Wisualarm Mains Powered Heat Alarm | Grade D2 | Class A1 54–65°C | 9V Battery Backup | Wired Interconnect

Description

The Wisualarm DHI-HY-HT5MB is a mains-powered Class A1 fixed-temperature heat alarm certified to BS 5446-2:2003, designed 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 includes a replaceable 9V alkaline battery as standby backup, classifying it as a Grade D2 device under BS 5839-6.

A high-precision thermistor triggers the alarm when the ambient temperature reaches 54°C–65°C, and the 85dB sounder runs 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 module — enabling a hybrid system that links wired and wireless devices across a property.

54-65°C

Alarm Trigger Range

85dB

Alarm Volume @ 3m

9V

Replaceable Battery

24

Max Interconnected Units

Grade D2

BS 5839-6 Classification

BS 5446-2

Compliance Standard

Grade D2 — Familiar Replaceable Battery

The HT5MB's replaceable 9V alkaline standby battery classifies it as a Grade D2 device under BS 5839-6. This is widely specified in rental properties and retrofit installations, where a familiar, low-cost 9V battery is straightforward for landlords or occupants to source and replace as part of routine maintenance.

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.

Annual Battery Check Recommended

With a typical battery life of around 1 year, the standby 9V alkaline cell should be checked and replaced as part of an annual maintenance visit, alongside the alarm's own test and silence function, to keep the unit operating correctly during a mains power interruption.

Replaceable 9V Standby Battery

A standard 9V alkaline battery provides backup power during mains interruptions and can be replaced by any competent person without specialist tools.

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.

Product Identity

Model number

DHI-HY-HT5MB

Brand

Wisualarm (by Dahua)

BS 5839-6 Grade

Grade D2

Detection

Sensor type

Thermistor

Detection class

Class A1 — fixed temperature

Alarm temperature range

+54°C to +65°C (+129°F to +149°F)

Sampling period

10 s

Power

Primary supply

AC 100V–250V, 50/60Hz (mains)

Standby battery

Replaceable 9V alkaline battery

Battery life

Approx. 1 year

Alarm Output

Alarm volume

≥85dB(A) at 3 metres

Alarm mode

Visual and audible, continuous until reset

Silencing

Yes — 9 minutes, including via IR remote

Indicators

Standby

Green LED remains lit

Alarm

Red LED flashes once per second

Sensor fault

Yellow LED flashes twice per minute

Low battery backup fault

Yellow LED flashes once per minute

Interconnection

Wired interconnect

Up to 24 hardwire interconnected units

Wireless interconnect

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 HT5MB 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.

How often does the backup battery need replacing?

The 9V alkaline standby battery has a typical life of around 1 year and should be checked and replaced as part of routine annual maintenance, so backup power remains available during any mains interruption.

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 HT5MB join the 868MHz WisuLink mesh alongside battery-powered wireless alarms.

What's the difference between the HT5MA and HT5MB?

Both are mains-powered Class A1 heat alarms with the same 54°C–65°C trigger range and 24-unit interconnect. The HT5MA uses a sealed 10-year rechargeable lithium battery (Grade D1), while the HT5MB uses a replaceable 9V alkaline battery (Grade D2).

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Room Dimensions

Length (in m):

Width (in m):

Height (in m):

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)

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Required Heating

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Watts

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