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2.9.2 Auxiliary Heating – Proportional Signal
Desert Aire will provide a proportional signal to modulate a heating coil control valve on units
equipped with an integral heating coil.
This signal is reverse acting or direct acting depending on the settings in the controller. It is
critical that units with hot water and steam coils be set properly for freeze protection. See
controller manual for details on the settings and outputs.
The SA dehumidifiers are equipped with a local man-machine interface on the face of the unit
controller located inside the electrical box of the unit. A separate, optional remote display
terminal can be ordered for service or remote access. See the controller manual for details on
wiring and environmental limits.
Most proportional valves have either three or four terminals for field-installed wiring.
• Four-terminal valves have two terminals for 24 VAC power and two terminals for the
signal input.
• Three-terminal valves have one terminal for the “hot” 24 VAC input, a second
terminal for the “positive” signal input, and a third, common terminal for the “neutral” 24
VAC input and the “negative” signal input.
You must follow the instructions included with the valve cut sheet. Observe the proper polarity,
or you may damage both the valve and the Desert Aire controller. See the unit wiring schematics
for information on signal wire connection points.
When the proportional signal is ordered, the binary heating output acts as an interlock. This can
be used to activate a pump, valve, or interlock that needs to be coordinated with the proportional
heating signal. The contact rating is shown on the electrical schematic. Use a transformer and
relay to energize loads that are higher than the contact rated current draw or power.
2.10 Gas Heater (Optional)
Several optional gas heater sizes and configurations are available to provide for heating of the
outdoor air during cold conditions. Several sizes, heat exchanger designs, and combinations of
capacities are available in natural gas or liquid propane fuel. Additionally, custom configurations
can be specified. The installation instructions below are guidelines for gas heater installation.
Refer to the separate gas heat instruction manual for additional instructions.
•
Corrosive environments may reduce gas heater service life. This furnace is not to be
used for temporary heating of buildings or structures that are under construction. Many
of the chemicals used during construction form acid-bearing condensate when burned.
This can substantially reduce the life of the heat exchanger.
•
LP Only:
Seamless copper tubing may only be used with gases that are not corrosive to it. See
the note below to check with your LP gas supplier before using copper. Seamless copper tubing
must comply with standard type K or L for seamless copper water tube, ASTM B 88; or seamless
copper tube for air conditioning field service, ASTM B 280.
Desert Aire - SA Manual
Summary of Contents for SA Series
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