Dexon Canada Air Systems Inc MDH Series Use Manual Version 07.2019
3.2 FEATURES:
Overheat protection: For Ordinary Location rated units one Klixon thermostat located at the
top of the element mounting panel will shut down the heating elements if the temperature at the
top of the heat exchanger rises above approx. 65°C. For Hazardous Location rated units,
additional thermostats on each element will cut power when the skin temperature of the
elements reaches approx. 107°C.
Low Temperature Shut Down: When the sensor at the discharge of the blower heater senses
temperature lower than 0°C (typically) the unit will go into a “Low Temp." shut down condition to
prevent freezing of the space. See sequence of operations for more information.
Discharge Temperature Sensor: Monitors the discharge temperature to regulate the heating
elements to maintain a preset discharge temperature of between +6°C to +18°C with an
adjustable 5° range (Example: A +6°C preset discharge temperature would be adjustable from
+5°C to +10°C and +15°C preset temp. would be adjustable from +13°C to +18°C).
Auto Reset: The blower heater will automatically restart when temperatures reach +2°C
(typically) after a “Low Temp.”shut down has occurred or when the elements have sufficiently
cooled from an “Overheat” condition.
Fan Boost Start: Provides a momentary full output voltage to the fan for cold start-up.
Proof of Fan Rotation: Provides an indication when the fan is no longer running and activates
remote alarms when the optional alarm module is included.
Staged Heating: Staged heating is provided for the larger SMDH and RVDH series blower
heaters only, to prevent high current draw when not required.
CSA Certified: Dexon blower heaters are CSA certified for Class 1, Div. 2, Gas Groups C & D
Locations, Temp. Code T2C and for Ordinary Locations. Any modifications to existing certified
units will require special CSA approvals/certification.
3.3 OPTIONS:
Various Installation Configurations: The MDH series blower heaters can be installed outdoor
free standing (See MDHIL series for indoor inline or indoor wall mounted). Outdoor units have
360°louvers and the MDHIL, indoor inline or wall mounted units have a 6” air inlet collar either
on the top or side of the cap. Outdoor air intake hoods can be provided for wall mounted units.
Available Voltages: All Dexon blower heaters require two circuits; one for controls and one for
heating elements. Controls require 120VAC and heating elements can be 120,208,240,480 or
600 Volt and can be 1 phase or 3 phase.
External Alarm Interfacing: An optional “95ALM” three alarm status output relay module is
available for interfacing with external alarms or PLC. The alarm module can be easily added
after installation if required.
Manual Mode Interfacing: A set of manual mode interfacing terminals is available for dry
contact only, input from PLC, Hatch/Lid Switch, Gas Detector etc. dry contacts to temporarily
initiate “Manual” mode (full fan speed) for added safety.
