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  1. #1
    Join Date
    Jul 2007
    Posts
    65

    T-Stat for zone control

    I am changing out an old lennox RTU next week. The existing system is controlled by actuators closing off flow to offices on cooling setpoint on main floor and second. The system is controlled by a A419 set to 70 in supply duct, blower runs all the time, in series with heat/cool switch, low ambient stat, air switch and time clock(for night setback). Is there a control that I can run that runs off supply temp with probe, but can auto change from cooling to heating year round to maintain same temp instead of old system which is one or the other. I would need Y1,Y2,W1,W2,R and G on control to rtu. This way I could eliminate all the other controls.

  2. #2
    Join Date
    Aug 2008
    Posts
    91
    Sounds like your asking if you could use an auto change over T-Stat. You might be able to upgrade to this type of control.

    However, you can't just eliminate all the other control's and expect it to work right. How would you control the damper's? You would also be increasing the energy consumption and defeating the purpose of the night set back to conserve energy and reduce the carbon foot print.

    This is the point of night set back now being used by all major power generating plant's to reduce the size of the carbon foot print for clean air generation and global warming and all that good stuff where Al Gore lives.

    Even hot air furnaces back in the fifty's used some type of fan controls and other goodies.

  3. #3
    Join Date
    May 2004
    Location
    SE Pennsylvania
    Posts
    894
    There are a few quick and easy zoning systems available for small tonnage systems like Honeywell's True Zone.

  4. #4
    Join Date
    Jan 2005
    Location
    steeler nation
    Posts
    2,036
    IV IV IX

    use your head for something other than a hat rack.......Gerry

  5. #5
    Join Date
    Jul 2007
    Posts
    65
    Hardwater the dampers are all controlled by individual stats that open dampers in each zone on a call for cooling. As for the carbon footprint thing I would say I was looking for a stat that would probaly be programmable and therefore it could be set back at night and not destroy the Earth.

  6. #6
    Join Date
    Aug 2008
    Posts
    91
    Quote Originally Posted by iceage View Post
    Hardwater the dampers are all controlled by individual stats that open dampers in each zone on a call for cooling. As for the carbon footprint thing I would say I was looking for a stat that would probaly be programmable and therefore it could be set back at night and not destroy the Earth.
    Well, in that case I would check out the Honeywell and decide on what type you like. They are an excellent T-Stat. I have used them for year's and I am kind of parcel to them. They also use the intelligent recovery that I can't think of the name right off. I think its smart response. It takes it about two weeks to learn but it works great. Someone else mentioned Honeywell. If it was me I'd go that route. Good Luck!

  7. #7
    Join Date
    Jul 2001
    Location
    Canada
    Posts
    1,806
    Quick and simple remedy for INDIVIDUAL zone control http://jacksonsystems.com/search/category/242

  8. #8
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,886
    The Z2000 modulating or the Z600 on/off zone panels would be great. With the Z600, T-21-P stats would work great. Can be set for reduced occupant control too. Or there's the wireless Z600 setup.

  9. #9
    Join Date
    Jul 2011
    Location
    East coast USA
    Posts
    955
    Quote Originally Posted by iceage View Post
    Is there a control that I can run that runs off supply temp with probe,
    you don't want to control discharge air temp with a probe. With a DX system this is almost impossible and not practical. is this a ducted return?

    there has been a few great options given, Carrier 3V or the CCN are also good. there are a lot of ways to go depending on your budget.

    I assume you have a bypass to deal with high static should zones start closing?

  10. #10
    Join Date
    Jul 2007
    Posts
    65
    With remote sensor off commercial t-stat, can you bypass temp at t-stat location and run system off remote bulb location In this case supply ducting,
    System has return ducting and relief dampers off actuators. With stat this way utilizing set back, auto changeover, safeties on rtu, limits etc. I could repace old system of time clock, heat/cool switch etc. Zone system in place by other contractors, running actuators in 7 zones controlled by cooling setpoint of stats, doesn't sound very efficient but is not my scope of job.

  11. #11
    Join Date
    Jul 2011
    Location
    East coast USA
    Posts
    955
    Quote Originally Posted by iceage View Post
    With remote sensor off commercial t-stat, can you bypass temp at t-stat location and run system off remote bulb location In this case supply ducting,
    System has return ducting and relief dampers off actuators. With stat this way utilizing set back, auto changeover, safeties on rtu, limits etc. I could repace old system of time clock, heat/cool switch etc. Zone system in place by other contractors, running actuators in 7 zones controlled by cooling setpoint of stats, doesn't sound very efficient but is not my scope of job.
    YOU can't run the RTU using a probe or remote probe to control the unit to maintain a constant supply air temp. its better to keep the stat in an open area close to a return intakes and find a set point that "most" are happy with and lock it out. you will have to adjust the temp as the seasons go.

    what kind of zone controls are on there now ?

  12. #12
    Join Date
    Jul 2007
    Posts
    65
    Quote Originally Posted by dlove View Post
    YOU can't run the RTU using a probe or remote probe to control the unit to maintain a constant supply air temp. its better to keep the stat in an open area close to a return intakes and find a set point that "most" are happy with and lock it out. you will have to adjust the temp as the seasons go.

    what kind of zone controls are on there now ?
    Existing system is running off supply temp, with A419 in supply duct in series with time clock, air switch , heat or cool switch, low ambient its apparently been like that for 15 years

    The zone controls in building now are Belimo actuators run off stats simply opening dampers in offices if they wish to have more air flow in this case opening on cooling setpoint.

  13. #13
    Join Date
    Jul 2011
    Location
    East coast USA
    Posts
    955
    Quote Originally Posted by iceage View Post
    Existing system is running off supply temp, with A419 in supply duct in series with time clock, air switch , heat or cool switch, low ambient its apparently been like that for 15 years

    The zone controls in building now are Belimo actuators run off stats simply opening dampers in offices if they wish to have more air flow in this case opening on cooling setpoint.
    If the system you have that runs off a supply air sensor, then it must have a chilled water/HW coils and is not a DX unit. Or you are using outside air when cold with mixing dampers and reheat and the dampers are what is helping controlling supply air temps.

    There has to be some kind of modulation of dampers or valves to modulate as temps rise and fall. If you relied on a DX RTU and trended the supply air temp you would see extreme spikes of when the AC kick on and off. and short cycling.

    The A419 Electronic Temperature Control can be used to control a wide variety of single-stage refrigeration or Heating Ventilating, and Air Conditioning (HVAC) equipment. Typical applications include:
    • retail store display freezers and reach-in coolers
    • supermarket display cases for produce/meats
    • retail store walk-in coolers and freezers
    • boiler operating control (used as a thermostat)
    • condenser fan cycling or staging
    • cooling tower pump and fan control
    space and return air temperature control

    read this http://cgproducts.johnsoncontrols.co...PDF/125188.PDF


    If the sensor is in the supply air duct for the past 15 yrs, it was wrong for 15 yrs.

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