CleaverBrooks 4WI, Operation, Service And Parts Manual

Page: 51 / 216

750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual 3-5
3.2 — Water Requirements
3.2.1.7 — Pump Location
It is recommended that the system circulating pumps take suction from the outlet connection on the boiler, and
that they discharge to the system load. The suction side is preferred because it decreases air entry into the system
and does not impose the system head on the boiler.
3.2.1.8 — Pump Operation
Pumps are normally started and stopped by manual switches. It is also desirable to interlock the pump with the
burner so that the burner cannot operate unless the circulating pump is running.
3.2.1.9 — Pressure
The design of the system and usage requirements often dictate the pressure exerted upon the boiler. Some systems
are pressurized with air, or with an inert gas such as nitrogen. Caution must be exercised to ensure that the proper
relationship of pressure-to-temperature exists within the boiler so that all of the boiler’s internal surfaces are fully
wetted at all times. For this reason, the internal boiler pressure, as indicated on the water pressure gauge, must be
held to the level shown in the Internal Boiler Pressure graph below.
FIGURE 3-3.
Internal Boiler Pressure
When initially firing a newly installed boiler, or when cutting an existing boiler into an operating system, the boiler
or boilers to be cut into operation MUST be pressurized equal to the system and/or other boilers prior to opening
the header valves.
It is advisable to have a thermometer installed in the return line to indicate return water temperature. Knowing the
supply water temperature, the boiler system differential can be established. With knowledge of the pumping rate,
the operator can easily detect any excessive load condition and take appropriate corrective action.