Xylem MM 244B Series 42S Replacement Snap Switch Assembly - Manual (Page 7)

7
SECTION 2 - Checking Switch Settings and Adjusting Switch Setpoints at
Operating Pressure
IMPORTANT: All switches have fixed differentials.
Adjustment of switches referred to in Section 2 and
3 are all based upon Pump Off and Burner Off set-
points. The Pump On and Burner On setpoints are
not adjustable. We strongly recommend that you check the con-
trol at both the operating pressure and at 0 pres-
sure. All boilers start at 0 psi regardless of the oper-
ating pressure.
The operating points will spread out as the pressure
goes up and shrink as the pressure goes down.
2"
(50.8mm)
1"
(25.4mm)
1"
(25.4mm)
3"
(76.2mm)
Casting
Cut-Off
Line
1. Cut out the "Switching Level Ruler" (page 11)
along the indicated lines.
D
3" (76.2mm) 2" (50.8mm) 1" (25.4mm) Casting
Cut-Off
Line
1" (25.4mm)
TOP
RULER
LEVEL
2a. Hold the ruler against the side of the
gauge glass in a position so the “Cast
Line” mark is on the same level as the
Cast Line on the float chamber of the
control (D) (a carpenter's level should be
used to insure the cast line on the float
chamber is at the same level as the one
on the ruler).
b. Once the ruler is properly positioned,
tape it to the gauge glass.
B
3a. Bring boiler up to normal operating pressure
and turn the pump off.
b. Remove the cover (B).
(Not to Scale. Template
located on page 11).