YSC
Precedent packaged · Reliatel · 3–10 t class
Trane Precedent rooftop (YSC gas/electric, TSC cool, WSC heat pump, YHC high-efficiency). Reliatel (RTRM) is the unit controller on the generation still covering most roofs under 15 tons. Symbio 700 is the newer board — do not mix the alarm lists.
Not Voyager 12.5–25 t (different cabinet). Not a residential S9V2 furnace. Not Symbio 700 until the board in the control box says so.
Chart, codes, and first check stay open. The rest of the walkthrough is Diagnose — sign in on that button.
Size
Precedent 3–10 t class on this chart. 12.5 t+ may be Voyager — different book.
Heat / cool
YSC gas, TSC cool/electric, WSC heat pump, YHC high-efficiency gas.
Controls
Reliatel RTRM / RTOM. Heat fail, cool fail, fan fail are Reliatel language.
This board
Reliatel (RTRM) — Precedent
- Reliatel LEDs and the service button, not a residential S-series 7-seg. Type the name as displayed: Heat Fail, Cool Fail, Fan Fail.
- Heat fail vs cool fail vs fan fail are different paths. Fan prove on VFD cabinets is a known nuisance if the motor is in limp — example: Fan Fail with the drive still at min Hz.
- If the board says Symbio 700, leave this Reliatel chart — alarm lists are not interchangeable.
Reliatel LEDs / last fail before you cycle 24V.
Field wiring
Written landings for Trane YSC. Not a factory schematic.
One cabinet. Occupied/G is the indoor fan. Y1 is mechanical cool — unless the economizer takes the call. W is gas heat on the IGC, not on the compressor contactor.
Written circuit description only — FieldBench does not redraw maker schematics. Example: R to W closes on a heat call; verify 24V at W1 before you change the IFC. Packaged: Y1 may go to the economizer, not the contactor; VFD enable is 24V, speed is 0–10 V.
Open manufacturer wiring diagramCabinet sequence
- 1Power. Disconnect → L1/L2/(L3) → unit transformer → RLine / 24V
- 2Fan. G / occupied → indoor blower proveBelt, ECM, or current switch
- 3Econo. Y1 → economizer module → damperMay satisfy cool with compressor off
- 4Cool. Y1 → contactor coil through HPS/LPS → compressor + OD fan~24 VAC coil
- 5Heat. W → IGC → inducer → PS → HSI → valve → flameHeat section only
- 6VFD. EN + 0–10 V → drive → indoor motorEnable 24V, speed analog
This indoor
Precedent Reliatel. Packaged — no S9V2 indoor.
24V thermostat or DDC
Conventional stat or a BAS landing R C Y1 Y2 W G. Not Infinity ABCD.
Wall / DDC
Unoccupied with G open looks like a dead unit. Occupied first.
- R24V hot from the unit transformer24V
- CCommon24V
- Y1Mechanical cool stage 124V
- Y2Cool stage 2 if this cabinet is two-stage24V
- W1Gas heat — goes to the IGC, not the contactor24V
- W2Heat stage 2 if equipped24V
- GIndoor fan / occupied24V
Unit controller
Cool, fan, economizer, safeties. Heat is handed to the IGC.
- Y1 outContactor coil through HPS / LPS24V
- G outIndoor blower / VFD enable24V
- W outHeat call to IGC24V
IGC / ignition module
Burner compartment. LED is heat-only.
- WHeat call from the unit board24V
- MVGas valve 24V during trial24V
- PSDraft / pressure switch24V
- LIMLimit / rollout in series24V
Economizer (JADE W7220 / W7212 / factory FDD)
Damper can satisfy Y without the compressor. FDD lives on this module, not on the IGC.
- ACTActuator 2–10 V (modulating) or 24 V floating — match the actuator that is on the shaft24V
- FBKActuator feedback pot. JADE ACT RANGE is this sliding off the shaft24V
- OA TOutside-air thermistor / SYLK OA sensor24V
- RA TReturn-air thermistor when differential / enthalpy is used24V
- MATMixed-air sensor — after the damper, before the evap24V
- CO2DCV 0–10 V. Failed high = damper open all day24V
- 24V / COMModule power from the unit transformer24V
Indoor-fan VFD (EcoBlue / Reliatel / aftermarket drive)
Enable and speed reference are 24V / 0–10 V from the unit board. Line is 3-phase at the drive.
