Circular Electric Duct Heaters

Heaters with built-in Thyristor Controls are available from stock.These heaters can be mounted in circular ducting and control the output air stream temperature to within + or – 1ºc.

Thyristor (pulse) control has superseded thermostat or step control, using time proportioned thyristor ‘pulse’ control to let through just the right amount of energy to match the set point temperature – thereby saving energy.

This method can respond to changes in airflow & input temperature without drifting or overshoot and is limited only by the quality of the temperature sensor.

The heater has a 0 – 35c set point (screwdriver) adjuster on the front, together with LEDs to signal heater pulse, airflow fault and the status of fan (depending on version).

Minimal Energy Loss

Quick Installation (no pipes, no pumps)

Quality Guarantee

Integral Thyristor pulse control (see options below)

MEMs airflow sensor

Fan-off delay timer

Optional BMS input/output

Remote adjustment

Pre-heat fresh air

Re-heat air from heat exchanger

Room heating

Vary individual room temperature



Heater Construction

Electric resistance heaters comprise of plain sheathed stainless steel mineral insulated type elements mounted in standard ISO duct sizes.
Casing is 0.9mm galvanised steel with an airtight seam.

The terminal box has knockouts for power input & signal inputs. A mains isolator will be required adjacent to the heater. Heating elements are stainless steel mineral insulated type, sized for air heating application. Overheat cut-out is fail safe, 120c pre-set, liquid gas type with contacts rated for direct load switching (single phase).

If you are providing your own controls, you need to allow for an air proving switch and a suitable power relay.



Control Options

Our heaters can be purchased with the following control options:


Ideal for customers who want to use their own system or remote control panel.

Each Heater includes:

  • Elements with 4 mm tails for cable connections, or copper busbars & clamps.
  • A fail safe, liquid filled, manual reset high temperature cutout. This can be used in series with the element or with a contactor on larger heaters.
  • Additional control items can be supplied on request.

The TC3 is a basic control for heaters up to 3kW.

Includes temperature & safety controls for a quick installation.

The TC8 is our Full Feature Built-In Set Point Control.


  • Thyristor ‘Pulse’ Control and set point
  • DTFS combined airflow & temperature sensor
  • Fused fan outputs         
  • Off delay timer
  • Remote start/stop
  • Fault signal
  • Various inputs
  • Heaters up to 42 kW
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