Traneheat pump

XV20i

ComfortLink · inverter heat pump

Trane/AS XV20i / 4TWV0 communicating inverter heat pump. Outdoor drive + ComfortLink data pair. Not an XR14 contactor unit. Indoor is on the bus (often XC95m / communicating air handler). Charge is weigh-in + line-set — not a piston superheat chart.

Not XR14 / XR15 / XR16 contactor + dual-cap singles. Not a 24V Y1/Y2 two-stage that you gauge like a piston 14 SEER. Do not pair diagnostics with S9V2 furnace E2.1.

Diagnose this model Install notes Board cross-ref Field wiring

Drive

Outdoor inverter scroll · variable capacity

Bus

ComfortLink / AccuLink data pair to stat and indoor

Fan

Variable outdoor fan on the drive — not a simple PSC + cap

Charge

Weigh-in + line-set adder. Not a piston SH chart.

Sister SKU

American Standard Platinum 20 / 4A6V0

This board

Outdoor inverter + ComfortLink

Stat / ComfortLink events first. The wall control names comm, sensor, and drive faults in English.
Then the outdoor drive LEDs: comm/data pair vs inverter overcurrent / overheat. Write both before you pull the disconnect — disconnect clears live status.
No conventional Y1/Y2 staging. Capacity is serial. A 24V stat will not run this outdoor as designed.
Do not read S9V2 furnace E-decimals onto this drive. Indoor E2.1 is a different box.

ComfortLink last events. Outdoor drive last-fault / LED if the stat is blank.

Universal swap

No universal

Inverter outdoor. No furnace IFC.

White-Rodgers

—

ICM

—

Honeywell

—

Indoor furnace universals (50A55, 50M56U, ICM282B, ICM2811). This is not an IFC.
Do not ‘adapt’ a furnace board to an outdoor inverter or defrost PCB.

After you pull the dead card

1OEM ComfortLink outdoor inverter control.

Field wiring

Written landings for Trane XV20i. Not a factory schematic.

ComfortLink / AccuLink inverter AC

ComfortLink data pairR-410A

Trane / American Standard XV18 class. Communicating inverter air conditioner. Not XR16 Y/C. Not XV20i (that outdoor has a reversing valve).

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.

Open manufacturer PDF

This indoor

ComfortLink indoor. This is the HP twin of XV18 — RV + defrost live on the drive.

ComfortLink pair

Communicating indoor (XC95m / communicating AH) and ComfortLink stat.

ComfortLink control

English events on the wall control. Data, not Y.

DATA+ComfortLinkData
DATA−ComfortLinkData
R24V if the control needs it24V
CCommon24V

Communicating indoor

S9V2 24V is a mixed pair — do not diagnose the outdoor with furnace E2.1.

DATA+ComfortLinkData
DATA−ComfortLinkData

Outdoor drive

Comm LED vs inverter-fault LED. Write both before the disconnect.

DATA+ComfortLinkData
DATA−ComfortLinkData

Outdoor line — inverter drive

208/230 into the drive. No contactor slam. DC bus can stay live after the disconnect.

L1Line to the driveLine
L2Line to the driveLine
GNDEquipment groundLine

Landing

DataStat pairindoor pairoutdoor pair
Data. Not 24 VAC Y.
LineL1 / L2drive
208/230

Prove it

ComfortLink event list. Bus vs drive vs pressure vs sensor.
Weigh-in + line-set. Not an XR16 piston SH chart.

Do not

Do not apply the XR16 / XR14 Y/C / dual-cap diagram.
Do not ohm a defrost sensor on XV18. That is XV20i.

DATA+/DATA− here means the ComfortLink pair on the silk — not a made-up J-number.

Sequence

1
Call
Stat requests capacity. Indoor IFC/AH sets CFM. Outdoor inverter ramps. No contactor slam.
2
Defrost
Drive + indoor coordinate. A failed outdoor coil / discharge sensor looks like ‘always iced’ or ‘never defrosts.’
3
Protect
HPS / LPS and inverter overcurrent / overheat park the drive. LEDs tell you which — not a furnace retry lockout.

Faults on this IFC

Step 1, then 2, then 3. Expected reading and the fail branch sit under each check.

Comm / data pair

ComfortLink indoor-outdoor drop

lockout

Stat, indoor, or outdoor off the bus. Outdoor silent while the indoor is calling is often this — or a dead drive. Check bus vs drive LEDs before you gauge.

