Results 1 to 45 of 45
  1. #1
    Join Date
    Jul 2008
    Location
    UK
    Posts
    31
    Rep Power
    0

    both lines in same insualtion



    I just want to check I'm right here. I have had a split system heat pump installed, at the condensing unit, both refrigerant lines are lagged individually, but where they run inside the building, hidden from view behind some panelling, both lines have been pulled through the same length of armourflex, as in both the copper lines touch one another.

    I dont think this is right, can anyone confirm?

    thanks



  2. #2
    Join Date
    Sep 2003
    Location
    ISRAEL
    Age
    65
    Posts
    4,109
    Rep Power
    37

    Re: both lines in same insualtion

    Not to worry, it works as some kind of heat exchanger. i don't see any problems with it.

  3. #3
    Join Date
    Aug 2006
    Location
    england
    Age
    43
    Posts
    3,790
    Rep Power
    38

    Re: both lines in same insualtion

    I asked that question on a manufacturers training course as i had also seen it done and was told it should not be done, both lines should be insulated separately.
    Mostly found in Oxfordshire, UK :)

  4. #4
    Join Date
    Dec 2006
    Location
    UK
    Posts
    96
    Rep Power
    13

    Re: both lines in same insualtion

    Most A/C systems incorporate the metering device at the condenser. As such you definitely want to insulate INDIVIDUALLY. If you place both sets of pipes in one length of lagging then you will have heat transfer from the delivery pipe to the return pipe, so will have less effect when it gets to the evaporator. i.e. the system may work, but it will be less efficient and cost more to run.

    I've seen the OP scenario done all too often, but I'm not bloody sure why! Despite the fact the installers should know better, surely it's harder work to insulate 2 pipes in 1 length of lagging!
    Last edited by Rtic; 10-05-2016 at 06:28 PM.

  5. #5
    Join Date
    Sep 2003
    Location
    ISRAEL
    Age
    65
    Posts
    4,109
    Rep Power
    37

    Re: both lines in same insualtion

    Quote Originally Posted by Rtic View Post
    Most A/C systems incorporate the metering device at the condenser.
    in that case I'm with you. if a TXV is used, its ok.

  6. #6
    Join Date
    Jul 2010
    Location
    NTH.QLD Australia
    Age
    55
    Posts
    1,755
    Rep Power
    26

    Re: both lines in same insualtion

    Quote Originally Posted by monkey spanners View Post
    I asked that question on a manufacturers training course as i had also seen it done and was told it should not be done, both lines should be insulated separately.
    Correct. Insulated pair coil tubing is my choice. Manufacturers sell it in 18 M coiled soft drawn. Just have to purchase the right combination. 1/4+ 3/8, 1/4+ 1/2, 1/4+ 5/8, 3/8+ 5/8 etc.
    To the optimist, the glass is half full. To the pessimist, the glass is half empty.

  7. #7
    Join Date
    Jul 2008
    Location
    UK
    Posts
    31
    Rep Power
    0

    Re: both lines in same insualtion

    Its a MHI split, where the lines are visible, they are lagged individually.

    but yes, I would have assumed that running them together would reduce efficiency at the very least.

    whats a TXV?

  8. #8
    Join Date
    Dec 2006
    Location
    UK
    Posts
    96
    Rep Power
    13

    Re: both lines in same insualtion

    An MHI split does ideally require both lines insulated individually. Like I said, the system will probably work, but the efficiency would be affected.

    Just out of interest, what is the distance of the two pipes that are insulated togeather?

    TXV = Thermostatic Expansion Valve. It's a metering device (where the state of the refrigeration is changed). For somebody I assume is not in the industry, the best way to think of it is the metering device is where the "cooling" starts. There are different types of metering devices; a TXV is mostly found in commercial refrigeration.

