No. 2 Switch
WARNING
CAUTION
!
®
Applications:
For series 47, 247, 63, 51, and 53 water
feeders to add the low water cut-off
function.
OPERATION
Electrical Ratings
INSTRUCTION MANUAL
MM-704B
No. 2 Switch
Motor Switch Rating (Amperes)
Voltage Full Load Locked Rotor Pilot Duty
120 VAC 10.2 61.2
240 VAC 5.1 30.6
• 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 a fire, do not use this low water cut-off to switch currents over 10.2A, 1/2 Hp at
120 VAC or 5.1A, 1/2 Hp at 240 VAC, unless a starter or relay is used in conjunction with it.
125 VA at
120 or 240 VAC
WARNING
Failure to follow this warning could cause property damage, personal injury or death.
B
OR
A
SCHEMATIC OF SWITCH OPERATION
Water Level
Normal
Burner On
Alarm Off
Low
Water
Alarm
Terminals
Low Water
Cut-Off
Terminals
C.
N.O.
N.C.
Water Level
Low
Burner Off
Alarm On
C.
N.O.
N.C.
N.
O.
N.C.
C.
The No. 2 Switch will help to maintain a minimum
WARNING
CAUTION
!
®
water level in the boiler during normal operation.
The switch will shut off the burner in the event the
boiler water level falls. Once the water level is
restored to its normal level, the switch will allow
the burner to operate.
INSTALLATION –
TOOLS NEEDED:
One (1) flathead screwdriver and one (1) 5/16” socket wrench.
STEP 1 - Switch Installation
a. Remove the four (4) screws that secure the
cover plate (A) or the existing switch.
b. Mount the new switch on top of the control (B)
using the (4) screws.
The No. 2 switch can be positioned with the conduit
opening facing toward or away from the float chamber.
These are the only positions in which the switch will
function properly. See drawing at right.
2
Neutral
120 V.A.C.
Supply Hot
Used as a Mainline Switch�
and/or Low Water Alarm
FIGURE 1
Used as a Pilot Switch to Coil�
of Relay or Motor Starter
Low
Water
Alarm
Load
Load
Line
C.
N.C.
N. O.
C.
N.C.
N. O.
E
E
STEP 2 - Electrical Wiring
a. Using the flathead screwdriver, remove the
two (2) screws that secure the switch housing (E).
b. Using copper wire only, follow the wiring
diagrams in Figure 1 to wire the No. 2
Switch. Terminals C and NC are the low
water cut-off switch. Terminals C and NO
are the alarm switch. If the electrical load
exceeds the rating of the switch, use an
auxiliary relay or motor starter.
c. Slide the switch housing (E) onto the
switch and, using a flathead screwdriver,
tighten the two (2) screws that secure the
switch housing.
INSTALLATION COMPLETE
STEP 3 - Testing
a. Check to see that the burner turns on and
off, by raising and lowering the water level
in the boiler.
b. Make sure there is travel in the float arm
after the burner goes on and off.
c. Repeat test several times.
3
STEP 4 - Switch Adjustment
L
M
Neutral
120 V.A.C.
Supply Hot
Used as a Mainline Switch�
and/or Low Water Alarm
FIGURE 1
Used as a Pilot Switch to Coil�
of Relay or Motor Starter
Low
Water
Alarm
Load
Load
Line
C.
N.C.
N. O.
C.
N.C.
N. O.
E
E
The control and switch have been factory adjusted and should not need any further adjustment in the field.
Observe the devices being activated by the control and switch and, should adjustment be needed, follow
the following steps.
a. Using a flat head screwdriver and 5/16” nut
driver, loosen adjusting screw (M) until cam
is set in lowest position.
b. Slowly, turn adjusting screw (M) raising the
cam until the switch clicks, opening the
common and normally closed contacts. Hold
adjusting screw (M) in position and tighten
nut (L) using 5/16” nut driver on the opposite
end.
c. Observe the devices being activated by the switch
and control to determine if the switch is activating
when desired.
If further adjustment is required, repeat Step c.
MAINTENANCE:
• Replace the switch every 10 years or when the components do not operate properly. More frequent
replacement may be required when severe conditions exists.
Xylem Inc.
8200 N. Austin Avenue
Morton Grove, Illinois 60053
Phone: (847) 966-3700
Fax: (847) 965-8379
www.xyleminc.com/brands/mcdonnellmiller
McDonnell & Miller is a trademark of Xylem Inc. or one of its subsidiaries.
© 2012 Xylem Inc. MM-704B April 2012 Part No. 210529
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