Xylem MM 243D User Manual
WARNING
CAUTION
!
Replacement Head Mechanism
42S-HD
(Snap Switch)
Replacement head mechanisms can be installed without
disturbing existing equalizing connections or disassembly
of components, making repairs simple and easy.
INSTRUCTION MANUAL
MM-243D
Replacement Head Mechanism
WARNING
• Before using this product read and understand instructions.
• Save these instructions for future reference.
• All work must be performed by qualified personnel trained in the proper application, installation, and maintenance of plumbing, steam, and electrical equipment and/or systems in
accordance with all applicable codes and ordinances.
• To prevent serious burns, the boiler must be cooled to 80˚F (27˚C) and the pressure must be
0 psi (0 bar) before servicing.
• To prevent electrical shock, turn off the electrical power before making electrical connections.
• This low water cut-off must be installed in series with all other limit and operating controls
installed on the boiler. After installation, check for proper operation of all of the limit and
operating controls, before leaving the site.
• To prevent serious personal injury from steam blow down, connect a drain pipe to the
control opening to avoid exposure to steam discharge.
• To prevent a fire, do not use this low water cut-off to switch currents over 7.4A, 1/3 Hp at
120 VAC or 3.7A, 1/3 Hp at 240 VAC, unless a starter or relay is used in conjunction with it.
Failure to follow this warning could cause property damage, personal injury or death.
NORMAL BOILER
WATER LINE
PUMP
OFF
BURNER
OFF
BURNER
“CUT-OFF LEVEL”
AT CAST LINE
1 3/8" (35mm)
CUT-OFF
LEVEL
NORMAL BOILER
WATER LINE
C
UT-OFF
LEVEL
PUMP OFF
PUMP ON
3/4" (19mm)
OPERATION
NORMAL BOILER
WATER LINE
BURNER
CUT-OFF LEVEL
AT CAST LINE
7/8" (22 mm)
BURNER ON
BURNER OFF
CUT-OFF
LEVEL
W
ARNI
NG
CAUTI
ON
!
Approved
®
Maximum Pressure: 50 psi (3.5 kg/cm2)
Electrical Ratings
Pump Circuit Rating (Amperes)
Voltage Full Load Locked Rotor Pilot Duty
120 VAC 7.4 44.4
240 VAC 3.7 22.2
45 VA at
3
120 or 240 VAC
Settings and Differential Pressures
Values are ± 8” (3.2mm).
Series 42S
Approximate
Distance Above
Cast Line Differential
Pressure
50 psi
(3.5 kg/
cm2)
Setting In. (mm) In. (mm)
Pump Off 13/8 (35)
Pump On
Burner On
5
/8 (16)
7
/8 (22)
3
/4 (19)
7
/8 (22)
Burner Off 0 (0)
otor Horsepower
M
Voltage Hp
20 VAC
1
1
240 VAC 1/3
/3
2
A
B
C
D
F
E
INSTALLATION –
!
!
TOOLS NEEDED:
O
ne (1) pipe wrench, one (1) flathead screwdriver, one (1) scraper, and one (1) 9/16" socket or wrench.
STEP 1 - Preparation
WARNING
• To prevent serious burns, the boiler must be cooled to 80˚F (27˚C) and the pressure must be 0 psi (0 bar)
before servicing.
• To prevent electrical shock, turn off the electrical power before disconnecting or making electrical connections.
Failure to follow this warning could cause property damage, personal injury or death.
a. Drain water in the boiler to a level which is
below the float chamber (A). Allow the boiler
to cool to 80˚F (27˚C) and release the boiler
pressure to 0 psi (0 bar).
b. Using a flathead screwdriver, remove the junction
ver (B). Disconnect, mar
x co
bo
supply wires and conduit connections
k, and remove the
.
CAUTION
There may be more than one source of power to the boiler.
e the existing head mechanism (C)
c. Remo
d. Using a scr
v
from the body (D).
aper, remove the old gasket (E).
Clean all debr
is from the float chamber
. The
gasket sealing surface (F) must be smooth
and clean.
3
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