Page 1 of 2 12 LastLast
Results 1 to 13 of 17
  1. #1
    Join Date
    Oct 2002
    Location
    Lexington, NC
    Posts
    5,193

    Commercial Office Building Zoning question

    I posted this in the controls area and didn't get any response, so hopefully you commercial gurus will have some ideas.

    I have a customer that has purchased a commercial office building, the kind where you may find small offices for accountants and the like. Most of the rooms are maybe 12 x 12 with a few larger. Building is a rectangle in shape, laid out king of like ffices on front, hallway, offices in middle, hallway, and then offices on the back side of building.
    So the hvac is (2) 4 ton heat pumps. One old Trane, one new Carrier. One does the front portion of the building , the other does the back side of the building, and for some reason they fed each of the center offices with a branch off of both units, which makes no sense to me. There are only 2 thermostats, and they are located in the hallways, which have no supplies or returns, so the thermostats are not measuring a realistic sample of the office temps.
    The owner is wanting to add a system for one problem area, but I think he has enough air, it just isn't zoned or being sampled for temperature in a proper way.

    So my first option to him is to place the thermostats in an office on their respective sides of the building to at least see what a room temperature is, instead of sensing an unsupplied hallway. Then ofcourse we have to ask which office.
    My next option is to find a sensor type thermostat that will sense the return air temperatures (ceiling return, but this is the bottom floor of a two story building, so it should be a decent sample of the combined room temps) in hopes that a mixed sample of the room temps will find a median. And lastly we can add a zoning system, but it will have to cover 5 to 8 zones for each system. I will have to seperate the middle rooms to only be supplied by one unit and just zigzag the rooms. The supply duct is a straight sheet metal run, so if zoned each room will have to have a sensor and damper. The dump zone can be the hall way or the ceiling return plenum.
    Anyway, I am hoping for some good suggestions and maybe a good brand of zoning system for an application like this. Hopefully the dampers can be mounted right on the 2x2 ceiling diffusers.
    Thanks
    The main thing is to keep the main thing the main thing!

    If "the grass is greener on the other side", it likely has been fertilized with Bull$hit!

  2. #2
    Join Date
    Apr 2011
    Location
    Coastal Maine
    Posts
    867
    Take a look at these man.

    http://www.forwardthinking.honeywell..._products.html

    It isn't the total answer, but might give you an idea of where to start. I used the retrofit package in a small law office recently. Worked pretty good for what I had to work with.

    I would try to split those two shared spaces up into one or the other. That can cause problems when trying to zone it off.

    Good Luck

  3. #3
    Join Date
    Mar 2011
    Location
    North Carolina Piedmont Area
    Posts
    451
    Check this out
    Attached Images Attached Images

  4. #4
    Join Date
    Apr 2011
    Location
    Coastal Maine
    Posts
    867
    Those look interesting. Have you used them yet?

  5. #5
    Join Date
    Oct 2010
    Location
    Baton Rouge, LA
    Posts
    1,113
    I would say you need to talk to Genduct.
    It sounds to me more like you need to do an air balancing and get some ceiling returns.
    I wouldn't necessary do a return sensor as your air is mixing. I would look more into reconfiguring the duct work but it sounds to me like you need to change the duct work to an interior/exterior. One unit running to the offices with outside walls and the second doing hallways and center offices.
    Not only should that help keep like rooms at a more comfortable temp it should help lower the electric usage.
    If you're too "open" minded, your brains will fall out.
    Artificial intelligence is no match for natural stupidity.

  6. #6
    Join Date
    Mar 2011
    Location
    North Carolina Piedmont Area
    Posts
    451
    Quote Originally Posted by meplumber View Post
    Those look interesting. Have you used them yet?
    I used them in an certain applications and it is the simplest form of control. Not always will they have the best control unless you are controlling the supply air in the main duct based an an average room temperature or some form of reset. There are options available which should be considered for accurate control.

    _______________________________________________
    Troubleshooting is not part of the repair......understand the symptoms and you will find the solution.

  7. #7
    Join Date
    Apr 2008
    Location
    Tucson, AZ
    Posts
    120
    I have seen a couple of these. They made the office people very unhappy. But when are they ever happy? It seemed to do poorly at different times of the year. The ceiling is apparently not a consistent simulator of room temp and air flow. I ripped it out so they could have some air.

  8. #8
    Join Date
    Apr 2008
    Location
    Tucson, AZ
    Posts
    120
    That's awesome. The wireless is impressive.

  9. #9
    Join Date
    Mar 2008
    Location
    Indiana
    Posts
    8
    There are several things you could do here IMO. Assuming the RTU's are in servicable condition, I would invest in some better controls and really rectify the issue. A couple of options would be to 1. Install zone dampers and /or VAV's. I will assume there is no Freq drives on the AHU's, so ideally you'd thow some on. You cannot simply damper down air as it has to go somewhere. Along with the valving and VFD's you'd need to add some sort of controller smart enough to accomplish the mentioned scenario. 2. I actually agree with basing the operation off of a plenum mounted sensor. It should give you a realistic space temp as long as you mount it close to a return. This option will not get you zoning however. To properly rectify this IMO, you need to lean towards option 1.

  10. #10
    Join Date
    Feb 2010
    Location
    Cal
    Posts
    1,596
    Zoning without a load calc is a big mistake. dampers at the grill will be noisy, that's why boxes have attenuators.

    Thermafusers can be another big mistake...tail wagging the dog. I acquired a building at on point littered with them... made good money and a loyal customer by ripping them out and installing vav boxes. Funny thing was that thermafuser wrote a PR article about the building"s project and how wonderful they are. Guess they did a very informal survey about occupant satisfaction. Best used to spot treat, not as a control scheme.

  11. #11
    Join Date
    Oct 2002
    Location
    Lexington, NC
    Posts
    5,193
    When you guys talk about VAVs, are you talking about the concept of installing a damper and t'stat just for that room that doesn't send a control signal to the units to operate?
    I have worked on VAVs with their own fans and heat coils, etc.
    I did have somebody mention the above to me about an option with the damper and they called it a VAV, so i am just wondering if that is what you are talking about here.
    The main thing is to keep the main thing the main thing!

    If "the grass is greener on the other side", it likely has been fertilized with Bull$hit!

  12. #12
    Join Date
    Nov 2008
    Location
    baltimore
    Posts
    26
    Installing VAV systems on two small rtu is not practical or cost effective. In my opinion a load calculation should be done. Then maybe split front and back of building into two smaller zones within each. Use the honeywell zoning controls and just dump supply to return. I have done this in my kids karate school/ gym.

  13. #13
    I used the retrofit package in a small law office recently. Worked pretty good for what I had to work with.

Page 1 of 2 12 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