FieldBench
Wiring

Infinity / Evolution furnace

ABCD

ABCD

59MN7 / 59TN6 / 987M / 986T class. Four-wire communicating furnace. D is 24V hot, not W and not Y.

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

Heat sequence

  1. 1Power. L1 / N → IFC120V
  2. 2Call. Data pair or 24V W → IFCBus or 24V
  3. 3Draft. IFC → inducer → proveTwo-stage PS or a pressure band
  4. 4Ignite. IFC → HSI → valve120V igniter
  5. 5Blow. IFC → serial ECMNo tap, no cap

ABCD only

Infinity or Evolution wall control and a matching outdoor.

Infinity / Evolution control

A/B data, C common, D 24V hot.

  • ADataData
  • BDataData
  • C24V common24V
  • D24V hot — not W24V

Infinity / Evolution IFC

Same ABCD. Do not convert it to 24V by landing W and walking away.

  • ADataData
  • BDataData
  • CCommon24V
  • D24V hot24V

Landing

  • DataStat A/BIFC A/Boutdoor A/B

    Data

  • 24VStat C/DIFC C/D

    24V common / hot. D is not Y or W.

IFC harness — communicating two-stage

Call arrives on the data pair (or 24V W). Gas train is still inducer / prove / igniter / valve.

Transformer + fuse

24V still exists for accessories and for a 24V outdoor. Data pair is not the transformer.

  • L1 / N120VLine
  • R / C24V strip24V
  • FUSEOn the IFC24V

24V safety chain

Limit / rollout / door still open the heat path. Codes are on THIS IFC language.

  • DOORInterlock24V
  • LIMITMain limit24V
  • ROLLOUTManual reset24V

Two-speed inducer + dual PS

Low vs high prove. Do not tee the hoses. Do not apply this to a modulating cousin.

  • IND LO/HITwo-speed inducerLine
  • LPSLow prove24V
  • HPSHigh prove24V

HSI + two-stage valve

Two solenoids or a two-stage valve. Staging is the bus or W1/W2, not a tap.

  • HSI120V igniterLine
  • MV / HV24V low / high solenoids24V
  • FLAMEµA DC24V

Serial variable-speed ECM

IFC talks to the motor on the serial harness. No F-taps. No dual run cap on this blower.

  • SERIALIFC-to-motor harness. Unplugged motor = CFM / comm fault, not a tap problem24V
  • CFMSet in the IFC menu / model plug / CoolCloud — not a dip switch on most of these24V

Landing

  • LineCallIFCinducerprove

    Low then high

  • LineIFCHSIvalve

    120V igniter, 24V or serial valve

  • 24VFlame rodIFC

    µA DC

  • DataIFCserial blower

    No F-taps. No PSC cap.

Prove it

  • Wall-control equipment list. The furnace and outdoor both present.
  • ABCD polarity. C still required.

Do not

  • Do not land W on a spare screw to make it 24V.
  • A 926T / 59TP6 / 59SC5 is the other diagram.

ABCD is the published Infinity / Evolution control.

Plates on this landing