Xylem McDonnell & Miller 150S Series User manual

2
Enclosure rating: NEMA 1 General Purpose
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 OFF
BURNER ON
7/8"
DIFFERENTIAL
(22mm)
PUMP
OFF
BURNER
OFF
NORMAL BOILER
WATER LINE
13/8"
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
113/16"
DIFFERENTIAL
(46mm)
OPERATION
Maximum Pressure: 150 psi (10.5 kg/cm2)
Electrical Ratings
Settings and Differential Pressures
Values are ± 8" (3.2mm).
Series 150S and 157S
150 psi (10.5 kg/cm2) Levels 150 psi (10.5 kg/cm2) Levels
0 psi
(0 kg/
cm2)
150 psi
(10.5 kg/
cm2)
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/
cm2)
150 psi
(10.5 kg/
cm2)
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

3
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 OFF
BURNER ON
7/8"
DIFFERENTIAL
(22mm)
MOTORIZED
VALVE
CLOSED
BURNER
OFF
NORMAL BOILER
WATER LINE
13/8"
DIFFERENTIAL
(35mm)
MOTORIZED
VALVE
CLOSED
MOTORIZED
VALVE
OPEN
3/4"
DIFFERENTIAL
(19mm)
Values are ± 8" (3.2mm).
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/cm2) Levels
0 psi
(0 kg/
cm2)
150 psi
(10.5 kg/
cm2)
Pressure
Settings and Differential Pressures (continued)
150 psi
(10.5 kg/
cm2)
MOTORIZED
VALVE
OPEN
CLOSED
3/4"
DIFFERENTIAL
(19mm)
MOTORIZED
VALVE
CLOSED
BURNER
OFF
NORMAL BOILER
WATER LINE
113/16"
DIFFERENTIAL
(46mm)
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 158S-MD
0 psi
(0 kg/
cm2)
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.

4
PUMP #1
OFF
PUMP #1
ON
NORMAL BOILER
WATER LINE
(19mm)
3/4"
DIFFERENTIAL
PUMP #2 ON
AT CAST LINE
7/8"
DIFFERENTIAL
(22mm)
PUMP #2
ON
PUMP #2
OFF
PUMP #1
OFF
PUMP #2
ON PUMP #2 ON
AT CAST LINE
NORMAL BOILER
WATER LINE
13/8"
DIFFERENTIAL
(35mm)
Values are ± 8" (3.2mm).
150 psi (10.5 kg/cm2) Levels
Approximate
Distance Above
Cast Line Differential
Setting In. (mm) In. (mm)
Pump #1 Off 15/16 (24) 5/16 (8)
Pump #1 On 5/8(16)
Pump #2 Off
5/8(16) 3/8(16)
Pump #2 On
1/4(6.4)
Pump #1 Off 13/8(41) 3/4(19)
Pump #1 On 5/8(16)
Pump #2 Off
7/8(22) 7/8(22)
Pump #2 On 0 (0)
Model 159S
0 psi
(0 kg/
cm2)
150 psi
(10.5 kg/
cm2)
Pressure
Settings and Differential Pressures (continued)

• 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.
!
WARNING
5
A
B
C
D
c. Remove the existing head mechanism (C)
from the body (D).
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
box cover (B). Disconnect, mark, and remove the
supply wires and conduit connections.
F
E
d. Using a scraper, remove the old gasket (E).
Clean all debris from the float chamber. The
gasket sealing surface (F) must be smooth
and clean.
STEP 1 - Preparation
INSTALLATION
TOOLS NEEDED:
One (1) pipe wrench, one (1) flathead screwdriver, one (1) scraper, and one (1) 9/16" socket or wrench.
There may be more than one source of power to the boiler.
!
CAUTION

d. Using a wrench, insert the eight (8) bolts and
tighten them to approximately 14-20 ft•lb
(19-27 N•m) in an alternating star pattern.
G
J
b. Align the bolt holes of the new head gasket (J)
on the sealing surface of the control body.
a. Carefully remove the new replacement head
mechanism from the carton. Handle it carefully
to prevent damage to the float rod (G).
K
D
c. Install the new replacement head (K) on the
body (D) by guiding the float into the control
body and aligning the bolt holes.
STEP 2 - Installing the Replacement Head Mechanism
6

