Precedent units with ReliaTel controls can have one or two compressors configured in single or dual circuit configurations:
- Precedent 3-5T Standard Efficiency, one single stage compressor
- Precedent 3-5T 17 Seer & High Efficiency Heat Pump, one 2-Stage compressor
- Precedent 6-10T Standard Efficiency, one single stage compressor
- Precedent 6-10T High Efficiency, two single stage compressors, dual circuit
- Precedent 7.5T-10T High Efficiency Heat Pump, one single stage & one 2-Stage compressor, single circuit
- Precedent 3-10T Ultra High Efficiency (Eflex), one variable speed compressor
Voyager II units with ReliaTel controls are all two compressor dual circuit machines except for some 25T High Efficiency units that have three compressors
Odyssey units with ReliaTel controls can have one or two compressors configured in single or dual circuit configurations:
- Single Compressor, single or 2-Stage
- Dual Compressor, single manifolded circuit
- Dual Compressor, dual circuit
For more information on compressor staging on Odyssey condenser, visit the link below:
Unit safeties
All ReliaTel controlled units utilize the same basic safety features for each unit. Below is a brief description for each set of safeties, associated diagnostics and troubleshooting.
High Pressure Cutout (HPC) and Discharge Temp Limit (DTL)
Every compressor will have a normally closed High Pressure Cutout (HPC) and a normally closed Discharge Temperature Limit Switch (DTL) on the discharge line of that compressor (standard on R410A and optional on older R22 units). These safeties are wired in series with the compressor contactor 24vac. A HPC or DTL trip (safety opens) would remove the voltage from the compressor contactor and can produce the following diagnostics:
- Diagnostic: Comp 1 Disable Input HPC
- Diagnostic: Comp 2 Disable Input HPC
- Diagnostic: Compressor 1 HPC Lockout
- Diagnostic: Compressor 2 HPC Lockout
If the HPC or DTL trip while the compressor is running, both compressors will shut down for 15 minutes. After the 15-minute timer has expired, the system will auto reset and begin compressor staging as necessary. This will produce a Compressor Proving Trip alarm and can happen up to 3 times in a row. If it happens a 4th time, the unit will lockout compressor operation and set a Compressor Proving Lockout requiring a manual reset.
Compressor 1 is always connected to RTRM J1-9 & 10:
- RTRM J1-10 is the 24vac out from the RTRM and is only present when the RTRM is calling for the compressor.
- RTRM J1-9 is the neutral/common side of Compressor Contactor 1 (CC1) and part of the compressor proving circuit.
Compressor 2 is always connected to RTRM J3-3 & 3-4:
- RTRM J3-4 is the 24vac out from the RTRM and is only present when the RTRM is calling for the compressor.
- RTRM J3-3 is the neutral/common side of Compressor Contactor 2 (CC2) also part of the compressor proving circuit.
For more detailed Compressor Proving Troubleshooting on ReliaTel controls see this link → Compressor Proving on ReliaTel Controlled Units
HPC ratings vary based on the refrigerant type:
- R22 Open 425 psi / Close 345 psi
- R410 Open 650 psi / Close 550 psi
DTL ratings also vary based on the refrigerant type:
- R22 Open 230 deg / Close 180 deg
- R410 Open 230 deg / Close 180 deg
HPC/DTL Troubleshooting
HPC trip troubleshooting should start with visual inspection of the condenser coil, validating condenser fan operation, TXV operation and checking pressures.
- A dirty condenser coil will obstruct air flow through the coil and reduce the surface area for heat transfer.
- Condenser fan operation varies based on unit type, number of condenser fans and outdoor temperature. Most units with fixed speed compressors utilize fixed speed/contactor started condenser fans.
- On Precedent units with a single fixed speed condenser fan, the fan will run anytime the compressors(s) are running. (a) (b)
- On Voyager II units with two fixed speed condenser fans, Condenser Fan 1 will run anytime there is a compressor running, Condenser Fan 2 operation is based on outdoor temperature: (a)
- If the OAT < 60°F, Condenser Fan 2 is disabled
- If the OAT > 65°F, Condenser Fan 2 is enabled
- Precedent and Voyager II units that utilize variable speed condenser fans, these vary condenser fan speed based on running cooling capacity and outdoor temperature. These fans utilize a PWM signal from the Variable Speed Module (VSM). This signal can be measured with a multimeter set to DC volts, valid range is 4 - 17.5vdc.
- On Odyssey units with a single fixed speed condenser fan, the fan will run anytime a compressor is running. (a)
- On single-circuit Odyssey units with two fixed speed condenser fans, both condenser fan run anytime a compressor is running. (a)
- On dual-circuit Odyssey units with two fixed speed condenser fans, Condenser Fan 1 runs with Compressor 1, Condenser Fan 2 runs with Compressor 2. (a)
- (a) Precedent heat pump units do not run the condenser fan in defrost.
- (b) Some R454B heat pumps with modulating hot gas reheat utilize fixed speed fans that will cycle off based on ambient temperature when the unit is in reheat
- Restrictions in the system will cause high head pressures.
- Filter dryer - a stopped up filter dryer is a sign of debris, bearing material, burned oil or organic contamination.
- The presence of bearing material in the system can come from compressor bearing damage due to liquid refrigerant in the oil and can be caused by missing or malfunctioning crankcase heaters and continued operation with liquid refrigerant flooding back to the compressor.
- The presence of burned oil is typically from extended compressor operation at high temperatures, failed compressor or poor system cleanup after compressor failure/replacement.
- The presence of debris and/or organic contamination in the system is typically from poor cleaning or evacuation practices during system repair.