- L1 L2 L3Line at the drive — same 3-phase as the unitLine
- U V WMotor leads. Megger with the drive disconnectedLine
- ENEnable 24 VAC (or digital). No enable = board never asked24V
- AI / 0–10Speed reference. 0 V with enable is a wire/board24V
- ALMDrive fault contact back to the unit board24V
Landing
- 24VStat Gunit boardindoor blower
Occupied / fan. Prove this before heat or cool.
- 24VStat Y1unit boardeconomizer OR contactor coil
Mechanical cool only if the damper is not taking the call.
- 24VContactor coil through HPS (LPS)
~24 VAC when the board commands the compressor
- 24VStat Wunit boardIGC WinducerPSHSIvalve
Heat path. Independent of Y.
- 24VOA T / RA T / MAT / CO2economizer moduleACT 2–10 Vdamper
FDD sensors and actuator. Not 24V Y.
- LineUnit board EN + 0–10 VVFDindoor motor
Enable 24V, speed analog, line 3-phase at the drive
- LineL1 L2 L3disconnectcontactors / VFD
Line. 3-phase rotation on 6–15 t.
Prove it
- G / occupied: indoor fan running and proving.
- Y1 at the unit board. Damper position vs command before you chase the contactor.
- W at the IGC, then the heat LED.
- VFD: enable 24V and 0–10 V under a high-fan call. Photograph the drive code before you cycle power.
Do not
- Do not treat this as a split furnace + condenser. There is no line set.
- Do not jump rollout, smoke detector, or fan-prove and walk away.
- Do not apply a 59-series / GR9T96 door card to this IGC.
- Do not throw a dual run cap at a VFD motor. Do not raise FLA to hide a dirty roof.
Written landings, not a factory schematic. Open the manufacturer wiring diagram from the plate’s literature link — FieldBench does not host or redraw it.
Sequence
- 1
Call
Occupied / G starts the indoor fan. Y1 is cool. W is gas heat. They are different boards in the same box.
- 2
Fan
Indoor blower must prove (belt, ECM, or current switch) before some controllers allow heat or cool.
- 3
Econo
If OA is below the economizer setpoint, the damper takes the cool call. Compressor stays off. That is not a dead contactor.
- 4
Cool
Y1 → unit board → compressor contactor through HPS (and LPS when equipped). OD fan on the same call or on head pressure.
- 5
Heat
W → IGC / ignition module: inducer → pressure switch → HSI → valve → flame rod → indoor blower on delay.
Faults on this IFC
Code, meaning, and the first check. Walk the rest in Diagnose — that is the seat.
Reliatel heat fail
Heat section did not prove. IGN module / PS / limit / flame.
1 Airflow before you touch the limit
On Trane YSC a limit is airflow or overfire until proven otherwise. Do not replace the limit first. Filter, blower wheel, A-coil, and the heat-speed setting for THIS motor (tap, model plug, or communicating CFM — not a sister SKU chart). W at Reliatel, then the ignition module in the heat section.
Expect: TES / static: External static vs the blower table for this tonnage — rooftops run dirty.
Walk the rest of Heat fail — 2 more checks after sign-in
Reliatel cool fail
Mechanical cool did not prove.
1 Write the live code and watch one cycle
On Trane YSC read Reliatel (RTRM) — Precedent before you pull power. Write Cool fail exactly. Watch one full sequence and note which step dies. Y1 at Reliatel. Economizer may be satisfying — check damper first.
Expect: Call: Occupied / G starts the indoor fan. Y1 is cool. W is gas heat. They are different boards in the same box.
Walk the rest of Cool fail — 2 more checks after sign-in
Reliatel fan fail
Indoor fan did not prove.
1 Write the live code and watch one cycle
On Trane YSC read Reliatel (RTRM) — Precedent before you pull power. Write Fan fail exactly. Watch one full sequence and note which step dies. Belt, ECM, or the proving pressure switch / current sensor.
