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Thread: ucp2 setpoints

  1. #1
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    ucp2 setpoints

    leaving water temp cutout setpoint is default is 36 degrees .when this setpoint is within 1.7 degrees of front panel chilled water setpoint, the front panel setpoint is increased along with this setpoint to maintain the differental.,
    y is this .,.,

    same thing for low refrigerant cutout temp setpoint., default is 32 degrees., when this setpoint is within 6 degrees front panel cws , front panel cws is increased along with this setpoint to maintain differential.,

    whats up with the differential ., how is this working?

    thx

    this is on a trane series r , rthc model ., but differential is all the same in all machines with differant setpoints

  2. #2
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    Quote Originally Posted by mlkwal1 View Post
    leaving water temp cutout setpoint is default is 36 degrees .when this setpoint is within 1.7 degrees of front panel chilled water setpoint, the front panel setpoint is increased along with this setpoint to maintain the differental.,
    y is this .,.,

    same thing for low refrigerant cutout temp setpoint., default is 32 degrees., when this setpoint is within 6 degrees front panel cws , front panel cws is increased along with this setpoint to maintain differential.,

    whats up with the differential ., how is this working?

    thx

    this is on a trane series r , rthc model ., but differential is all the same in all machines with differant setpoints
    It just gives the machine a little fudge factor. (To keep from giving nuisance trips on low evap. refrigerant temp. and on low leaving solution temp).

  3. #3
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    What C said.... It's a way to create a 'stop load' or 'force unload' condition to prevent a safety shutdown.

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    Thumbs up

    Quote Originally Posted by klove View Post
    What C said.... It's a way to create a 'stop load' or 'force unload' condition to prevent a safety shutdown.
    gotcha., nuisance trips can be aggervating.,
    i was reading an iom manual , under service test., what and when would one do a dry run., i went to a tear down school in lacross on centra vac and they said at this time is only time that test needs to be performed., what u think?

  5. #5
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    Quote Originally Posted by mlkwal1 View Post
    gotcha., nuisance trips can be aggervating.,
    i was reading an iom manual , under service test., what and when would one do a dry run., i went to a tear down school in lacross on centra vac and they said at this time is only time that test needs to be performed., what u think?
    Dry Run, if I understand your question correctly, is used to troubleshoot starter components with high voltage de-energized & 115 volt test power connected.

  6. #6
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    The control reponse to low leaving water temp and low refrigerant temp is unit shutdown and issuing either an automatic or manual reset diagnostic, depending on which one tripped. You can see what would happen if your low chilled water temp cutout were the same as your chilled water temp setpoint. You wouldn't be able to keep the machine on.

    A starter dry run can be done any time you need to troubleshoot starter components like contactors, auxiliaries, inputs/outputs.

    The purpose is to keep from starting and stopping the motor repeatedly and exposing yourself to dangerous voltages.
    "There is no greater inequality than the equal treatment of unequals."

    -Thomas Jefferson

  7. #7
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    Quote Originally Posted by mlkwal1 View Post
    gotcha., nuisance trips can be aggervating.,
    i was reading an iom manual , under service test., what and when would one do a dry run., i went to a tear down school in lacross on centra vac and they said at this time is only time that test needs to be performed., what u think?
    I believe you're thinking of an air run, you do these after an overhaul, to verify trim balance. Dry run is what said by BergerRob & Jsherhvac.
    Sic Semper Tyrannis.

  8. #8
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    Quote Originally Posted by txhvac View Post
    I believe you're thinking of an air run, you do these after an overhaul, to verify trim balance. Dry run is what said by BergerRob & Jsherhvac.
    exactly, how does this work ? one would not do this with all the impellers on would they? that would bring in alot of air even know that the machine is open anyways. it this to just check the runout ono the shaft? also what about the high voltage?

  9. #9
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    i know this is off the subjuct we r talking about.,.,opppps.,lol.,

    i am assuming that low oil flow has a simillar alarm of low evep temp. i know if oil filter is plugged or valve may b close will cause a restriction and send an alarm, can u help explain this alittle please, also on the liquid level sensor, does it have an eye or a float with an arm, what could happen if the level gets too low or high?
    thanks

  10. #10
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    Quote Originally Posted by mlkwal1 View Post
    i know this is off the subjuct we r talking about.,.,opppps.,lol.,

    i am assuming that low oil flow has a simillar alarm of low evep temp. i know if oil filter is plugged or valve may b close will cause a restriction and send an alarm, can u help explain this alittle please, also on the liquid level sensor, does it have an eye or a float with an arm, what could happen if the level gets too low or high?
    thanks
    The oil flow diagnostics can be caused by,1- low diff. press. between the low and the high side pressures.(a screw needs this diff. to move oil) diff switch on high and low is I believe 25 psi so many seconds after startup or it locks out and can't be restarted for like 60 min.(don't have a book in my hand. 2- there is a diff. press. switch on the oil line checking for press. drop on the oil filter. 3- there is a (wet) sensor in the oil supply line also. On the ref. float, think of it as the the sending unit in your cars gas tank that tells you how much gas you have, except this one goes from -1 to +1 inch. This sensed level controls the EXV and it's trying to maintain right in between -1 and +1 at 0. When liquid level is at 0, it is correct. If level get's to -1 and EXV is 100% it's either low of ref.(from gas pump solenoids leaking, lol) or problems with EXV. If level get's low your gonna trip on low evap. temp. If level get's too high, well I don't know(never seen this). whew!

  11. #11
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    Quote Originally Posted by cperk View Post
    The oil flow diagnostics can be caused by,1- low diff. press. between the low and the high side pressures.(a screw needs this diff. to move oil) diff switch on high and low is I believe 25 psi so many seconds after startup or it locks out and can't be restarted for like 60 min.(don't have a book in my hand. 2- there is a diff. press. switch on the oil line checking for press. drop on the oil filter. 3- there is a (wet) sensor in the oil supply line also. On the ref. float, think of it as the the sending unit in your cars gas tank that tells you how much gas you have, except this one goes from -1 to +1 inch. This sensed level controls the EXV and it's trying to maintain right in between -1 and +1 at 0. When liquid level is at 0, it is correct. If level get's to -1 and EXV is 100% it's either low of ref.(from gas pump solenoids leaking, lol) or problems with EXV. If level get's low your gonna trip on low evap. temp. If level get's too high, well I don't know(never seen this). whew!
    thank you ., u r da man.,.

  12. #12
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    as far as problems with the exv goes., what r some of the problems that u see., is the most common problem that the stepper module goes bad or the motor on the valve., i know that the liquid level sensor and the exv work together, what else is related to the exv., is the exv also looking at superheat or is that what liquid level sensor is kinda doing? what is ur experience with issues with the exv?

  13. #13
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    Level only. I personally have never seen an EXV go bad. We had a Trane tech. change out an EXV and ended up not being the problem, it was about 200#s shy of gas from one of the solenoids on the gas pump leaking. I take care of 4 RTHC's and RTHD's and have changed the gas pump solenoids on all of them, some more than once, because of them leaking. These are opened and closed by time to fill and dump liquid from bottom of evap. to comp. for oil return. I don't gripe though, because the RTHA's and RTHB's I work on have no oil return whatsoever, they rely on oil returning with suction gas. I have put compressors on all of these (from running at low loads for extended periods) and running out of oil. Their oil loss protection sucks, just a diff. switch on oil filter, it does'nt know if it's reading diff. on oil, or just discharge gas with no oil in it.

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