Page 1 of 2 12 LastLast
Results 1 to 13 of 22
  1. #1
    Join Date
    Dec 2006
    Location
    In a Mess
    Posts
    1,028

    York 7.5 Ton Split, Low Ambient Problems

    I have a unit that is locking out overnight. York H5CE 090A88A. This job was passed on to me by a co worker who couldn't get back to it today. Lockouts on this unit are either high head or low suction pressure.

    There is a 90 second bypass for the low pressure on startup, I don't think this is long enough. for the low temperatures.

    Unit has an ICM325 fan control, not sure which sensor it's using.

    http://www.icmcontrols.com/products/...php?prod_pk=58

    on start up ambient around 25*F the compressor starts without fan running and during the first minute the head pressure rises and when temperatuer at sensor reaches 80*F fan turns on then slows down then at 65*F it shuts off shortly after that suction drops to around 15/20psi then unit shuts off.

    I jusmped out low press switch on board and watched it go again and system ran and when suction dropped low it didn't stay down for long then settled at around 56-58psi, suction line was @ 44*F

    I didn't spend that much time with it today but I think I'll go back and play with that fan control re check the sensor type and placement, aparently it will run all day but the lockouts have been happening at night

    anyone knaow nomenclature on Texas instruments screw on pressure switches? i tried to search for it but TI website is too big hah

    switch:
    Texas instruments
    PSL PMAX17B
    PS80C2F0195038-023
    7465
    6(6)A240VAC
    291R05
    Sig removed by mod. G-Rated site

  2. #2
    Join Date
    Apr 2005
    Posts
    517
    Confirm the sensor is correct or replace it with the 95 to 120. An aircooled condenser operates at 120* condensing temps.

    Water cooled operates at 105*

  3. #3
    Join Date
    Dec 2006
    Location
    philadelphia pa
    Posts
    171
    Is this a rooftop pkg. unit? If so, why no economizer

  4. #4
    Join Date
    Dec 2006
    Location
    In a Mess
    Posts
    1,028
    nope she's a split.... see title

    besides if it were a rooftop package it probably wouldn't have a econo, the air space is a controlled enviroment (a lab) and the wouldn't want outside air let in, actually I'm having a humidity problem here aswell but maybe i'll post that in another thraed maybe!

    I have a feeling I may have the 70-100 sensor on there but I didn't install that control so I don't know

    anyone know on what the set points are on that screw on pressure switch?

    I was thinkin maybe I'll throw a ranco pressure control on there waith a 2psi cut out on it, there is a freeze stat in the ait handler, that may prevent these low ambient lock outs, it shouldn't run in a vacuum

    Thanks for the input
    -Mike
    Sig removed by mod. G-Rated site

  5. #5
    Join Date
    Nov 2005
    Location
    Shreveport, Louisiana
    Posts
    2,338
    Adjust the head pressure control to maintain a 100 liquid temprature to the metering device.

    After you have achieved that then you will have to check your subcooling and superheat. Check your metering device....

  6. #6
    Join Date
    Dec 2006
    Location
    In a Mess
    Posts
    1,028
    Quote Originally Posted by berg2666 View Post
    Adjust the head pressure control to maintain a 100 liquid temprature to the metering device.
    I picked up another ICM sensor(ICM 95-120) at Totalline nad stuck that on there, LL temp when fan came on was 103f/104F in that area, liquid pressure got up to 375psi fan came on and pressure dropped and so did did LL temp

    this did not work because discharge sensor opened up and locked it out, the liquid pressure was 375 and the sensor which opens at 420(360 reset) located 4 inbches from compressor in discharge opened up.

    I replaced the OEM low pressure sensor which is 23psi open and 38 reset with another which is 5psi open and 20 reset, so hopefully that will prevent the low pressure lockouts, I pit the 70-95F ICM sensor and cycled the fan at the lower Liquid temp range,

    I'm not a big fan of fan cycling but it's not my equipment or choice on what is there so I have to do with ai can and with the Really low ambients (sometimes as liw as -10F) that this poor units have to work in some times fan cycling isn't the best option.

    lets see what happens
    -Mike
    Sig removed by mod. G-Rated site

  7. #7
    Join Date
    Mar 2005
    Location
    Pacific Time Zone
    Posts
    4,223
    Placement of the liquid line sensor is very critical on these type of head pressure controllers. They typically are very specific on where to place the sensor and to make sure it is well insulated and has good contact. Have you gone through the installation guide and made sure it is done correctly? Here is some info. from a similar model
    "Mounting a sensor into the condenser
    versus mounting it on the liquid line
    When a sensor is mounted into the condenser, the control responds more rapidly
    to changes in head pressure than when it is mounted on the liquid line. This is
    especially true for high efficiency condensers.
    When the sensor is mounted on the liquid line, the control responds more slowly
    and the result can be a fan that cycles on and off.
    Therefore, whenever possible, it is preferable to mount the sensor in the upper 1/3
    of the condenser instead of mounting it on the liquid line"

