially as you picked up previously used ASHP unit, to have local refrigeration repair shop to come and check it for you - it is not expensive - and worth every penny as preventative care - as replacing the compressor unit can be very expensive - some times more than new unit (parts and labor combined).

    4. It is a good idea to find alternative heating solution in sub-zero temperatures - as only very few expensive ASHP models can really produce any heat efficiently under zero dC temperatures - and even if they do, COP factor is closer to 1 rather to 3 - in real life. Most cost efficient heating setup is for sub zero temperatures - as Kenny pointed out - to plumb in heating coil run from house central heating system.

    Just my five cents I guess....
    Thanks for the info! I was concerned about it becoming dirty and clogged up as my filter system is pump fed, so I decided to plumb it in with its own separate pump pulling water from my final filter bay. I have a submerged pump which I may put in a mesh bag to prevent any large particles entering the machine. I shall definitely get the unit checked over as I want it to be as efficient as possible. I'm not expecting it to work below 0.C so i have my existing electro heater on standby to kick in if needed.

    PROBLEM: The thermostat can not be set below 18 degrees! I hope to heat in the winter to 13. So I had an idea to use a temperature controller to switch the device on and off (luckily it remembers temp settings when power is cut). Also a temperature controller like the INKBIRD ITC308 will allow me to control the fluctuation to +- 0.1 degrees and has built in WIFI for controlling the pond temp from my phone and setting temperature alerts etc which i thought was pretty cool. However....will I do any damage to the heat pump turning it off via the mains instead of using the built in controller? It has a built in compressor delay timer of 1 minute when turning on so i assume turning it on from the mains poses no damage risks.

    What do you think?

  31. #19
    Quote Originally Posted by willshill View Post

    PROBLEM: The thermostat can not be set below 18 degrees! I hope to heat in the winter to 13. So I had an idea to use a temperature controller to switch the device on and off (luckily it remembers temp settings when power is cut). Also a temperature controller like the INKBIRD ITC308 will allow me to control the fluctuation to +- 0.1 degrees and has built in WIFI for controlling the pond temp from my phone and setting temperature alerts etc which i thought was pretty cool. However....will I do any damage to the heat pump turning it off via the mains instead of using the built in controller? It has a built in compressor delay timer of 1 minute when turning on so i assume turning it on from the mains poses no damage risks.

    What do you think?
    Upfront I need to clarify, that I am not an expert - just a bit informed user using ASHP for many years as the main heating of our house (so via separate heating circuit this 14.5 kW Zubadan unit also heats our pond to 7 dC in the winter - works at 100% heat output down to -25dC) and than separate 5kW ASHP for pond tempering - I have similar issue - mine has low limit 15 dC setting - so I just use it as long as it is economical - keeping the 15dC, adding the house central heating loop on top of it - when night freeze arrives in NOV I just switch off the ASHP loop - and set house heating loop to 7dC - so in relatively short period of time - say one week - pond drops down to 7dC - and I keep it there till March - when restarting ASHP loop - and during 4 - 5 days heat it up to 15dC again - the point is to shorten the period between 10 - 12 dC as much as possible not to give any upper hand to Aeromonas bad bugs.

    In your case I would suggest to call your ASHP manufacturer / distributor / service and check if they have as spare part replacement thermostat allowing you to go down to 10/ 15dC - this would allow you to use similar scheme as the above mentioned if desired w/o need to setup any separate thermostat controller.

    Now your setup as described will work - the only consideration should be given to limiting frequent starts and stops of compressor unit - normally hysteresis (on - off switching temperature difference) of 1dC is sufficient - if really precision required, 0.5 dC may be used - but aiming at 0,1 dC is an overkill not needed - and requiring frequent starts and stops of your ASHP. Compressor unit does not like to be switched off abruptly when working by power cut off as proposed in your case - this is why I would recommend you to talk to your ASHP service first - many ASHP units have also internal connectors for external thermostat controller addition - this would be ideal solution - as it will minimize your ASHP compressor wear.

    Alternatively there are many ASHP owners manuals / wiring diagrams available on line - so google it out and check directly what yours is capable of.

    Good luck!
    Last edited by milaz; 19-07-2019 at 04:04 PM.
    You get what you pay for - or better - what you make yourself.

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  33. #20
    Senior Member Rank = Nanasai Tom Koi's Avatar
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    Quote Originally Posted by milaz View Post
    Upfront I need to clarify, that I am not an expert - just a bit informed user using ASHP for many years as the main heating of our house (so via separate heating circuit this 14.5 kW Zubadan unit also heats our pond to 7 dC in the winter - works at 100% heat output down to -25dC) and than separate 5kW ASHP for pond tempering - I have similar issue - mine has low limit 15 dC setting - so I just use it as long as it is economical - keeping the 15dC, adding the house central heating loop on top of it - when night freeze arrives in NOV I just switch off the ASHP loop - and set house heating loop to 7dC - so in relatively short period of time - say one week - pond drops down to 7dC - and I keep it there till March - when restarting ASHP loop - and during 4 - 5 days heat it up to 15dC again - the point is to shorten the period between 10 - 12 dC as much as possible not to give any upper hand to Aeromonas bad bugs.

    In your case I would suggest to call your ASHP manufacturer / distributor / service and check if they have as spare part replacement thermostat allowing you to go down to 10/ 15dC - this would allow you to use similar scheme as the above mentioned if desired w/o need to setup any separate thermostat controller.

    Now your setup as described will work - the only consideration should be given to limiting frequent starts and stops of compressor unit - normally hysteresis (on - off switching temperature difference) of 1dC is sufficient - if really precision required, 0.5 dC may be used - but aiming at 0,1 dC is an overkill not needed - and requiring frequent starts and stops of your ASHP. Compressor unit does not like to be switched off abruptly when working by power cut off as proposed in your case - this is why I would recommend you to talk to your ASHP service first - many ASHP units have also internal connectors for external thermostat controller addition - this would be ideal solution - as it will minimize your ASHP compressor wear.

    Alternatively there are many ASHP owners manuals / wiring diagrams available on line - so google it out and check directly what yours is capable of.

    Good luck!
    Hasn't the ashp got a heating element in it for winter time, bit pointless having one otherwise, as winter time is when its must needed

 

 
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