Reznor GA1 User manual

Revision: CAUA-GA1-GA9 (04-22) 170640-A
OUTSIDE AIR/RETURN AIR MIXING BOX INSTALLATION FOR
GAS-FIRED INDOOR HEATER
Supersedes: I-CAUA-MB (04-15) PN170640R2
OPTION GA1, GA2, GA3, GA4, GA5, GA6, GA7, GA8, OR GA9 FOR MODEL CAUA
Table 1. Replacement Filters
Type
Unit Size
150, 200 250–400
Size PN (Quantity) Size PN (Quantity)
Pleated disposable 2 × 16 × 16 104109 (2)
2 × 16 × 16
104109 (6)
2 × 16 × 20 104110 (2)
Pleated permanent (aluminum) 2 × 16 × 16 104103 (2) 104103 (6)
2 × 16 × 20 101620 (2)
NOTE: Installation should be done by a qualified agency in accordance with these instructions
and in compliance with all codes and requirements of authorities having jurisdiction.
GENERAL INFORMATION
•The optional mixing box for the model CAUA heater is designed to provide the system with a supply air mixture
of return air and outside air. Application with a mixed air temperature <35°F (<2°C) requires that the CAUA unit
be ordered with option AD4.
•The mixing box is available in an assortment of configurations with a selection of actuators and controls for both
heating and cooling (requires optional cased cooling coil) modes. The mixing box is factory-assembled for field-
installation on the rear of the heater.
•All mixing box inlet air openings have duct flanges for connecting ductwork.
•Refer to the installation manual provided with the heater for important safety information and for instructions to
install the heater. The heater should be in its final installation location before installing the mixing box.
Filters
If the box was ordered with filters (option AW9 or AW11), it is shipped with the filters installed. Removable door
panels provide for filter access from either end of the cabinet. Replacement filters are listed in Table 1.
Airflow Configurations
The mixing box is installed on the rear of the heater and is available in a variety of airflow configurations (refer to
Table 2).
Table 2. Airflow Configurations
Option Opening for Outside Air Opening for Return Air
Location on Mixing Box Dampers Included? Location on Mixing Box Dampers Included?
GA1 Top Yes Bottom or Rear No
GA2 Rear Yes Top or Bottom No
GA3 Bottom Yes Top or Rear No
GA4 Bottom Yes Rear Yes
GA5 Bottom Yes Top Yes
GA6 Rear Yes Top Yes
GA7 Rear Yes Bottom Yes
GA8 Top Yes Rear Yes
GA9 Top Yes Bottom Yes

2CAUA-GA1-GA9 (04-22) 170640-A
GENERAL INFORMATION—CONTINUED
Dimensions
Table 3. Mixing Box Dimensions
Unit Size
Dimension (See Figure 1)
A B C
Inches (mm)
150, 200 38 (965) 22 (578) 7-5/8 (194)
250–400 50 (1270) 36-1/2 (927) 6-3/4 (171)
NOTE: Dimensions are applicable for an inlet location on top, bottom, or rear of mixing box.
Figure 1. Mixing Box Dimensions (Refer to Table 3)

3
CAUA-GA1-GA9 (04-22) 170640-A
Table 4. Control Options
Damper Motor Operating
Mode
Damper Control
Option** Action
Option*Description
GB2 Two-position
actuator
Heating or
heating and
cooling
— While unit is operating, outside air damper is open
Cooling
GC3C
When sensor detects low enthalpy in outside air, control opens outside air damper
to minimize cooling energy consumption and equipment cycling
When sensor detects high enthalpy in outside air, control closes outside air
damper
GC3C and GC4 In addition to above GC3C actions, control delays opening of outside air damper
based on return air temperature to provide faster cool down of supply air
GB3 Modulating
actuator
Heating or
heating and
cooling
GC1A or GC1B Outside air damper controls mixture of inlet air (requires manual setting of
potentiometer to desired minimum position)
GC1A or GC1B
with GC3A
In addition to above GC1A or GC1B action, dampers are modulated based on
mixed inlet air temperature in heating mode
GC1A or GC1B
with GC4
In addition to above GC1A or GC1B action, opening of outside air damper is
delayed based on return air temperature to provide faster cool-down (cooling
mode) or warm-up (heating mode) of supply air
GC1A or GC1B
with GC3A and
GC4
Includes all above GC1A, GC1B, GC3A, and GC4 actions
Heating
GC3A Control modulates dampers based on mixed inlet air temperature
GC3A and GC4 In addition to above GC3A action, control delays opening of outside air damper to
provide faster warm-up of supply air
GB4
Modulating
actuator with
proportional
enthalpy
control
Cooling and
heating
GC3B
In cooling mode, one sensor detects enthalpy of outside air and another sensor
detects enthalpy of return air to modulate dampers to maintain most economic mix
of inlet air (normally set to maintain between 50–56°F)
In heating mode, sensor detects mixed air temperature to modulate damper
GC3B and GC4
In addition to above GC3B action, control delays opening of outside air damper
based on return air temperature to provide faster cool-down (cooling mode) or
warm-up (heating mode) of supply air
*Damper motor option GB2 is used on all mixing box options. GB3 and GB4 are used only on mixing box options GA4, GA5, GA6, GA7,
GA8, and GA9.
**Refer to Table 5.
Control Options
NOTES:
• IMPORTANT: The standard model CAUA heater is designed for a maximum temperature rise of
75°F. At an outside air temperature >35°F (>2°C), any percentage of outside air is permitted.
• For optimum operation and to prevent condensation, the mixed air temperature going to the heat
exchanger must not be <35°F (<2°C). This inlet air temperature restriction does not apply to a
unit ordered with makeup air option AD4, which includes stainless steel components and a flue
wrapper condensate drain to permit an inlet air temperature <35°F (<2°C).
• In all cases when the unit shuts down, the outside air damper closes.
Table 5. Damper Control Descriptions
Damper Control
Option Description
GC1A Manually-adjustable (range = 0–100°F, factory setpoint = 35°F) potentiometer mounted in mixing box
GC1B Manually-adjustable (range = 0–100°F, factory setpoint = 35°F) potentiometer mounted remotely
GC3A Mixed air temperature controller (heating only)
GC3B Dual setpoint modulating enthalpy control for heating and cooling (used only with GB4 damper motor)*
GC3C Two-position enthalpy control (factory setpoint = 75°F/40% humidity) used with two-position damper motor (cooling only)
GC4 Senses return air temperature to delay opening of outside air damper and provide warm-up or cool-down time
*With two enthalpy setpoints, damper operation can be interlocked with a time clock or other device to provide a different mix depending on
occupancy or other determining factor.