1 Let it cool, then read the drive LED
On Trane XV20i overcurrent / overheat is often a dirty coil, a failed OD fan, or a locked compressor — not a dead inverter. Clear airflow, confirm the OD fan, and read the drive LED before you order a control. Data pair landing and polarity at outdoor, indoor, and stat. No 24V on the pair.
Expect: OD fan running. Coil clean. Drive LED decoded from THIS outdoor’s card.
2 Voltage and compressor windings
Incoming voltage in range (this plate’s line-voltage code). Compressor windings even, no ground. A shorted compressor will kill a new drive. Outdoor board powered (line voltage). Comm LED vs inverter-fault LED — they are different stories.
Expect: Balanced windings. No winding to ground. Line voltage stable under load.
3 Charge and the drive last
A starved or flooded compressor will overcurrent. Confirm SH/SC and charge weight. Only then condemn the inverter. Isolate: indoor-only bus, then add outdoor. A cooked drive can take the whole ComfortLink down.
Expect: Charge on the nameplate. Drive code gone after a cool-down and a clean coil.

Inverter OC / OH

Drive overcurrent / overheat (drive LED)

lockout

Outdoor inverter protection. Read the drive LED / ComfortLink text. Not a contactor or dual-cap failure.

1 Let it cool, then read the drive LED
On Trane XV20i overcurrent / overheat is often a dirty coil, a failed OD fan, or a locked compressor — not a dead inverter. Clear airflow, confirm the OD fan, and read the drive LED before you order a control. Compressor to ground and winding integrity. Heat sink / drive cooling path.
Expect: OD fan running. Coil clean. Drive LED decoded from THIS outdoor’s card.
2 Voltage and compressor windings
Incoming voltage in range (this plate’s line-voltage code). Compressor windings even, no ground. A shorted compressor will kill a new drive. Supply voltage at the outdoor (208–230 class). Brownout plus a long line-set is a real trip.
Expect: Balanced windings. No winding to ground. Line voltage stable under load.
3 Charge and the drive last
A starved or flooded compressor will overcurrent. Confirm SH/SC and charge weight. Only then condemn the inverter. Weigh-in vs nameplate before you condemn a drive on a charge-related overcurrent.
Expect: Charge on the nameplate. Drive code gone after a cool-down and a clean coil.

HPS / LPS

Pressure protection

lockout

Still real on an inverter. High = outdoor airflow / overcharge / restriction. Low = charge, indoor airflow, metering.

1 Let it cool, then read the drive LED
On Trane XV20i overcurrent / overheat is often a dirty coil, a failed OD fan, or a locked compressor — not a dead inverter. Clear airflow, confirm the OD fan, and read the drive LED before you order a control. Outdoor fan actually running? A failed outdoor fan on this unit is a drive/fan-motor path, not a cap.
Expect: OD fan running. Coil clean. Drive LED decoded from THIS outdoor’s card.
2 Voltage and compressor windings
Incoming voltage in range (this plate’s line-voltage code). Compressor windings even, no ground. A shorted compressor will kill a new drive. Coil cleanliness both sides.
Expect: Balanced windings. No winding to ground. Line voltage stable under load.
3 Charge and the drive last
A starved or flooded compressor will overcurrent. Confirm SH/SC and charge weight. Only then condemn the inverter. Charge is weigh-in + line-set. Do not ‘top off’ to a piston SH number.
Expect: Charge on the nameplate. Drive code gone after a cool-down and a clean coil.

Discharge / coil sensors

Outdoor thermistors

warn

Discharge or outdoor-coil sensor open/short/out of range. ComfortLink will name which. Defrost and drive protection both lie when these are wrong.

1 Is it actually in defrost?
On Trane XV20i confirm the board thinks it is in defrost: OD fan off, RV shifted, indoor calling heat/aux. A failed OD fan in heat ices the coil and looks like a defrost board. Ohms vs the XV20i / 4TWV0 sensor chart. Connector at the drive.
Expect: Defrost only with a cold outdoor coil, not on every call.
2 Coil sensor and termination
Defrost sensor / coil thermistor ohms vs the chart. A sensor hanging off the coil never terminates. Time/temp terminate should end with the fan back on. A physically iced coil with a good sensor is airflow or charge — not a ‘bad defrost board’ from an XR14.
Expect: Sensor seated and in range. Defrost ends. Fan restarts.
3 Board vs the valve
If the board never initiates on a frozen coil, force a defrost and watch outputs. If it initiates and never ends, sensor or board. Do not leave it in a forced defrost.
Expect: One forced defrost that terminates. Then a normal heat cycle.

Outdoor fan

Failed outdoor fan

lockout

Fan not following the drive. Head pressure climbs, HPS or inverter OH follows.

