General System Operation; Installation Safety Instructions - Field Controls CAS-4JR Manual

GENERAL SYSTEM OPERATION

1. The thermostat (wall thermostat, or Aquastat) calls for heat and energizes a relay which activates the CAS
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 fi re. 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 fi re.
2. After the heating requirement has been satisfi ed, the thermostat circuit will open and deactivate the burner
and CAS unit.
3. For power vented systems with a post purge device, the power venter and CAS operate for a period of time
after the burner has shut off to purge remaining fl ue gases from the vent system.

INSTALLATION SAFETY INSTRUCTIONS

CAUTION: This device must be installed by a qualifi ed installer in accordance with the manufacturer's installation
instructions.
1. This combustion air system must be installed by a qualifi ed installer. "Qualifi ed Installer" shall mean an individual
who has been properly trained or a licensed installer.
2. Plan the system layout before installation to avoid the possibility of accidental contact with concealed wiring or
plumbing inside walls.
3. Disconnect power supply before making wiring connections to prevent electrical shock and equipment damage.
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 defi ned regions shown correspond to the CAS airfl ow characteristics when using 4" and 6"
diameter sheet metal duct pipe. Follow the guidelines below to properly size and set up the CAS.
1. Determine the maximum input fi ring rate of the appliance, or the maximum total combined input fi ring rate of
multiple appliances that will be used.
2. On Diagram A, locate the point that corresponds to the maximum total combined input fi ring rate along the
horizontal axis.
3. Draw a vertical line through the point on the horizontal axis.
4. Draw a horizontal line through the point where the vertical line intersects the 4" duct pipe curve.
5. The horizontal line will intersect the vertical axis of the graph at the maximum allowable equivalent length of
4" duct pipe, for the given fi ring rate.
6. Position the motorized CAS unit according to the guidelines in the "Installation" section.
7. Determine where the intake air vent hood will be located based on the recommendations in the
"Installation" section.
8. Calculate the total equivalent length of duct pipe including elbows and fi ttings needed to connect the CAS unit
to the vent hood. DO NOT add any equivalent length for the intake hood; the hood effect is fi gured into the
graph.
9. Using Table 1, verify that the calculated total equivalent length of pipe does not exceed the maximum length
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.
10. EXAMPLE: A gas fi red appliance fi ring at 100,000 BTU/hr where the CAS unit needs to be placed 30
equivalent feet from the intake hood.
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