Field Controls B794589 User Manual

COMBUSTION AIR SYSTEM

MODEL: CAS-4JR

This product is designed for use with any natural gas or LP burning furnace, water heater, or boiler with a
24 VAC control system. It may be used with a residential water heater with additional hardware. It may
also be used with more than one appliance. The CAS unit mechanically draws air into a structure and
disperses it near the combustion air intake of an appliance. Refer to Diagram A and Table 1 for guidance
in setting up the CAS system based on the size and length of the connecting ductwork and the input rating
of the appliance.

ITEMS INCLUDED IN KIT:

1- CAS fan unit
1- 4" galvanized intake Air Vent Hood
2- Mounting brackets to secure the CAS to a wall
2- Wire/conduit connector(s)
1- Instruction Sheet

READ THESE INSTRUCTIONS CAREFULLY AND COMPLETELY BEFORE PROCEEDING WITH THE INSTALLATION.

This device MUST be installed by a qualified agency in accordance with the manufacturer's installation instructions. The definition of
a qualified agency is: any individual, firm, corporation or company which either in person or through a representative is engaged
in, and is responsible for, the installation and operation of HVAC appliances, who is experienced in such work, familiar with all the
precautions required, and has complied with all the requirements of the authority having jurisdiction.

Please retain these instructions after installation.

Installed By: Phone:

www.fieldcontrols.com

Installation Date:

GENERAL SYSTEM OPERATION

The thermostat (wall thermostat, or Aquastat) calls for heat and energizes a relay which activates the CAS 1.
unit. After the CAS fan has come up to speed, an internal air pressure switch closes and completes the circuit
to allow the burner to fire. If the appliance is power vented, the venter and CAS activate simultaneously. After
the CAS comes up to speed, a pressure switch in the unit closes and allows the appliance to fire.
After the heating requirement has been satisfied, the thermostat circuit will open and deactivate the burner 2.
and CAS unit.
For power vented systems with a post purge device, the power venter and CAS operate for a period of time 3.
after the burner has shut off to purge remaining flue gases from the vent system.

INSTALLATION SAFETY INSTRUCTIONS
CAUTION: This device must be installed by a qualified installer in accordance with the manufacturer's installation

instructions.

This combustion air system must be installed by a qualified installer. "Qualified Installer" shall mean an individual 1.
who has been properly trained or a licensed installer.
Plan the system layout before installation to avoid the possibility of accidental contact with concealed wiring or 2.
plumbing inside walls.
Disconnect power supply before making wiring connections to prevent electrical shock and equipment damage.3.

SIZING AND SETUP

Diagram A shows the maximum equivalent length and size of duct pipe that should be used when installing the
CAS system. Using the chart will help ensure that the proper amount of air is drawn into the structure as needed
by the appliance. The defined regions shown correspond to the CAS airflow characteristics when using 4" and 6"
diameter sheet metal duct pipe. Follow the guidelines below to properly size and set up the CAS.

Determine the maximum input firing rate of the appliance, or the maximum total combined input firing rate of 1.
multiple appliances that will be used.
On Diagram A, locate the point that corresponds to the maximum total combined input firing rate along the 2.
horizontal axis.
Draw a vertical line through the point on the horizontal axis.3.
Draw a horizontal line through the point where the vertical line intersects the 4" duct pipe curve.4.
The horizontal line will intersect the vertical axis of the graph at the maximum allowable equivalent length of 5.
4" duct pipe, for the given firing rate.
Position the motorized CAS unit according to the guidelines in the "Installation" section.6.
Determine where the intake air vent hood will be located based on the recommendations in the 7.
"Installation" section.
Calculate the total equivalent length of duct pipe including elbows and fittings needed to connect the CAS unit 8.
to the vent hood. DO NOT add any equivalent length for the intake hood; the hood effect is figured into the
graph.
Using Table 1, verify that the calculated total equivalent length of pipe does not exceed the maximum length 9.
of 4" pipe as found in Step 5. If so, repeat Step 5, drawing a horizontal line where the vertical line drawn
intersects the next larger size duct pipe curve and verify from steps 6-8 that the total equivalent length does
not exceed that as found in Step 5 for the larger size duct pipe.
EXAMPLE:10. A gas fired appliance firing at 100,000 BTU/hr where the CAS unit needs to be placed 30
equivalent feet from the intake hood.

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0

20

40

60

80

100

120

140

160

180

200

220

240

260

280

300

50,000 60,000 70,000 80,000 90,000 100,000 110,000

CAS-4JR SIZING CHART

Max. Equivalent Duct Length, feet

Input Firing Rate, BTU/hour

Max. equivalent length of 4" pipe
available when using the 4" CAS hood

Max. equivalent length of 6" pipe
available when using the 4" CAS hood

Table 1

TOTAL INPUT OF APPLIANCE MAXIMUM EQUIVALENT FEET OF DUCT PIPE

(BTU/hr) 4" Pipe 5" Pipe 6" Pipe

50,000 230 300 300
60,000 16 0 300 300
70,000 105 300 300
80,000 70 214 300
90,000 40 122 300

100,000 25 76 180

110,000 15 46 80

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Diagram A