Wayne P250 - Page 15

64659-001 REV. A 07/06/18
15
Table 5 - Orifice Sizes and Approximate Air Shutter Settings to Achieve a Given Firing Rate
Natural gas
Propane gas
Btu/hr
Letter/
Decimal
(in.)
Air
shutter
Btu/hr
Letter/
Decimal
(in.)
Air
shutter
Number
Number
50,000
1/8
0.1250
0.50
50,000
45
0.0820
0.25
60,000
30
0.1285
0.50
60,000
44
0.0860
0.50
65,000
29
0.1360
0.50
65,000
43
0.0890
0.50
70,000
28
0.1405
0.50
70,000
3/32
0.0940
0.75
75,000
26
0.1470
0.50
75,000
40
0.0980
1.00
80,000
24
0.1520
0.50
80,000
37
0.1040
1.00
85,000
5/32
0.1562
0.50
85,000
36
0.1065
1.25
100,000
17
0.1730
1.00
100,000
35 (7/64)
0.1100
1.25
110,000
14
0.1820
1.25
110,000
31
0.1200
1.50
120,000
10
0.1935
1.50
120,000
3.1 mm
0.1220
1.50
130,000
7
0.2010
1.50
130,000
1/8
0.1250
2.00
140,000
5 (13/64)
0.2055
1.75
140,000
30
0.1285
2.50
150,000
4
0.2090
2.00
150,000
29
0.1360
2.75
160,000
3
0.2130
2.50
160,000
28 (9/64)
0.1405
2.75
170,000
1
0.2280
2.75
170,000
27
0.1440
3.00
175,000
A
0.2340
2.75
175,000
26
0.1470
3.00
185,000
B
0.2380
3.00
185,000
25
0.1500
3.25
190,000
C
0.2420
3.00
190,000
24
0.1520
3.25
200,000
E (1/4)
0.2500
3.25
200,000
22 (5/32)
0.1570
3.50
210,000
F
0.2570
3.50
210,000
20
0.1610
3.75
220,000
G
0.2610
3.75
220,000
19
0.1660
4.00
230,000
H
0.2660
4.00
230,000
18
0.1695
4.25
240,000
I
0.2720
4.00
240,000
11/64
0.1720
4.25
250,000
J
0.2770
4.25
250,000
16
0.1770
4.50
This table shows the recommended orifice sizes and air shutter settings based on Btu/hr required. For example, an
application running propane gas that needs 157,000 Btu/hr would use an orifice drilled with a #28 drill bit. This orifice would
have a 0.1405” hole. The air shutter would be set to the 2.75 position.