32
COOLING SEASON—
Thermostat set at “Cool” and “Fan
Auto,” outside air damper goes to “minimum fresh air” position
when cooling thermostat closes, energizing mechanical cool-
ing. When cooling thermostat is satisfied, mechanical cooling
is de-energized, and outside air damper closes.
INTERMEDIATE SEASON—
Same as for cooling season,
except that cooling thermostat closes, starting indoor blower
motor, the enthalpy control, mounted on outside air, deter-
mines if “free” cooling or mechanical cooling should be utilized.
If outside air conditions are suitable for cooling, the mechani-
cal cooling remains off and the mixed air controller modulates
the damper motor to assume the proper damper position to
maintain mixed air setting. If outside conditions are not suit-
able for cooling, then the dampers go to “minimum fresh air”
position and mechanical cooling is energized.
HEATING SEASON—
Damper always stays at “minimum fresh
air” position while fan motor is operating. Outside air damper
closes when blower motor is off. “Minimum fresh air” position
must not allow mixed air temperatures to air handler below
50°F. during heating seasons.
CAUTION:
Because of the possibility of freeze damage, it is
not recommended that hot water or steam coils be used with
the mixing box accessory, unless provision is made to shut-off
the outside air duct 100% during freezing conditions.
Another possible system enhancement would be to install an
air proving switch in the air handler supply duct wired in series
with the compressor contactor coil (24V) which would lock out
the compressor in the event of air flow failure.
5.2 MIXING BOX KITS
ACCESSORY MODEL RXHM-A74F
NOTE:
The bottom of the air handler should be sloped in
two planes that pitch the condensate to the drain
connection. The drain pan shall not leave puddles
larger than 2 inches in diameter and
1
/
8
inch deep
for more than 3 minutes.
VERTICAL APPLICATION
A
27
B
54
HORIZONTAL APPLICATION
C
27
D
79
