FieldBench

Trane

XV20i

Heat pump · 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.

Walk this in Diagnose

This plate

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.

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

  • 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.

    • Data pair landing and polarity at outdoor, indoor, and stat. No 24V on the pair.
    • Outdoor board powered (line voltage). Comm LED vs inverter-fault LED — they are different stories.
    • Isolate: indoor-only bus, then add outdoor. A cooked drive can take the whole ComfortLink down.
  • 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.

    • Compressor to ground and winding integrity. Heat sink / drive cooling path.
    • Supply voltage at the outdoor (208–230 class). Brownout plus a long line-set is a real trip.
    • Weigh-in vs nameplate before you condemn a drive on a charge-related overcurrent.
  • HPS / LPS

    Pressure protection

    lockout

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

    • Outdoor fan actually running? A failed outdoor fan on this unit is a drive/fan-motor path, not a cap.
    • Coil cleanliness both sides.
    • Charge is weigh-in + line-set. Do not ‘top off’ to a piston SH number.
  • 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.

    • Ohms vs the XV20i / 4TWV0 sensor chart. Connector at the drive.
    • A physically iced coil with a good sensor is airflow or charge — not a ‘bad defrost board’ from an XR14.
  • Outdoor fan

    Failed outdoor fan

    lockout

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

    • Command vs spin. Fan motor and drive output — there is no dual run cap to throw first.
    • Debris, ice, seized bearing.

Workflows

Outdoor silent, indoor calling

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

  1. ComfortLink event list first. Bus fault vs drive fault vs pressure vs sensor — do not gauge up on a comm code.
  2. Outdoor powered? Drive LEDs: comm/data pair vs inverter overcurrent / overheat. Write them.
  3. If the bus is healthy and the drive is faulted, treat OC/OH / HPS / LPS / fan / sensors next. Still not a contactor.
  4. Charge last, and only as weigh-in + line-set. Superheat on a variable drive is not a piston SH chart.
  5. Do not pair this call with S9V2 furnace E2.1. Indoor furnace retry lockout is a different box and a different chart.

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

  • trane-xv18 — TruComfort inverter AC-only cousin — no RV, no defrost.
  • trane-xr16 — XR single-stage contactor AC. Opposite of this drive.
  • trane-xc95m — ComfortLink indoor commonly paired with this outdoor.
  • trane-s9v2 — 24V furnace. Do not mix E2.1 / CoF / Ht1 with outdoor drive faults.