Overview of Primary Product

45
Boiler Controls
Boiler Controls
McDonnell & Miller
Model H J K L M N P Q R S T
NPT NPT
42S-N
2
9
⁄16 (65)
2
9
⁄16 (65)
1
3
⁄4 (45)
3
11
⁄16 (94)
1
13
⁄16 (46)
1
1
⁄16 (27)
1
1
⁄16 (27)
1
1
⁄2 (38)
3
⁄8
1
⁄4 2
5
⁄8 (67)
Model
A
B
C
DEFG
NPT NPT
42S 12
1
⁄4 (311) 2
9
⁄16 (65) 1 8
7
⁄8 (225) 3
11
⁄16 (94) 3
1
⁄8 (79)
1
⁄2
42S-A
12
1
⁄4 (311)
2
9
⁄16 (65)
1
7
1
⁄4-16
11
⁄16 (184-347)
2
3
⁄4 (45)
3
1
⁄8 (79)
1
⁄2
42S-N 12
1
⁄4 (311) 2
9
⁄16 (65) 1 8
7
⁄8 (225) 3
11
⁄16 (94) 3
1
⁄8 (79)
1
⁄2
B
D
E
F
A
C
C
CUT-OFF 
L
EVEL
G
• For residential, commercial, and industrial low and
medium pressure steam boilers with a separate
water column
• For boilers of any steaming capacity
• Monel bellows provides corrosion resistance
• Single pole, single throw snap action switches
• Enclosed junction box protects switches
• Optional features
– Quick hook-up fittings
– Gauge glass connector
• Maximum pressure 50 psi (3.5 kg/cm
2
)
SERIES 42S
T
B
F
E
D
A
C
G
C
CUT-OFF 
LEVEL
MODEL 42S-A
A
N
F
K
M
J
L
E
D
P
Q
B H
G
C
R
S
CUT-OFF 
L
EVEL
MODEL 42S-N
Dimensions, in. (mm)
Ordering Information
Series 42S
Low Water Cut-Off/Pump Controllers
®
®
Model Part Weight
Number
Number
Description lbs. (kg)
42S
129302 Combination low water cut-off/ 15.5 (7.0)
pump controller
42S-A 129702 42S w/quick hook-up fittings 21.3 (9.7)
42S-N 129802 42S w/glass connector 21.3 (9.7)
Electrical Ratings
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
Alarm Circuit Rating (Amperes)
Voltage Amps
120 VAC 1
240 VAC 1/2
with
MERCURY FREE
Snap-Action Switches
Low Water Cut-Offs
Combination Low Water Cut-Off/Pump Controllers for Steam Boilers