7
IMPORTANT: There must be a
minimum space of 1/2" (13mm)
between connector fittings and
electrical live metal parts.
STEP 3 - Electrical Wiring
a. Reconnect conduit and wires which were disconnected prior to head removal.
b. Re-attach the junction box cover (B).
B
Note:
Cover must be installed correctly as shown
• To prevent a fire, do not use this product 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.
• 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.
• Modification of the switch assembly before or after installation could cause damage to the boiler and/or
boiler system.
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.
!
WARNING

8
Switch Operation
For all Models except 158S and 159S
For Model 158S
Boiler feed pump off,
burner on, alarm off.
Boiler feed pump on,
burner on, alarm off.
Boiler feed pump on,
burner off, alarm on.
12 4 5 6 12 4 5 6 12 4 5 6
Motorized valve closed,
burner on, alarm off.
Motorized valve open,
burner on, alarm off.
Motorized valve open,
burner off, alarm on.
4 5 6
12 3 4 5 12 3 4 5 12 3
6 6
For Model 159S
Pump #1 off,
pump #2 off.
Pump #1 on,
pump #2 off.
Pump #1 on,
pump #2 on.
12 5 6 12 5 6 12 5 6

9
WIRING DIAGRAMS
For Motorized Valves, refer to the valve manufacturer's wiring instructions.
Pump Control Only
1. Install a starter or relay in pump control circuit,
as shown, to prevent damage to snap switch
and help insure proper switch/control operation.
Failure to do so may shorten the life of the switch
when actual amperage exceeds switch rating.
2. Connect wires from holding coil of pump starter
or relay to terminals 1 and 2 as shown.
1. Main Line Switch - For burner circuits within
the switch’s electrical rating.
2. Pilot Switch - To holding coil of a starter when
the burner circuit exceeds the switch’s electrical
rating.
12 456
ALARM
NEUTRAL
HOT
ALARM
NEUTRAL
HOT
12 4 56
12 456
SEE PUMP
CONTROL
CIRCUIT
TO NEUTRAL
TO BURNER CONTROL CIRCUIT
HOT
ALARM
12 456
LOAD
LINE (3 PHASE)
SEE PUMP
CONTROL
CIRCUIT
ALARM
12 456
LOAD
LINE
OR
OR
Combination Pump Control, Low Water Cut-Off and Alarm
Alarm Circuit Only
1. Low Water Alarm 2. High Water Alarm
NOTE
To help insure most effective operation,
balance boiler feed pump(s) to deliver
required water feed rate to match boiler
steaming requirements.
NOTE
For Model 159S, use terminals 5 and 6 from
starter or relay for pump #2.
Low Water Cut-Off Only
1. Main Line Switch - For burner circuits within the
switch’s electrical rating.
LINE LOAD
12 456
12 456
LOAD
LINE
OR
2. Pilot Switch - To holding coil of a starter when
the burner circuit exceeds the switch’s electrical
rating.

K
To prevent serious personal injury from steam pipe blow
down, connect a drain pipe to the control opening to
avoid exposure to steam discharge.
Failure to follow this caution could cause personal injury.
!
CAUTION
INSTALLATION COMPLETE
10
Snap Switch Models
STEP 4 - Testing
OFF
ON
a. Turn on the electric power to the boiler.The pump should go on
and the burner must remain off.
IMPORTANT: Follow the boiler manufacturer’s start-up and operating instructions along with all applica-
ble codes and ordinances.
This control is factory calibrated for specific level
settings as shown on pages 2-4 in the “Operation”
section.
The following testing procedure is only meant to
serve as a verification of proper operating
sequence.
If the burner comes on, immediately turn the boiler off and make the
necessary corrections.
Failure to follow this warning could cause an explosion or fire and
result in property damage, personal injury or death.
!
WARNING
b. The boiler should begin to fill with water.
As the water level rises in the sight glass,
the burner should turn on and then the
pump should turn off at appropriate levels.
For manual reset models, press the reset
button (K) when the water reaches appro-
priate level.
If the burner does not turn on or pump
turn off at appropriate levels, immediately
turn off the boiler and make necessary
corrections.
Location of Manual Reset Button
c. Blow down the control when the water in the boiler is at
its normal level and the burner is on. Follow Blow Down
Procedure found in Maintenance Section on page 11 of
these instructions.