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  1. #1
    Join Date
    Nov 2019
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    multizone manual bypass damper

    Hi everyone,

    1 year in as a maintenance technician in Florida.

    I was doing a maintenance the other day on a 2 zone system. During the process I noticed that my return air was 64 degrees and none of the rooms in the house were above 70 degrees.

    After a quick look at the ductwork I noticed a manual bypass damper going directly from the supply back to the return.

    I put my temp probe in each side and found the same 44 degree air on both sides telling me it was at leat partially open.

    Is this a normal set up?

    thanks!

  2. #2
    Join Date
    Feb 2019
    Location
    Maricopa, Arizona
    Posts
    47
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    When a zoned system is being used and all thermostats are being called for, than that bypass damper should be closed. Depending on the pressure coming through that bypass, it may open slightly at the very most. You should also verify that the blower wheel is on the proper speed tap as it may just be putting too much air pressure through the system. Now the arrow on that damper should also point in the direction of the return, "direction of air flow". There's been times where i have found those to be installed backwards.

  3. #3
    Join Date
    Nov 2019
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    7
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    Thread Starter
    Thank you!

    That makes sense. I'm not sure if it was variable speed or multi speed. 18 month old 20x20x5 merv 16 media filter. Suction pressure was a little low, with the filter in.

    Customer indicated some rooms were hotter or colder than others. We got him some new filters. I am going to get with my manager and show him the pictures of the damper and what I found. I want to get service over ther to take a look maybe.

  4. #4
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    26,081
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    Have you measured the static pressure? Can you measure the static pressure?

  5. #5
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
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    Quote Originally Posted by mattschrader View Post
    Thank you!

    That makes sense. I'm not sure if it was variable speed or multi speed. 18 month old 20x20x5 merv 16 media filter. Suction pressure was a little low, with the filter in.

    Customer indicated some rooms were hotter or colder than others. We got him some new filters. I am going to get with my manager and show him the pictures of the damper and what I found. I want to get service over ther to take a look maybe.
    What exactly does “suction pressure was a little low” mean?

  6. #6
    Join Date
    Nov 2019
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    Thread Starter
    120psi. Now that I think about it though with that 64 degree air at the return, maybe not so bad.

  7. #7
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
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    Quote Originally Posted by mattschrader View Post
    120psi. Now that I think about it though with that 64 degree air at the return, maybe not so bad.
    Now your beginning to Think!

    I'll be blunt...……..With less then a year you really shouldn't be on your own! What little if any training is turning you into the typical tech today, guessing and parts changing. I do applaud you coming here and asking the question so please stick around, apply for pro status and continue learning you've got a long way to go.

    Learn to measure

    Superheat
    Subcooling
    Amperage
    Static Pressure
    TSEP

    Get the IOM's and read them, parts literature and read them, books and read them

  8. #8
    Join Date
    Nov 2019
    Posts
    7
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    Thread Starter
    Pecmsg,

    Thank you for the input. Definitely have a long way to go.

    Update. Showed a couple supervisors what was going on. One told me that all zones cant call at once. The next had no idea what I was talking about.

    Finally went to one of our lead service techs and figured out that the damper is weighted and can be adjusted. I had no idea. I just had a gut feeling something wasn't right and kept bugging people until I had an answer that made sense to me. I sent my service manager the photos I had and they are sending a service tech over there.

    I use the fieldpiece joblink probes with measurequick. It's really changed how I do things as far as my routine.

    I feel like they are really accurate. For the first month I kept double checking with gauges and k type temp clamps. Now I just trust them.


    Readings were 280/120
    Subcool 4
    Superheat 18
    Suction line temp 58
    Liquid line temp. 87

    It was a lennox unit. Data plate called for 3 subcool. About 40 ft line set length.

    I do not know any maintenance techs at my company that measure static pressure. I do not know of any who are encouraged to do so.


    Most of what I have learned, I have learned on my own time.

    Looking forward to learning more!

  9. #9
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    26,081
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    Keep Learning, that will put you above the average tech in short order.

  10. #10
    Join Date
    Oct 2011
    Location
    Gladstone, Oregon (Portland)
    Posts
    1,995
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    Is it a barometric damper or a better design like the honeywell truzone?

  11. #11
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    26,081
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    Dampers I like power open spring closed. Set them so they’ll only close 50 - 75%

    Have the smallest zone call and measure the stat pressure and determine the CFM rating. Set the bypass to allow the minimum CFM required.

  12. #12
    Join Date
    Nov 2019
    Posts
    7
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    Thread Starter
    Comparing the photos I took to images online 'm almost positive it is the honeywell SPRD. Static pressure regulating damper.

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