Expect: Call: Occupied / G starts the indoor fan. Y1 is cool. W is gas heat. They are different boards in the same box.
Walk the rest of Fan fail — 2 more checks after sign-in
Space / air sensor
Supply, return, or OA sensor out of range.
1 Damper position vs command
On Trane YSC look at the economizer before the compressor. Commanded open? Blade actually open? Linkage off the shaft is a rooftop weekly. Ohm vs a real thermometer. Reliatel will not stage right on a failed MAT/OA.
Expect: Blade matches the module command. Stuck open = overventilation. Stuck closed = no free cooling.
Walk the rest of SA / RA — 2 more checks after sign-in
High pressure
Discharge / liquid opened the high-pressure switch.
1 Prove inducer and the live code
Do not pull power — that clears the Trane YSC active code. Write HPS. Is the inducer spinning on this call? Silent inducer is not a pressure switch. OD coil packed. Fan running and correct rotation on 3-phase.
Expect: 120 VAC at the inducer on a heat call. Wheel turning.
If fail: 120 VAC missing → IFC / door switch / incoming power. Voltage + dead motor → inducer.
If pass: Inducer running + this code → trap, hose, switch, vent (step 2).
Walk the rest of HPS — 2 more checks after sign-in
Low pressure / freeze
Suction dropped out the low-pressure switch.
1 Prove inducer and the live code
Do not pull power — that clears the Trane YSC active code. Write LPS. Is the inducer spinning on this call? Silent inducer is not a pressure switch. Charge / leak. Filters and indoor coil first — a dirty rooftop ices like a starved piston.
Expect: 120 VAC at the inducer on a heat call. Wheel turning.
If fail: 120 VAC missing → IFC / door switch / incoming power. Voltage + dead motor → inducer.
If pass: Inducer running + this code → trap, hose, switch, vent (step 2).
Walk the rest of LPS — 2 more checks after sign-in
No start / hum
Y1 at the board, compressor not running.
1 Is Y actually at the contactor?
On Trane YSC a silent outdoor is often no Y. Measure 24 VAC coil-to-C at the contactor on a cool call. 24 VAC across the coil. Then dual cap (if this chassis has one) or VFD / two-stage unload.
Expect: ~24 VAC at the coil when the indoor is calling.
If fail: Indoor Y / IFC / stat — not a capacitor.
Walk the rest of Contactor — 2 more checks after sign-in
Smoke / firestat
Supply or return smoke detector, or a firestat, has the unit locked out.
1 Which detector tripped
On Trane YSC supply and return smoke, or a firestat, shut the unit down. Find which device is open before you reset. Welding and a dirty return nuisance-trip these. Reset only after you know why it tripped. Welding and dirty returns nuisance-trip these.
Expect: The tripped detector identified. Space not actually in alarm.
Walk the rest of Smoke — 2 more checks after sign-in
Phase loss / rotation
Three-phase monitor opened.
1 Three legs at the disconnect and the contactor
On Trane YSC measure L1 L2 L3 at the disconnect and at the compressor contactor. A phase monitor trips on loss, imbalance, or reverse rotation. Measure all three legs at the disconnect and at the contactor.
Expect: All three legs, nameplate voltage ±10%, phase monitor closed.
Walk the rest of Phase — 2 more checks after sign-in
Economizer FDD
Start here when the hood is the complaint. Title 24 FDD classes: sensor, not-economizing, false-economizing, damper not modulating, excess OA.
1 Damper position vs command
On Trane YSC look at the economizer before the compressor. Commanded open? Blade actually open? Linkage off the shaft is a rooftop weekly. Read the module in THIS hood (JADE W7220 / W7212 / Reliatel / Prodigy / factory FDD). Type the live LCD string — examples: MA SENS ERR, OA SENS ERR, CO2 SENS ERR, ACT ERROR.
Expect: Blade matches the module command. Stuck open = overventilation. Stuck closed = no free cooling.
Walk the rest of Econo — 2 more checks after sign-in
MA SENS ERR (JADE LCD example)
JADE two-line LCD: MA / SENS ERR. Mixed-air sensor failed. This one alarms immediately on power-up — others wait the 60-minute setup window.
