Overview#
The Blue Star NG500-02 is a 500-kilowatt natural-gas-only standby generator built on the PSI 21.9LHO high-output V12 platform. It is rated 500 kWe standby on natural gas at 60 Hz / 1800 RPM. LP fuel is not available on this model — the high-output engine tuning is incompatible with LP operation. Three-phase only (208V, 240V, 480V, 600V).
The NG500-02 is one of two 500 kW natural gas standby models in the Blue Star lineup. The other — the NG500-01 — uses the larger PSI 32L V12 and supports LP but in a 210×96 in OPU. The NG500-02 delivers 500 kWe in the smaller 156×86 in footprint at the cost of LP capability.
The PSI 21.9LHO#
The PSI 21.9LHO is the high-output variant of the 21.9-liter V12:
- 764 bHp (570 kWm) at 1800 RPM standby — 80 bHp more than the standard 21.9L (684 bHp)
- Same 21.9L displacement (1,336 cu in) — output increase comes from high-output turbocharging and NG-optimized fuel delivery
- Natural gas only — LP operation not supported (same pattern as NG350-02 and the 14.6LHO)
- Standard deration: 1.5% per 10°F above 77°F inlet air temperature; 2.5% per 1,000 ft above 1,200 ft altitude
NG500-02 vs. NG500-01: choosing between the platforms#
| NG500-02 (21.9LHO) | NG500-01 (32L) | |
|---|---|---|
| Standby output NG | 500 kWe | 500 kWe |
| LP available | No | Yes (400 kWe) |
| OPU dimensions | 156×86×98 in | 210×96×103 in |
| Dry weight | 11,450 lbs | 15,500 lbs |
| Deration base | 77°F / 1,200 ft | 97°F / 4,200 ft |
| NG consumption @ 100% | 5,330 ft³/hr | 5,878 ft³/hr |
The NG500-02 is the right choice when the site has natural gas only, space is limited to the 156-in footprint, and deration thresholds are manageable. The NG500-01 is preferred when LP backup is required or deration tolerance at altitude/heat is a concern.
Alternator configurations#
| Voltage | Phase | Alternator | Connection |
|---|---|---|---|
| 120/208V | 3 | Stamford HCI534E | 12-lead WYE |
| 240V | 3 | Stamford HCI534E | 12-lead DELTA |
| 277/480V | 3 | Stamford HCI534D | 12-lead WYE |
| 347/600V | 3 | Stamford HCI534D | 4-lead WYE |
All configurations carry 125°C standby temperature rise and ±0.5% voltage regulation.
When to spec the NG500-02#
- 425–500 kW standby loads on natural gas only — no LP requirement
- Sites constrained to the 156×86×98 in OPU footprint (same as NG400/425/450 family)
- Applications where the standard deration thresholds (77°F / 1,200 ft) are acceptable and LP is not needed
Our service experience#
The PSI 21.9LHO is less common in service territories than the standard 21.9L, but parts cross-reference to the same PSI catalog. Higher standby output increases thermal loading on V12 ignition and fuel components — budget for more frequent spark plug service than a comparable standby-rated standard 21.9L.
