Model CFC
ClearFire Commercial Boilers
21
Rev. 05-2012
(90.5
C) is set for normal boiler operation.
While proper overpressure is required, a means to relieve excess pressure at or
beyond the design pressure of the boiler must be provided. As boiler water is
heated, expansion occurs. And this expansion must be accounted for either with an
expansion tank (air filled) or with a bladder type tank. These devices permit the
water pressure to expand outside of the boiler and not impact the pressure vessel or
pressure relieving device. But, in accordance with Code, each boiler is equipped
with an ASME approved safety relieving device should pressure build-up occur (See
Table B5-16 and Table B5-15).
Air Venting
The elimination of entrained air is required. It is recommended that each unit be
piped to an expansion tank. If this is not possible, then an auto air vent should be
provided on the vent connection of the boiler. The caveat in using an auto vent is
that free oxygen can be introduced to the vesel as the boiler cools, or in some
instances the vent can become plugged.
Table B5-12. CFC Flow Rates
System Temperature Drop
0
F
10
20
30
40
50
60
70
80
90
100
110
120
Boiler
Size
Flow Rate GPM
500
95
48
33
24
19
16
12
11
10.5
9
8
7
750
131
66
44
33
26
22
19
16
15
13
12
11
1000
176
88
59
44
35
29
25
22
20
18
16
15
1500
260
130
87
65
52
43
37
33
29
26
24
23
1800
351
176
117
88
70
59
50
44
39
35
32
30
2500
470
235
157
118
95
79
67
59
52
48
43
39
3300
620
310
207
155
124
103
89
78
69
62
56
52
Flow rate as a function of Delta T at 94% efficiency and maximum firing capacity