1 Damper position vs command
On Trane YSC look at the economizer before the compressor. Commanded open? Blade actually open? Linkage off the shaft is a rooftop weekly. Probe mixed air after the damper vs MAT on the module.
Expect: Blade matches the module command. Stuck open = overventilation. Stuck closed = no free cooling.
Walk the rest of MA ERR — 2 more checks after sign-in
OA SENS ERR (JADE LCD example)
JADE LCD: OA / SENS ERR (or OA SYLK ERR). Outside-air thermistor failed or lost SYLK. Board thinks the roof is 20 °F or 120 °F.
1 Which sensor is this code?
On Trane YSC OA ERR is a specific thermistor — indoor return/pipe, outdoor coil, discharge, or ambient. Unplug that sensor and ohm it vs the OEM temperature/resistance chart. Probe OA at the hood vs the module. Several degrees off is a sensor, not a damper.
Expect: Ohms move with temperature. Not open, not shorted.
Walk the rest of OA ERR — 2 more checks after sign-in
RA SENS ERR (JADE LCD example)
JADE LCD: RA / SENS ERR. Return-air thermistor failed. Differential / enthalpy changeover compares OA to RA.
1 Damper position vs command
On Trane YSC look at the economizer before the compressor. Commanded open? Blade actually open? Linkage off the shaft is a rooftop weekly. Probe RA in the return vs the module.
Expect: Blade matches the module command. Stuck open = overventilation. Stuck closed = no free cooling.
Walk the rest of RA ERR — 2 more checks after sign-in
CO2 SENS ERR (JADE LCD example)
JADE LCD: CO2 / SENS ERR. DCV sensor failed or the 0–10 V input is floating. Damper holds open; compressor never runs.
1 Damper position vs command
On Trane YSC look at the economizer before the compressor. Commanded open? Blade actually open? Linkage off the shaft is a rooftop weekly. Read CO2 in an empty space. 400–800 ppm typical empty retail. 2000 ppm empty is a failed sensor.
Expect: Blade matches the module command. Stuck open = overventilation. Stuck closed = no free cooling.
Walk the rest of CO2 ERR — 2 more checks after sign-in
ACT ERROR (JADE LCD example)
JADE LCD: ACT ERROR / ACT RANGE. Actuator did not follow command. Feedback pot off the shaft is the weekly.
1 Damper position vs command
On Trane YSC look at the economizer before the compressor. Commanded open? Blade actually open? Linkage off the shaft is a rooftop weekly. Command min → 100%. 2–10 V (or 24 V floating) at the actuator vs blade travel.
Expect: Blade matches the module command. Stuck open = overventilation. Stuck closed = no free cooling.
Walk the rest of ACT ERR — 2 more checks after sign-in
FREEZING (JADE LCD example)
JADE LCD: FREEZING. Mixed air below the low-limit. Damper drives shut; mechanical cool may lock.
1 Damper position vs command
On Trane YSC look at the economizer before the compressor. Commanded open? Blade actually open? Linkage off the shaft is a rooftop weekly. MAT vs a real probe. A failed MAT lying low is this, not a frozen DX coil.
Expect: Blade matches the module command. Stuck open = overventilation. Stuck closed = no free cooling.
Walk the rest of FREEZE — 2 more checks after sign-in
Not economizing when it should
OA is in the free-cooling window and the damper stayed shut. Title 24 FDD class.
1 Damper position vs command
On Trane YSC look at the economizer before the compressor. Commanded open? Blade actually open? Linkage off the shaft is a rooftop weekly. Confirm OA really is below the high-limit / enthalpy changeover on THIS module (not a 55 °F guess).
Expect: Blade matches the module command. Stuck open = overventilation. Stuck closed = no free cooling.
Walk the rest of Not econ — 2 more checks after sign-in
Economizing when it should not
Damper open with OA above changeover. Space hot, high OA bills, or wet coil.
1 Damper position vs command
On Trane YSC look at the economizer before the compressor. Commanded open? Blade actually open? Linkage off the shaft is a rooftop weekly. OA vs changeover setpoint. Sensor lying low (see OA T) is the usual.