- Filter dryer - a stopped up filter dryer is a sign of debris, bearing material, burned oil or organic contamination.
- TXV operation - TXV sensing bulb location should be checked to ensure that it is the optimal location. TXV operation can be checked by holding the sensing bulb and watching the pressures, a working valve should open as it warms up. For units with two TXVs on the evaporator coil, testing would require that one TXV sensing bulb be placed in water or in a media that has a fixed or steady temperature to get that valve to "hold" its operation while holding/warming up the other bulb.
DTL trip can be caused by any scenario that also causes HPC trip. Operating with a restriction causing low refrigerant flow back to the compressor can cause compressor overheating leading to DTL trip.
Low Pressure Cutout (LPC)
All Precedent, Voyager II and Odyssey units utilize one LPC per circuit mounted on the suction line near the compressor. When the LPC trips, it can produce the following diagnostics:
- Diagnostic: Comp 1 Disable Input LPC
- Diagnostic: Comp 2 Disable Input LPC
- Diagnostic: Compressor 1 LPC Lockout
- Diagnostic: Compressor 2 LPC Lockout
If the LPC trips while the compressor is running, both compressors will shut down for 3 minutes. After the 3 minute timer has expired, the system will auto reset and begin compressor staging as necessary. This will produce a Diagnostic: Comp x Disable Input LPC alarm and can happen up to 3 times in a row. If it happens a 4th time, the unit will lockout compressor operation and set a Diagnostic: Compressor x LPC Lockout requiring a manual reset.
LPC Ratings vary by model, type (HP or Cooling only) and refrigerant. The list is too extensive for this document. For assistance with switch ratings, visit https://www.tranesupply.com/ and use you unit serial number to locate the switch and ratings (typically ratings are in the part description).
LPC Troubleshooting
LPC trip troubleshooting should start with visual inspection of the evaporator coil, air filters, air flow, TXV operation and checking pressures.
- A dirty evaporator coil reduces the surface area available for the heat transfer from the air to the refrigerant. This will also cause issues with potential liquid slugging back to the compressor and reduced refrigerant flow to the compressor.
- Dirty air filters and low air flow due the duct work restrictions or improperly set indoor supply fan will produce the same issues as a dirty coil.
- TXV operation - TXV sensing bulb location should be checked to ensure that it is the optimal location. TXV operation can be checked by holding the sensing bulb and watching the pressures, a working valve should open as it warms up. Units with two TXVs on the evap coil, testing would require that one TXV sensing bulb be placed in water or in a media that has a fixed or steady temperature to get that valve to "hold" its operation while holding/warming up the other bulb.
Frostat (FOS)
FOS initially was an option on R22 units and all constant volume R410A units and could be field installed. All variable speed and multispeed fan R410A units have a FOS standard. The FOS is either a capillary style switch wired normally open and mounted next to the (Voyager II) or above the evaporator coil (Precedent) or on Microchannel coils, it is a clip-on style 2-wire switch mounted on the suction line near the evaporator coil. All versions are wired back to the RTOM J7-1 & 2 . When the FOS trips, it will produce the following diagnostic:
- Diagnostic: Frostat Trip
FOS Ratings vary by model, type (HP or Cooling only) and refrigerant. The list is too extensive for this document. For assistance with switch ratings, visit https://www.tranesupply.com/ and use you unit serial number to locate the switch and ratings (typically ratings are in the part description).
On Precedent and Voyager II, when the FOS trips all compressor operation is stopped and the indoor fan will stay on at low speed to thaw the coil. This is an auto-reset alarm and once the FOS resets (closes) or EDC on Odyssey, the compressors will begin staging up as necessary. This alarm does not have a hard lockout/manual reset mode, it can trip indefinitely with auto-resets.
All Electromechanical and ReliaTel controlled Odyssey AHU utilized an Evaporator Defrost Switch (EDC) switch on the indoor coil instead of a FOS. On ReliaTel, the EDC on the AHU was wired back to the condenser and connected between LTB1-R (24vac) and LTB1-CD (Compressor Disable). This drops the power to LPC1 & 2 (if equipped) and will produce the same LCP alarms on Odyssey as well as the same sequence of operations as an LPC trip.
Condensate Overflow
Precedent and Voyager II can have an optional Condensate Overflow Switch (COF) installed either at the factory or in the field (Voyager II only). This switch is a basic 2 wire normally open (close on high water) float switch. It is mounted in the corner of the condensate pan near the drain connection and wired back to the RTOM J6-1 & 2. When the COF trips it can produce:
- Diagnostic: Drain Pan Overflow
When the COF trips (closes) ReliaTel will shutdown all unit operation including the indoor fan. Once the COF resets (opens), the unit will start back up normally. There is not reset time, it is based on how fast the drain clears. The switch can trip up to two times in a 72 hour period and auto-reset each time, this will produce a Diagnostic: Drain Pan Overflow. If the switch trips a third time in 72 hours, ReliaTel will produce the same diagnostic and will require a manual lockout. Note, the 72 hour timer is based on the last COF trip.
- If COF trips and resets two times in 24 hours, the 72 hour timer started at the first trip
- Once it has been 72 hours since the first trip, the timer is reset to when the 2nd trip occurred
- If the COF does not trip again within 72 hours of the 2nd trip, the timer is reset to 0 until the next COF trip
Odyssey units do not utilize a COF as part of the configuration, requirements for a COF would involve a aftermarket switch tied into the added in series between phase monitor and control transformer in the condenser. If a smoke detector is also required on the unit, it will need to be wired in series with the aftermarket COF.