RTHB180 "LOW DIFF RFGT PRES"
THE ABOVE ALARM EVENT APPEARED TWICE IN THE LAST TWO WEEKS. THE CUSTOMER RESET IT THE FIRST TIME AND THE CHILLER RAN FOR TWO WEEKS WHEN THE SAME ALARM APPEARED AGAIN.
ANY BULLETINS OR ADVISE TO OBTAIN A BETTER UNDERSTANDING - THE DIAGNOSTICS IS INDICATING CHECKING THE EXV, STEPPER MODULE, AND SENSOR OPERATION NEED TO BE CONFIRMED.
APPRECIATE CONSIDERATION OF EXPERT FEEDBACK
Condenser water temp ?? Condenser water temp control ??
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I"m not a service tech.. I"m a thermodynamic transfer analyst & strategic system sustainability specialist
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I will be going to the job site tomorrow. Your suggesting I check to if the condenser water temp is below the manufactures recommendations??
also, there are two of these units, but only the one has had the alarm event cause it to shut down. It would seem that the condenser temp would affect both units the same everything was equal.
Might depend on the sequencing of the two chillers?
Originally Posted by macmec
Low Differential Rfgt Pressure: A Low differential Temperature/Pressure condition was detected that existed for more than 600 contiguous seconds. Trip point is 10 PSID.
check your temperature sensors and pressure transducers. if all are correct, how close are your condensing and evaporating pressures? what are your evaporator and condensor water temperatures (in and out)?
from Trane RLC-EB-4, Models RTHB & RTHC Condenser Water Control:
Condenser leaving water temperature must be 25F degrees higher than evaporator leaving water temperature within 15 minutes from startup, and maintained thereafter. Note RTHB chillers may not be able to load until this temperature differential is achieved.
The required system pressure differential (condenser pressure minus evaporator pressure) is 25psid for all RTHC models, 35psid for RTHB 130-215, and 50psid for RTHB255-450.
if your system can not load up, then the evaporator water heats up and the evaporator pressures get too close to condensing pressures and...poof...you trip. one of the reasons that you may be experiencing a diagnostic on one chiller and not the other is the oil line system pressure drop. the chiller does not have an oil pump. it uses system pressures to move the oil. the chiller uses the oil for bearings, rotor sealing AND moving the chiller slide valve which allows it to load up.
in the oil line system is an oil filter, solenoid valve and a check valve. if the filter is too dirty and you have low condensor water temperatures...then you don't trip on the oil flow diagnostics...you just don't load up...then...poof....your pudding gets too warm!
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Usually, each chiller has it's own "Head Pressure" control.
Originally Posted by macmec
"Wheel" mechanics work on "Wheel" chillers