Page 2 of 4 FirstFirst 1234 LastLast
Results 14 to 26 of 46
  1. #14
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Quote Originally Posted by key1cc View Post
    I have room to also expand the 8x9.5 to 16x8. Do you think that will be enough or is more still required?

    Key1
    It would help,but can't say how much,or how it will effect the room by room air flow and resulting temperatures.If we were on site and tested,we could predict the performance,can't tell from here.

    Pictures of the supply plenum and trunk take-offs could tell a lot.Often these can be improved to reduce the static.

    Here's a sketch of a furnace,coil and plenum,showing how adding vanes or an angled take-off can reduce the static.This was for another thread ,a while back.In your case you'd want to improve all the trunk take-offs ,not just one.
    Attached Images Attached Images

  2. #15
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,743
    He posted pics in another thread, a couple weeks ago. I think you posted in that thread also.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  3. #16
    Join Date
    Apr 2008
    Location
    Princeton, NJ
    Posts
    581
    The thread with all the pics and details is called "Finally getting Static Pressure checked" by key1cc.
    I don't know how to link it but if you do a search-then advanced search- then search for poster key1cc you will find it.
    Key1cc

  4. #17
    Join Date
    Apr 2002
    Location
    Omaha, NE
    Posts
    1,561
    Quote Originally Posted by key1cc View Post
    The thread with all the pics and details is called "Finally getting Static Pressure checked" by key1cc.
    I don't know how to link it but if you do a search-then advanced search- then search for poster key1cc you will find it.
    Key1cc
    http://hvac-talk.com/vbb/showthread.php?t=172134

  5. #18
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,743

  6. #19
    Join Date
    Apr 2008
    Location
    Princeton, NJ
    Posts
    581
    Quote Originally Posted by beenthere View Post
    On 4 ton A/C systems installed on furnaces.
    .8" static is usually not too hard to attain. Some times when a 5 ton evap coil is used, .9" is doing good on a swap out, with duct alterations.

    It depends on what you have to work with. And how much money you are willing to spend.
    Well the work has already started and it is divided into three stages.
    Stage 1 is to add the new 14x14 trunk which transitions to a 16x 12 then a 16x8 before linking up with seven 5" round runs which will be converted to 6" rounds. After that is done The static and air flow will be assessed then....
    Stage 2 will be considered which will widen the 8x9.5 trunk to 16x8 and all five of the 5" round runs will be converted to 6" round.
    Stage 3 will be to convert the 24x10 return drop into a 24x16 return drop with a 5" media filter cabinet.

    Hopefully all of that will get me down to my realistic target of 0.7 or less.

    Key1

  7. #20
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,743
    Don't forget to install balancing dampers.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  8. #21
    Join Date
    Apr 2008
    Location
    Princeton, NJ
    Posts
    581
    Quote Originally Posted by beenthere View Post
    Don't forget to install balancing dampers.
    I won't ...

    Thanks for all of the help....

    I will post again after stage 1 is complete with a SP update.

    Key1

  9. #22
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Quote Originally Posted by key1cc View Post
    Well the work has already started and it is divided into three stages.
    Stage 1 is to add the new 14x14 trunk which transitions to a 16x 12 then a 16x8 before linking up with seven 5" round runs which will be converted to 6" rounds. After that is done The static and air flow will be assessed then....
    Stage 2 will be considered which will widen the 8x9.5 trunk to 16x8 and all five of the 5" round runs will be converted to 6" round.
    Stage 3 will be to convert the 24x10 return drop into a 24x16 return drop with a 5" media filter cabinet.

    Hopefully all of that will get me down to my realistic target of 0.7 or less.

    Key1
    did you view the sketch I posted?

    from the pics in the other thread,a lot could have been done to improve the take-offs from the plenum and on the return as well.

    Increasing the size isn't the only way to reduce the static.

    Adding a 5" filter to the side of the furnace,isn't the best way to do it.

    Wondering if the furnace is large enough to requie,bottom or returns from both sides,might want to check on that.

  10. #23
    Join Date
    Aug 2006
    Location
    Dallas (Plano), TX
    Posts
    168
    Quote Originally Posted by key1cc View Post
    ... Stage 3 will be to convert the 24x10 return ... into a 24x16 return ...
    I'm surprised this is step 3, and instead not an earlier step.

    Doesn't changing the return from 24x10 to 24x16 change the return cfm capacity from about 1050 to about 1600 cfm (assuming 700 fps)?

    And since the unit is 4 ton, would the aproximate max cfm capacity be 1600, assuming 400 cfm/ton?

    Thus, simply to have the return sized to the capacity of the 4 ton unit, shouldn't the return be at least 24x16?

    Thanks and best regards,

    Bill

  11. #24
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,743
    His return is more restrivtive then his supply.
    So increasing the return first would increase his upply static and possibly make a noise problem.

    The 16 x 24 return will allow him to get get a longer life from his media filter before the pd across it becomes too much.

    When he puts his factory filter in, his supply static goes from .55" to .62", so his supply needs attention.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  12. #25
    Join Date
    Aug 2006
    Location
    Dallas (Plano), TX
    Posts
    168
    beenthere, thank you.

    Interesting.

    Sound like in fact, both the supply and return sides need to be fixed to really have an optimized system that runs with maximum efficiency.

    Best regards,

    Bill

  13. #26
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,888
    Quote Originally Posted by dash View Post
    It would help,but can't say how much,or how it will effect the room by room air flow and resulting temperatures.If we were on site and tested,we could predict the performance,can't tell from here.

    Pictures of the supply plenum and trunk take-offs could tell a lot.Often these can be improved to reduce the static.

    Here's a sketch of a furnace,coil and plenum,showing how adding vanes or an angled take-off can reduce the static.This was for another thread ,a while back.In your case you'd want to improve all the trunk take-offs ,not just one.
    Liked your drawing, the turning vanes & extra area at the duct take-offs make a huge difference!

    Well, I would design a heat pump duct system at 450-cfm per/ton or 1800-cfm.

    It is not easy to design for 1800-cfm & above on residential systems.
    You should try for the 0.5" ESP, at least at a 350-cfm per/ton you might achieve the 0.5" ESP. ESP is after the filter & before the blower & before the evaporator coil.

    For the ESP, I would want it before the condenser coil on a high efficiency condensing furnace, otherwise it won't yield the full ESP. There ought to also be predrilled capped holes to check the drop across the HE furnace condensing coil.
    http://www.udarrell.com/proper_cfm_b...g_systems.html - Darrell

Page 2 of 4 FirstFirst 1234 LastLast

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