    "Install the temperature probe several bends into the
    condenser. It can be attached to the U-bend or placed
    between the fins in the upper 1/3 of the condenser (see
    Pages 10-12 for more information).
    Note: The response of the system can be fine tuned by
    repositioning the probe."
    Let us know.
    "How it can be considered "Open" is beyond me. Calling it "voyeur-ed" would be more accurate." pka LeroyMac, SkyIsBlue, fka Freddy-B, Mongo, IndyBlue
    BIG Government = More Dependents
    "Any 'standard' would be great if it didn't get bastardised by corporate self interest." MatrixTransform
    http://threedevilskennel.com/ - not my website.
    Versatile Hunting Dog Federation - www.vhdf.org/


  8. #8
    Join Date
    Dec 2006
    Location
    In a Mess
    Posts
    1,028
    this condenser had a header and multiple circuite through out it, now i have it mounted on the outlet (liquid) line of the condenser mounted in place with a gear clamp some heat transfer paste around it and wrapped in amaflex tape

    If i can find a good spot on the condenser maybe i'll find a spot fot the 95-120 sensor and give that on a earlier part of the condenser
    -Mike
    Sig removed by mod. G-Rated site

  9. #9
    Join Date
    Nov 2005
    Location
    Shreveport, Louisiana
    Posts
    2,338
    Quote Originally Posted by MikeySq View Post
    this condenser had a header and multiple circuite through out it, now i have it mounted on the outlet (liquid) line of the condenser mounted in place with a gear clamp some heat transfer paste around it and wrapped in amaflex tape

    If i can find a good spot on the condenser maybe i'll find a spot fot the 95-120 sensor and give that on a earlier part of the condenser
    -Mike

    DO you mean it has multiple circuits as being a two stage unit or multiple refrigerants circuits with one compressor?

    If it has one compressor then install it in the upper 1/3 of the condenser.
    If it has more then one compressor then you must determine the coil arrangement and mount it appropriately. Is it intertwined coils circuits or over and under kind of configuration.

  10. #10
    Join Date
    May 2004
    Location
    Los Angeles, CA
    Posts
    1,560
    Dear MikeySq,

    A better condensing fan control than the ICM325K is the Johnson Control #P66 (single input for your application), it has multiple adjustments for min/max fan RPM and pressures. Looks like your on the right path though.

    Your high humidity problem in the Laboratory downstairs is most likely due to a low evaporative heat load at your air handler is low ambient outside conditions. This can be easily corrected by one of several different means:

    1. Evaporator reheat

    2. Hot gas bypass

    3. Multiple evaporator TXVs

    4. Ect……….


    Hope this helps……….

    Respectfully Submitted,
    John J. Dalton CM

  11. #11
    Join Date
    Nov 2005
    Location
    Shreveport, Louisiana
    Posts
    2,338
    Quote Originally Posted by berg2666 View Post
    DO you mean it has multiple circuits as being a two stage unit or multiple refrigerants circuits with one compressor?

    If it has one compressor then install it in the upper 1/3 of the condenser.
    If it has more then one compressor then you must determine the coil arrangement and mount it appropriately. Is it intertwined coils circuits or over and under kind of configuration.
    Also If I remember correctly you can use two sensors on the ICM module..

  12. #12
    Join Date
    Nov 2005
    Location
    Shreveport, Louisiana
    Posts
    2,338
    Quote Originally Posted by john dalton View Post
    Dear MikeySq,

    A better condensing fan control than the ICM325K is the Johnson Control #P66 (single input for your application), it has multiple adjustments for min/max fan RPM and pressures. Looks like your on the right path though.

    Your high humidity problem in the Laboratory downstairs is most likely due to a low evaporative heat load at your air handler is low ambient outside conditions. This can be easily corrected by one of several different means:

    1. Evaporator reheat

    2. Hot gas bypass

    3. Multiple evaporator TXVs

    4. Ect……….


    Hope this helps……….

    Respectfully Submitted,
    John J. Dalton CM

    Does the indoor unit contain a heat strip?

    IF so you can get some kind of control to reheat using the heat strips.

    I think a Vision Pro that has this capability. I will have to see exactly which one it is, if I am correct at all.

  13. #13
    Join Date
    May 2004
    Location
    Los Angeles, CA
    Posts
    1,560
    Dear Berg2666,

    We do not know if the evaporative section contains a hest strip of not because MikeySq did not post what the make, model number, and options that are on the evaporator are.

    Granted if the heat strips are there, and of sufficient capacity, then this could be utilized as a form of reheat.

    A Honeywell VisionPro thermostat Model #TH8321U 1006 has the capability to monitor and control humidity for de-humidification purposes by turning on the air conditioning to de-humidify and turning on the heat (strip heaters) in case the temperature drops below the heating set-point.
    Hope this helps……………

    Respectfully Submitted,
    John J. Dalton CM

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