Expect: Blade matches the module command. Stuck open = overventilation. Stuck closed = no free cooling.
Walk the rest of False econ — 2 more checks after sign-in
Excess outdoor air
Damper open past the commanded minimum with no economizer or DCV request.
1 Damper position vs command
On Trane YSC look at the economizer before the compressor. Commanded open? Blade actually open? Linkage off the shaft is a rooftop weekly. Commanded position vs blade. Feedback saying 80% when the board asked 15% is actuator/linkage.
Expect: Blade matches the module command. Stuck open = overventilation. Stuck closed = no free cooling.
Walk the rest of Excess OA — 2 more checks after sign-in
Damper not modulating
Damper is two-position (0 or 100) instead of tracking 2–10 V. Title 24 FDD class.
1 Damper position vs command
On Trane YSC look at the economizer before the compressor. Commanded open? Blade actually open? Linkage off the shaft is a rooftop weekly. 2–10 V at the actuator while OA is in the window. 0 V or 24 V only = module output or a two-position actuator installed by mistake.
Expect: Blade matches the module command. Stuck open = overventilation. Stuck closed = no free cooling.
Walk the rest of No mod — 2 more checks after sign-in
VFD / indoor-fan drive
The indoor fan is a drive, not a contactor + cap. Type the keypad string: oC, Uv, ov, GF, oH, PF.
1 Read the drive before you cycle power
On Trane YSC photograph the VFD keypad or the unit-board fan alarm (OC, LU, OU, GF, OH, limp). Power-cycle wipes what you needed. Photograph the drive keypad before you cycle power. Yaskawa/ABB show oC / Uv / ov; EcoBlue / Reliatel may say fan fail instead.
Expect: Live drive code written down. Line voltage at L1/L2/L3 of the drive.
Walk the rest of VFD — 2 more checks after sign-in
VFD enable missing
Drive has line voltage but will not run — the unit board never enabled it.
1 Read the drive before you cycle power
On Trane YSC photograph the VFD keypad or the unit-board fan alarm (OC, LU, OU, GF, OH, limp). Power-cycle wipes what you needed. 24 VAC (or the digital enable this drive uses) at the enable terminals while G / occupied / heat / cool is on.
Expect: Live drive code written down. Line voltage at L1/L2/L3 of the drive.
Walk the rest of Enable — 2 more checks after sign-in
VFD speed reference
Drive is enabled but stays at min Hz or 0 because analog / serial speed is missing.
1 Read the drive before you cycle power
On Trane YSC photograph the VFD keypad or the unit-board fan alarm (OC, LU, OU, GF, OH, limp). Power-cycle wipes what you needed. 0–10 VDC at the speed-reference pair under a high-fan call. Typical occupied cool is not 10 V — check the unit-board fan table.
Expect: Live drive code written down. Line voltage at L1/L2/L3 of the drive.
Walk the rest of 0-10V — 2 more checks after sign-in
oC / OC — overcurrent
Keypad example: oC (Yaskawa) or OC. Output current trip. Locked rotor, dirty filters, or FLA set too low.
1 Read the drive before you cycle power
On Trane YSC photograph the VFD keypad or the unit-board fan alarm (OC, LU, OU, GF, OH, limp). Power-cycle wipes what you needed. Spin the wheel by hand (power off). Debris, seized bearing, belt wrapped.
Expect: Live drive code written down. Line voltage at L1/L2/L3 of the drive.
Walk the rest of oC — 2 more checks after sign-in
Uv / LU — undervoltage
Keypad example: Uv (Yaskawa) or LU. DC bus dropped. Incoming power or a missing phase.
1 Read the drive before you cycle power
On Trane YSC photograph the VFD keypad or the unit-board fan alarm (OC, LU, OU, GF, OH, limp). Power-cycle wipes what you needed. Three legs at the drive line terminals, under load. A single-phased 3-phase drive nuisances Uv / oC.
Expect: Live drive code written down. Line voltage at L1/L2/L3 of the drive.
Walk the rest of Uv — 2 more checks after sign-in
ov / OU — overvoltage
Keypad example: ov (Yaskawa) or OU. DC bus high. Usually regen on decel, not a new drive.
