Dexon Canada Ventilation Equipment
- Outdoor Free Standing With Filter -

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The Regulated velocity Blower Heaters will maintain a preset airflow (set point). At start-up the blower heater will run at a preset idle speed for a short period to allow the temperature sensor signal to stabilize.  The fan speed will then increase until the preset airflow (set point) is reached.  In order to maintain the set point the fan speed will increase up to max speed as required to compensate for airflow obstructions or until the obstruction is removed. When the obstruction or restriction is removed it will then return to it’s set point. An LED bar graph on the status indicator will monitor the increase required to maintain the airflow set point.

The temperature leaving the unit is maintained at an adjustable preset temperature.  Typically if the discharge air temperature drops below 0º C the power to the fan and element is shut off in “Low Temp” condition to prevent freezing. A timer overrides the low temperature signal for an initial period of approx. 8 minutes every time the blower heater is reset at the status board, or control power is cycled.  The blower heater will automatically restart again once the temp sensor detects 2º C or more.  A high temperature sensor will cut the power to the heating elements if it senses temperatures above the normal operating range. After cooling down the elements will automatically restart if there is a demand.


Solid state controller designed and manufactured by Dexon provide the following features:

  • DISCHARGE TEMPERATURE SENSOR - A sensor located in the discharge air flow monitors the temperature leaving the unit to maintain a preset temperature and will also activate the Low Temp Shut Down
  • LOW TEMP SHUT DOWN - The Discharge Temperature Sensor sends a signal to the controller to shut down the fan and elements in the unit when the discharge temperature drops below 0º C. (typically)
  • LOW TEMP SHUT DOWN OVERRIDE- At start up or upon reset a short period of time is provided to allow the elements time to warm up the sensor to prevent the unit from going into a Low Temp Shut Down condition. The manual switch will also override the Low Temp. Shut down
  • OVERHEAT PROTECTION - A High Temperature Sensor located above the elements will cut power to the elements if it senses temperatures above the normal operating range. Class 1, Div. 2, Group C & D Locations will also have a sensor on each element. As sensors cool the elements will automatically restart if there is a demand
  • AIR PROOFING DEVICE -  An airflow sensor located near the base of the unit will provide a second overheat protection.  When it senses a no or low airflow it will also cut power to the elements. The air-proofing device will also provide a signal for “No Air” indication on the status board. (Please note the Blower Heater will operate normally without the air-proofing device)
  • FAN SPEED CONTROL - A potentiometer is provided on the controller to preset and adjust the fan set speed to desired air flow
  • FAN BOOST START - A full voltage boost start is applied to the fan upon start up before the fan goes into it’s preset idle speed to ensure a start up in a low speed setting
  • ELEMENT STAGING - The controller will activate stages two and three as required to maintain the preset discharge temperature, and will also send a signal to the Status Board to corresponding stages
  • PROPORTIONAL INTEGRAL FAN SPEED CONTROL - An airflow sensor at the discharge provides a signal to the controller which adjusts the fan speed as required to maintain the airflow requirements
  • STATUS INDICATION - The controller provides power and output signals to a remote Status Board to provide the following indications:

- “Blower Speed - Set Level” - this bar indicates the fans preset level required to meet the needs of the application (required air flow). This level is pegged on the “Running Level” bar to serve as a marker
- “Blower Speed - Running Level” - indicates the actual running speed of the fan necessary to maintain the required air flow
- “Low Temp”. - indicates elements are no longer able to maintain the preset temperature. The unit will completely shut down unless Low Temp Shut Down is overridden by timer or manual switch 
- “No Air”- Indicates air proofing device has detected a substantial loss of air flow at discharge. When it senses low or no flow it will cut power off to the elements to prevent over heating
- “Max Speed” - indicates the blower has reached it’s maximum speed and can no longer compensate for air flow obstruction. It will also indicate that the unit is in manual mode
- “Over Heat” - indicates an overheat condition has occurred
- “Element No.1”- indicates there is a heat demand and the elements in stage one are satisfying that demand. The LED will modulate as it meets the demand and will stay on if the demand cannot be satisfied by stage one alone
- “Element No.2" - indicate elements in stage two are required to maintain the preset temperature. This LED will not modulate
- “Element No.3" - indicate elements in stage three are required to maintain the preset temperature. This LED will not modulate
-“Man. Blower Auto” - is a manual switch provided to override the Low Temp Shut Down and put the fan to max speed
- “Reset” - a reset switch is provided to restart the unit and reset the Low Temp Override timer after a low temp condition has occurred

Status Info
  • ALARM MODULE - An optional Alarm Module is provided that would mount to the back of the status board to provide alarm for either a “No Air”, “Low Temp”, “Overheat” or Maximum Speed condition, or any combination of the four.  This Alarm Module will interface with warning devices such as automatic telephone dialing equipment, central monitoring devices, or other audible or visual alarms, etc.


  • Control voltage 120V 60 Hz at 150 to 1200 watts maximum
  • Control fused as per configuration requirements. Fused remote (by others) for Class 1, Div.2 Locations and fused internally for Ordinary Locations
  • Element voltage 208, 240, 480, or 600 Volt, one or three phase, from 3000 to 40500 watts maximum
  • Elements must be fused remote as required based on capacity.
  • A standard 8 meters of status cable is provided
  • A separate conduit is required for power, status board, and optional interfacing features used.


  • Provide a discharge duct or down pipe, as per shop drawings, dimension will vary with capacity. Typical discharge is a rectangular protruding collar. An internal transition may be provided for a round flat bottom discharge or round protruding collar if requested   
  • Four 3/8 x 1 ½ inch stainless steel bolts, nuts and washers are supplied for mounting to either a flange steel down pipe or directly on top of structure
  • The SRVDH series is flat bottomed with neoprene gasket supplied
  •  If flange mounted, flanged downpipe supplied by others
  • (We recommend raising the unit to facilitate control access due to possible snow load or flooding)
  • Avoid mounting unit with louvers facing prevailing winds
Set Level Running Level LED Indicators Warning Man-Auto Switch Low Temp No Air Max Speed Over Heat Element No.1 Element No.2 Element No.2 Reset
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