Page 12 of 12 FirstFirst ... 256789101112
Results 144 to 150 of 150
  1. #144
    Join Date
    Jun 2011
    Location
    NE Ohio
    Posts
    839
    Post Likes
    Quote Originally Posted by icemeister View Post
    Thanks. Just to verify the performance check you mentioned in Post #1, at 20#/220# (-16F/97F) the Danfoss Coolselector2 program shows 8.2 amps, just what you said.


    I've always put a lot of confidence in performance chart results, enough so it would convince me not to simply replace the compressor when nothing else appears to resolve the problem. If there's going to be "one last try" with one of these types of jobs where nothing seems to improve matters, let the performance data be that last try, not the cost and bother of a new compressor.

    In the end, these headbangers sometimes need to be brought into the shop so you can fiddle with it in your time. It's certainly of no use to the customer as it sits now.
    are you able to calculate some BTU numbers of the compressor vs .042 x 10 ' capillary vs TXV ?

  2. #145
    Join Date
    Jul 2000
    Location
    Guayaquil, EC
    Posts
    13,461
    Post Likes
    Quote Originally Posted by hvacskills View Post
    are you able to calculate some BTU numbers of the compressor vs .042 x 10 ' capillary vs TXV ?
    For cap tube sizing, I use the Tecumseh program: http://boxload.tecumseh.com/SelectCapTube.aspx

    This compressor at -27F/99F has a capacity of 0.179 tons or 2148 Btuh. Based on that and 89F liquid temperature and 36" heat exchange length, I get 66" of 0.042" cap tube would be required.

    This program has always given me sizes that work from the start with no fussing about.

  3. #146
    Join Date
    Jun 2011
    Location
    NE Ohio
    Posts
    839
    Post Likes
    Quote Originally Posted by icemeister View Post
    For cap tube sizing, I use the Tecumseh program: http://boxload.tecumseh.com/SelectCapTube.aspx

    This compressor at -27F/99F has a capacity of 0.179 tons or 2148 Btuh. Based on that and 89F liquid temperature and 36" heat exchange length, I get 66" of 0.042" cap tube would be required.

    This program has always given me sizes that work from the start with no fussing about.
    think OP may want to look into capillary tube length

    question ..... 1/4 ton TXV ... is that while the valve is modulating within it operating temperature range or at full flow ? question being suppose the sensing bulb is not cold enough to start metering the valve closed and is still wide open ?

    even if not 1/4 ton looks slightly large and might explain the lower head pressure if it was wide open

  4. #147
    Join Date
    Jul 2000
    Location
    Guayaquil, EC
    Posts
    13,461
    Post Likes
    Quote Originally Posted by hvacskills View Post
    think OP may want to look into capillary tube length

    question ..... 1/4 ton TXV ... is that while the valve is modulating within it operating temperature range or at full flow ? question being suppose the bulb is not cold enough to start metering the valve closed and is still wide open ?

    even if not 1/4 ton looks slightly large and might explain the lower head pressure if it was wide open
    The 1/4 ton is the nominal rating of the valve at its standard conditions. The conditions for a specific application will be different and so the valves flow capacity will vary accordingly. Since when a valve is selected the closest valve capacity will most always be a little greater than the required capacity. the valve will tend to feed wide open to its max flow capacity if above the design conditions but modulating if it's at design temperature.

    A higher suction and condensing temp during pulldown with a TXV as compared to a cap tube would be expected. A TXV with an MOP, pressure limiting powerhead would be somewhere in between.

    If the compressor capacity is sufficient, one would expect the box temperature to pull down to design within a reasonable time. When it doesn't and all else look good, you have a problem which may be difficult to find, but often has a simple explanation.

  5. #148
    Join Date
    Jun 2011
    Location
    NE Ohio
    Posts
    839
    Post Likes
    Quote Originally Posted by icemeister View Post
    The 1/4 ton is the nominal rating of the valve at its standard conditions. The conditions for a specific application will be different and so the valves flow capacity will vary accordingly. Since when a valve is selected the closest valve capacity will most always be a little greater than the required capacity. the valve will tend to feed wide open to its max flow capacity if above the design conditions but modulating if it's at design temperature.

    A higher suction and condensing temp during pulldown with a TXV as compared to a cap tube would be expected. A TXV with an MOP, pressure limiting powerhead would be somewhere in between.

    If the compressor capacity is sufficient, one would expect the box temperature to pull down to design within a reasonable time. When it doesn't and all else look good, you have a problem which may be difficult to find, but often has a simple explanation.

    that is why understanding how and why refrigerant is supposed to act / re act within a system is important

  6. #149
    Join Date
    Jul 2000
    Location
    Guayaquil, EC
    Posts
    13,461
    Post Likes
    Quote Originally Posted by hvacskills View Post
    that is why understanding how and why refrigerant is supposed to act / re act within a system is important
    However it's those little things you overlooked or dismissed that are behind you. That's why they often bite you in the butt.

  7. #150
    Join Date
    Jun 2011
    Location
    NE Ohio
    Posts
    839
    Post Likes
    Quote Originally Posted by icemeister View Post
    However it's those little things you overlooked or dismissed that are behind you. That's why they often bite you in the butt.
    if too long of a capillary tube was installed and refrigerant was added to raise the lowside pressure to be somewhat reasonable for the box temperature I would expect to see a noticeably elevated highside pressure

Page 12 of 12 FirstFirst ... 256789101112

Posting Permissions

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

Related Forums

Plumbing Talks | Contractor MagazineThe place where Electrical professionals meet.