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8. Draw a horizontal line on Diagram A or B that passes through the point located in step 5. The
position of the point along this line relative to the left and right borders of the region it falls into
indicates the relative position that the balance weight of the VRV should be adjusted to. If the
point falls near the leftward border of a region, then the VRV balance weight should be adjusted to
it's minimum position. This corresponds to turning the balance weight screw as far counter-
clockwise as possible.
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.
From Diagram A or B, the point at 100,000 BTU/Hr on the "Gas Firing Rate" scale
and 30 equivalent feet falls in the "4 inch Duct, Hood, and Orifice Ring" region.
The point is approximately 2/3 of the horizontal distance between the left and right
boundary of the region. The left boundary is the edge of the graph, the right
boundary is the diagonal line that says "4 inch Duct, Hood & Orifice Ring."
Therefore, place the Orifice Ring into the inlet of the CAS so that it sits on the
ledge above the fan. It does not matter which way the Orifice Ring is turned as
long as it is pushed down against the ledge completely. Use 4" diameter pipe to
connect the vent hood and the CAS unit. Install a VRV-6 and the included 4x6
inch Increaser on top of the CAS unit and adjust the balance weight to 2/3 of the
distance of it's full adjustment range from it's minimum setting. The minimum
setting is with the balance weight turned all of the way counterclockwise.
Table 1
Total Input of
Appliance
CAS-4,4mV
Gas
(BTU/hr)
50,000
75,000
100,000
125,000
150,000
175,000
200,000
225,000
250,000
300,000
350,000
400,000
450,000
Maximum Equivalent Feet of Installation
4" Duct And Hood
W/Restrictor
Intake Air Hood
HI
LOW
300
300
300
300
300
300
300
300
300
300
220
300
174
108
232
99
48
152
52
14
102
20
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Page 3
4" Duct And 4"
6" Duct And 6"
Intake Air Hood
HI
LOW
HI
300
300
300
300
300
300
220
300
118
300
63
300
32
300
68
13
300
45
NA
300
16
NA
300
NA
NA
193
NA
NA
109
NA
NA
56
LOW
300
300
300
300
300
300
300
239
150
53
8
NA
NA
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