AAON HB-005 - Manual (Page 8)

8
Multiple Unit Operation
When several units are used in conditioning the space,
and any are combination heating-cooling units, all
system thermostat switches must be set at either
heating, cooling, or set at ‘OFF’. Do not run part of a
system switched to an opposite mode. Cooling only
units should be switched to ‘OFF’ at the thermostat
during the heating season.
Wiring Diagrams
A complete set of unit specific wiring diagrams in both
ladder and point-to-point form are laminated in plastic
and affixed to the inside of the service access door.
Condensate Piping
A drain trap must be connected to the drain connection
located on the back of the unit. If codes require a
condensate drain line, it should be the same pipe size
as the drain nipple and should pitch downward for its
entire length toward the drain.
A “P” Trap is factory supplied and shipped in the
control access compartment for field installation. An
air break should be used with long runs of condensate
lines.
Normal Thermostat Operation
For Heating
- Set system switch to ‘HEAT’
- Set fan switch to ‘AUTO’ or ‘ON’
- Set the desired temperature
For Cooling
- Set system switch to ‘COOL’
- Set fan switch to ‘AUTO’ or ‘ON’
Air Circulation
-
Set the system switch to ‘OFF’
- Set the fan switch to ‘ON’
System Off
-
Set the system switch to ‘OFF’
- Set the fan switch to ‘AUTO’
- Do not change temperature setting
- With these settings the system is shut down,
except for the 24-volt control system power, and
the compressor crankcase heater (approx. 60W).
Night and Vacancy Operation
To reduce the operation time during low load periods,
it is recommended that the temperature setting be
increased by 5
°F during non-occupied periods of the
cooling season in commercial buildings, such as nights
and weekends. Decrease the temperature by 10
°F at
these times during the heating season.
Gas Heating System
The heating section is for use with natural gas supply
pressure of 6” to 10.5” w.g. The unit may also utilize
propane gas (after installation of a field conversion kit)
with a supply pressure to the valve of 11” to 12” w.g.
The rating plate on the furnace must be inspected to
make sure the unit is stamped for proper gas. A 1/8”
pressure tap should be field supplied by the installer in
the piping just ahead of the gas valve. The pressure
tap on the outlet end of the gas valve can be checked
to verify manifold pressure of 3.2” to 3.5” w.g. for
natural gas or 11” to 12” w.g. for propane.
A centrifugal blower that draws in outside air through a
protected
opening supplies combustion air.
This induced draft blower introduces the air to the
blower tubes, which assures even primary and
secondary airflow.
Gas heating units use AAON’s patented high efficiency
twisted tube, or dimpled heat exchanger. All heating
system and related safety controls are 100% tested on
each unit prior to shipment.
Twisted Tube
Dimpled Tube
Figure 8a, HB Gas Heat Exchangers