BOILER BOOK CFC-E ENGINEERING DATA
21
Figure 14. Waterside Pressure Drop CFC-E 2000
System Operating Parameters
To prevent water flashing to steam within the boiler or system, hot water boilers must operate with
proper over-pressure. System over-pressure requirements are shown in Table 9.
Maximum Allowable Working Temperature (MAWT) is 210°F (99°C).
Maximum operating set point is 194°F (90°C)
Maximum Allowable Working Pressure is 125 PSIG (963 KPA)
Practical operating pressure limit is 112 PSIG (874 KPA)
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 10).
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
vessel as the boiler cools, or in some instances the vent can become plugged.
Table 9. Model CFC-E Minimum Over Pressure Requirements
Outlet Water Temperature Minimum System Pressure
(°F) (°C) PSIG Bar
80-180 27-82 12 0.83
181-185 83-85 15 1.03
186-195 86-91 18 1.24
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