  9. #9
    Join Date
    Jul 2008
    Location
    UK
    Posts
    31
    Rep Power
    0

    Re: both lines in same insualtion

    im not in the industry, but I'm in charge of our buildings, hvac, etc so I do have a decent knowledge of how the systems work and types of cooling etc. Thanks for the explanation

    The pipes are run together for about 8 meters, then about 600mm separated. It's only a 5kW unit, so probably wont make a massive difference, but everything counts with energy costs now. It just looked rough to me

  10. #10
    Join Date
    May 2007
    Location
    Auckland
    Age
    67
    Posts
    3,362
    Rep Power
    31

    Re: both lines in same insualtion

    Hi Jono,
    the majority of indoor section of a split system, at the unit the pipes are in one insulated sleave to point of flare connections, they should be individually insulated from that point to the out door unit.
    8 meters in a single insulation sleave will derate cooling/heating capacity somethng terrible.
    Would seem system installed by inexperienced and probably non qualified people

  11. #11
    Join Date
    Jul 2008
    Location
    UK
    Posts
    31
    Rep Power
    0

    Re: both lines in same insualtion

    Thats all I wanted to know. FGas certs are to be produced when its commissioned, and I have seen their qualifications.

    thanks for everyone's help

  12. #12
    Join Date
    Dec 2008
    Location
    UK
    Posts
    509
    Rep Power
    17

    Re: both lines in same insualtion

    If you are going to snag the installation, then it might be prudent to mention your concerns to your contractor or their company before the job is completed. That way it might prevent additional disruption to your occupiers.
    The efficiency losses could be sufficient enough to cause the unit to run for longer periods of time than are absolutely necessary and if the cooling capacity is borderline, on higher ambient days the system might not achieve the designed cut out temperature.
    Mobile A/C at its best, see avatar.

  13. #13
    Join Date
    May 2007
    Location
    Auckland
    Age
    67
    Posts
    3,362
    Rep Power
    31

    Re: both lines in same insualtion

    Hi Jono
    for future reference and less hassles, best you write an install specification statement. So that everyone understands your requiremments, then only legitimate professional suppliers and installation people will provide quotes.
    Will save a lot of greif and your time.

  14. #14
    Join Date
    Dec 2010
    Location
    Greece
    Posts
    177
    Rep Power
    8

    Re: both lines in same insualtion

    this method of installation is commonly used in Greece also.contractors prefer that way of insulation in order to reduce the cost of installation ,reducing the heating-cooling capacity though.

  15. #15
    Join Date
    Oct 2008
    Location
    newbury
    Age
    56
    Posts
    1,349
    Rep Power
    29

    Re: both lines in same insualtion

    Quote Originally Posted by Magoo View Post
    Hi Jono,
    the majority of indoor section of a split system, at the unit the pipes are in one insulated sleave to point of flare connections, they should be individually insulated from that point to the out door unit.
    8 meters in a single insulation sleave will derate cooling/heating capacity somethng terrible.
    Would seem system installed by inexperienced and probably non qualified people
    Can you expand on this as 'something terrible' isn't very scientific. I would have assumed both pipes to be very similar in temperature along the length so the heat transfer would be quite small?

    Interestingly as the pipes exit the indoor unit they are supplied with one piece of armaflex for wrapping both so the manufacturers aren't that hung up about separation...

  16. #16
    Join Date
    Feb 2015
    Location
    India
    Posts
    37
    Rep Power
    0

    Re: both lines in same insualtion

    In my home I have hitachi and Daikin air con, inlet and outlet copper tubings are lagged separately. Rtic was very comprehensive and �� on TXV!

  17. #17
    Join Date
    Oct 2008
    Location
    newbury
    Age
    56
    Posts
    1,349
    Rep Power
    29

    Re: both lines in same insualtion

    Quote Originally Posted by vikky1971 View Post
    In my home I have hitachi and Daikin air con, inlet and outlet copper tubings are lagged separately. Rtic was very comprehensive and �� on TXV!

    This is how splits come from the factory, both pipes in the same lagging..

