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Electric Heater Application/Operation
Factory installed electric heaters can be provided for preheat and/or post-heat. An electric preheater warms
the outdoor air prior to the energy recovery wheel to prevent frosting on the wheel. An electric post-heater
warms the air leaving the energy recovery wheel to a user specified discharge temperature. Electric heaters are
available in 208, 230, or 460 Vac (refer to heater nameplate for voltage).
Preheaters: Preheaters are standard as 2-stage, step control. Step control heaters are designed with
multiple stages made up of equal increments of heating capability. For example, a 10 kW
heater with two stages will be composed of two 5-kW stages. Preheaters are single point
wired at the factory. A temperature sensor (with field adjustable set point) is mounted in the
outdoor airstream after the preheater to turn the preheater on. See Frost Control Application
/Operation for typical set points. If the temperature falls below the set point, the first stage of
the preheater will turn on. If the first stage does not satisfy the set point, the second stage will
also turn on.
Post-heaters: Post-heaters are standard as SCR control. Post-heaters are not single point wired (see
Electrical Connections). A temperature sensor (with field adjustable set point) is mounted in
the outdoor airstream after the post-heater to turn the post-heater on. A SCR heater provides
an infinitely modulating control of the heat to provide an accurate discharge temperature. A
call for heat is required.
Electric Post-Heater
Post-Heater Control Panel
The post-heater is not single point
wired to the HRE control center.
Separate power must be supplied
to the post-heater disconnect
(located in unit control center).
Access to the post-heater control
panel is through the exhaust filter
door. The indirect evaporative
cooling media must be removed
from the unit along with the exhaust
filters to access.
Electric Preheater
The preheater is single
point wired to the HRE
control center. Access to the
preheater control panel is
through the supply filter door.
OPTIONAL ACCESSORIES