Xylem MM 244B User Manual
Replacement Snap Switch Assembly
!
SWA-42S
For Series 42S Low Water Cut-Off/
Pump Controllers (All Models)
INSTRUCTION MANUAL
MM-244B
Replacement Switch Assembly
WARNING
TION
AU
C
G
NIN
R
A
W
• 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 all sources of electrical power before servicing unit.
• This low water cut-off must be installed in series with all other limit and operating controls
installed on the boiler. After servicing unit, check for proper operation of all of the limit and
operating controls before leaving the site.
• 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.
Verify that you have the Correct Replacement Switch Assembly Model
IMPORTANT:
• Installation of an incorrect switch-assembly could cause damage to the boiler and/or boiler system.
• Modification of the switch assembly before or after installation could cause damage to the boiler
and/or boiler system.
• Series 42S Replacement Snap Switch Assemblies are not interchangeable with Series 42 Mercury Switch
Replacement Assemblies.
• Series 42S Replacement Snap Switch Assemblies are not interchangeable with Series 150S Snap Switch Replacement
Assemblies, nor with Series 150 Mercury Switch Replacement Assemblies.
For Model Repl. Switch
Model No. Description
42S
42S-A SWA-42S Snap-action
42S-N switch assembly
42S-HD
Model SWA-42S
P/N 310488
2
BURNER
ON
BURNER
OFF
NORMAL BOILER
WATER LINE
BURNER
CUT-OFF LEVEL
AT CAST LINE
7/8
" (22mm)
PUMP
OFF
BURNER
OFF
NORMAL BOILER
WATER LINE
BURNER
CUT-OFF LEVEL
AT CAST LINE
1 3/8
" (35mm)
PUMP
OFF
PUMP
ON
NORMAL BOILER
WATER LINE
3/4
" (19mm)
OPERATION
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
345 VA at
120 or 240 VAC
Settings and Differential Pressures
Values are ±1/8” (3.2mm).
Series 42S
Approximate
Distance Above
Cast Line Differential
Pressure
50 psi
(3.5 kg/
cm2)
Setting In. (mm) In. (mm)
Pump Off 1
Pump On
Burner On
3
/8 (35)
5
/8 (16)
7
/8 (22)
3
/4 (19)
7
/8 (22)
Burner Off 0 (0)
Motor Horsepower
Voltage Hp
120 VAC
1/3
240 VAC 1/3
3
LOW WATER
CUT-OFF
TERMINALS
BURNER
SWITCH
PUMP
SWITCH
PUMP CIRCUIT
TERMINALS
OFF
ON
A
INSTALLATION –
!
SECTION 1 - Switch Bracket Replacement
WARNING
• 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.
Failure to follow this warning could cause electrical shock, an explosion and/or a fire, which could result in
property damage, personal injury or death.
1. Turn the boiler off.
2. Allow the boiler to cool to 80˚F (27˚C) and
release the boiler pressure to 0 psi (0 bar).
Drain water in the boiler to a level which is
below the float chamber (A).
3. Remove the cover (B).
4. Mark and remove the pump switch
and burner/alarm switch wires from
terminal block.
B
4
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