4CAUA-GA1-GA9 (04-22) 170640-A
INSTALLATION
1. Cut inlet air opening and drill mounting holes (see Figure 2):
⚠ WARNING ⚠
Cut edges of metal cabinets are sharp.
a. Locate four embosses in metal panel on rear of heater where mixing box is to connect to heater. Embosses
are corner indicators for inlet air opening.
b. Carefully cut straight lines between embosses to create inlet opening using tin snips or aviation shears.
c. Mark and drill six 1/8-inch (3-mm) mounting holes as shown.
Figure 2. Embosses and Mounting Holes (Refer to Table 6)
EMBOSSES
MOUNTING HOLES

5
CAUA-GA1-GA9 (04-22) 170640-A
2. For option GA1, GA2, or GA3, select return air location:
NOTE: The mixing box was manufactured with an outside air opening with dampers in either the
top, rear, or bottom. There are two openings for return air allowing for a choice of location. When
the mixing box is shipped, one return air opening is left open and the other is covered. Depending
on the installation, the cover may be in the correct position or it may need to be moved.
a. Determine whether or not cover needs to be moved.
NOTE: Depending on which return air opening is being covered, the cover may be re-installed after
the mixing box is connected in step 3.
b. If cover requires moving, remove existing screws that secure cover, position cover over return air opening that
will not be used, and install cover using existing screws.
3. Connect mixing box:
a. On rear of heater, remove row of existing screws along bottom (save screws).
b. Position mixing box against rear of heater. If installing mixing box with one damper, reach through return air
opening or remove end panel(s). If installing mixing box with two dampers, remove one or both access panels
on ends of box.
c. Reaching inside mixing box, install existing screws to secure bottom edge of mixing box to heater.
d. Install sheet metal screws provided with mixing box in holes drilled in step 1c to secure both sides and across
top.
4. For option GA4, GA5, GA6, GA7, GA8, or GA9, adjust damper linkage:
NOTE: Both dampers are closed for shipping.The linkage for the return air damper must be adjusted
prior to use.
a. Remove access panel on end of mixing box where damper controls are located.
b. Loosen setscrew on return air damper rod at damper arm.
c. Manually open return air dampers to automatically move damper rod and arm to its correct position.
d. Tighten setscrew on return air damper rod at damper arm.
e. Replace access panel on end of mixing box.
5. Connect damper motor wires:
NOTE: Wiring depends on the damper motor and control options selected (refer to Table 4).
a. Remove door panel on front of heater.
b. Run wires from damper motor into heater cabinet, up past side of burner box (same side as blower motor
wires), and into control compartment.
c. Connect wires to terminals in accordance with wiring diagram provided with heater.
d. Replace door panel on front of heater.
Table 6. Inlet Air Opening and Mounting Hole Dimensions
Unit Size
Dimension (See Figure 2)
A B C (No. of Holes) D
Inches (mm)
150, 200 3 (76) 8 (203) 5 33 (838)
250–400 2-1/2 (64) 9 (229) 6 45 (1143)

6CAUA-GA1-GA9 (04-22) 170640-A
INSTALLATION—CONTINUED
6. Refer to installation manual provided with heater to complete installation of heater.
NOTE: To reduce noise transmission,use of a flexible duct boot to connect ductwork is recommended.
⚠ CAUTION ⚠
Ductwork must be supported—do not rely on the mixing box to support the ductwork.
7. Connect outside air ductwork to duct flange on outside air inlet of mixing box.
8. If system includes return air ductwork, connect it to duct flange on return air inlet.
9. When heater and ductwork installation is complete, turn ON electric power and gas, start up heater, and check
for proper operation of damper motor and controls.

7
CAUA-GA1-GA9 (04-22) 170640-A
NOTES

Specifications and illustrations subject to change without notice or incurring obligations.
Latest version of this manual is available at www.reznorhvac.com.
©2022 Nortek Global HVAC LLC, O’Fallon, MO. All rights reserved.
CAUA-GA1-GA9 (04-22) 170640-A