The Wisualarm DHI-HY-HT5MA is a mains-powered Class A1 fixed-temperature heat alarm certified to BS 5446-2:2003, built for rooms where a smoke alarm would cause persistent false activations — principally kitchens, garages, utility rooms and loft spaces. It draws its primary power from a permanent 230V mains connection and backs this up with a 10-year rechargeable lithium battery, removing the ongoing cost and hassle of replacing a standby battery over the alarm's working life.
A high-precision thermistor triggers the alarm when the ambient temperature reaches 54°C–65°C, sounding an 85dB alert continuously until reset. The unit interconnects by wire with up to 24 other Wisualarm mains-powered smoke and heat alarms, and can optionally join the WisuLink wireless mesh by adding the DHI-HY-MRF50-R8 wireless interconnect module — enabling a hybrid system that links wired and wireless devices across a property.
54-65°C
Alarm Trigger Range
85dB
Alarm Volume @ 3m
10-Yr
Lithium Battery Back-up
24
Max Interconnected Units
Grade D1
BS 5839-6 Classification
BS 5446-2
Compliance Standard
Grade D1 — Sealed Rechargeable Back-up
With its non-replaceable 10-year rechargeable lithium battery providing standby power, the HT5MA is classified as a Grade D1 device under BS 5839-6. This eliminates the battery-replacement obligation that applies to Grade D2 alarms, making it well suited to new-build and long-term rental properties where minimal maintenance is a priority.
Heat Alarms, Not Smoke Alarms, for These Rooms
Heat alarms respond to a rise in ambient temperature rather than smoke particles, so they resist the false alarms that cooking fumes, steam and dust can trigger in a photoelectric smoke alarm. Fit heat alarms — not smoke alarms — in kitchens, garages and similar spaces, and always follow the room-by-room guidance in BS 5839-6 or your project specification.
Wired by Default, Wireless-Ready
The HT5MA interconnects over its own dedicated wiring with other Wisualarm mains-powered smoke and heat alarms as standard. Fitting the optional DHI-HY-MRF50-R8 wireless module lets it also join a WisuLink 868MHz wireless network, useful where running new interconnect cable to every room isn't practical during a retrofit.
10-Year Rechargeable Battery
A sealed rechargeable lithium battery provides standby power for the alarm's full 10-year service life, with no battery changes required.
High-Precision Thermistor Sensor
A thermistor-based heat sensor samples the surrounding air every 10 seconds and triggers at 54°C–65°C, avoiding the false alarms smoke detection can suffer from steam or cooking fumes.
Hardwired Interconnect, 24 Units
Connects to up to 24 other mains-powered Wisualarm smoke and heat alarms over standard interconnect wiring, so one triggered alarm sounds every linked unit in the property.
Optional Wireless Expansion
Adding the DHI-HY-MRF50-R8 module lets this alarm also communicate over the 868MHz WisuLink wireless mesh, bridging wired and wireless zones in the same system.
IR Remote Test & Silence
Supports test and 9-minute silence functions via any working infrared remote control, letting installers and occupants manage the alarm from floor level rather than a ceiling-mounted button.
Three-LED Status Reporting
A tri-colour LED indicator reports standby, alarm and fault conditions at a glance, so a technician or occupant can read the alarm's state without opening the unit.
Up to 24 units via optional DHI-HY-MRF50-R8 WisuLink module
Physical & Environmental
Dimensions
Ø148.6mm × H68.4mm
Weight
310 g
Colour / casing
White, PC+ABS
Installation
Ceiling mount
Operating environment
Indoor
Operating temperature
-10°C to +55°C
Operating humidity
≤95% RH, non-condensing
Certification
Certifications
CE, UKCA, RCM, PSTI, BSI, Activfire
Compliance standard
BS 5446-2:2003, AS 1603.3:2018
Should I fit a heat alarm or a smoke alarm in my kitchen?
A heat alarm such as the HT5MA is the correct choice for kitchens, since cooking fumes and steam routinely trigger false alarms on smoke detectors. Always check the room-by-room detector guidance in BS 5839-6 or your project's fire strategy for the specific grade and category required.
Does this alarm need its battery replaced?
No. The HT5MA uses a sealed 10-year rechargeable lithium battery that is not user-replaceable and is designed to last the alarm's full service life, provided it remains powered from the mains between any outages.
How many alarms can be linked together?
Up to 24 Wisualarm mains-powered smoke and heat alarms can be hardwired together on the interconnect line, so that any single alarm triggering sounds every linked unit in the property.
Can this alarm work with wireless Wisualarm devices?
Yes, if fitted with the optional DHI-HY-MRF50-R8 wireless interconnect module, which lets the HT5MA join the 868MHz WisuLink mesh alongside battery-powered wireless alarms.
What does the yellow LED mean?
A yellow LED flashing twice per minute indicates a sensor fault and the unit should be replaced; flashing once per minute indicates a low battery backup fault requiring attention.
BTU & WATT Calculator
Room Dimensions
Room Type
Living Room
Bedroom
Kitchen
Bathroom
Conservatory
Hallway
Glazing Type
Single Glazed
Double Glazed
Triple Glazed
External Walls
0 Wall
1 Wall
2 Walls
3 Walls
4 Walls
Insulation Level
Poor
Average
Good (New Build)
Required Heating
0
Watts
0
BTUs
Do you have a question about this product?
One of our expert advisors will be happy to help you!
