Reznor SHH (Indoor PreevA) Unit Installation Manual - Manual (Page 25)

Form I-PDH/SDH/PEH/SHH/PXH, Page 25
6.4.4.3 Mixing Box
Damper and Control
Options
Mixing box options vary by model. Depending on the control option ordered (identified
on the wiring diagram), the mixing box may or may not have dampers. Depending on
the configuration and controls, dampers may be outside air only or outside and return
air with manual or motorized control. Damper motor may be 2-position, 3-position, or
modulating and may be controlled by unit operation, unit operation and a damper posi-
tion dial (potentiometer), discharge temperature, mixed inlet air temperature, building
pressure, or a building automation system.
Dampers always close on shutdown.
TABLE 17 - Air Inlet and Damper Controls by Mixing Box Option
Mixing Box
Configuration
(FIGURE 17)
Air Inlet
Control
Option
Dampers
Damper Motor Function
(damper position)
Damper Controlled by
Option GD1,
GD2, or GD3
GE3
Outside
Air only
2-position (open/closed) Unit operation.
GE4 3-position (2 open/closed) Unit operation with damper "stop" set by unit-mounted adjustable damper dial
(potentiometer).
Option GD4
or GD5
NONE No factory-installed dampers or controls
GE5
Outside
and
Return
Air
None Damper controlled by a manual quadrant.
GE6
2-position (outside air
open/return air open)
System control (switch or field-supplied time clock).
*GE7
Return air temperature provides warm-up or cool-down by delaying opening of outside air
damper.
GE8
3-position (2 mixed/return
air only)
Unit operation with damper "stop" set by unit-mounted adjustable damper dial
(potentiometer).
GE10 Modulates outside air
and return air dampers to
provide mixture of outside
and return air in response
to control
Unit operation with damper "stop" set from a remote adjustable damper dial (potentiometer).
Requires installation of shipped-separate potentiometer; follow manufacturer's instructions.
GE11 Discharge air temperature.
GE12
Discharge air temperature with unit-mounted adjustable damper dial (potentiometer) set to
always provide a minimum amount of outside air.
*GE13
Modulates outside air
and return air dampers to
provide mixture of outside
and return air in response
to control
Discharge air temperature plus return air temperature setting to provide warm-up or cool-
down by delaying opening of outside air damper.
*GE14
Discharge air temperature plus return air temperature providing warm-up or cool-down
by delaying opening of outside air damper and with unit-mounted adjustable damper dial
(potentiometer) set to always provide a minimum amount of outside air after delay.
GE15
Building pressure. Requires installation of shipped-separate pressure null switch. See page
26 and follow manufacturer's instructions.
GE16 DDC control from field-supplied automated building system.
GE21
Applies to PREEVA with cooling operation; outside air damper is controlled by enthalpy (heat
content in a lb of air) using an economizer logic module. On a call for low stage cooling if the
enthalpy of outdoor air becomes low, the outdoor air damper opens to reduce the cooling
load in the building. As enthalpy of outdoor air increases, the outdoor air damper closes to a
preset minimum condition. During economizer operation, the mechanical cooling is operated
by stage 2 cooling on the space thermostat. The economizer is automatically locked out
during heating and holds the outdoor air damper at the minimum position or closed setting.
The enthalpy sensor is shipped loose for field installation in the outside air duct. See
instructions starting on page 27.
GE22
Applies to PREEVA with cooling. In cooling mode, both outside air and return air dampers
are modulated by enthalpy (heat content in a lb of air) using an economizer logic module.
On a call for low cooling if the outdoor air enthalpy is lower than the return air enthalpy, the
outdoor air damper proportions open. If the outdoor air enthalpy is higher than the return
air enthalpy, the outdoor air damper closes to minimum position. If outdoor air enthalpy and
return air enthalpy are equal, the outdoor air damper proportions open. During economizer
operation, the mechanical cooling is operated by stage 2 cooling on the space thermostat.
The economizer is automatically locked out during heating and holds the outdoor air damper
at the minimum position or closed setting. Two enthalpy sensors are shipped loose for field
installation, one in the return air duct and one in the outside air duct. See instructions starting
on page 27.
*GE7 provides ASHRAE Cycle I; GE14 provides ASHRAE Cycle II; GE13 provides ASHRAE Cycle III
( NOTE: Electrical damper
control GE options are
listed on the unit wiring
diagram.)
Adjust the Damper
Linkage
When a mixing box has both an outside air and a return air damper, both dampers
are closed for shipping. The linkage for the return air damper must be adjusted prior to
use. Follow instructions to adjust damper linkage.
1) Open the door on the side of the mixing box.
2) Loosen the setscrew on the return air damper rod at the damper arm.
3) Manually open the return air damper. While the damper blades are opening, the
damper rod and arm assembly will automatically move to the correct position.
4) Tighten the setscrew. Close the door.