W Tombling Ltd - activair
 about W Tombling Ltd - activair How to contact us Please send me a quotation sign up for our free activair newsletter


Heater Homepage
High air volume fan heaters
Wall mounted electric heaters
Portable heaters
- 3 phase
Portable electric heater
- single phase
Portable radiant heater
Wall mounted radiant heaters
Portable dehumidifier
Typical Applications
Heat Loss Calculation
Controlling Our Heaters
Installing Our Heaters
Commercial Buildings
Green Houses
Condensation Control
Heater FAQ's

Search this site:

Using : 
All Words 
Any Words

W. Tombling Ltd.

Wembley House
Dozens Bank
West Pinchbeck
PE11 3ND

+44 (0) 1775 640 049

+44 (0) 1775 640 050


controlling activair fan heaters using thermostats, time switches and control panelsControl panels, thermostats and time switches for Activair fan heaters --------------  


Element control
The elements may be controlled either:

  • ON/OFF using a electromechanical relay (contactor)

  • PHASE ANGLE control using electronic switching.


    Element currents
    Heater size kW 6 10 13.2 20
    Single phase (240V) A 25 42 55 84
    Three phase (415V) A   14   28

Element current per phase for different models is given in the table opposite, whatever control method is chosen it must be current rated correctly.


Fan motor control
Speed control MUST NOT be used.

The fan motor may be switched on/off with the element assembly, or run continuously. Some systems incorporate an additional relay to:

  • start the fan before the switching the elements on. This is useful in high humidity environments where moisture build up on the element ceramics may cause nuisance tripping of the element mcb.

  • run the fan for a short period after the element switches off to purge residual heat, extending the elements lifespan.

The fan motor in all models (including 3phase heaters) is 240V, single phase, 50Hz. 1.8A full load current.

Operation of fan motor overload or over current protective circuits MUST disconnect the elements.

Safety overheat cutout
Each Activair ACE fan heater is fitted with a safety overheat cutout. Under normal conditions the contacts are closed, if the temperature within the heater exceeds safe working conditions the contacts will open. Once the temperature has fallen the cutout will automatically reset.

The cutout is rated 4A (resistive) at 240V. Operation of the cutout should immediately shut down the elements AND fan.

Activair fan heaters MUST  be isolated by a suitable 1ph+N or 3ph+N isolator.  

Activair fan heaters MUST BE earthed.

Terminal connections
For 3 phase Activair electric fan heater:

Terminal connections for 3 phase fan heater

In single phase heaters terminals 2 and 3 are omitted.

Circuit diagram  
click for circuit diagram

This example illustrates a basic wiring design for a single 3 phase electrical fan heater. It can be expanded on in several ways:

  • Incorporate a time switch in series with the thermostat.
  • Add a fan overrun relay to purge excess heat
  • Replace the contactor with an electronic device. Note the fan will have to be controlled separately.
  • Add fan motor overload protection. Note because the fan motor is less than 250W, in the UK overload protection is optional.
Activair control panelsActivair electrical control panels for our fan heaters  
To simplify and speed up the installation of Activair ACE fan heaters we supply a range of off the shelf control panels. Each one contains all the electrical switchgear necessary for our heaters. Activair control panels feature:
  • Rugged steel enclosure
  • Isolator fitted with door interlock
  • Element contactor
  • Element over current protection (optional)
  • Fan motor over current protection
  • Fan mode switch - continuous operation or switch with elements
  • Visual indication of fan running and elements on

The only external item required is a suitable thermostat, humidisat or time switch.

Control device
Activair fan heaters can be controlled by a wide range of thermostats and time switches
Activair ACE fan heaters are compatible with a wide range of thermostats, time switches and environmental controllers.

Activair manufactures electronic programmable thermostats specifically designed for use in harsh industrial environments, all of which are suitable for use with our heaters.

In addition we also supply a range of thermostats, humidistats and time switches from other manufacturers.

Copyright 2002/6, W. Tombling Ltd.