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Engineered for Commercial Reliability
The York Millennium Z-Series combines high-durability cabinet construction with modular component access to minimize downtime and maintenance labor.
Slide-Out Blower Assembly
Dynamically balanced centrifugal wheel mounted on glide tracks. Enables rapid belt tensioning, bearing lubrication, and motor swaps without dismantling ductwork.
Dual Scroll Circuits
Independent tandem R-410A scroll compressors with internal thermal overload, 650 PSI high-pressure cutouts, and freeze protection switches.
Microchannel Condenser
All-aluminum coils engineered for superior heat transfer, up to 40% reduced refrigerant charge, and heavy-gauge wire grille hail guards.
Simplicity® DDC Control
Integrated low-voltage microprocessor control board with on-board LED flash code diagnostics, 3-phase line monitor, and BAS communication.
Diagnostic Fault Code Directory (Codes 1–14)
The Simplicity® control board inside the low-voltage control cabinet uses flashing green and amber LEDs to communicate system status and trip conditions.
Simplicity® Elite & SEC Diagnostic Interface
Count the repeated LED pulses on the control board. If an active lockout occurs (3, 4, 5, or 6 flashes), the board shuts down the affected circuit to protect the scroll compressors from catastrophic failure.
| LED Code | System Condition | Diagnostic Root Cause | Required Service Action |
|---|---|---|---|
| Steady ON | Normal Operation | System operating within normal limits, no faults stored. | Routine inspection only. |
| 2 Flashes | Anti-Short Cycle Delay (ASCD) | 5-minute compressor restart timer active after power cycle or thermostat call. | Wait 5 minutes for timer expiration. |
| 3 Flashes | High Pressure Lockout (C1) | Discharge pressure exceeded 650 PSI. Dirty coils, condenser fan failure, or overcharge. | Order Pressure Switch → |
| 4 Flashes | High Pressure Lockout (C2) | Circuit 2 discharge pressure exceeded safety threshold. Restricted liquid line drier. | Order Switch / Drier → |
| 5 Flashes | Low Pressure Lockout (C1) | Suction pressure dropped below 45 PSI for >180 seconds. Low refrigerant or frozen evaporator. | Consult Master Tech → |
| 6 Flashes | Low Pressure Lockout (C2) | Circuit 2 suction loss or blower failure during low ambient operation. | Inspect Blower Belt → |
| 7 Flashes | Freeze Stat Lockout | Evaporator coil temperature dropped below 28°F. Clogged air filters or defective TXV. | Order TXV Valve → |
| 8 Flashes | Outdoor Temp Sensor Failure | Open or shorted ambient thermistor. Economizer disabled. | Replace Thermistor → |
| 9 Flashes | Phase Monitor Trip / Reversal | Loss of phase, voltage unbalance >3%, or reverse phase rotation. | Order Phase Monitor → |
| 11 Flashes | Gas Ignition / Flame Failure | Spark ignition lockout after 3 retries. Dirty flame sensor or blocked vent. | Order Ignition Module → |
| 14 Flashes | Control Board Internal Error | EEPROM corruption or relay driver failure on motherboard. | Order Simplicity Board → |
York Millennium Z-Series Replacement Parts
Factory-authorized replacement parts in stock with guaranteed fitment for York Millennium Z22, Z23, and Z24 packaged rooftop units.
Simplicity® DDC Control Board
High Pressure Cutout Switch (650 PSI)
3-Phase Voltage & Phase Loss Monitor
Condenser Fan Motor (3/4 HP, 460V)
Millennium Z-Series Technical Data Matrix
Physical capacities, electrical service requirements, and blower characteristics for models Z22, Z23, and Z24.
| Specification | Model Z22 (25 Ton) | Model Z23 (30 Ton) | Model Z24 (40 Ton) |
|---|---|---|---|
| Nominal Cooling Capacity | 300,000 BTUh (25.0 Ton) | 360,000 BTUh (30.0 Ton) | 480,000 BTUh (40.0 Ton) |
| Refrigerant Type & Circuit | R-410A (Dual Scroll Tandem) | R-410A (Dual Scroll Tandem) | R-410A (Quad Scroll Circuits) |
| Standard Voltage Options | 208/230V · 460V · 575V 3-Ph | 208/230V · 460V · 575V 3-Ph | 460V · 575V 3-Phase |
| Blower Nominal Airflow (CFM) | 10,000 CFM | 12,000 CFM | 16,000 CFM |
| Indoor Blower Motor HP | 7.5 HP (Belt Drive) | 10.0 HP (Belt Drive) | 15.0 HP (Belt Drive) |
| Condenser Fans Quantity & HP | (4) × 3/4 HP Direct Drive | (4) × 3/4 HP Direct Drive | (6) × 3/4 HP Direct Drive |
| Approximate Operating Weight | 2,950 lbs (1,338 kg) | 3,220 lbs (1,460 kg) | 4,150 lbs (1,882 kg) |
Model Number Nomenclature Decoder
Locate your unit model string on the serial rating plate to verify tonnage, heat configuration, and factory options.
R-410A Subcooling & Superheat Metrics
Follow factory charging procedures to maintain target subcooling at the liquid line service port under design ambient conditions.
| Outdoor Ambient (°F) | Target Subcooling (°F) | Target Superheat (°F) | Normal Liquid Pressure (PSIG) |
|---|---|---|---|
| 75°F (24°C) | 10°F ± 2°F | 12°F – 16°F | 275 – 305 PSIG |
| 85°F (29°C) | 11°F ± 2°F | 10°F – 14°F | 320 – 355 PSIG |
| 95°F (35°C) | 12°F ± 2°F | 8°F – 12°F | 375 – 410 PSIG |
| 105°F (41°C) | 13°F ± 2°F | 7°F – 10°F | 430 – 475 PSIG |
York® Millennium Z-Series Technical Guide (Form 5276180-YTG)
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