York Millennium Z-Series (R-410A) Commercial Rooftop Units
Official technical field reference, diagnostic fault code resolution, genuine OEM replacement parts directory, and certified 24/7 commercial mechanical contractor dispatch for Models Z2 (25 Ton), Z3 (30 Ton), and Z4 (40 Ton).
⚙️ Genuine OEM Replacement Parts Directory
● Verified InventoryFactory-certified replacement boards, sensors, and motors for York Millennium Z-Series packaged units. Available with overnight express freight:
⚡ Diagnostic Fault Code Reference (Simplicity Board)
LED Sequence TableYork Millennium Z-Series control boards communicate operating status and safety lockouts via diagnostic LED flash sequences:
| Status Code | Operating Condition | Diagnostic Root Cause | Action / Parts |
|---|---|---|---|
| HP1 / HP2 | High Pressure Lockout Circuit > 650 PSIG |
Condenser coil debris blockage, failed outdoor fan motor, or non-condensable contamination. | Order Pressure Switch → |
| LP1 / LP2 | Low Pressure Trip Circuit < 50 PSIG |
Refrigerant undercharge, TXV metering restriction, dirty filters, or evaporator freeze-up. | Order TXV / Sensor → |
| Flash 3 | Supply Fan Failure Air proving switch open |
Broken blower drive belt, sheared pulley key, or tripped VFD motor thermal overload. | Order Blower Belt → |
| Flash 5 | Board Microprocessor Lock Internal board trip |
Incoming power surge, control voltage drop (<19V AC), or failed main pilot relay. | Order OEM Board → |
| Phase Mon | Phase Monitor Red LED Reverse / loss phase |
Utility power disturbance, blown 3-phase line fuse, or reversed main input legs. | Dispatch Electrician → |
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📊 Engineering Specifications (Z2, Z3, Z4 Models)
Factory Data TableFactory engineering parameters for York Millennium commercial packaged cooling systems:
📄 Wiring Sequence & Field Installation Manuals
Cooling Sequence of Operation (Stage 1 & Stage 2)
1. Call for cooling closes G (indoor blower contactor) and Y1 (cooling stage 1).
2. Simplicity board verifies high and low pressure cutouts for closed continuity.
3. 5-minute anti-recycle delay completes; Compressor 1 and Condenser Fan 1 energize.
4. Upon call for Y2, Compressor 2 and Condenser Fan 2 stage on for 100% capacity.
Economizer & Low Ambient Operating Limits
Standard mechanical cooling operates down to 35°F (1.7°C). For sub-35°F ambient operation, verify factory low-ambient head pressure damper packages and crankcase heaters.