Xylem MM 235E User Manual
Replacement Snap Switch Assembly
SWA-150S SWA-158S
SWA-150S-MD SWA-159S
For Series 150S and 157S Low
Water Cut-Off/Pump Controllers
(All Models)
INSTRUCTION MANUAL
MM-235E
Replacement Switch Assembly
WARNING
!
CAUTION
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 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.
• We recommend that secondary (redundant) Low Water Cut-Off controls be installed on all
steam boilers with heat input greater than 400,000 BTU/hour or operating above 15 psi of
steam pressure. At least two controls should be connected in series with the burner
control circuit to provide safety redundancy protection should the boiler experience a
low-water condition. Moreover, at each annual outage, the low water cutoffs should be
dismantled, inspected, cleaned, and checked for proper calibration and performance.
• 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.
For Model
Repl. Switch
Model & Part No.
150S
150S-B
150S-M*
150S-B-M*
150S-M-MD*
150S-B-M-MD*
157S
157S-A
157S-P
157S-R
157S-RL
157S-M*
157S-A-M*
157S-R-M*
157S-RB-M*
157S-RL-M*
157S-M-MD*
157S-M-RB-P-MD*
150S-MD
150S-B-MD
157S-MD
157S-P-MD
157S-R-MD
157S-RB-MD
157S-RB-P-MD
157S-RD-MD
157S-RLS-MD
158S
158S-M*
158S-M-MD*
159S
SWA-150S
310462
SWA-150S-MD
310464
SWA-158S
310468
SWA-159S
310470
2
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 150S and 157S Replacement Snap Switch Assemblies are not interchangeable with Series 150 and 157 mercury
switch controls.
• Replacement Switch Assemblies are not interchangeable and must be selected and ordered for the specific control
model in which it will be installed.
Model SWA-150S
P/N 310462
Model SWA-159S
P/N 310470
September 2003 (03J)
and Older
NOTE: Models with (*) will require head replacement
if manufactured before September 2003 (03J)
October 2003 (03K)
and Newer
Model SWA-158S
P/N 310468
Model SWA-150S-MD
P/N 310464
Manual Reset Models
Pump Circuit Rating (Amperes)
Voltage Full Load Locked Rotor Pilot Duty
120 VAC 7.4 44.4
345 VA at
240 VAC 3.7 22.2
120 or 240 VAC
Approximate
Distance Above
Cast Line Differential
Setting In. (mm) In. (mm)
Pump Off
15
/16 (24)
5
/16 (8)
Pump On
5
/8 (16)
Burner On
5
/8 (16)
3
/8 (16)
Burner Off
1
/4 (6.4)
Pump Off 13/8 (41)
3
/4 (19)
Pump On
5
/8 (16)
Burner On
7
/8 (22)
7
/8 (22)
Burner Off 0 (0)
BURNER
“CUT-OFF LEVEL”
AT CAST LINE
BURNER OFF
BURNER ON
7
/8"
DIFFERENTIAL
(22mm)
PUMP
OFF
BURNER
OFF
BURNER
“CUT-OFF LEVEL”
AT CAST LINE
NORMAL BOILER
WATER LINE
1
3
/8"
DIFFERENTIAL
(35mm)
PUMP OFF
PUMP ON
3
/4"
DIFFERENTIAL
(19mm)
PUMP OFF
PUMP ON
3
/4"
DIFFERENTIAL
(19mm)
PUMP
OFF
BURNER
OFF
NORMAL BOILER
WATER LINE
1
13
/16"
DIFFERENTIAL
(46mm)
BURNER CUT-OFF LEVEL
3
/8
"
(9.5mm) BELOW
CAST LINE
OPERATION
3
Maximum Pressure: 150 psi (10.5 kg/cm2)
Electrical Ratings
Settings and Differential Pressures
Series 150S and 157S
150 psi (10.5 kg/cm
2
) Levels
150 psi (10.5 kg/cm
2
) Levels
0 psi
(0 kg/
cm2)
150 psi
(10.5 kg/
cm
2
)
Approximate
Distance Above
Cast Line Differential
Setting In. (mm) In. (mm)
Pump Off
15
/16 (24)
3
/8(16)
Pump On
9
/16 (14)
Burner Off 0 (0) N/A
Pump Off 17/16 (37)
3
/4 (19)
Pump On 11/16 (17)
Burner Off -
3/8 (-16)
N/A
Model 150S-MD and 157S-MD
0 psi
(0 kg/
cm
2
)
150 psi
(10.5 kg/
cm
2
)
Pressure
Pressure
Alarm Circuit Rating
Voltage Amps
120 VAC 1
240 VAC 1/2
Motor Horsepower
Voltage Hp
120 VAC
1/3
240 VAC 1/3
4
Approximate
Distance Above
Cast Line Differential
Setting In. (mm) In. (mm)
Motorized
15
/16 (24)
Valve Closed
5
/16 (8)
Motorized
5
/8 (16)
Valve Open
Burner On
5
/8 (16)
3
/8 (16)
Burner Off
1
/4 (6.4)
Motorized 13/8 (41)
3
/4 (19)
Valve Closed
Motorized
5
/8 (16)
Valve Open
Burner On
7
/8 (22)
7
/8(22)
Burner Off 0 (0)
BURNER
“CUT-OFF LEVEL”
AT CAST LINE
BURNER OFF
BURNER ON
7
/8"
DIFFERENTIAL
(22mm)
MOTORIZED
VALV E
CLOSED
BURNER
OFF
BURNER
“CUT-OFF LEVEL”
AT CAST LINE
NORMAL BOILER
WATER LINE
1
3
/8"
DIFFERENTIAL
(35mm)
MOTORIZED
VALV E
CLOSED
MOTORIZED
VALV E
OPEN
3
/4"
DIFFERENTIAL
(19mm)
NOTE: Due to the slower operation of some
motorized valves, complete valve opening
or closing will occur at slightly different levels than indicated above.
Model 158S
150 psi (10.5 kg/cm
2
) Levels
0 psi
(0 kg/
cm
2
)
150 psi
(10.5 kg/
cm
2
)
Pressure
Operation
Settings and Differential Pressures (continued)
150 psi
(10.5 kg/
cm
2
)
MOTORIZED
VALUE
OPEN
CLOSED
3
/4"
DIFFERENTIAL
(19mm)
MOTORIZED
VALV E
CLOSED
BURNER
OFF
NORMAL BOILER
WATER LINE
1
13
/16"
DIFFERENTIAL
(46mm)
BURNER CUT-OFF LEVEL
3
/8
"
(9.5mm) BELOW
CAST LINE
Approximate
Distance Above
Cast Line Differential
Setting In. (mm) In. (mm)
Pump Off
15
/16 (24)
3
/8(16)
Pump On
9
/16 (14)
Burner Off 0 (0) N/A
Pump Off 1
7
/16 (37)
3
/4 (19)
Pump On 11/16 (17)
Burner Off - 3/8 (-16)
N/A
Model 158S-MD
0 psi
(0 kg/
cm
2
)
Pressure
150 psi (10.5 kg/cm2) Levels
NOTE: Due to the slower operation of some
motorized valves, complete valve opening
or closing will occur at slightly different levels than indicated above.
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