The updated Kidde Firex KF20 and KF20R alarms are mains powered, interlinking optical smoke alarms that use up to 70% less energy than previous Firex models. The KF20 has an alkaline battery back-up and the KF20R, a self-charging lithium battery back-up. The units are hard wired and can be interlinked with other units from the series to create all round fire protection within the home.
Please note: The Kidde Firex KF20 (previously KF2 / 4973 / PADC240) and KF20R (previously KF2R / 4985 / PAR230) are replacements for the Kidde 223/9HI and 223/9HILL series, and can be electrically interlinked. However, the new models cannot be used on the old base plates for the 223/9HI and 223/9HILL series as they use different style connector blocks. This means that base plates must be swapped over on those stated models and connectors need to be replaced.
D F
21st September 2026
C G
All good straight replacement
16th September 2026
W P
Simple to replace old KF1 a straight forward DIY job
16th September 2026
| Product Code | KEKF20 |
|---|---|
| Brand | Kidde |
| Manufacturer's Part Number | KF20 |
| Approvals & Markings | CE Marked |
| Back-Up Battery Type | Alkaline |
| British Standard Grade | Grade D2: Mains Powered (replaceable backup) |
| Colour | White |
| Compliance | BS 5839-6 |
| BS EN 14604:2005 | |
| Connection | Wired |
| Display | LED Indicators |
| Fixing Options | Screws (included) |
| Installation Position | Ceiling |
| Local Legislation | Scottish Legislation (2022) |
| Welsh Legislation (2022) | |
| Material | Plastic |
| Maximum Number of Linked Devices | 24 Devices |
| Operating Temperature | 0°C To +40°C |
| Positioning | Bedrooms |
| Hallways | |
| Living Rooms | |
| Power Type | Mains Powered (230V) |
| Product Range | Kidde Firex |
| Recyclable | Yes - Valpak's WEEE Distributor Take-back Scheme |
| Relative Humidity | Up To 93% |
| Sensor Type | Optical |
| Sound Level | 85dB |
| Suitability | Home |
| Warning Type | Audible - Alarm Sounder |
| Warranty | 6 Years |
| Dimensions (Unit) |
|
| Weight | 280g |
Alarms from the Same Series
The table below shows all the units that can interlink with the Firex KF Series.
| Model Number | Type of Unit | Type of Interlink |
| KF10 | Ionisation Smoke Alarm | Hardwire interlink |
| KF10R | Ionisation Smoke Alarm with Rechargeable Lithium Cell | Hardwire interlink |
| KF20 | Optical Smoke Alarm | Hardwire interlink |
| KF20R | Optical Smoke Alarm with Rechargeable Lithium Cell | Hardwire interlink |
| KF30 | Heat Alarm | Hardwire interlink |
| KF30R | Heat Alarm with Rechargeable Lithium Cell | Hardwire interlink |
| KF1 | Ionisation Smoke Alarm | Hardwire interlink |
| KF1R | Ionisation Smoke Alarm with Rechargeable Lithium Cell | Hardwire interlink |
| KF2 | Optical Smoke Alarm | Hardwire interlink |
| KF2R | Optical Smoke Alarm with Rechargeable Lithium Cell | Hardwire interlink |
| KF3 | Heat Alarm | Hardwire interlink |
| KF3R | Heat Alarm with Rechargeable Lithium Cell | Hardwire interlink |
Carbon Monoxide Alarms
| Model Number | Type of Unit | Type of Interlink |
| 4MCO | CO Detector with Rechargeable Lithium Cell | Hardwire interlink |
| K4MCO | CO Detector with Rechargeable Lithium Cell | Hardwire interlink |
Compatible Alarms
| Model Number | Type of Unit | Type of Interlink |
| 1239HI | Ionisation Smoke Alarm with Alkaline Battery | Hardwire interlink |
| 1239HILL | Ionisation Smoke Alarm with Lithium Battery | Hardwire interlink |
| 2239HI | Optical Smoke Alarm with Alkaline Battery | Hardwire interlink |
| 2239HILL | Optical Smoke Alarm with Lithium Battery | Hardwire interlink |
| 3239HI | Heat Alarm with Alkaline Battery | Hardwire interlink |
| 3239HILL | Heat Alarm with Lithium Battery | Hardwire interlink |
| 4870 | Ionisation Smoke Alarm with Alkaline Battery | Hardwire interlink |
| 4881 | Ionisation Smoke Alarm with Lithium Battery | Hardwire interlink |
| 4973 | Optical Smoke Alarm with Alkaline Battery | Hardwire interlink |
| 4985 | Optical Smoke Alarm with Lithium Battery | Hardwire interlink |
| 4899 | Heat Alarm with Alkaline Battery | Hardwire interlink |
| 4892 | Heat Alarm with Lithium Battery | Hardwire interlink |
| I240C | Ionisation Smoke Alarm with Alkaline Battery | Hardwire interlink |
| PADC240 | Optical Smoke Alarm with Alkaline Battery | Hardwire interlink |
I highly recommend this company good product good price and a good all round service