EngA ENGINEERED AIR HE Series

A HE, DE & RE MANUAL
IOM-26 14 of 33 Oct 12 R4
FIELD INSTALLED DAMPERS
At times it is desirable to have a damper external to the unit. In some cases the operation of these
dampers may cause a “gas trap”, which is a volume of air trapped within the unit between damper sections.
In this case a pre-purge cycle shall be used to provide at least four air changes in the ducting before an
ignition attempt.
Where external dampers of any kind are used, the make-up air unit shall be electrically interlocked with the
dampers in such a way as to prevent ignition attempt unless the dampers are fully open.
3 Position inlet dampers on dual capacity units:
 On low capacity: the profile plate bypass damper should be closed. The outside air inlet dampers
should be open about 1" (25mm).
 On high capacity: the profile plate bypass damper should be open and the outside air inlet dampers
should be fully open.
HE WITH RECIRCULATING MIX BOX OR RE SERIES (IN USA ONLY).
DE WITH RECIRCULATING MIX BOX (CANADA OR USA).
Warning:
On heaters which recirculate room air, outside ventilation air must be provided
in accordance with the information shown on the name plate.
Recirculation of room air in HE, DE & RE units may be hazardous in the presence of:
A. Flammable solids, liquids, and gases and
B. Explosive material (i.e.: grain dust, coal dust, gunpowder, etc.) and
C. Substances which may become toxic when exposed to heat (i.e.: refrigerants, aerosols, etc.)
Recirculation units are not recommended in uninsulated or poorly insulated buildings where
outside temperatures fall below 32°F (0°C).
The ventilation air (outside air) shall be ducted directly to the heater. The outside air intake shall
not be located within 20 ft (6 m) horizontally of the vertical plane in which combustible gas, vapor
or dust is present.
Excessive recirculation or insufficient ventilation air (outside air), which results in inadequate
dilution of the products of combustion products generated by the recirculating HE with mix box or
RE heater, may create hazardous concentrations of carbon dioxide, carbon monoxide, nitrogen
dioxide, and other combustion products in the heated space.
If propane powered forklift trucks or other fossil fuel powered equipment are utilized in the
conditioned space, additional ventilation requirements for the facility must be addressed
separately.