Field Controls B794668 User Manual

COMBUSTION AIR SYSTEM

Model: CAS-6, CAS-6SK, CAS-7, and CAS-7SK

This product is designed for use with any oil or gas fired furnace, water heater, or boiler with 24 VAC or
120 VAC control systems. It may also be used with millivolt water heaters and 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 Diagrams A & B for guidance in setting up the CAS system based on the size and length
of the connecting duct work and the input rating of the appliance.

ITEMS INCLUDED:

1- CAS Unit (ETL Listed) "Fan-In-A-Drum"
1- Star Kap (only on SK Models)
2- Mounting Brackets for CAS Unit
2- Wire/Conduit connectors
1- 24VAC Control Relay (SPDT)
1- 120VAC Control Relay (SPDT)

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:

Installation Date:

www.fieldcontrols.com

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 will typically activate before
the CAS unit.

After the heating requirement has been satisfied, the thermostat circuit will open and deactivate the 2.
burner and CAS unit.

For power vented systems with a post purge device, the power venter will operate for a period of time 3.
determined by the post purge timer setting 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 1.
individual who has been properly trained or a licensed installer.

Plan the system layout before installation to avoid the possibility of accidental contact with concealed 2.
wiring or plumbing inside walls.

Disconnect power supply before making wiring connections to prevent electrical shock and 3.
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-6 system; Diagram B shows the same for the CAS-7. Using this table 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's airflow characteristics when using various sizes of duct pipe for the CAS-6 and CAS-7. Follow the
guidelines below to properly size and set up the CAS system.

Determine the input firing rate of the appliance, or the total firing rate of multiple appliances that will 1.
be used.

Determine the location of the CAS unit according to the guidelines in the Installation section.2.
Determine where the intake air StarKap will be located based on the recommendations in the Installation 3.

section.
On Diagram A or B (as appropriate), locate the point that corresponds to the firing rate along the 4.

horizontal axis and draw a vertical line through this point.
The line should pass through at least one of the pipe size regions on the table. The regions correspond to 5.

the maximum equivalent lengths of the given diameter duct pipe that will be adequately sized for
the application.

Calculate the equivalent length of the smaller diameter duct pipe that may be used with the particular 6.
CAS system, including elbows, reducer/increaser and other fittings (except the StarKap, see the Field
Controls Contractor Reference Guide). The effects of the StarKap are already figured into the diagram,
so do not attempt to include any value for the StarKap in your calculation for equivalent length. Draw a
horizontal line through the point corresponding to the equivalent length on the vertical axis.

Locate the intersection of the two drawn lines. If the intersection lies in the region for the equivalent length 7.
of pipe for which the equivalent length was calculated, then that diameter of duct pipe will be of sufficient
size for the application. If not, then repeat step 7 using a larger diameter duct, then proceed to step 9.

If the intersection of the two lines falls into the larger duct region, then that diameter duct will be of 8.
sufficient size for the application. If it falls to the right of the larger pipe region, then even larger pipe or
additional CAS units will be required for the application. For assistance in this case, call Field Controls
Technical Support at 1-800-742-8368.

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0.0

25. 0

50. 0

75. 0

100. 0

125. 0

150. 0

175. 0

200. 0

400 600 800 1000 1200

2.90 3.90 4.90 5. 90 6. 90 7. 90

12"

PIPE

10"

PIPE

6"

PIPE

8"

PIPE

6" DUCT
REGION

8" DUCT
REGION

10"DUC T

REGION

12" DUCT

REGION

OIL INPUT FIRING RA TE, GPH

INPUT FIRING RATE (BTU/H x 1000)

#2 OIL = 140,000 BT U/GA LL ON

EQUIVALENT LENGTH OF PIPE (ft.)

DIAGRA M A

CAS-6 (FAN + STARKAP SK-10) SIZING C HART

MAX. EQUIV ALENT FEET OF PIPE

Example: An oil fired appliance firing at 10.5 gph where a CAS-7 unit needs to be placed at a location
requiring 80' of pipe from the StarKap, using two 90

o

elbows:

From Diagram B, a vertical line is drawn through the point at 10.5 gph on the Oil Firing Rate scale. For 80
feet of 10" pipe, two 90 degree elbows, and two increaser/reducers, the equivalent length is 80 + 18 + 18 +
6 + 6 = 128' of equivalent length. A horizontal line drawn through the point at 128' on the Equivalent Length
scale intersects the vertical line in the 12" duct region of the diagram. Since the intersection is not in the 10"
duct region, recalculate the equivalent length using 12" duct: 80 + 21 + 21 + 7 + 7 = 136' of equivalent
length. A horizontal line drawn through the 136 point on the Equivalent Length scale intersects the vertical line
within the 12" duct region of the diagram; therefore, 12" duct will be of sufficient size for the application.

Diagram A

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DIAGRA M B

CAS-7 (FAN + STARKAP SK-12) SIZING CHART

MAX. EQ UIVALENT FEET OF PIPE

0.0

25.0

50.0

75.0

100.0

125.0

150.0

175.0

200.0

800 1000 1200 1400 16 00 1800 200 0

INPUT FIRING RA TE (BTU/H x 1000)

#2 OIL = 140,000 BT U/GALLON

EQUIVALENT LENGTH OF PIPE (ft.)

5.7 6.7 7.7 8.7 9.7 10.7 11.7 12.7 13.7

OIL INPUT FIRING RA TE, GPH

12"
PIP

E

10 "

PIPE

8"

PIPE

14"
PIPE

8" DUCT

REGION

10" DU CT

REGION

12" DU CT

REGION

14"

DUCT

REGION

Diagram B

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