Field Controls 46255400, CAS-1 User Manual

COMBUSTION AIR SYSTEM

Model: CAS-1

4” IAH HOOD

4” VRV

This product is designed for use on the Beckett AFII Series oil burners and
AF/AFG Series oil burner with a combustion air intake. For the purpose of routing
combustion air directly to the burner, with the added safety feature of the vacuum
relief valve.

Note: For burner inputs up to 2.0 GPH.

THE PURPOSE OF THE VACUUM RELIEF VALVE (VRV)

The Vacuum Relief Valve is a safety device to guard against
combustion problems associated with directly connecting oil
burners to the outside. Typical problems can be caused by
blockage of the intake termination, icing up of the duct work and
effects of leeward side wind effects on a building. The VRV gate
operates on changes in the vacuum pressure generated by the
inlet to the oil burner.

VRV OPERATION

The VRV gate will remain closed during normal burner operation.
During an abnormal operation (i.e., blockage of the intake or
change in external building pressures) an increased negative
pressure on the intake of the burner causes a reduction in burner
air flow. Under this condition the VRV gate opens, stabilizing and
maintaining proper air flow to the burner. The VRV gate closes
again once the abnormal condition is corrected.

Figure 1

INSTALLATION
MOUNTING ON BECKETT AFII SERIES BURNER

1. Remove burner inlet cover. (See Figure 1)

2. Mount VRV tee assembly or 90o elbow onto the burner inlet.
Fasten using three (3) sheet metal screws on all joints. (See
Figure 2)

3. Assemble VRV balance weight onto the gate. Screw the
weight all the way in. Then attach lock nut and knurl nut.
(See Figure 3)

4. Mount the VRV assembly into the tee and fasten with a
screw and nut in collar tabs. (See Figure 4) To ensure
proper operation, check the gate for being level across the
pivot point and plumb.

MOUNT ON BECKETT AF/AFG SERIES BURNERS WITH A COMBUSTION
AIR INTAKE

1. Mount VRV tee assembly or 90o elbow onto the combustion
air intake inlet. Fasten using three (3) sheet metal screws on
all joints. (See Figure 5)

Figure 2

Figure 3

Figure 4

2. Assemble VRV balance weight onto the gate. Screw the
weight all the way in. Then attach lock nut and knurl nut.
(See Figure 3)

3. Mount the VRV assembly onto the tee and fasten with a
screw and nut in collar tabs. (See Figure 4) To ensure
proper operation, check the gate for being level across the
pivot points and plumb.

Page 2

Figure 5

TERMINATION LOCATION GUIDELINES

1. Mount intake hood 12 inches above finished
grade. If mounting on the side of a building
prone to drifting snow, mount 12 inches
above the snow line.

2. Mount at least 12 inches away and on the
same wall if sidewall venting.

3. Always mount with the inlet vent termination
opening pointing down.

INLET VENT TERMINATION INSTALLATION

1. Cut a 4 1/4" diameter hole through the
sidewall of the building.

2. Slide the inlet vent pipe through the hole and
fasten to the wall with appropriate fasteners.
Seal the edges of the mounting plate with a
silicone sealant or equivalent.

Figure 6

DUCT WORK INSTALLATION

1. Duct length distance, a maximum of 30
linear feet of standard duct pipe and two (2)
90o elbows. Subtract 7 feet from the
maximum linear feet for every 90o elbow
added. Maximum linear footage will be less
for flex duct. Consult manufacturer for

Figure 7

equivalent lengths.

2. Route duct work from the VRV tee to the inlet vent termination with as minimum a number of
elbows as possible.

3. Secure and support the duct work for the design and weight of the material used, to prevent
physical damage and separation of joints. For guidelines refer to recognized national building
codes or according to any local codes.

4. To reduce uncontrolled air leakage into the duct, tape all joints and seams using standard duct
tape.

Note: To prevent sweating on the outside of the duct, when operating in areas that have -10oF or

below design temperatures. Insulate the duct work at least 10 feet from the inlet vent termination.

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PN 46255400 Rev D 06/00