Two-stage 24V · Y1 / Y2
Conventional Y1 / Y2 / C
Two-stage scroll. High stage is Y2 at the outdoor. A single-stage stat never gets you there. Still not Infinity ABCD.
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 PDF24V two-stage
Outdoor has Y1 and Y2. Not an inverter drive.
Wall thermostat
Two-stage cool. A single-Y stat never pulls high.
- R24V hot24V
- C24V common24V
- Y1Low-stage cool24V
- Y2High-stage cool24V
- GIndoor fan24V
- WHeat. Stays at the indoor.24V
Indoor IFC / AHU
Y1 and Y2 both have to leave this cabinet on high.
- RTransformer hot24V
- CCommon — run it to the outdoor24V
- Y1Low-stage in / out24V
- Y2High-stage in / out24V
- GBlower24V
- W1Heat24V
Outdoor — Y1 / Y2
Low vs high is these two screws, not an inverter L-code.
- Y1Low-stage request24V
- Y2High-stage request24V
- C24V common24V
Outdoor line
208/230 through the disconnect to the contactor line side.
- L1LineLine
- L2LineLine
- GNDEquipment groundLine
Dual run capacitor
C / FAN / HERM on the can. An inverter outdoor does not have this part.
- CCommon — both windingsCap
- FANOutdoor fanCap
- HERMCompressorCap
Landing
- 24VIndoor Rstat R · C throughout
~24 VAC
- 24VStat Y1indoor Y1outdoor Y1
Low-stage coil / request
- 24VStat Y2indoor Y2outdoor Y2
High-stage. Missing Y2 = stuck on low.
- LineL1 / L2disconnect
208/230
Prove it
- Y1 at the outdoor on a 1-cool call. Then Y2 on a 2-cool / staging call.
- If Y2 never arrives, the outdoor is not weak — the stat, indoor IFC, or the Y2 wire is.
Do not
- Do not hunt ABCD / L-codes. If you see an inverter, you are on 24VNA6 / 191VAN / XV18.
- InteliSense ≠ Evolution ABCD.
Preferred / Performance / Elite two-stage land here. Bryant 187B Evolution two-stage does not — that one is ABCD.