    DSC_0436[1].jpg

  18. #18
    Join Date
    Jul 2010
    Location
    NTH.QLD Australia
    Age
    55
    Posts
    1,755
    Rep Power
    26

    Re: both lines in same insualtion

    I know what you are saying RB. That lagging is split after the steel bending spring on the Suction line. They might run both lines together for that distance as there is bugger-all room for independent pipe insulation.
    To the optimist, the glass is half full. To the pessimist, the glass is half empty.

  19. #19
    Join Date
    Dec 2006
    Location
    UK
    Posts
    96
    Rep Power
    13

    Re: both lines in same insualtion

    Quote Originally Posted by r.bartlett View Post
    This is how splits come from the factory, both pipes in the same lagging..

    DSC_0436[1].jpg
    That (very) small run is going to do very little damage to the efficiency of the system; 8 metres, on the other hand, is going to have a big effect on the efficiency of the system. For any installer to install a system and insulate both lines together shows a complete lack of knowledge of how the system actually works... I'm guessing the installer of that 8m pipe run system is a plumber.

  20. #20
    Join Date
    Oct 2008
    Location
    newbury
    Age
    56
    Posts
    1,349
    Rep Power
    29

    Re: both lines in same insualtion

    Quote Originally Posted by Rtic View Post
    That (very) small run is going to do very little damage to the efficiency of the system; 8 metres, on the other hand, is going to have a big effect on the efficiency of the system. For any installer to install a system and insulate both lines together shows a complete lack of knowledge of how the system actually works... I'm guessing the installer of that 8m pipe run system is a plumber.
    Can you quantify what the big effect is? I sense there is a lot of assuming and nothing to back it up.

    The suction pipe will be returning very close to zero. The phase change line will be at a similar state. What transfer is actually happening and which way is it going.

  21. #21
    Join Date
    Oct 2008
    Location
    newbury
    Age
    56
    Posts
    1,349
    Rep Power
    29

    Re: both lines in same insualtion

    Quote Originally Posted by mikeref View Post
    I know what you are saying RB. That lagging is split after the steel bending spring on the Suction line. They might run both lines together for that distance as there is bugger-all room for independent pipe insulation.
    All I'm saying is people are stating things as fact but not actually backing it up with any :-)

  22. #22
    Join Date
    Dec 2006
    Location
    UK
    Posts
    96
    Rep Power
    13

    Re: both lines in same insualtion

    Quote Originally Posted by r.bartlett View Post
    Can you quantify what the big effect is? I sense there is a lot of assuming and nothing to back it up.

    The suction pipe will be returning very close to zero. The phase change line will be at a similar state. What transfer is actually happening and which way is it going.
    Rule 101 of thermodynamics...

    Hot travels to cold! What you have is a 8-metre heat exchanger; what effect do you think that would have?

  23. #23
    Join Date
    Oct 2008
    Location
    newbury
    Age
    56
    Posts
    1,349
    Rep Power
    29

    Re: both lines in same insualtion

    Quote Originally Posted by Rtic View Post
    Rule 101 of thermodynamics...

    Hot travels to cold! What you have is a 8-metre heat exchanger; what effect do you think that would have?
    what temperature do you think

    a) Suction pipe
    b) phase change pipe


    plus they are almost certainly not touching the whole of the 8m length so whatever the effect is reduced.

    Happy to be convinced but your nowhere near providing any relevent evidence in this instance to back up your statement

  24. #24
    Join Date
    Dec 2006
    Location
    UK
    Posts
    96
    Rep Power
    13

    Re: both lines in same insualtion

    Quote Originally Posted by r.bartlett View Post
    what temperature do you think

    a) Suction pipe
    b) phase change pipe


    plus they are almost certainly not touching the whole of the 8m length so whatever the effect is reduced.

    Happy to be convinced but your nowhere near providing any relevent evidence in this instance to back up your statement
    Sorry; but what part of Hot travels to cold, do you not understand? Also; it's just as likely that both pipes ARE touching!