1 Let it cool, then read the drive LED
On Trane XV20i overcurrent / overheat is often a dirty coil, a failed OD fan, or a locked compressor — not a dead inverter. Clear airflow, confirm the OD fan, and read the drive LED before you order a control. Command vs spin. Fan motor and drive output — there is no dual run cap to throw first.
Expect: OD fan running. Coil clean. Drive LED decoded from THIS outdoor’s card.
2 Voltage and compressor windings
Incoming voltage in range (this plate’s line-voltage code). Compressor windings even, no ground. A shorted compressor will kill a new drive. Debris, ice, seized bearing.
Expect: Balanced windings. No winding to ground. Line voltage stable under load.
3 Charge and the drive last
A starved or flooded compressor will overcurrent. Confirm SH/SC and charge weight. Only then condemn the inverter.
Expect: Charge on the nameplate. Drive code gone after a cool-down and a clean coil.

Workflows

Outdoor silent, indoor calling

House is calling cool or heat, indoor blower may be moving, outdoor is dead quiet.

1 Prove the call and the live code
ComfortLink event list first. Bus fault vs drive fault vs pressure vs sensor — do not gauge up on a comm code.
Expect: Write whatever Outdoor inverter + ComfortLink is showing. ComfortLink last events. Outdoor drive last-fault / LED if the stat is blank.
If fail: No call at the IFC → stat / harness. Do not change gas parts.
2 Isolate the first failed step in the sequence
Outdoor powered? Drive LEDs: comm/data pair vs inverter overcurrent / overheat. Write them.
Expect: Defrost: Drive + indoor coordinate. A failed outdoor coil / discharge sensor looks like ‘always iced’ or ‘never defrosts.’
3 Confirm with a number, then the next part
If the bus is healthy and the drive is faulted, treat OC/OH / HPS / LPS / fan / sensors next. Still not a contactor. Charge last, and only as weigh-in + line-set. Superheat on a variable drive is not a piston SH chart. Do not pair this call with S9V2 furnace E2.1. Indoor furnace retry lockout is a different box and a different chart.
Expect: Bus: ComfortLink pair at the outdoor. Data, not 24 VAC Y. · Drive LEDs: Comm vs inverter protect. Write both before the disconnect.
If fail: Stay on this plate. The out-of-range reading is the part.
If pass: Reading in range → the next step in this workflow is the repair.

Test points

Bus

ComfortLink pair at the outdoor. Data, not 24 VAC Y.

Drive LEDs

Comm vs inverter protect. Write both before the disconnect.

Charge

Recover and weigh. Nameplate + ounces/ft. Not piston SH.

Gotchas

XR14-style contactor/cap diagnostics do not apply. There is no dual run cap to change first.
American Standard Platinum 20 / 4A6V0 is the badge twin.
Indoor may be XC95m (ComfortLink modulating furnace) or a communicating air handler. An S9V2 24V indoor is a mixed pair — do not diagnose the outdoor with furnace E2.1.
Inverter DC bus can hold a charge after disconnect. Treat the drive as live until it is proven down.

Related plates

Install this plate

Install XV20i as ComfortLink inverter outdoor. Weigh-in. Pair to XC95m-class indoor.

Inverter HP · ComfortLink · weigh-in · not a 24V contactor outdoor

Pair & charge

Communicating cable to the ComfortLink indoor. A 24V S9V2 furnace is the wrong control story.
Weigh-in + adder. Drive faults live on this outdoor.

First fire

1Bus pair, weigh-in, cool then heat.

Do not on Trane XV20i

Do not apply S9V2 E2.1 / CoF indoor codes to this drive.

Maker literature

FieldBench does not host manufacturer files. Each link opens the maker’s own literature page in a new tab.

XV20i product pageProduct pageOpen manufacturer PDF
Trane owner’s guidesOwner guidePublic owner manuals. Install / service literature lives in Trane e-Library (dealer).Open manufacturer PDF
Trane e-Library (public search)Literature searchSearch the plate (S9V2, S9X2, XV20i). Full I/O often needs a dealer login.Open manufacturer PDF
Trane e-Library searchLiterature searchSearch Trane XV20i on the maker’s literature page.Open manufacturer PDF

Warranty and bulletins

Affected models, serial range, symptom, remedy, date. Maker files open on the manufacturer site.

All bulletins

Residential limited warranty
warranty sheet
Trane furnace warranty hub
Registered residential furnace warranty · Limited warranty certificate
Open facts Open manufacturer PDF
Dealer portals
dealer
Where remaining service letters live
Current-year service letters not on a public literature page · Maker dealer portal
Open facts Open manufacturer PDF