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Help with a old york rooftop

Discussion in 'Commercial' started by Snoring Beagle, Mar 25, 2009.

  1. Snoring Beagle

    Snoring Beagle Need Little - Want Less - Love More

    Messages:
    11,131
    I am dealing with an 1974 York frooftop AC with a economizer pkg.

    The york
    MN 2FR06700106A
    SN NENY119331

    The AC is working fine, it's the economiser pkg that has me puzzled. I have no literature and it appears to be ok. I just don't fully understand it.

    There is a rheostat thermal control knob on the hood that has the ability to switch between mechanical cooling and economizer. It appears to do this using a relay between the t-stat and contactor. There is also a stat next to the mod motor that seems to effect the damper.

    Anyone familiar with this York? There are ten of them on this bldg.
     
  2. NZ All Blacks Fan

    NZ All Blacks Fan Just Another swinging Dick

    Messages:
    9,389
    Location:
    West Coast - Canada
    1 is the abcd signal old school style before the honeywell 7415 7459
    the other is the mixed air temp controller

    what else would you like to know?
     
  3. Snoring Beagle

    Snoring Beagle Need Little - Want Less - Love More

    Messages:
    11,131
    Yes is there a backdoor to Yorks website for info and literature?
     
  4. Snoring Beagle

    Snoring Beagle Need Little - Want Less - Love More

    Messages:
    11,131
    Enthalpy controller??
     
  5. refrigerationtech

    refrigerationtech Nut Case!

    Messages:
    2,005
    Location:
    Cold Place
    he aint using a honeywheel enthalpy controller, befor that. mix ait temp either opens damper or starts compressor.
     
  6. NZ All Blacks Fan

    NZ All Blacks Fan Just Another swinging Dick

    Messages:
    9,389
    Location:
    West Coast - Canada

    I should clarify - the old stuff pre 80 I think) used a combination of single controls to achieve what was replaced by honeywell 7415 and the 7459A damper motor and enthalpy controllers


    it increased the reliability but made it harder for the hacks to actually troubleshoot the controllers.


    the controller ( a19 or similar ) sometimes called compressor monitor ( lennox) simply switched the signal fro y1/y2 from the mechanical cooling to power the damper motor relay and controls - the mixed air sensor or stat might have been an a 19 ( on/off) or more likely a T991a ( RBW) with a 135 hom pot controll wired to the damper motor controls - this allows a reasonably well controlled supply air temp - set it to 50° supply air temp and it would mix when the air was below 50° and be full open at 50° and above - if the cooling wasn't being met y2 (if available) would bring on 1st or 2nd stg mech cool ( depending upon how its wired)


    Failure - normally the 135ohm pot on the controller dirty outa wack etc

    don't forget there should be a min position pot on the damper motor
    I don't have links to york - I'll look for you
    All I have is 25 yrs experience on various ref/hvac equipment
     
  7. NZ All Blacks Fan

    NZ All Blacks Fan Just Another swinging Dick

    Messages:
    9,389
    Location:
    West Coast - Canada
    york/JC website blows
     
  8. NZ All Blacks Fan

    NZ All Blacks Fan Just Another swinging Dick

    Messages:
    9,389
    Location:
    West Coast - Canada
    It took me 15 yrs before I fully understood economisers ( all brands) correctly
    then they all go and change things up on me
     
  9. Snoring Beagle

    Snoring Beagle Need Little - Want Less - Love More

    Messages:
    11,131
    Don't worry NZ you are helping.
    I am going to be there again. they done went and rearranged the office lay out again. new rooms, new walls, new open areas. We will be assaying and balancing airflows and now would be a good time to really get to know these old Yorks.

    Thanks. :thumb:

    you too refertech!
     
  10. NZ All Blacks Fan

    NZ All Blacks Fan Just Another swinging Dick

    Messages:
    9,389
    Location:
    West Coast - Canada

    Generally there will be 24v to the damper motor all the time ( might be off the fan relay so no fan no damper power) and the min pos knob will be in circuit - a relay will disengage the min pos and engage the mixed air sensor so the damper will drive off the mixed air sensor


    I'll look around all my old shait and see if I gotta diagrahm of the old school stuff - might be generic but will help you figure it all out
     
  11. otto

    otto Bakery Chef

    Messages:
    19,840
    Location:
    in a van down by the river
    Ihave just pulled out all the old economizer controls on a few Carriers and a York before just because there were too many controls that might/will go bad even after you diagnose the current problem. Replaced them with Honeywell electronic controls and have had no problems with them. Perhaps this might be an option that you can offer the customer. Lots of rewiring but, in the end a more reliable unit.
     
  12. CincyHVAC

    CincyHVAC Hoptimus Prime, Master of Beer-Fu

    Messages:
    46,995
    Location:
    Ohio's Southern Shoreline
    Yeah, but the cost to convert is astronomical. Close to $3,000 for the conversion kit. We spent $295 for the actuators for the condenser fan dampers. Then again, this was on a Trane chiller and not a rooftop packaged unit.
     
  13. Abby Normal

    Abby Normal On Permanent Vacation

    Messages:
    8,897
    Location:
    19.3 North
    The aftermarket parts are outrageous

    I had a pair of noisy chillers and a near by residential area (100 yards away, thorugh some brush) was complaining. Trane wanted about 10 grand for some insulation kit to deaden the sound.

    It was cheaper to build a block wall to block the sound which is what we did
     
  14. Abby Normal

    Abby Normal On Permanent Vacation

    Messages:
    8,897
    Location:
    19.3 North
    I did a few custom built units in my time, our cheapest economizer was just a two stage stat. First stage cooling was open up the outside air (may or may not have the luxury of a T991 driving a mod motor to mix to 55). We had a high ambient setback which was a bulb thermostat that put the motor back to minimum position once it got too warm outside. Second stage cooling brought on the DX and drove the damper back to minimum position as well.