    This is the basics, that most engineers should know. Furthermore, we as professionals in our industry are entrusted to do a good and proper job, so that the system runs as efficiently as possible. Insulating both lines individually is paramount to achieving this.

    Of course, you can just throw a system in and just be happy that it works; forget insulating the lines properly, getting the charge right or leak testing the system. Hell, just purge the system, why should we bother vacuuming; I mean it seems to work...

  25. #25
    Join Date
    Oct 2008
    Location
    newbury
    Age
    56
    Posts
    1,349
    Rep Power
    29

    Re: both lines in same insualtion

    Quote Originally Posted by Rtic View Post
    Sorry; but what part of Hot travels to cold, do you not understand? Also; it's just as likely that both pipes ARE touching!

    This is the basics, that most engineers should know. Furthermore, we as professionals in our industry are entrusted to do a good and proper job, so that the system runs as efficiently as possible. Insulating both lines individually is paramount to achieving this.

    Of course, you can just throw a system in and just be happy that it works; forget insulating the lines properly, getting the charge right or leak testing the system. Hell, just purge the system, why should we bother vacuuming; I mean it seems to work...
    Why not answer the questions which would actually help your 'big effect' contention.

    what temperature in this example do you think
    a)the suction pipe is
    b ) what temperature the phase change pipe is
    c)which of these two is the 'hot' one in your opinion

    what is the actual contact area between two touching (or not) round 8m pipes lose in a piece of lagging in sq milimetres

    then calculate how much heat transfer is happening in this real life example . Please confirm if you are working on the two pipes touching 100%,75% 50% etc of the 8m as 1/2" and especially 1/4" are very difficult to get to lie straight.

    Once you come back with an answer based on an actual calculation rather than a shooting from the hip 'big affect' we can confirm if it does or does not have any real effect on efficiency.

    I await your 'professional engineer' response.
    Last edited by r.bartlett; 18-05-2016 at 11:41 PM.

  26. #26
    Join Date
    Dec 2006
    Location
    UK
    Posts
    96
    Rep Power
    13

    Re: both lines in same insualtion

    a) In cooling mode the entire line (delivery & return) is the suction; as you should know, and as I explained earlier in this thread (the metering device is located at the condenser).
    b) This is variable
    c) In cooling mode the return is hotter (depending on if you are a refrigeration engineer or not, the definition of "HOT" may vary).

    The actual contact area is impossible to tell without seeing the install, it could be the entire length, there could be no contact, and everything in between. What I can say for certain, is if both pipes were insulated separately, there is no chance of ANY heat transfer.


    Hot travels to cold; the delivery is colder than the return so heat transfer will occur. Heat transfer will occur if both pipes run in one length of insulation, and the longer the run, the more heat transfer.

    Like I said; I like to see the job done properly.
    Last edited by Rtic; 19-05-2016 at 01:22 AM.

  27. #27
    Join Date
    Oct 2008
    Location
    newbury
    Age
    56
    Posts
    1,349
    Rep Power
    29

    Re: both lines in same insualtion

    Quote Originally Posted by Rtic View Post
    a) In cooling mode the entire line (delivery & return) is the suction; as you should know, and as I explained earlier in this thread (the metering device is located at the condenser).
    delivery and return is the suction?

    b) This is variable
    from what to what (in deg C)?

    c) In cooling mode the return is hotter (depending on if you are a refrigeration engineer or not, the definition of "HOT" may vary).
    are you sure, can you confirm that with actual measurements or explanations to show that this is the case?
    it's usual I believe the that the phase change line runs at higher pressure than the suction.


    The actual contact area is impossible to tell without seeing the install, it could be the entire length, there could be no contact, and everything in between. What I can say for certain, is if both pipes were insulated separately, there is no chance of ANY heat transfer.


