FieldBench

Carrier

24TPA7

AC · Performance · two-stage condensing unit

Carrier Performance two-stage air conditioner. Y1/Y2, two-stage scroll, InteliSense-capable on late boards. Not Infinity ABCD and not a single-stage 24ACC6.

Not 24VNA6 / 26VNA1 (inverter, no Y2). Not 24ACC6 / 26SCA5 (single-stage, one Y). Not 26TPA8 (R-454B two-stage).

Maker PDFs

Walk this in Diagnose

This plate

Stages
Two-stage scroll · Y1 low / Y2 high
Control
24V Y1/Y2. InteliSense when paired with a participating stat
Refrigerant
R-410A on this generation
Sister
Bryant 148TAN / 187B (Preferred / Evolution two-stage cousins — different bus on 187B)

This board

Two-stage outdoor — Y1/Y2, not Infinity drive

  • No inverter L-codes. If you see them, you are on 24VNA6.
  • High stage is Y2 at the outdoor. A single-stage stat never pulls high.
  • HPS in the coil circuit on typical Performance wiring.

Sequence

  1. Y1. Low-stage compressor. Indoor blower on low/mid cool.
  2. Y2. High-stage. Head and SC should rise.
  3. HPS. Opens the coil. Silence or chatter — not an L-code.

Faults on this IFC

  • HPS

    High pressure switch open

    lockout

    Outdoor HPS opened — coil circuit is dead. Not an inverter pressure fault and not an L-code.

    • HPS continuity, reset if manual, wiring in series with the coil.
    • Outdoor airflow: dirty coil, bent fins, fan not running (see ODF / cap).
    • Overcharge or non-condensables — confirm indoor metering before you recover (SH vs SC).
    • Do not treat this as a 25VNA drive trip.
  • ODF

    Outdoor fan fail

    warn

    Fan not turning. Compressor may still run and then HPS.

    • Dual-cap FAN section µF vs sticker. A good HERM and a dead FAN is the usual Comfort call.
    • Fan motor ohms / ground, blade clearance, capacitor wiring (C / FAN / HERM).
    • Not an inverter fan module — there isn’t one.
  • Contactor

    Contactor / coil

    warn

    Will not pull, chatters, or is welded.

    • 24 VAC at the coil under a Y call. Low voltage = long stat wire, weak indoor transformer, or a furnace 24 (fuse) problem.
    • Coil ohms / burned turns. Pitted or welded points — replace, do not file and leave.
    • Chatter: low 24V, bad coil, weak transformer — not an inverter ramp.
  • Cap

    Dual run capacitor

    warn

    HERM and/or FAN section out of rating. Single-stage Comfort dies this way all summer.

    • Both sections vs microfarad rating, not just one.
    • Bulged can, open bleed, wrong replacement (single vs dual, voltage).
    • Hard-start add-ons do not fix a dead FAN section.
  • Charge

    Charge (SH piston / SC TXV)

    warn

    Wrong charge method is as common as wrong charge.

    • Indoor piston: charge by superheat. Indoor TXV: charge by subcooling.
    • Do not use Greenspeed weigh-in-only as the only method unless the factory TXV rating plate on THIS outdoor says so. Most 24ACC are piston/TXV conventional.
    • Line-set length and indoor coil match still matter. Weigh-in after a repair, then finish on SH or SC.

Workflows

24TPA7 stuck on low

Runs but never gets cold enough on a design day.

  1. Y2 at the outdoor under a 2-cool call. Missing Y2 is a stat / indoor IFC / wire issue, not a weak compressor.
  2. Then SC on the TXV indoor. Two-stage charge is not a 24ACC6 single-stage shortcut.
  3. This is not 24VNA6. There is no drive to reset.

Identify 24TPA7 vs 24ACC6 vs 24VNA6

Invoice just says Carrier AC.

  1. One Y / one contactor / dual cap = 24ACC6 Comfort.
  2. Y1 and Y2 / two-stage scroll = 24TPA7 (this plate).
  3. No contactor + ABCD + inverter = 24VNA6.

Test points

Contactor coil
Stable ~24 VAC on Y. Chatter = voltage, coil, or HPS. No ABCD to probe.
Dual cap
HERM and FAN both within ~6% (or OEM) of the stamped µF.
Charge
SH target on piston indoor; SC target on TXV indoor. Weigh-in is a start, not a Greenspeed-only finish.
HPS
Closed at rest. Open under high head = airflow/charge, not an inverter L-code.

Gotchas

  • InteliSense does not turn this into Infinity ABCD.
  • 26TPA8 is the R-454B replacement shape.

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