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PROTHERM Ray 21kW electric heating boiler (v.14)

PROTHERM Ray 21kW (RAY 21 KE /14 EU) is a wall-mounted electric boiler for hydronic heating systems with automatic output modulation. Its heating output is regulated from 2.3 to 21 kW through nine output stages: 2.3 / 4.7 / 7 / 9.3 / 12 / 14 / 16 / 19 / 21 kW. The boiler uses three 7 kW electric heating elements.
The RAY KE series features eBUS communication, continuous output modulation, automatic diagnostics and integrated weather-compensated control. With an outdoor temperature sensor connected, the heating-water temperature can be automatically adapted to outdoor conditions. PROTHERM also specifies quiet operation, balanced loading of the heating elements, HDO signal control and frost protection.
A high-efficiency heating circulation pump and an 8-litre expansion vessel are integrated into the boiler. Heating-water temperature can be adjusted from 25 to 85 °C and heating-system operating pressure is 0.8–3 bar. Efficiency is 99.5%, while the space-heating energy efficiency class is D.
PROTHERM Ray 21 KE can also prepare domestic hot water in an external indirect cylinder using the appropriate connection accessories. DHW temperature can be set from the boiler control panel within a range of 35–70 °C.
RAY 21 KE is designed for a three-phase 3 × 230/400 V, 50 Hz electrical supply. Maximum current is 3 × 32 A and the manufacturer specifies a 40 A protective circuit breaker. Electrical protection is IP40. The current PROTHERM 2026 catalogue specifies a weight of 37.9 kg and dimensions of 410 × 315 × 740 mm. The official product number is 0010023675.
Main advantages
- Maximum heating output 21 kW
- Heating output range 2.3–21 kW
- 9 output stages
- Three 7 kW heating elements
- Continuous output modulation
- Efficiency 99.5%
- eBUS communication
- Integrated weather-compensated control
- Outdoor temperature sensor support
- Automatic diagnostics
- High-efficiency circulation pump
- Integrated 8 l expansion vessel
- Frost protection
- Balanced heating-element loading
- HDO signal control
- External DHW cylinder support
- Heating-water temperature 25–85 °C
- DHW temperature 35–70 °C
- 3 × 230/400 V, 50 Hz connection
- 40 A protective circuit breaker
- IP40 protection
Technical information
| Parameter | Value |
|---|---|
| Manufacturer | PROTHERM |
| Series | Ray |
| Model | RAY 21 KE /14 EU |
| Version | v.14 |
| Product type | Wall-mounted electric heating boiler |
| Heating output range | 2.3–21 kW |
| Maximum heating output | 21 kW |
| Heating elements | 3 × 7 kW |
| Output stages | 2.3 / 4.7 / 7 / 9.3 / 12 / 14 / 16 / 19 / 21 kW |
| Switching step | 2.3 kW |
| Efficiency | 99.5% |
| Space-heating energy efficiency class | D |
| Heating-water temperature | 25–85 °C |
| DHW temperature with external cylinder | 35–70 °C |
| Heating-system operating pressure | 0.8–3 bar |
| Expansion vessel | 8 l |
| Heating connections | G 3/4" |
| Electrical connection | 3 × 230/400 V, 50 Hz |
| Maximum current | 3 × 32 A |
| Protective circuit breaker | 40 A |
| Electrical protection | IP40 |
| Communication | eBUS |
| Weather-compensated control | Yes |
| Automatic diagnostics | Yes |
| Frost protection | Yes |
| High-efficiency circulation pump | Yes |
| External DHW cylinder support | Yes |
| Dimensions (W × D × H) | 410 × 315 × 740 mm |
| Weight | 37.9 kg |
Warranty, months: 24