50FC

This board

WeatherMaker unit board · no IGC

• There is no ignition LED to count. Cool, fan, electric heat, economizer, and HP defrost live on the unit board.
• Electric heat: sequencer / kit fuses / 24V on W1/W2 at the board.

Sequence

1. Call. Y1 cool, O/B or W1 heat-pump heat, W2/E electric heat. Same cabinet — no line set to a split outdoor.
2. Fan. Indoor blower on G or on the unit controller. Defrost still needs indoor air.
3. Econo. Economizer can satisfy cool without the compressor. Heat-pump heat ignores the damper.
4. Shift. RV solenoid is in this box. No shift = O/B at the board, then coil ohms, then stuck piston.
5. Defrost. Time/temp or demand defrost on the unit controller. Electric heat may run as aux during defrost.

Faults on this IFC

• HPS

  High pressure

  lockout

  Discharge / liquid opened the high-pressure switch.

  • OD coil packed. Fan running and correct rotation on 3-phase.
  • Overcharge or non-condensables. Recirc over a low roof screen.
  • Indoor airflow so bad the refrigerant has nowhere to go — still an HPS trip.
• LPS

  Low pressure / freeze

  lockout

  Suction dropped out the low-pressure switch.

  • Charge / leak. Filters and indoor coil first — a dirty rooftop ices like a starved piston.
  • TXV / orifice. Economizer dumping 40 °F OA on the coil can look like a freeze-stat trip.
  • Do not add gas because suction is low.
• Contactor

  No start / hum

  lockout

  Y1 at the board, compressor not running.

  • 24 VAC across the coil. Then dual cap (if this chassis has one) or VFD / two-stage unload.
  • 3-phase: phase loss, reverse rotation. A scroll run backwards is loud and pumps no gas.
  • Internal overload. Let it cool; find why it overheated.
• Fan prove

  Indoor fan proving

  lockout

  Controller did not see blower current / pressure.

  • Belt off, ECM alarm, or current switch around the wrong lead.
  • VFD in limp mode on some Trane/VFD cabinets will not make the prove switch.
  • Do not jumper fan-prove and walk away — heat will fire into a dead blower.
• Smoke

  Smoke / firestat

  hazard

  Supply or return smoke detector, or a firestat, has the unit locked out.

  • Reset only after you know why it tripped. Welding and dirty returns nuisance-trip these.
  • The unit board sees this as a shutdown, not a refrigerant fault.
• Phase

  Phase loss / rotation

  lockout

  Three-phase monitor opened.

  • Measure all three legs at the disconnect and at the contactor.
  • Condenser fan and compressor rotation. Swap two legs only after you confirm this unit is 3-phase on the plate.
• Econo

  Economizer FDD

  warn

  Start here when the hood is the complaint. Title 24 FDD classes: sensor, not-economizing, false-economizing, damper not modulating, excess OA.

  • 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.
  • Blade vs command first. Then OA / RA / MAT vs a real thermometer. Then Y1 vs compressor.
  • Do not add refrigerant because mixed air is cold — that is often the damper.
• MA ERR

  MA SENS ERR (JADE LCD example)

  warn

  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.

  • Probe mixed air after the damper vs MAT on the module.
  • Ohm the MA sensor. Open/short or a sensor in the OA stream is this code.
  • MAT lying high keeps mechanical cool off. MAT lying low drives the damper shut or trips FREEZING.
• OA ERR

  OA SENS ERR (JADE LCD example)

  warn

  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.

  • Probe OA at the hood vs the module. Several degrees off is a sensor, not a damper.
  • Ohm / SYLK the OA sensor. Cut 2-wire in the hood is weekly.
  • Sun-soaked hood vs a shaded probe — measure the air the sensor sees.
• RA ERR

  RA SENS ERR (JADE LCD example)

  warn

  JADE LCD: RA / SENS ERR. Return-air thermistor failed. Differential / enthalpy changeover compares OA to RA.

