FieldBench

ICP

N4A5S

AC · Comfortmaker / Heil / Tempstar · single-stage · R-410A

ICP-platform single-stage R-410A condensing unit (Comfortmaker N4A5S / N4A4S; Heil H4A5; Tempstar T4A5). Contactor + dual cap. Carrier Comfort-class physics. Not the N5A5S R-454B replacement.

Not N5A5S (R-454B). Not N4A7T / N5A8T two-stage. Not a Carrier 24VNA inverter.

Walk this in Diagnose

This plate

Refrigerant
R-410A
Stages
Single-stage · one Y
Sister
Carrier 24ACC6 / 24SCA5 · Heil H4A5 · Tempstar T4A5

This board

ICP Comfort contactor · R-410A

  • No Infinity outdoor.
  • Plate R-410A. N5A5S is R-454B.

Sequence

  1. Y. Indoor stat Y → 24 VAC across outdoor C and contactor coil. Contactor pulls in → compressor + outdoor fan on the dual cap.
  2. HPS. High-pressure switch opening drops the coil. Contactor drops. No inverter alarm, just silence or chatter.
  3. Charge. Piston indoor: set by superheat. TXV indoor: set by subcooling. Rating-plate weigh-in is a starting point, not the Greenspeed-only method.

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

No cool, N4A5S / H4A5

Indoor running, outdoor dead.

  1. 24 VAC at the contactor.
  2. Dual cap, then 410A SH or SC.
  3. N5 on the plate = other refrigerant.

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

  • Heil / Tempstar / Arcoaire / Day & Night singles with a 4A5 / 4A4 body search here.

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