Cleaver-Brooks CBH 40 - Page 19

pressure to the burner nozzles. This pressure is
read on the oil pressure gauge.
Oil flow to the burner nozzles is controlled by sole-
noid valves. At the proper time in the operating se-
quence, the primary, or safety, shut-off valve
(LFOV-1) and the low fire valve (LFOV-2) are
energized by the programming control. The open-
ing of these valves allows the oil to flow to the low
fire nozzle.
When the damper motor moves to the high fire
position, an auxiliary switch actuated by the
motor, energizes a high fire valve.
PILOT GAS
MAIN GAS
MAIN GAS
SHUTOFF VALVE
Chapter 1-General Description and Principles of Operation
Figure 1-8 shows the valves used on the 25 through
40 and 50A size boilers. The orifice block between
the valves prevents a sudden pressure drop when
the high fire valve opens.
The oil discharge from the pump on the 50 through
100 size flows into a manifold block (Figure 1-9).
The intermediate valve is energized prior to the
high fire valve. The purpose for this is to make the
change from low to high fire smoother by balanc-
ing the oil input with the increasing flow of air as
the damper opens. The return line from the mani-
fold is orificed to maintain a constant pressure.
I
MAIN GAS
VALVE(S)
FIGURE 1-10. SCHEMATIC GAS FLOW DIAGRAM
1-11