    Hot travels to cold; the delivery is colder than the return so heat transfer will occur. Heat transfer will occur if both pipes run in one length of insulation, and the longer the run, the more heat transfer.
    This is all very wishy washy.

    How have you confirmed what the amount of transfer is sufficient here to make your 'big effect' comment. ?

    I'm happy to see where this goes but you and at least 2 others have made sweeping statements about loss of performance but failed to back it up with any actual evidence.

    I'm curious to learn how much a 'hot' suction pipe of <5c is going to put so much heat into a phase change line to have a 'big effect' have on a 5kw split performance

  28. #28
    Join Date
    Dec 2006
    Location
    UK
    Posts
    96
    Rep Power
    13

    Re: both lines in same insualtion

    Quote Originally Posted by r.bartlett View Post
    delivery and return is the suction?



    from what to what (in deg C)?



    are you sure, can you confirm that with actual measurements or explanations to show that this is the case?
    it's usual I believe the that the phase change line runs at higher pressure than the suction.



    This is all very wishy washy.

    How have you confirmed what the amount of transfer is sufficient here to make your 'big effect' comment. ?

    I'm happy to see where this goes but you and at least 2 others have made sweeping statements about loss of performance but failed to back it up with any actual evidence.

    I'm curious to learn how much a 'hot' suction pipe of <5c is going to put so much heat into a phase change line to have a 'big effect' have on a 5kw split performance
    In cooling mode, on a MHI split system (where the metering device is at the condenser), both the delivery line to the evaporator is the suction, and the return to the condenser is also the suction. Phase change has occurred in the evaporator (ideally at the end; but with a 8-metre heat exchanger perhaps earlier ).

    All you keep doing is replying about "actual evidence", but I'm not the installer of the original system, nor do I have access to the site. I have put my thought on this subject and have provided in detail why I think that insulating both lines will indeed have a "big effect".

    You have said "at least 2 others have made sweeping statements about loss of performance but failed to back it up with any actual evidence", but that's because when on a refrigeration forum, after the OP question has been answered using what is basic knowledge that most refrigeration engineers should know, there is little more to add. However, you seem to want us to either go to the site to take accurate measurements or set up a test rig to prove what is already known .

    Sigh... so go on then give me your standard "actual evidence" reply.

  29. #29
    Join Date
    Oct 2008
    Location
    newbury
    Age
    56
    Posts
    1,349
    Rep Power
    29

    Re: both lines in same insualtion

    Quote Originally Posted by Rtic View Post
    In cooling mode, on a MHI split system (where the metering device is at the condenser), both the delivery line to the evaporator is the suction, and the return to the condenser is also the suction. Phase change has occurred in the evaporator (ideally at the end; but with a 8-metre heat exchanger perhaps earlier .
    If I understand you correctly the flow into an evaporator from the expansion device is a suction pipe? From my comprehension the suction line is the pipe from the evaporator to the compressor no more. I don’t think anyone here will agree with you on this.

    However phase change starts from the expansion device therefore this pipe is below liquid line pressure and temperature but not yet at suction line pressure or temperature. Would you agree with this?


    All you keep doing is replying about "actual evidence", but I'm not the installer of the original system, nor do I have access to the site. I have put my thought on this subject and have provided in detail why I think that insulating both lines will indeed have a "big effect".
    Err no you haven’t all you’ve said it ‘big effect’ you haven’t actually provided any information let alone detailed to back this up in any way shape or form.

    I asked you what temperature you think the pipes would be as this is fundamental to your assumption and you have failed to even consider what they might be..

    You have said "at least 2 others have made sweeping statements about loss of performance but failed to back it up with any actual evidence", but that's because when on a refrigeration forum, after the OP question has been answered using what is basic knowledge that most refrigeration engineers should know, there is little more to add. However, you seem to want us to either go to the site to take accurate measurements or set up a test rig to prove what is already known

    Sigh... so go on then give me your standard "actual evidence" reply.
    Heat transfer relies on a temperature difference. I ask again what temperature difference would you expect between a suction pipe and a phase change pipe on any split let alone this one?

