Commercial Products  > Commercial Systems
Modulating Overdraft Damper System
Excessive Draft. No More.

Excessive draft due to vertical length inflates the operating cost of your heating appliances because heat vents up the chimney instead of going where it is needed. Too much draft can also create a dangerous operating condition for your boiler by lifting the flame off the burner. The ENERVEX Modulating Overdraft Control System stops this. 

  • High-temperature design
  • Multi-blade damper for fast accurate draft control
  • Modulating Damper Control System provides 100% overdraft control
  • Improves efficiency for any heating appliance.
  • Compact design saves valuable space
  • Flexibility accommodates both condensing & non-condensing applications
  • Maintains low emissions
  • Fast-acting, direct-drive actuator with brushless motor
  • Listed to UL378, Standard for Draft Equipment for 1400°F.
  • Maintenance-free, service-friendly design
  • Prevents flame failure and erratic performance
  • Increases boiler output
  • Extend equipment life
  • Reduces fuel cost by improving appliance efficiency
  • Reduces emissions
  • Brings most non-compliant venting installations into code compliance
  • Improves safety

The MODS system consists of the MDF, Modulating Damper and the EBC31, Modulating Fan Control along with an OPS, Over Pressure Switch. The EBC31 maintains a constant draft for the heating appliances by modulating the position of the damper.

The MODS system is supplied as a complete package with a multi-bladed damper and attached actuator, control(s), pressure sensor, draft probe and over-pressure safety switch.

Each appliance is interlocked with the control. A call for heat opens the damper completely. After a programmable pre-purge time period, the EBC31 allows the burner to fire (draft must be established within 60 seconds, or the burner will be shut down). Once the draft reaches the draft set-point the damper modulates maintaining a constant draft. The sequence is repeated every time a new heating appliance calls for heat. When an appliance shuts down, the damper will close slightly while still maintaining the draft setting. When the last appliance shuts down the damper will stay partly open in post-purge mode for a preset time period.

The integrated proven draft function will shut down the entire system in case of a power failure to the actuator or other mechanical failure. During a following call for heat, the Operating Priority function will detect if one or more appliances can be operated safely and with proper draft. If so, the appliance(s) will be able to operate without damper operation.

After two (2) hours, damper operation is checked and if present, the control will go back to normal operation. Otherwise, it will continue to operate in Operating Priority mode. The self-check is repeated every two (2) hours infinitely. During a period without actuator operation, the control is in alarm mode.

If the damper actuator has been out of commission for seven (7) days, the Bearing Cycle Activation function will open the damper for a short time and then close again. This is automatically repeated every seven (7) days, if the actuator has not been operating.

The system has over-pressure protection, so if excessive pressure builds up between the boiler outlet and the damper, the boiler will be shut down and the damper will open completely to relieve the pressure. Any errors detected during operation are shown on the digital display screen.

MODS Modulating Overdraft Damper System with modulating damper and fan control, over pressure switch
EBC 31 Modulating Pressure Controller—multi-use draft and pressure controller with integrated web server and remote access
Modulating Pressure Controller

A sophisticated multi-use draft and pressure controller with integrated webserver and remote access used with fans and dampers to monitor and maintain a constant pressure in commercial boiler and building applications.