Results 1 to 11 of 11
  1. #1
    Join Date
    Jun 2001
    Posts
    161
    Hi

    I have an office building with 2 TED600 RTU's and VCEF
    vav boxes. It's controlled by a Tracer system. Everything is about 3 years old. The question I have is I don't know how the system knows it is okay to use economizer. I believe it is determined by the RTU. The RTU has differential enthalpy. I'm trying to find out if it uses an offset of so many btu/lb. I would like to increase the offset so if the outside air enthalpy is only slightly lower than the return air enthalpy it is not okay to economize. The problem is the system is running a lot of the time with 100% OA in the spring and fall and it plays havoc with the owner's entrance door closers.

    thanks

    Brent

  2. #2
    Join Date
    Jan 2004
    Posts
    389
    What problem are you having with the doors ?? is the bld over pressurized or negitive ?? this is not a Tracer problem, check your exh. fan if equipped or relief dampers, also your bld pressure set point.

  3. #3
    Join Date
    Jun 2001
    Posts
    161
    The building is over pressurized and the doors do not latch without someone pushing them closed. The power exhaust works. The power exhaust comes on based on what percentage the econ dampers are open. I believe there are 2 power exhaust fans but I think there both turn on at the same time. The power exhaust fans are only rated at 60% or something like that of the supply fan cfm. You are right it is not a problem with the actual tracer system.

    Brent

  4. #4
    Join Date
    Jan 2004
    Posts
    389
    Well then I cant see how we can be over pressurizing unless the dampers themselfs are not stroking. Are there returns in these area,s?? One other note, are you doing morning warm up, this will drive all the vav,s open 100% and maybe thats where we get the high pressure. Whats the vav, max cfm setpt??

    [Edited by bku46 on 06-02-2005 at 04:48 PM]

  5. #5
    Join Date
    Dec 2003
    Location
    Middle of Florida
    Posts
    2,159
    Oil the door hinges!
    sorry, just being an assclown.
    If common sense is so common how come so few of us have it!

  6. #6
    Join Date
    Jun 2001
    Posts
    161
    The vestibules do have returns to the open plenum. We are doing morning warmup. We probably would blow the doors open at that time but nobody is there to complain about it. What I want to change is with comparitive enthalpy if the outside air is only slightly better than the return air then the unit determines it is ok to economize. This leads to for a lot of the spring and fall the economizer is open 100% and the compressors run. This isn't a problem except for the high building pressure keeping the doors from closing. I want to make an adjustment so it only uses the economizer when the outside air enthalpy is considerably lower than the return air enthalpy.

    brent

  7. #7
    Join Date
    Jan 2004
    Posts
    389
    Are the units equipped with HI touch pad boards? If so you can offset the enthalpy thru set up menue. If not and every thing is done thru Summit, then try setting the unit up for referance humidity not comparative, this way it will only referance OA humidity to make econ ok or not. You will need to change unit config to avoid diagnostics.

  8. #8
    Join Date
    May 2000
    Location
    Stafford, Va. USA
    Posts
    213
    Hi Brent,
    You said that your Voyager units are doing differential enthalpy, also known as comparative enthalpy.
    There are no adjustments for the enthalpy in the Voyager, the unit compares return air enthalpy to outside air enthalpy and whichever air stream is lower is the one chosen to provide air.
    If you let Summit control the economizer, and I don't think you should, there still is no adjustment for the enthalpy like you want to make.
    As for the building being overpressurized, you are going to have to adjust the exhaust fan setpoint lower to try to balance the building pressures.
    Good luck,
    Allen

  9. #9
    Join Date
    Jun 2005
    Posts
    128
    It Depends if RTU is Voyager then Exhaust fan is controlled locally from Econo board, if the RTU is I-pack there two ways of controlling Exhaust Fan: from position of OAD or from space pressure. in this case there is a 1/4''tubing going from space to pressure transducer located above RA/OA Damper motor. From my expirience this tubing is pinched or most likely was not connected so it senses negative pressure all the time.

  10. #10
    Join Date
    Jun 2001
    Posts
    161
    Do you know if I can change from comparitive enthalpy to reference enthalpy. Can I just disconnect the wires from the return air temp and humidity sensor? Does the OA enthalpy sensor have a A,B,C,D dial? The main problem is the economizer is allowed to operate too much. If I just allow the economizer to operate when the OA enthalpy is very low I think I will solve the problem 95% of the time.

    brent

  11. #11
    Join Date
    May 2000
    Location
    Stafford, Va. USA
    Posts
    213
    Hi Brent,
    Yes, you can disconnect the return air sensors so that the unit will do reference enthalpy. There will be a couple of alarms after you remove the sensors. Summit will remember seeing the sensors, and now they are gone, result... alarm.
    Disconnect the sensors with the power off. When you reapply power, the Voyager will wake up and do reference enthalpy. You can adjust the reference number at the economizer module DIP switches.
    The Summit alarms can be made to go away by using the Toolbar, Tools And pressing " Clear Ram and Reset." All of the equipment that is connected to the system will shutdown. Then Summit will go and poll each of equipment, pulling out the needed UCM information to load into the database. Then all of the equipment will restart normally in just a few minutes. The sensor alarm will also be gone.
    Good Luck
    Allen

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