1 Read the drive before you cycle power
On Trane YSC photograph the VFD keypad or the unit-board fan alarm (OC, LU, OU, GF, OH, limp). Power-cycle wipes what you needed. ov on shutdown = decel too fast; lengthen decel.
Expect: Live drive code written down. Line voltage at L1/L2/L3 of the drive.
Walk the rest of ov — 2 more checks after sign-in
GF — ground fault
Keypad example: GF. Drive sees current to ground on the motor leads.
1 Read the drive before you cycle power
On Trane YSC photograph the VFD keypad or the unit-board fan alarm (OC, LU, OU, GF, OH, limp). Power-cycle wipes what you needed. Megger the motor with the drive disconnected. A wet rooftop motor after a rain is this code.
Expect: Live drive code written down. Line voltage at L1/L2/L3 of the drive.
Walk the rest of GF — 2 more checks after sign-in
oH — heatsink overtemp
Keypad example: oH. Drive thermal trip.
1 Read the drive before you cycle power
On Trane YSC photograph the VFD keypad or the unit-board fan alarm (OC, LU, OU, GF, OH, limp). Power-cycle wipes what you needed. Drive fan spinning. Heat sink packed with roof lint.
Expect: Live drive code written down. Line voltage at L1/L2/L3 of the drive.
Walk the rest of oH — 2 more checks after sign-in
PF — input phase loss
Keypad example: PF. Missing or imbalanced incoming phase.
1 Three legs at the disconnect and the contactor
On Trane YSC measure L1 L2 L3 at the disconnect and at the compressor contactor. A phase monitor trips on loss, imbalance, or reverse rotation. L1 L2 L3 at the drive and at the disconnect. Tight lugs.
Expect: All three legs, nameplate voltage ±10%, phase monitor closed.
Walk the rest of PF — 2 more checks after sign-in
VFD limp / min Hz — fan prove
Drive is running too slow to close the prove switch, so the unit board reports fan fail. Reliatel example: Fan Fail with the drive still at min Hz.
1 Read the drive before you cycle power
On Trane YSC photograph the VFD keypad or the unit-board fan alarm (OC, LU, OU, GF, OH, limp). Power-cycle wipes what you needed. Min-frequency / limp parameter vs the prove-switch setpoint (often ~0.07" on some Reliatel cabinets).
Expect: Live drive code written down. Line voltage at L1/L2/L3 of the drive.
Walk the rest of Limp — 2 more checks after sign-in
Condensate / float
Float switch or tripped condensate opened 24V.
1 Float and the pan
On Trane YSC a drain / float code is water until proven otherwise. Pan full? Float stuck? Secondary drain piped? Roof drain pan, trap, and the overflow to the roof — not a furnace collector.
Expect: Pan dry after you clear it. Float moves freely.
Walk the rest of Drain — 2 more checks after sign-in
Limit / aux limit
Heat-exchanger or supply limit opened.
1 Airflow before you touch the limit
On Trane YSC a limit is airflow or overfire until proven otherwise. Do not replace the limit first. Filter, blower wheel, A-coil, and the heat-speed setting for THIS motor (tap, model plug, or communicating CFM — not a sister SKU chart). Filters, belt, blower rotation (3-phase indoor motors reverse).
Expect: TES / static: External static vs the blower table for this tonnage — rooftops run dirty.
Walk the rest of Limit — 2 more checks after sign-in
Rollout / flame spill
Flame left the burner box.
1 Treat this as flame outside the exchanger
Do not reset the Trane YSC rollout and walk away. Write the code, kill the call, and look for flame at the burners, crossover, and vestibule before you do anything else.
Expect: No flame outside the exchanger. Burners seated. Crossover lit.
If pass: Still inspect secondary / flue / condensate before you reset.
Walk the rest of Rollout — 2 more checks after sign-in
Ignition lockout
Trial for ignition failed after the IGC retries.
1 Watch one full try — do not reset
Write the Trane YSC code. Watch inducer, HSI glow, valve click, flame, µA. The step that dies is the repair. Resetting only burns another try into a harder lockout. Watch one try: inducer → PS → glow → valve click → flame. The dead step is the repair.