    No one apart from Chemi has considered that the two pipes are nearly identical in temperature coupled with the potential that they would only be touching sporadically along the 8m length which may negate any real heat exchange effect. In fact there is a possibility that the suction pipe is colder than the phase change pipe which may turn your argument on it’s head.

    The reason I ask for ‘actual evidence’ is that there is an assumption that it has a detrimental effect yet no one can provide any actual evidence to back this up.

  30. #30
    Join Date
    Dec 2006
    Location
    UK
    Posts
    96
    Rep Power
    13

    Re: both lines in same insualtion

    Whatever you say; I stand by my own posts, and think any engineer who thinks it's acceptable to insulate both pipes in one length of insulation is doing the job wrong. I do feel like your intention was not to discuss the OP issue, but to argue and belittle others who disagree with you.

    You know, it's users like you that make this forum a generally unpleasant place to be, and the very reason I won't bother anymore.
    Last edited by Rtic; 19-05-2016 at 10:48 PM.

  31. #31
    Join Date
    Feb 2015
    Location
    India
    Posts
    37
    Rep Power
    0

    Re: both lines in same insualtion

    Rtic very mature approach. In my home two pipes are individually insulated but wrapped together together in with white vinyl tape, to match with wall colour.
    I maintain, everything I have, myself.

  32. #32
    Join Date
    Dec 2007
    Location
    ireland
    Age
    48
    Posts
    262
    Rep Power
    19

    Re: both lines in same insualtion

    Just a thought but if the metering device is at the outdoor unit and the refrigerant starts boiling after it , it has to take in heat from somewhere to boil into a vapour , if the superheated suction coming back to the compressor comes into contact with this boiling line whats to stop it giving up its superheat to it and turning back into a liquid on way back to compressor. Similar to passing a coldroom suction uninsulated through a freezer room.

  33. #33
    Join Date
    Oct 2008
    Location
    newbury
    Age
    56
    Posts
    1,349
    Rep Power
    29

    Re: both lines in same insualtion

    Quote Originally Posted by Rtic View Post
    Whatever you say; I stand by my own posts, and think any engineer who thinks it's acceptable to insulate both pipes in one length of insulation is doing the job wrong. I do feel like your intention was not to discuss the OP issue, but to argue and belittle others who disagree with you.

    You know, it's users like you that make this forum a generally unpleasant place to be, and the very reason I won't bother anymore.
    My intention was for someone (anyone) to substantiate the claim that it has 'a big effect' or indeed any noticeable effect and if so what evidence is there to back this claim up.

    No one has been able to even come close to responding to that request.

    I said several times I was happy to be shown how this could be but again no one -including you- has done so .

    You made the fundamental statement 'hot travels to cold'. That's fine and not in dispute but when I asked what temperature you think the two pipes would be you (and everyone else free to jump in) repeatedly avoided to consider it.

    The pipe temperature delta T is fundamental to the rate of transfer in this (and any other) case. Therefore it's not unreasonable to pose what this differential is likely to be.

    Unfortunately again and again you (and everyone else) avoided responding. That's a shame. The obvious conclusion is that most realise they are likely to be very close in temperature and hence the rate of transfer is likely to be quite small.

    Again as I say I'm happy to be corrected but as yet no one wants to go near this....???????


    This forum is about discussing all things refrigeration, to expand on knowledge and question what we do and why. If someone (anyone) makes a statement then someone (anyone) should be free to question it. That's how these things work.

    This was never an attack on you so I'm sorry if you've gone all 'poor me' over this but you have simply failed to address the questions I pose.

    If you don't like being asked questions about what you think is correct, then you're right, this isn't the forum for you but your best bet is to stick around. Good luck with your learning curve :-)
    Last edited by r.bartlett; 20-05-2016 at 08:11 AM.

