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  1. #1
    Join Date
    Sep 2007
    Location
    Yuma, Arizona
    Posts
    252

    Chilled water coil plumbing...

    The installers of a heating coil and a chilled water coil apparently installed them backwards at one of our buildings. This was brought to my attention by the engineer. The chilled water coil entering the coil is on the bottom (like I expected) but it is on the front or the face of the coil. The engineer says I can expect to see a 15% efficiency loss. The same goes for the heating coil. I believe they are going to "correct" this by supplying the coil from the top which is located on the back or rear of the coil.

    I believe this will be a loss of efficiency as well but I don't have any information to back this up as I am not a smooth talker like the engineer. He claims to have worked for Heatcraft and he explained to me the reasoning for wanting the chilled water to enter on the back side of the coil and not the front. He also explained to me why you enter from the bottom of the chilled water coil and not the top. Yet I believe they are going to enter the top of the coil even though it is incorrect.

    Question: I am pissed off and would like to see it corrected, but should I be?
    Is entering the top of the coil sufficient?

  2. #2
    Join Date
    May 2008
    Location
    Central Pennsylvania
    Posts
    438
    Rotaryfrk, You may want to conferm the the coil configuration is infact wrong with the manufacture before you change anything. I ran into this same issue about two years ago with a carrier air handler. I would have sworn that it was wrong, but I talked to several carrier engineers and they said it was designed to be installed that way, with the water entering the downstream side of the coil. I ran the system and everything was fine. Actually I slightly increased the gpm to the coil and decreased the chilled water temp to squeeze out as much performance as possible through the air handler. Ended up getting 73 tons of cooling from a 50 ton coil. Hopefully this might save you a few headaches but your situation may be different.

  3. #3
    Join Date
    Mar 2003
    Posts
    7,321
    coldest water to coldest air. Inverse for heating. engineer noty only knows how to drive trains, he knows a bit about hvac as well.

  4. #4
    Join Date
    May 2008
    Location
    Central Pennsylvania
    Posts
    438
    Yep, I'd think the reasoning is to obtain as much dehumidification as possible. Cooler air has a lower dewpoint so you need to hit it with the coldest water. My perticular situation was a two pipe system though so only one coil, works fine in heating as well.

  5. #5
    Join Date
    Feb 2006
    Location
    SouthEastern Virginia
    Posts
    1,075
    Flange is correct.This is true for air or water heat exchangers. The air leaving a cold coil should pass through the entering water component of the coil on the downstream side of the coil.
    It might get loud!

  6. #6
    Join Date
    Nov 2004
    Posts
    210
    Generally,coils should be designed for counterflow,which gives the best heat transfer.The air and liquid flow in opposite directions, so that the supply piping enters on the side the airflow leaves. good luck.

  7. #7
    Join Date
    Sep 2007
    Location
    Yuma, Arizona
    Posts
    252
    Thanks for your comments. I still have not heard whether or not they plan on leaving the coil set up as it is, or if they will flip it over 180degrees.

    My reccomendation to them was to set it up the way it was designed to operate so that there can't be any problems down the road related to an incorrect installation.

    Currently I have chilled water cooling a Tuberculosis isolation area with (9) reheats performing dehumidification. We bring in outside air and dump air outside to maintain a negative area pressure. Problem is during monsoon season the space gets hella humid. Not enough dehum taking place.

    Engineers plan is to add an additional CHW coil and a HW coil in the existing ductwork in front of the existing CHW coil and increase the supply fan motor to 20hp due to the (2) new coils causing a restriction. Add humidity sensors in the seperate (9) zones to control humidity. I believe the theory is as follows...

    (1) Chill air with first CHW coil... dehumidify
    (2) Chill air once more with additional CHW coil... dehumidify
    (3) Knock air temp down with new HW coil... dehumidify
    (4) Warm air again with reheats... dehumidify

    I've been running 45degree chilled water, and I typically see 55degree discharge air. HW I believe never runs hotter than 140.

  8. #8
    Join Date
    Aug 2006
    Posts
    28
    Ther is no problem that can't be engineered to death the biggest problem is 110 degree outside air @ 100% is still 110 degrees so to get 55 degree supply air is a hard sell for me but the V E segment during cut & slash pre-construction meetings always show up on days like last Monday (the 1st 110 degree day here in Phoenix. The monsoon will bring a whole new set of V E
    (VALUE ENGINEERING) problems. This is the problem that came when book keepers and risk accessment types took over our industry not too bitter.

  9. #9
    Join Date
    Nov 2004
    Posts
    210

    Thumbs up

    Quote Originally Posted by colddr469 View Post
    Ther is no problem that can't be engineered to death the biggest problem is 110 degree outside air @ 100% is still 110 degrees so to get 55 degree supply air is a hard sell for me but the V E segment during cut & slash pre-construction meetings always show up on days like last Monday (the 1st 110 degree day here in Phoenix. The monsoon will bring a whole new set of V E
    (VALUE ENGINEERING) problems. This is the problem that came when book keepers and risk accessment types took over our industry not too bitter.
    I couldn't agree more!

  10. #10
    Join Date
    Oct 2001
    Posts
    6,942
    i'am on a job now where the unit was shipped for LH pipe up and access doors....they must of missed that wall that the unit was 5" from as it was being re-assembled?so all had to be flipped to the right hand side,so the CHWTR has it going in at the top and out on the bottom.the fitters said the RA hitting the coil wants to be precooled with the return water exiting first,then chilled down with that supply chilled water entering as it comes off the coil and thru the fan...and down into the space.this factory says the in/out don't matter but draining of the coil in winter might be? hey it could be worst...i had a job where the complaint over 2 summers was constant water in the MER during cooling season WHY???? they piped the hot water to the chilled water coil and the chilled to the heating coil! when was the last time you saw a wet coil for heat with a condensate pan.
    "when in doubt...jump it out" http://www.youtube.com/watch?v=U1qEZHhJubY

  11. #11
    Join Date
    Jan 2008
    Location
    windy city
    Posts
    4,426
    airdata & flange are correct in counter flow.ya mentioned flippin' the coil 180 - on the nozzle end, that won't accomplish much. did that a looong time ago, didn't end up with desired configuration. you may be able to flip the coil end over end, if you have the room on the backside for piping & service

  12. #12
    Join Date
    Mar 2008
    Location
    NC
    Posts
    1,460
    rotaryfrk, I came across some information not too long ago regarding your dehum problem. the numbers provided on the website looked good, but i don't have any firsthand experience with the technology.maybe some of the other guys have run into the technology. if you look up 'heat pipes' on the web you will find tons of info .

  13. #13

    "Counterflow" is more important than you may think

    Quote Originally Posted by ncboston View Post
    rotaryfrk, I came across some information not too long ago regarding your dehum problem. the numbers provided on the website looked good, but i don't have any firsthand experience with the technology.maybe some of the other guys have run into the technology. if you look up 'heat pipes' on the web you will find tons of info .
    This is the Ask Our Pro's forum. In order to post a response here, you must have verified qualifications and have been approved by the AOP Committee. You may ask a question by starting a new thread.

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    Last edited by jpsmith1cm; 08-16-2012 at 04:27 PM. Reason: Non AOP member

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