Expect: Call → Fan → Econo → Cool → Heat
Walk the rest of Ignition — 2 more checks after sign-in
Workflows
First step is on the chart. The sequence after that is Diagnose.
No cool, YSC
Space hot. Indoor fan may or may not be running.
1 Prove the call and the live code
This is a packaged rooftop. There is no split outdoor to walk to. Cool, heat, and the economizer share this curb.
Expect: Write whatever Reliatel (RTRM) — Precedent is showing. Reliatel LEDs / last fail before you cycle 24V.
If fail: No call at the IFC → stat / harness. Do not change gas parts.
Continue this workflow — 2 more steps in Diagnose
No heat, YSC
Cool works or the space is cold on a W call.
1 Prove the call and the live code
Heat is the IGC / ignition module in the heat section — not the economizer board and not the compressor contactor.
Expect: Write whatever Reliatel (RTRM) — Precedent is showing. Reliatel LEDs / last fail before you cycle 24V.
If fail: No call at the IFC → stat / harness. Do not change gas parts.
Continue this workflow — 2 more steps in Diagnose
Economizer, YSC
Building hot with the compressor off, or high OA bills, or mixed air wrong.
1 Prove the call and the live code
Read the module in THIS hood (JADE W7220 / W7212 / Reliatel / Prodigy / factory FDD). Write the live alarm — OA T, MAT, CO2, ACT, not-economizing, excess OA.
Expect: Write whatever Reliatel (RTRM) — Precedent is showing. Reliatel LEDs / last fail before you cycle 24V.
If fail: No call at the IFC → stat / harness. Do not change gas parts.
Continue this workflow — 2 more steps in Diagnose
High static / limit / belt, YSC
Limit trips, noisy cabinet, or poor airflow on a rooftop.
1 Prove the call and the live code
Total external static vs the blower table for THIS tonnage and heat size. Rooftop ductboard and dirty 2" filters are the usual miss.
Expect: Write whatever Reliatel (RTRM) — Precedent is showing. Reliatel LEDs / last fail before you cycle 24V.
If fail: No call at the IFC → stat / harness. Do not change gas parts.
Continue this workflow — 2 more steps in Diagnose
VFD / indoor fan, YSC
Fan prove, no airflow, drive display in alarm, or EcoBlue / Reliatel limp.
1 Prove the call and the live code
Read the drive keypad (OC, LU, OU, GF, OH) or the unit-board fan alarm before you cycle 24V.
Expect: Write whatever Reliatel (RTRM) — Precedent is showing. Reliatel LEDs / last fail before you cycle 24V.
If fail: No call at the IFC → stat / harness. Do not change gas parts.
Continue this workflow — 2 more steps in Diagnose
Test points
Y1 at controller
~24 VAC on a mechanical-cool call. 0 V if the economizer is satisfying.
Contactor coil
~24 VAC when the board commands the compressor. 0 V with Y1 present = board or lockout.
HPS / LPS
Closed in the run circuit when pressures are legal. Open is a switch or a real pressure problem.
3-phase
All three legs, correct rotation. Nameplate voltage ±10%.
TES / static
External static vs the blower table for this tonnage — rooftops run dirty.
OA / MAT
Module reading vs a real thermometer at the hood and in the mixed-air stream.
Actuator
2–10 V (or 24 V floating) tracks commanded damper. Blade moves with voltage.
VFD enable
~24 VAC (or this drive’s digital enable) while G / occupied / a call is on.
VFD 0–10 V
Analog speed present under a high-fan call. 0 V with enable is a board/wire, not a motor.
IGC W
~24 VAC on a heat call.
Flame rod
µA DC per the IGC sticker in this heat section. Rising while running.
Manifold
Rating plate wins. Roof gas piping often starves high-fire.
Gotchas
- Packaged rooftop — one nameplate. Do not pick a split furnace + condenser pair for this call.
- Economizer can run the building without the compressor. Look at the damper before you condemn a scroll.
- 3-phase rotation and a roof full of lint are the first two measurements, not a charge chart.
