Kidde Sentry KF21R & KF31R Mains Powered Smoke and Heat Alarm Kit with Rechargeable Lithium Battery Back-Up

The Kidde Sentry Alarm Kit combines the KF21R Optical Smoke Alarm and KF31R Heat Alarm to provide reliable, whole-home fire detection for residential properties. Designed for mains-powered installation, both alarms feature sealed rechargeable lithium battery back-up protection and can be interconnected with up to 23 compatible Kidde FIREX alarms.

This advanced fire alarm kit delivers dependable smoke and heat detection across living spaces, escape routes, kitchens, garages and lofts, helping homeowners meet UK Building Regulations while improving property safety.

Each alarm is supplied with Kidde’s Quick-Fit Slide-On Base for faster installation and features integrated cable management to keep wiring secure and organised. The 150mm flared base plate also provides a neat finish when retrofitting existing alarms.

Kit Contents

• 1 x Kidde KF21R Optical Smoke Alarm
• 1 x Kidde KF31R Heat Alarm

KF21R Optical Smoke Alarm Features

The Kidde KF21R optical smoke alarm is designed to detect slow, smouldering fires caused by electrical faults, upholstery or cigarettes. Ideal for hallways, bedrooms and living spaces, the optical sensor provides reliable early warning protection.

• Mains-powered optical smoke alarm with sealed rechargeable lithium battery back-up
• Optical sensor with dust compensation and bug screen
• Interconnects with up to 23 Kidde FIREX alarms
• Alarm memory identifies the activated alarm
• Combined Test/Hush button
• Auto reset after activation
• Tamper-resistant locking mechanism
• Suitable for hallways, bedrooms, lofts and living rooms
• BSI certified to BS EN14604:2005
• 10-year warranty

KF31R Heat Alarm Features

The Kidde KF31R heat alarm is designed for kitchens, garages and loft spaces where smoke alarms may be unsuitable due to steam, cooking fumes or dust. Its thermistor heat sensor provides dependable heat detection while helping to reduce nuisance alarms.

• Mains-powered heat alarm with sealed rechargeable lithium battery back-up
• Thermistor heat sensor for reliable heat detection
• Interconnects with up to 23 Kidde FIREX alarms
• Alarm memory identifies the activated alarm
• Combined Test/Hush button
• Auto reset after activation
• Tamper-resistant locking mechanism
• Ideal for kitchens, garages and loft spaces
• BSI certified to BS 5446 Part 2:2003
• 10-year warranty including battery

Key Benefits

• Complete smoke and heat alarm solution for residential properties
• Sealed rechargeable lithium battery back-up for maintenance-free operation
• Interlinked alarms provide whole-home warning when danger is detected
• Quick-Fit bases for fast and simple installation
• Integrated cable management for tidy wiring
• Suitable for compliance with UK Building Regulations
• Grade D1 domestic fire alarm system solution
• Fully compatible with Kidde FIREX smoke, heat and CO alarms

Technical Specifications

KF21R Optical Smoke Alarm

• Model: KF21R
• Power Supply: 230V mains with sealed rechargeable lithium battery back-up
• Sensor Type: Optical
• Alarm Volume: 85dB minimum at 3 metres
• Dimensions: 150mm x 150mm x 53mm
• Weight: 260g
• Operating Temperature: -10°C to +40°C
• Warranty: 10 Years

KF31R Heat Alarm

• Model: KF31R
• Power Supply: 230V mains with sealed rechargeable lithium battery back-up
• Sensor Type: Thermistor heat sensor
• Alarm Volume: 85dB minimum at 3 metres
• Dimensions: 150mm x 66mm
• Weight: 245g
• Operating Temperature: -10°C to +40°C
• Warranty: 10 Years including battery

Please Note: Alarms are supplied individually within the kit. Installation should be completed by a qualified electrician.

Downloads

KF21R Data Sheet:
Download KF21R Data Sheet

KF31R Data Sheet:
Download KF31R Data Sheet

KF21R Instruction Manual:
Download KF21R Instruction Manual

KF31R Instruction Manual:
Download KF31R Instruction Manual