  • Probe RA in the return vs the module.
  • A missing RA sensor on a differential setup looks like false economizing.
• CO2 ERR

  CO2 SENS ERR (JADE LCD example)

  warn

  JADE LCD: CO2 / SENS ERR. DCV sensor failed or the 0–10 V input is floating. Damper holds open; compressor never runs.

  • Read CO2 in an empty space. 400–800 ppm typical empty retail. 2000 ppm empty is a failed sensor.
  • 0–10 V at the DCV input vs the sensor. If DCV is unused, set the input OFF on JADE.
• ACT ERR

  ACT ERROR (JADE LCD example)

  warn

  JADE LCD: ACT ERROR / ACT RANGE. Actuator did not follow command. Feedback pot off the shaft is the weekly.

  • Command min → 100%. 2–10 V (or 24 V floating) at the actuator vs blade travel.
  • Linkage on the shaft. Seized blades. A 24 V actuator on a 2–10 V output.
• FREEZE

  FREEZING (JADE LCD example)

  warn

  JADE LCD: FREEZING. Mixed air below the low-limit. Damper drives shut; mechanical cool may lock.

  • MAT vs a real probe. A failed MAT lying low is this, not a frozen DX coil.
  • Damper stuck open dumping 30 °F OA on the mixed-air sensor — walk ACT ERROR first.
  • True freeze: indoor airflow and charge after the damper is explained.
• Not econ

  Not economizing when it should

  warn

  OA is in the free-cooling window and the damper stayed shut. Title 24 FDD class.

  • Confirm OA really is below the high-limit / enthalpy changeover on THIS module (not a 55 °F guess).
  • Y1 present? Some modules will not economize without a cool call.
  • Min-position only, jammed blades, or a MAT low-limit holding the damper closed.
  • Mechanical cool running in 50 °F OA is this fault until the damper moves.
• False econ

  Economizing when it should not

  warn

  Damper open with OA above changeover. Space hot, high OA bills, or wet coil.

  • OA vs changeover setpoint. Sensor lying low (see OA T) is the usual.
  • Min position cranked to 40% on a small store. DCV failed high.
  • Power-fail default on some actuators is spring-open — they dump OA with 24 V lost.
• Excess OA

  Excess outdoor air

  warn

  Damper open past the commanded minimum with no economizer or DCV request.

  • Commanded position vs blade. Feedback saying 80% when the board asked 15% is actuator/linkage.
  • Barometric relief / power exhaust stuck open looks like excess OA at the space.
  • Unoccupied damper should go to the unoccupied minimum, often 0. A 24 V occupancy point stuck high holds min all night.
• No mod

  Damper not modulating

  warn

  Damper is two-position (0 or 100) instead of tracking 2–10 V. Title 24 FDD class.

  • 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.
  • JADE set for 2-position vs modulating. Direct-coupled actuator vs a 24 V floating that someone landed on analog.
  • Stuck at 50% is a failed actuator, not ‘modulating.’
• VFD

  VFD / indoor-fan drive

  lockout

  The indoor fan is a drive, not a contactor + cap. Type the keypad string: oC, Uv, ov, GF, oH, PF.

  • Photograph the drive keypad before you cycle power. Yaskawa/ABB show oC / Uv / ov; EcoBlue / Reliatel may say fan fail instead.
  • Enable present? Speed reference present? Motor spinning and proving?
  • Do not throw a dual run cap at a VFD motor.
• Enable

  VFD enable missing

  warn

  Drive has line voltage but will not run — the unit board never enabled it.

  • 24 VAC (or the digital enable this drive uses) at the enable terminals while G / occupied / heat / cool is on.
  • 0 V enable with a live G = unit board output or a smoke/firestat shutdown still open.
  • Some EcoBlue / Reliatel cabinets enable on a board relay, not on G from the stat.
• 0-10V

  VFD speed reference

  warn

  Drive is enabled but stays at min Hz or 0 because analog / serial speed is missing.