- Type the live string in Diagnose. Examples: IGC 2-flash / 8-flash, JADE MA SENS ERR / ACT ERROR, Reliatel Fan Fail, VFD oC / Uv / GF. The sticker or LCD in THIS cabinet is the book.
- YSC vs YHC: efficiency and options. Reliatel language is shared until Symbio shows up.
- WSC is the heat-pump Precedent — add RV/defrost, drop the IGC.
Related plates
Install this plate
Install Trane YSC as Precedent packaged · Reliatel · 3–10 t class.
Precedent packaged · Reliatel · 3–10 t class
This plate — not the sister SKU
- Not Voyager 12.5–25 t (different cabinet). Not a residential S9V2 furnace. Not Symbio 700 until the board in the control box says so.
- Packaged rooftop — one nameplate. Do not pick a split furnace + condenser pair for this call.
- Economizer can run the building without the compressor. Look at the damper before you condemn a scroll.
- 3-phase rotation and a roof full of lint are the first two measurements, not a charge chart.
- Type the live string in Diagnose. Examples: IGC 2-flash / 8-flash, JADE MA SENS ERR / ACT ERROR, Reliatel Fan Fail, VFD oC / Uv / GF. The sticker or LCD in THIS cabinet is the book.
Controller on this rooftop
- Reliatel LEDs and the service button, not a residential S-series 7-seg. Type the name as displayed: Heat Fail, Cool Fail, Fan Fail.
- Heat fail vs cool fail vs fan fail are different paths. Fan prove on VFD cabinets is a known nuisance if the motor is in limp — example: Fan Fail with the drive still at min Hz.
- If the board says Symbio 700, leave this Reliatel chart — alarm lists are not interchangeable.
Hardware
- Size: Precedent 3–10 t class on this chart. 12.5 t+ may be Voyager — different book.
- Heat / cool: YSC gas, TSC cool/electric, WSC heat pump, YHC high-efficiency gas.
- Controls: Reliatel RTRM / RTOM. Heat fail, cool fail, fan fail are Reliatel language.
First fire
- 1This is a packaged rooftop. There is no split outdoor to walk to. Cool, heat, and the economizer share this curb.
- 2Prove 24 VAC Y1 at the unit controller under a cool call. Occupied/G first — a unoccupied shutdown looks like a dead compressor.
- 3Look at the economizer. Damper commanded open on cold OA? Mixed-air sensor lying? Compressor off by design is not a failed contactor.
- 4If the board is actually asking for mechanical cool: 24 VAC at the contactor coil, then cap, then rotation on 3-phase, then HPS/LPS, then pressures.
- 5Roof condenser: cottonwood, cardboard, hail guards packed with lint. High head here is dirt until proven otherwise.
Do not on Trane YSC
- Not Voyager 12.5–25 t (different cabinet). Not a residential S9V2 furnace. Not Symbio 700 until the board in the control box says so.
- Packaged rooftop — one nameplate. Do not pick a split furnace + condenser pair for this call.
- Economizer can run the building without the compressor. Look at the damper before you condemn a scroll.
Maker literature
Spec sheets open the manufacturer’s PDF. FieldBench does not host those files. Install I/O is often dealer-gated — the literature search is for that, not a homepage.
- Open manufacturer wiring diagramWiring / I/OMaker I/O / wiring for this rooftop. Opens the manufacturer site — FieldBench does not host or redraw the schematic.Open manufacturer wiring diagram
- Honeywell JADE W7220 economizer moduleWiring / I/OPublic module page for the FDD economizer in many 3–15 t hoods. Wiring silk is on the module — FieldBench does not host the I/O PDF.Open manufacturer wiring diagram
- Trane e-Library (public search)Literature searchSearch the plate (S9V2, S9X2, XV20i). Full I/O often needs a dealer login.Open literature search
Warranty and bulletins
Affected models, serial range, symptom, remedy, date. Maker files open on the manufacturer site.
Residential limited warranty
warranty sheetTrane furnace warranty hub
Registered residential furnace warranty · Limited warranty certificate
Dealer portals
dealerWhere remaining service letters live
Current-year service letters not on a public literature page · Maker dealer portal