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  1. #1
    Join Date
    Jun 2010
    Location
    New Orleans
    Posts
    87

    What would you do?

    I have a really old area that is getting renovated. It use to be open but they will be putting up walls to create offices. There is one trunk with about 9 drops feeding this area and it works out to about one drop per office. The trunk is fed by one dual duct mixing box and has a reheat coil directly after the mixing box. The mixing box was controlled by one pneumatic sensor in a central location.

    I'm already in the works of changing out the pneumatics with ddc.

    What would you do to give each office its own user adjustable set point? keeping it as simple and cheap as possible.

    I will be using JCI wireless sensors in the area, so those can be used in your scheme.


  2. #2
    Join Date
    Jun 2010
    Location
    New Orleans
    Posts
    87
    And when I say user adjustable set point I mean like warmer cooler or +/- a few degrees. Not a huge amount.

  3. #3
    Join Date
    Feb 2007
    Location
    Helena, Montana
    Posts
    2,155
    To be honest, with this set up the occupants are almost always going to complain. Best I could think of is do a high select for heating or cooling and reset the box based on that. Of course with them all having a sensor, they will all think they control their area!
    Don't worry zombies are looking for brains, you're safe...

  4. #4
    Join Date
    Jan 2011
    Location
    Bartlesville, Ok
    Posts
    114
    There are a few control systems that use a 2 wire bus that handles multiple wall devices. I know of Reliable, Distech, and Delta. So, you could read several zones into the one controller and decide what you want to do. This would allow the option of weighted zone averaging, highest, lowest, you name it. The best part is it can be done and redone on the fly, with no more install labor.

    Of course, the standard priority for a multizone control scheme is 1) the highest ranking person in area, 2) anybody else.

  5. #5
    Join Date
    Aug 2007
    Location
    Western Colorado
    Posts
    497
    Can you not install a reheat coil in each of the 9 drops? That'd give you some options!
    RealEyes
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  6. #6
    What I've seen elsewhere:

    Ditch existing reheat. RHC for each zone, Reliable SMARTSpace controller or equivalent in each zone. Operate mixing box to satisfy warmest space. Let the SSCs control the zone reheats to satisfy individual zones.

  7. #7
    Join Date
    Jan 2003
    Location
    USA
    Posts
    1,685
    >each office its own user adjustable set point? keeping it as simple and cheap as possible.

    A. Cheap and easy is to drop the stat in one office (highest rank) and call it a day.

    B. You could add more stats but you still have a crap situation with only one box for 9 spaces. Waste of time and money IMHO.

    C. Or open your wallet and do it right by adding reheats to each space.

    C is the only way each space is going to have its own setpoint.
    Propagating the formula. http://www.noagendashow.com/

  8. #8
    Join Date
    Jul 2011
    Location
    East coast USA
    Posts
    969
    there is no cheap way if you plan to make them all happy. you can give each room their own control using this system which i have used on occasion, http://www.price-hvac.com/Literature...12_Prodigy.pdf

    another way is to break up the offices into two each and install Fan Powered Terminal units/w electric heat and have one stat controlling two offices.

    or (as said before) get rid of the main RHC and install 9 RHCs with its own stat. not the best idea

    or if there is a way to maintain a constant discharge air temp and just add motorized dampers controlled by a Tstat in each room would work. But its impossible to use an electric coil to maintain a constant air temp.

    the first two options are the best, but i would need to know more info on the type of building you have, for example open plenum or not and what type of HVAC system you have.

  9. #9
    Join Date
    Dec 2011
    Location
    Up-state NY
    Posts
    17
    242 is right and pink slips eliminate the complainers.

    You can keep most of the employees happy some of the time and some of the employees happy most of the time but once you've touched it you own it.

  10. #10
    Join Date
    Oct 2011
    Location
    Dallas, Texas
    Posts
    167
    I agree mostly with Orion242 and dlove...

    The better way would be to add some sort of reheat to each individual zone and let the mixing box just make cold air.

    Ofcourse that's not the 'best' way because even though it may be 'cheap' to put in up front it will probably cost you thousands over the long term. Do you think your boss will be happy with your cheap solution after a spring and a fall pass by where people start feeling cold while others hot and the electric heaters start kicking on when it in the 70s outside?

    Be careful... Allowing them control over their setpoints when the main system is providing cold air means the heaters kick on to help make the +2 or +3 room setpoint for one office.

    My question lies with if the main trunk as you call it, which is actually the 'drop' from the dual duct box, is fed from a terminal box... What is actually feeding the system? Is it a Roof Top unit or AHU that feeds a number of other boxes?

    Dual Duct systems are very antiquated and the few systems that are still used out there are special in that they require strict airflow requirements regardless of temperature, therefore you need to supply hot and cold air at all times.

    The best way to supply air to individual offices like that would be with Fan Powered Boxes if they have large glass windows or with VAVs w/ reheat if not or are not located on the building perimeter. BUT that is a VERY costly change involving some sheet metal work and additional terminal boxes.

    nasaguyjoe, I hope you get a chance to come back to the forums and let us know what the final outcome was.

    Here in San Antonio they have been going through similar changes to old Air Force hangars and converting them to office space, but their budgets allowed for a complete mechanical change out since the units were 20-30 year old constant volume units that just dumped air in the hangar and called it a day.

  11. #11
    Join Date
    Jun 2010
    Location
    New Orleans
    Posts
    87
    Hey guys thanks for all of the input.

    This is a office building that was built in the 60s. It was originally wide open wall to wall open space. Over the years partitions/walls and offices have been built and now its a cluster F***.

    The building has 16 AHUs that range from 25k-40k CFM, each AHU has 7-9 "zones". Each zone/trunk is fed by one mixing box.

    We also have an issue with asbestos so any mods to the duct work are challenging. The only thing I can mess with is the drops from the truck that are on flex.

    I think I migh swap out the diffusers with thermafuser that have a remote control set point.

  12. #12
    Quote Originally Posted by nasaguyjoe View Post
    Hey guys thanks for all of the input.

    This is a office building that was built in the 60s. It was originally wide open wall to wall open space. Over the years partitions/walls and offices have been built and now its a cluster F***.

    The building has 16 AHUs that range from 25k-40k CFM, each AHU has 7-9 "zones". Each zone/trunk is fed by one mixing box.

    We also have an issue with asbestos so any mods to the duct work are challenging. The only thing I can mess with is the drops from the truck that are on flex.

    I think I migh swap out the diffusers with thermafuser that have a remote control set point.
    Hey, how did it go? Have you made any progress?

    I have a 2-level 1960 office building with two constant volume systems, one serving each floor. Each unit is controlled by one or two t-stats. It was an open floor plan originally that has since been partitioned into smaller offices and conference rooms. The occupants complain about temperature. There is perimeter heat. Some are too hot and some are too cold.

    I am looking at therma-fusers, and some testing and balancing. I am concerned that the static may exceed in the offices that get the most airflow, but I think we can resolve that by adjusting a damper to that room.

  13. #13
    Join Date
    Sep 2006
    Location
    Alaska
    Posts
    462

    Return Air

    Control the area at the return air plenum
    Law Of The Thermostat: He who has the thermostat wins!!!!!

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