Results 1 to 10 of 10
  1. #1
    Join Date
    Dec 2009
    Posts
    10

    Oversized water coils and superheat

    Several manufacturers now advertise over-sized water coils, including for water-water units, as a feature that increases efficiency.

    How is this done and still keep the superheat within the desired range? Or doesn't it matter with water coils?

  2. #2
    Join Date
    Mar 2008
    Location
    northern Indiana
    Posts
    114
    The industry as a whole has been increasing coil size on air and water alike to increase efficiency. The superheat is controlled by the TXV and system charge assuming proper flow rates.
    Scrolls are the norm these days and somewhat forgiving in such matters.

  3. #3
    Join Date
    Dec 2009
    Posts
    10
    Quote Originally Posted by teeball57 View Post
    The industry as a whole has been increasing coil size on air and water alike to increase efficiency. The superheat is controlled by the TXV and system charge assuming proper flow rates.
    Scrolls are the norm these days and somewhat forgiving in such matters.
    "Somewhat forgiving" is one matter. It would seem to me that more than _doubling_ the water coil size as at least one geothermal manufacturer has done is quite another matter -- especially in the context of the incessant drumbeat 'out there' admonishing to not oversize air coils.

    Question: Is increasing the system charge sufficient to allow the TXV to maintain desired superheat if one doubles up on coils (as one manufacturer does) keeping the compressor size the same?

  4. #4
    Join Date
    Mar 2008
    Location
    northern Indiana
    Posts
    114
    Question: Is increasing the system charge sufficient to allow the TXV to maintain desired superheat if one doubles up on coils (as one manufacturer does) keeping the compressor size the same

    I think we need to keep this in perspective here.
    In the case of a w to w unit we have 2 matched coils evaporator and condenser. If you increase the size of the coils and match the TXV, the gas charge would increase to accommodate the the extra liquid needed in the system. This is done in a lab environment to monitor the performance.
    In a stand alone unit they can dial in the gas charge to the oz.

    Not sure what you mean by "doubles up on coils". Do you have specifics?

  5. #5
    Join Date
    Dec 2009
    Posts
    10
    Quote Originally Posted by hult View Post
    Question: Is increasing the system charge sufficient to allow the TXV to maintain desired superheat if one doubles up on coils (as one manufacturer does) keeping the compressor size the same?

    Quote Originally Posted by teeball57 View Post
    I think we need to keep this in perspective here.
    In the case of a w to w unit we have 2 matched coils evaporator and condenser. If you increase the size of the coils and match the TXV, the gas charge would increase to accommodate the the extra liquid needed in the system. This is done in a lab environment to monitor the performance.
    In a stand alone unit they can dial in the gas charge to the oz.
    So -- keeping it in perspective -- Is the/your answer "Yes" for standalone water-to-water units ? ;-)

    Not sure what you mean by "doubles up on coils". Do you have specifics?
    Here is a GSHP manufacturer using coils rated at 5 tons for 2-ton units and two 5-ton coils -- "doubled up" -- in a 5-ton unit.

    http://www.geothermalheatpump.com/features.htm

    Sunteq-Enviroteq shows a picture of its apparently proprietary (?) parallel configuration of two coils (which are actually six coils in parallel in two separate units).

    Packless sells coils with manifolds that are two identical colis duplexed ("doubled up")

    http://www.packless.com/catalog/ItemView.aspx?id=49

    and quadruplexed ("quadrupled")

    http://www.packless.com/catalog/ItemView.aspx?id=59 -- click on "More Images" and then "Next".

    so this by itself is an industry standard, and not unusual.

    Quote Originally Posted by hult View Post
    Question: Is increasing the system charge sufficient to allow the TXV to maintain desired superheat if one doubles up on coils (as one manufacturer does) keeping the compressor size the same?
    Is this question clearer now?

    Other than 1) increasing amount of charge and assuring that 2) the TXV temperature sensor and 3) the TXV external connection are properly position on the manifold, what else would be needed for a manufacturer to offer a system with efficiency increased by "doubling up" ?

    TIA ... Marc

  6. #6
    Join Date
    Mar 2008
    Location
    northern Indiana
    Posts
    114
    The Sunteq units use 2 compressors in a single refrigeration circuit. That idea has been abandoned by most all GEO manufactures for many reasons such as cost and size constraints. (not to mention service and reliability issues) So it would not be considered an industry norm.
    The Packless coax is manifolded together on the water side for commercial units. An example would be a 10 ton unit would have 2 separate 5 ton refrigeration circuits or 2 stages of heat or cool. They manifold the water side so only one water connection to the unit is needed. Helps save space too.
    The "double up" of the coax is not done for higher efficiency.