  34. #34
    Join Date
    Oct 2007
    Location
    manchester
    Age
    44
    Posts
    5,707
    Rep Power
    39

    Re: both lines in same insualtion

    007.jpgwrights wac pac units were installed in computer suites with liquid an suction pipes within the same lagging- also used heating (lead free solder for joints on r22)
    Last edited by install monkey; 20-05-2016 at 06:06 PM. Reason: piccy as back up of my statement

  35. #35
    Join Date
    Aug 2010
    Location
    England
    Age
    46
    Posts
    77
    Rep Power
    10

    Re: both lines in same insualtion

    Quote Originally Posted by install monkey View Post
    007.jpgwrights wac pac units were installed in computer suites with liquid an suction pipes within the same lagging- also used heating (lead free solder for joints on r22)
    back int day...... i used to do this on Wrights jobs and would run some of the lead free solder in between the two pipes to act as a heat sink and to keep them together whist lagging them.

    Doesnt answer the question, mind, but not to worry

  36. #36
    Join Date
    Nov 2010
    Location
    wales
    Posts
    51
    Rep Power
    9

    Re: both lines in same insualtion

    I always believed you insulated the line from the metering device so that you didn't have it dripping water when no longer refrigerating, so it doesn't matter about heat transfer as long as the pipework is insulated, but having said that, the installation instructions on imi marstair was to insulate both lines seperatly.

  37. #37
    Join Date
    Dec 2007
    Location
    australia
    Posts
    2,461
    Rep Power
    27

    Re: both lines in same insualtion

    I have read through but can't see any mention of heat pump as first posted.
    If on heating, surely lines insulated together is a no no

  38. #38
    Join Date
    May 2012
    Location
    England
    Age
    53
    Posts
    1,236
    Rep Power
    28

    Re: both lines in same insualtion

    .

    Working with a 10 K temperature difference over the evap coil
    and an evaporating temperature approximately 10 k bellow air off,
    if average room temperature is 20 deg C then air on evap is about
    25 deg c air off about 15 ish?

    If air off evap is about 15 ish then evaporating temperature would
    be about 5 ish deg c. If air on evap is 25 ish c then superheated suction
    vapour would be 4 k to 7 k above saturation temp and obviously no
    higher than ambient.

    5 dag c evaporating temp and 4 to 7 k superheat would leave the suction
    return temp at between 9 deg c and 12 deg c.

    Assuming the saturated liquid line is in contact with the suction for half the
    distance then the two pipes will have a temperature difference of at least
    the superheated vapour value of between 4 and 7 k.

    But inside the insulation the two pipes will exchange heat to the air space
    around the pipe and inside the insulation so heat exchange will still take place
    but at a reduced level.

    Assuming that level is half the level of the contacting pipes, you could imagine
    the difference to be 2 to 3 k instead of the 4 to 7 k.

    That means over the length of the 18 mtrs there is a temperature difference of
    on average maybe somewhere about 4 ish k????

    If the evaporating temperature is increased that means that the suction temp
    will be decreased, the return temperature to the compressor will be reduced by
    a few degrees as the evaporating temperature is increased by a few degrees??

    That means the evaporating temperature is not plus 5ish it is plus 7ish so the air
    off is going to respectively higher and so is the room temperature?????

    For the system to deliver the same duty as the double insulated system the compressor
    it will have to work a little longer or harder??? If the suction return is cooler
    the condensing temperature would be lower ( by how much I do not know) so
    that would affect the condensing temperature and that in turn would affect
    the overall performance of the system?????

    Guesswork and assumptions I know, I have no proof to back this up but
    City & guilds have a figure for AC systems that claim every degree reduced
    between the evaporating temperature and the condensing temperature
    increases efficiency by 3% and reduces costs by 3%, if that is true the extra
    workload of the two pipes touching could effect the whole system by at least
    1 deg c and maybe as much as 4 deg c????

    That could be an increase in costs of at least 3% and maybe as much as 12%???

