U-5 IOM
5
Optional preheat section
The preheat section is located after the outside air
damper section and the filter section. It can be
access via access panels on either side of the heat
pump (see Figure 4).
Electric Preheat — Optional
The Mammoth 100% Outdoor Air unit provides
optional electric heat to preheat the outdoor air to a
point where efficient compressor heating can take
place.
The electric heater is a pre-assembled package
designed to be installed internal to the unit. The
elements are constructed of nichrome wire and
include thermal limits, duct high limit, air proving
switch, and nonfused disconnect switch. The heater
operation is determined by outside air temperature, to
maintain a minimum 40 F entering air temperature to
the airside coil.The minimum entering air temperature
to the air coil is 40 F to allow operation of the
mechanical refrigeration for heating.
Figure 5. Optional preheat wiring diagram
The heater includes its own control box separate
from the unit’s electrical panel. It is mounted on the
outside of the unit casing, which houses all the heater
control components and safety devices. The heater is
U.L. listed. A separate power source from the unit is
required.
Hot Water Preheat — Optional
The Mammoth 100% Outdoor Air unit provides
optional hot water coils to preheat cold outdoor air to
a point where efficient compressor heating can take
place.
The hot water coil is constructed of aluminum fins
bonded to seamless copper tubes.
Units with the optional temperature control system
include a two-way, two-position, spring return valve
actuator. The valve actuator is controlled to maintain
a minimum 40 F entering air temperature to the air
coil to allow operation of the mechanical refrigeration
for heating. A freezestat closes the outdoor air
dampers and stops the fan and compressor if mixed
air is below 33 F.