    The size of the coax has increased over the years as has the condenser coil on the split air units to improve efficiency.

  7. #7
    Join Date
    Dec 2009
    Posts
    10
    Quote Originally Posted by teeball57 View Post
    The Sunteq units use 2 compressors in a single refrigeration circuit. That idea has been abandoned by most all GEO manufactures for many reasons such as cost and size constraints. (not to mention service and reliability issues) So it would not be considered an industry norm.
    No one has stated in this thread that two compressors are the norm.

    What Sunteq does unambiguously state at the url I sited is that they use (eg) five tons of coil for a two-ton unit a 2.5:1 ratio. This constitutes (more than) doubling the coil size over standard. And that they do this to increase efficiency. They state:

    " " [T]he heat exchangers on Enviroteq's closed loop models are greatly oversized - 200% on average - for incredibly high heat extraction efficiency. " "

    Quote Originally Posted by teeball57 View Post
    The Packless coax is manifolded together on the water side for commercial units. An example would be a 10 ton unit would have 2 separate 5 ton refrigeration circuits or 2 stages of heat or cool. They manifold the water side so only one water connection to the unit is needed. Helps save space too
    The "double up" of the coax is not done for higher efficiency
    Are you describing an application of a different coil than the ones I cited? They clearly have a single input and a single output for both water _and_ refrigerant. If refrigerant valving/connections are such that only one five-ton compressor is operating in a two-compressor, 10-ton system that always circulates refrigerant to all coils (re-view diagram of the coils I cited) , how is this not "doubling up" and why would not it not increase efficiency ?

    But my reference was simply to point out the availabilty of actual parts from an actual principal standard coil suppplier that would actually allow a manufacturer to actually "double up" coils (both literally and quantitatively) without so much as actually making a single additional braze *if* the answer to my question is "Yes" -- For example, "doubling up" by using a Packless "duplexed" (2-coils + manifold ) 10-ton COAX-3010-S instead of a Packless 5-ton single coil COAX-2500-S.

    Quote Originally Posted by teeball57 View Post
    The size of the coax has increased over the years as has the condenser coil on the split air units to improve efficiency
    Yes. Understood. We've been here before. The question I asked that has not been answered is:
    Quote Originally Posted by hult View Post
    Other than 1) increasing amount of charge and assuring that 2) the TXV temperature sensor and 3) the TXV external connection are properly position on the manifold, what else would be needed for a manufacturer to offer a system with efficiency increased by "doubling up" ?
    Thank you for your patience (and thanks in advance to others who may still also reply ) ... Marc

  8. #8
    Join Date
    Mar 2008
    Location
    northern Indiana
    Posts
    114
    The heat exchangers on Enviroteq's closed loop models are greatly oversized - 200% on average - for incredibly high heat extraction efficiency.

    The problem here is a see no numbers backing this claim.
    Most manufacturers back their claims with spec sheets showing EER & COP.
    I found no such information on that site.

    As I have been told "without data you only have opinion".

  9. #9
    Join Date
    Dec 2009
    Posts
    10
    Quote Originally Posted by teeball57 View Post
    The heat exchangers on Enviroteq's closed loop models are greatly oversized - 200% on average - for incredibly high heat extraction efficiency.

    The problem here is a see no numbers backing this claim.
    Most manufacturers back their claims with spec sheets showing EER & COP.
    I found no such information on that site.

    As I have been told "without data you only have opinion".
    But you have stated/repeated:

    Quote Originally Posted by teeball57 View Post
    The size of the coax has increased over the years as has the condenser coil on the split air units to improve efficiency
    Quote Originally Posted by teeball57 View Post
    The industry as a whole has been increasing coil size on air and water alike to increase efficiency.
    So strking the word "incredibly" from Sunteq's assertion and you would appear to be in complete agreement. Even we include the descriptive term "incredibly" and so consider the phrase in its entity, yours would be only a qualitative difference of opinion, not of quantitatively different facts.

    The question I posed that remains unanswered while we circle 'round and 'round is:

    Quote Originally Posted by hult View Post
    Other than 1) increasing amount of charge and assuring that 2) the TXV temperature sensor and 3) the TXV external connection are properly position on the manifold, what else would be needed for a manufacturer to offer a system with efficiency increased by "doubling up" ?
    Paraphrasing Daniel Patrick Moynihan: "We are entitled to our own opinions, but not our own facts" .

    ... Marc Hult hult@hydrologist.com

  10. #10
    Join Date
    Mar 2008
    Location
    northern Indiana
    Posts
    114
    Ahh , but we have no proof that "doubling up" an already larger coax will increase the efficiency. Do you suppose the larger GEO manufacturers have given that any thought. After all they spend a lot of time and money squeezing every bit of efficiency they can out of design.

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event