    But if the discharge is reduced as a result, maybe that would have an effect on
    the subcooling. Subcooling with air cooled condensers can only achieve about 4 k to
    7 k at best, but if the subcooling is reduced then there would be more physical
    liquid present after the metering device and not as much flash gas??

    When I started this I thought I would prove that the system is bound to be less
    efficient, but after thinking about it and writing it out long hand, I can say I
    honestly don't know. My gut reaction is to say it is wrong but if I'm honest it
    would take a lot better person than me to prove this one way or the other???

    No help at all, Rob

    .
    .. ... -. .----. - / -- --- .-. ... . / -.-. --- -.. . / --. --- --- -..

  39. #39
    Join Date
    Jul 2010
    Location
    NTH.QLD Australia
    Age
    55
    Posts
    1,755
    Rep Power
    26

    Re: both lines in same insualtion

    Rob. Your comment is appreciated. This ^ is surely what most of us following this thread are scratching our heads over. TD across the Evaporator in cooling mode is 12 to 14 Degrees C with fan speed at 50%. Using ambient at 32C and room temp at 23C on a one to one basis. One evap, one condensing unit, independent insulated pipe run.

    Reverse cycle obviously paints a different Picture.
    Can't answer RB's Question so...no help from this side of the Planet
    Last edited by mikeref; 21-05-2016 at 10:20 AM. Reason: Chose not to comment on a 2006 registered Fridgie.
    To the optimist, the glass is half full. To the pessimist, the glass is half empty.

  40. #40
    Join Date
    Oct 2007
    Location
    manchester
    Age
    44
    Posts
    5,707
    Rep Power
    39

    Re: both lines in same insualtion

    always wondered how they lagged it- the installs were always top notch- lagging identified as r22, this kit was running for +20yrs, bombproof, and good for recycling too as it took 4 of us to lift a 4 circuit evap coil
    002 (3).jpg001.jpg002.jpg031.jpg
    Last edited by install monkey; 21-05-2016 at 10:35 PM.

  41. #41
    Join Date
    Dec 2007
    Location
    australia
    Posts
    2,461
    Rep Power
    27

    Re: both lines in same insualtion

    Quote Originally Posted by RANGER1 View Post
    I have read through but can't see any mention of heat pump as first posted.
    If on heating, surely lines insulated together is a no no
    So on cooling mode no big deal liquid & suction together if metering device on condensing unit.
    On reverse cycle discharge & liquid line together, so poorer performance, 70 or so deg C discharge & 22 deg C liquid line touching each other, or close proximity.
    Last edited by RANGER1; 21-05-2016 at 10:16 PM.

  42. #42
    Join Date
    Dec 2008
    Location
    UK
    Posts
    509
    Rep Power
    17

    Re: both lines in same insualtion

    Interesting thoughts have been raised by this question.
    Whilst I was firmly convinced that it would not be best practice and this still is my gut feeling, I am unable to add conclusive proof either way.
    The Wrights wacpac units were normally cooling only, so it would be liquid and suction line together, as the expansion valve would have been on the DX coil, creating a full length heat exchanger which may well have marginally improved the operational efficiency.
    Mobile A/C at its best, see avatar.

  43. #43
    Join Date
    Apr 2001
    Location
    New Port Richey, Florida - USA
    Age
    72
    Posts
    5,069
    Rep Power
    28

    Re: both lines in same insualtion

    Methinks some confuse efficiency with capacity, but... carry on.

  44. #44
    Join Date
    Dec 2008
    Location
    UK
    Posts
    509
    Rep Power
    17

    Re: both lines in same insualtion

    Gary,
    Good to see you back on board.
    Mobile A/C at its best, see avatar.

  45. #45
    Join Date
    Apr 2001
    Location
    New Port Richey, Florida - USA
    Age
    72
    Posts
    5,069
    Rep Power
    28

    Re: both lines in same insualtion

    Thanks, hyperion

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •