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16
Installation instructions
Selecting inlet air restrictor
Note: Before installing the combustion air inlet
accessory, the appropriate inlet air restrictor must
be determined using Tables 6, 7 and 8.
Refer to Fig. 15 for mounting sequence.
B Determine the total length of the straight sections of
3" stainless steel exhaust and enter that length in line
1.
B Count the number of 90° elbows used and enter that
value in line 2.
B Count the number of 45° elbows used and enter that
value in line 3.
B For model GWH 345 ESR, enter a 1 in line 4 for
model GWH 450 ESR enter a 1 in line 5.
B Repeat steps 1 through 4 for the 3" intake pipe and
enter those values in the intake section.
B Add the totals from the Exhaust table and the Intake
table to determine the equivalent vent length. Use
this value in Table 6 to determine which restrictor
size to use.
Example
Exhaust
• 10 - 3' straight sections
• 1 - 1' straight section
Total length 31'
•1 - 90° elbow
• 1 - GWH 450 ESR termination.
Intake
• 5 - 4' straight sections
• 2 - 1' straight sections
Total length 22'
•2 - 90° elbows
• 1 - GWH 450 ESR termination.
Example
Using table 8, the following restrictors would be
required:
• GWH 450 ESR NG - restrictor 55
• GWH 450 ESR LP - restrictor 55.
Exhaust
1
Straight section length __ x 1 = ____
2
90° elbows (qty) __ x 6 = ____
3
45° elbows (qty) __ x 3 = ____
4
GWH 345 ESR termination __ x 15 = ____
5
GWH 450 ESR termination __ x 12 = ____
6 Total:
____
Intake
1
Straight section length __ x .5 = ____
2
90° elbows (qty) __ x 3 = ____
3
45° elbows (qty) __ x 1.5 ____
4
GWH 345 ESR termination __ x 6 = ____
5
GWH 450 ESR termination __ x 3 = ____
6
Total: ____
7
Total equivalent vent length = ____
Table 6 Determining equivalent vent length (see
example in Table 7)
Exhaust
Straight section length
21
x 1 = 21
90° elbows (qty) 1 x 6 = 6
45° elbows (qty) 0 x 3 = 0
GWH 345 ESR termination 0 x 15 = 0
GWH 450 ESR termination 1 x 12 = 12
Total:
39
Intake
Straight section length
22
x .5 = 11
90° elbows (qty) 2 x 3 = 6
45° elbows (qty) 0 x 1.5 = 0
GWH 345 ESR termination 0 x 6 = 0
GWH 450 ESR termination 1 x 3 = 3
Total: 20
Total equivalent vent length = 59
Table 7 Determining equivalent length example