Results 1 to 9 of 9
  1. #1
    Join Date
    Aug 2006
    Posts
    2,607

    Lobby VAV, here we go again.

    I have a lobby they change the use of. You enter thru the new 7' 4" x 7' 4" opening auto sliding doors. Over the slider is a heated air door, that you can't get adjusted to specs. due to its location. Forward and above you is the original massive peaked sky light, faced and shaded by the rest of the building so there is no Winter solar gain. To the right they dropped the ceiling, put in couches, table chairs and a TV set, WIFI, etc. The area to the left is original, I don't have too much of a problem with that area. In the problem area there is a bypass VAV box way above the ceiling. It has 3/4" stubbed heating coil, I could modify it to 1" stubs. A 1/2" 3 way auto valve, 1 1/4" shut off valves to the system, same as shown on prints. Need to get more heat out of the VAV coil and move fan wire off of low speed.

    Plan A) Install wet rotor pump for VAV and speed up water flow.
    Plan B) Repipe the VAV to 1", with a 1" 3 way valve, and 1" piping. {Very difficult do to location of VAV box. Lots of soldering in a tight location}

    Do you think I could hotrod this box and get anything extra out of it? It had a 14F water split on low speed last year, lobby temp.was 62F.

  2. #2
    Join Date
    Nov 2005
    Location
    Shreveport, Louisiana
    Posts
    2,337
    Quote Originally Posted by madhat View Post
    I have a lobby they change the use of. You enter thru the new 7' 4" x 7' 4" opening auto sliding doors. Over the slider is a heated air door, that you can't get adjusted to specs. due to its location. Forward and above you is the original massive peaked sky light, faced and shaded by the rest of the building so there is no Winter solar gain. To the right they dropped the ceiling, put in couches, table chairs and a TV set, WIFI, etc. The area to the left is original, I don't have too much of a problem with that area. In the problem area there is a bypass VAV box way above the ceiling. It has 3/4" stubbed heating coil, I could modify it to 1" stubs. A 1/2" 3 way auto valve, 1 1/4" shut off valves to the system, same as shown on prints. Need to get more heat out of the VAV coil and move fan wire off of low speed.

    Plan A) Install wet rotor pump for VAV and speed up water flow.
    Plan B) Repipe the VAV to 1", with a 1" 3 way valve, and 1" piping. {Very difficult do to location of VAV box. Lots of soldering in a tight location}

    Do you think I could hotrod this box and get anything extra out of it? It had a 14F water split on low speed last year, lobby temp.was 62F.



    SO I take it that they remodeled the space and did not take into consideration the air and heating requirements for the remodeled space?

  3. #3
    Join Date
    Aug 2006
    Posts
    2,607
    Not only did they remodel the space they put that stinking auto sliding door in, facing NNE, and every time it opens it like throwing the barn doors open. I've asked for a second set of doors, and make a vestible. Asked for a contractor to install a bigger VAV, asked for radiant heat like they have to the left of the entry. All denied.

  4. #4
    Join Date
    Aug 2000
    Location
    USA
    Posts
    4,995
    Guess they dont want heat then, sucks to be them!!!
    Quote Originally Posted by madhat View Post
    Not only did they remodel the space they put that stinking auto sliding door in, facing NNE, and every time it opens it like throwing the barn doors open. I've asked for a second set of doors, and make a vestible. Asked for a contractor to install a bigger VAV, asked for radiant heat like they have to the left of the entry. All denied.
    Your poor planning does not constitute an emergency on my part!!!!

  5. #5
    Join Date
    Jun 2004
    Location
    St Paul, minnesota
    Posts
    1,244
    Quote Originally Posted by madhat View Post
    Not only did they remodel the space they put that stinking auto sliding door in, facing NNE, and every time it opens it like throwing the barn doors open. I've asked for a second set of doors, and make a vestible. Asked for a contractor to install a bigger VAV, asked for radiant heat like they have to the left of the entry. All denied.
    how about wiring the door heater fan on constant low speed, put the heater portion on a room line voltage stat, & when the door opens fan goes to high speed.

  6. #6
    Join Date
    May 2007
    Location
    Pacific Northwest
    Posts
    38

    You can't make a silk purse out of a sow's ear!!

    Quote Originally Posted by madhat View Post
    Not only did they remodel the space they put that stinking auto sliding door in, facing NNE, and every time it opens it like throwing the barn doors open. I've asked for a second set of doors, and make a vestible. Asked for a contractor to install a bigger VAV, asked for radiant heat like they have to the left of the entry. All denied.
    I totally agree with absrbrtek. As resistant as they seem to be to spending any money, it doesn't sound like they are all that concerned about the lack of heat. Whatever the situation was at that location somebody droppped the ball by remodeling the space and not taking the new HVAC requirements into consideration. Don't you just love it when someone else's incompetence or penny-pinching suddenly becomes your problem??

    Since I am un-familiar with your specific job, I will take a guess and probably bet that increasing the stubs, pipe-size, or flow will not be enough to accomplish what you want. If you were only able to warm it up to 62 then you probably need a much bigger coil and probably more airflow than you can get with putting the existing fan to HIGH.

    To do this right you should do some basic load calcs and see what you need to be in the ball-park. If you were to increase the box size (and coil), are you going to need more/larger diffusers? Do you have enough water flow available at that location of the circuit? I guess my point is you could spend a lot of time trying to put a band-aid on this thing and still have problems.

    One other thing that comes to mind..... During the winter(cold) season, is your building static pressure positive or negative? If it is negative then that would just compound your problem because you would be sucking in the cold outside air. Might be worth checking into and see what you can do to keep it positive.

    Good Luck!!
    Knobber

  7. #7
    Join Date
    Feb 2005
    Posts
    284
    drop a 2x4 radiant ceiling panel heater in there

  8. #8
    Join Date
    Oct 2007
    Posts
    12
    vav damper with a fan? damper closes off supply air to a minimum position when it's in heat, and the fan comes on to pull warmer air from above the ceiling?
    does it have ddc controls that tells you how many cfm and all your temps?
    is this damper functional? because if it's open the a/c is on
    What is the air td across the coil,
    temp above the ceiling,
    supply air temp,
    did they open the space to the air above the ceiling making it colder above the ceiling,
    could you/ should you reduce the supply air minimum cfm,
    if you turned up this units supply air temp for the winter would it help this space w/o creating problems elsewhere, would this save energy or use more, are you blowing cold air just to re-heat it in a lot of zones, economizers work good or compressors running when its cold out.

    I'd check out the vav box thoughly first, then tell you boss whoever designed the space f'd you guys. The ceiling tile idea is good,

    trying to hot rod it might not get you to far, fan in high might help depending on temp above ceiling. ceiling tiles might be best idea. Just throwing a idea out there, electric reheats pretty cheap (initially) cut a hole in the side of the duct and run a thermostat and power.

  9. #9
    Join Date
    Aug 2006
    Posts
    2,607
    I told them they need to get an Architect/Engineer to tell them what they need to do. I proved last year that the VAV would heat his area by locking the sliding doors on a day no meetings were held. This also kept people who use that building and the two adjoining buildings from walking thru that door. Also they have a door propped open between the two buildings that is a fire door. Plus the loading dock swinging doors are being pushed open, relieving the air coming in the Lobby. The AHU that delivers the air has no heat source, the warmest I can get it is 63F on a cold day.

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