CleaverBrooks WB, Owner'S Operation And Maintenance Manual

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Installation Instructions
2-2 750-136
Model WB Electric Boiler Manual
2.3 — Piping
This boiler is intended for use on forced circulation systems with a pump of adequate capacity to overcome the
system head loss (pressure drop at required flow rate), and to provide a flow rate adequate to permit the boiler to
generate its full heat output. Radiators and convectors in the system must have adequate capacity to dissipate
the boiler output at system design operating water temperature.
The pressure drop through the boiler is equivalent to the pressure drop through 30 feet of pipe equal to the
diameter of the inlet and outlet fittings.
Failure to provide adequate radiator capacity may create a low flow rate through the boiler, raising the tempera-
ture too high, and will result in “short cycling” of the boiler due to operation at the limiting or maximum tempera-
ture. This also will prevent the boiler from supplying its rated output to the system.
Tight-closing valves should be installed on the inlet and outlet piping to facilitate isolating the boiler from the sys-
tem for annual boiler internal inspection and/or repair that requires the boiler to be drained.
An expansion tank should be provided with a volume equal to 1/16 of the total water volume of the system,
inclusive of the boiler vessel, radiators, coils, and all piping. The expansion tank may be connected to the fitting
provided on top of the boiler vessel. If another location for the expansion tank connection is used, the boiler
opening must be plugged.
Water for make-up during operation should be added manually or automatically directly to the expansion tank.
The boiler drain valve should be piped to the drain.
2.4 — Heat Pump Systems with High Flow Rates
The Model WB will accept flow rates that will give a minimum temperature rise across the boiler as low as 3º F
when supplied with optional inlet baffle or oversized connections. Minimum temperature rise can also be
obtained by installing a bypass piping arrangement to adjust the flow through the boiler.
Use the following formula to determine the maximum and minimum flow rates of a given boiler:
FLOW (GPM) = KW x 6.816
T
where T is equal to any temperature rise between 3º F and 30º F, as indicated by TI1 and TI2 in Figure 2-1.
If the system flow rate is greater, a bypass around the boiler with a balancing cock or globe valve will be required
to bypass the appropriate portion of the system flow.
The relief valve outlet should be piped to a safe point of discharge where no serious personal injury or death to per-
sons, or impaired access to the boiler controls, would result from unexpected discharge of hot water from the relief
valve.
! Warning