  • 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.
  • 0 V with enable = broken analog wire, board analog dead, or the drive is set for a different reference (serial vs 0–10).
  • 10 V at all times = board commanding 100%. High static / oC will follow.
• oC

  oC / OC — overcurrent

  lockout

  Keypad example: oC (Yaskawa) or OC. Output current trip. Locked rotor, dirty filters, or FLA set too low.

  • Spin the wheel by hand (power off). Debris, seized bearing, belt wrapped.
  • Total external static vs this blower table. A rooftop with 1.4" TES and a 0.8" motor is an oC waiting to happen.
  • FLA / motor-data parameters vs the motor nameplate. Do not raise FLA to hide a dirty coil.
  • Ramp-up too fast on a high-inertia wheel — lengthen accel before you change a drive.
• Uv

  Uv / LU — undervoltage

  lockout

  Keypad example: Uv (Yaskawa) or LU. DC bus dropped. Incoming power or a missing phase.

  • Three legs at the drive line terminals, under load. A single-phased 3-phase drive nuisances Uv / oC.
  • Do not ignore Uv on a 480 V roof with a 208 V drive, or the reverse.
• ov

  ov / OU — overvoltage

  lockout

  Keypad example: ov (Yaskawa) or OU. DC bus high. Usually regen on decel, not a new drive.

  • ov on shutdown = decel too fast; lengthen decel.
  • Incoming voltage high or a utility swell. Measure line first.
• GF

  GF — ground fault

  hazard

  Keypad example: GF. Drive sees current to ground on the motor leads.

  • Megger the motor with the drive disconnected. A wet rooftop motor after a rain is this code.
  • Cable from drive to motor — insulation rubbed through the curb or the fan deck.
  • Do not reset-and-run a GF. That is a grounded winding or a damaged VFD output.
• oH

  oH — heatsink overtemp

  warn

  Keypad example: oH. Drive thermal trip.

  • Drive fan spinning. Heat sink packed with roof lint.
  • Cabinet door left off in the sun is not always the drive — still clean the sink.
• PF

  PF — input phase loss

  lockout

  Keypad example: PF. Missing or imbalanced incoming phase.

  • L1 L2 L3 at the drive and at the disconnect. Tight lugs.
  • A rooftop fuse that opened one leg looks like a dead motor until you read PF.
• Limp

  VFD limp / min Hz — fan prove

  warn

  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.

  • Min-frequency / limp parameter vs the prove-switch setpoint (often ~0.07" on some Reliatel cabinets).
  • A dirty filter that drops the motor into current-limit limp will never make prove. Clean first.
  • Do not jumper the prove switch. Heat will fire into a near-dead blower.
• Drain

  Condensate / float

  warn

  Float switch or tripped condensate opened 24V.

  • Roof drain pan, trap, and the overflow to the roof — not a furnace collector.
  • A clogged pan on a curb soaks the deck. Fix the drain before the board.
• RV

  No shift

  lockout

  Reversing valve did not stroke.

  • O/B 24 VAC at the board on a heat call (or cool, depending on this controller’s logic — confirm silk).
  • Coil ohms. Then the piston — a stuck RV is not a charge call.
• Defrost

  Defrost fault

  warn

  Stuck in defrost or never defrosts.

  • OD coil sensor / defrost control on this packaged HP.
  • Aux heat on during defrost is normal. Aux heat only, all day, is not.
• EH

  Electric heat

  warn

  Strips not coming on, or on when they should not.

  • W1/W2 at the unit board. Sequencer 24V, then element ohms, then kit fuses.
  • A unit that only runs strips on a 50FCQ is a failed HP circuit.

Workflows

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.

O/B

~24 VAC on the heat-pump heat (or cool) call this controller uses. Confirm silk.

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.
• 50FCQ / 50TCQ are heat-pump packaged. O/B and defrost are in this box.

Related plates

• carrier-48fc — Gas-heat sibling. IGC lives there, not here.