Overview of Primary Product

Page 2
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 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.
2. After the heating requirement has been satisfied, 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 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.
1. This combustion air system must be installed by a qualified installer. "Qualified 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 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.
1. Determine the maximum input firing rate of the appliance, or the maximum total combined input
firing rate of multiple appliances that will be used.
2. On Diagram A, locate the point that corresponds to the maximum total combined input firing 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 firing 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 fittings needed to connect
the CAS unit to the vent hood. DO NOT add any equivalent length for the intake hood; the hood
effect is figured 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 fired appliance firing at 100,000 BTU/hr where the CAS unit needs to be
placed 30 equivalent feet from the intake hood.