Gas
Low-NOx Condensing Gas Storage Water Heater – PRO Series
- Thermal efficiency ≥107%
- NOx < 30 mg/m³
- 30–99 kW
Gas
Commercial Low-NOx Gas Storage Water Heater – PLUS Series
A 400 L fully premixed gas storage water heater with three-pass counterflow heat exchange, designed for commercial buildings that need low-NOx hot water in 73 kW and 99 kW sizes.
- Thermal efficiency up to 98%
- NOx < 30 mg/m³
- 400 L tank
- Indoor & outdoor (IPX4)
Key features
Heat exchange
TRIPLE-HEAT three-pass counterflow heat exchange technology with thermal efficiency up to 98%.
Combustion
PRE-MIX full premix combustion with a constant air-fuel ratio; NOx < 30 mg/m³.
Standard
Designed to meet China’s national standard GB 18111-2021.
Installation
Indoor units use a balanced intake and exhaust system that does not draw combustion air from the room. Outdoor units have an IPX4 waterproof design and can be installed without a dedicated plant room.
Control
IoT connectivity and intelligent group control for multi-unit systems.
Technical specifications
Indoor (RSTQ) and outdoor (RSTW) models
| Model | RSTQ73-400 | RSTW73-400 | RSTQ99-400 | RSTW99-400 |
|---|---|---|---|---|
| Storage capacity (L) | 400 | 400 | 400 | 400 |
| Thermal efficiency | ≥98% | ≥98% | ≥98% | ≥98% |
| Rated heat input (kW) | 73 | 73 | 99 | 99 |
| Rated heat input (kcal/h) | 62,440 | 62,440 | 85,646 | 85,646 |
| Gas consumption (m³/h) | 7.3 | 7.3 | 9.9 | 9.9 |
| Electric power (W) | 280 | 280 | 280 | 280 |
| Rated working pressure (MPa) | 1.1 | 1.1 | 1.1 | 1.1 |
| Temperature setting range (°C) | 30–80 | 30–80 | 30–80 | 30–80 |
| Hot water output at Δt = 25 °C (L/h) | 2,478 | 2,478 | 3,398 | 3,398 |
| Hot water output at Δt = 35 °C (L/h) | 1,770 | 1,770 | 2,427 | 2,427 |
| Hot water output at Δt = 55 °C (L/h) | 1,126 | 1,126 | 1,545 | 1,545 |
| Inlet/outlet pipe diameter | DN50 | DN50 | DN50 | DN50 |
| Gas connection | DN20 | DN20 | DN20 | DN20 |
| Safety valve / drain valve | DN25 / DN50 | DN25 / DN50 | DN25 / DN50 | DN25 / DN50 |
| Air intake / flue outlet diameter | Φ110 / Φ110 | Φ110 / Φ110 | Φ110 / Φ110 | Φ110 / Φ110 |
| Net weight (kg) | 355 | 355 | 355 | 355 |
| Total height / outlet height / inlet height (mm) | 2000 / 1730 / 460 | 2000 / 1730 / 460 | 2000 / 1730 / 460 | 2000 / 1730 / 460 |
| Body diameter / max. depth (mm) | 710 / 790 | 710 / 790 | 710 / 790 | 710 / 790 |
Data as published by OTTMEL. Specifications may change; please confirm the current datasheet with our sales team before ordering. Gas type, voltage and other market-specific requirements should be confirmed for each project.
Typical applications
- Hotels
- Schools and campuses
- Hospitals and care facilities
- Office and commercial buildings
Related products
Gas
Commercial Gas Storage Water Heater – CLASSIC Series
- 22–99 kW
- 220–360 L tanks
- Pressure rating 1.1 MPa
Gas
Condensing Premix Storage Fire-Tube Boiler
- 240–700 kW
- NOx 22.3–24.7 mg/m³
- Modulation up to 12:1
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