11 switch RP

11 switch RP
MM-705B
7/31/07
12:54 PM
Page 2
McDonnell & Miller
Installation & Maintenance
Instructions
MM-705(B)
No. 11, 11M and 11MV
Replacement Switch
For use on Series 61, 64, 764, 67,
767, 69 and 70 Low Water Cut-Offs
11
General Purpose (BLACK terminal panel)
11M Manual Reset Option (BLACK terminal panel)
11MV Millivolt / 24V Option (RED terminal panel)
Electrical Ratings
Motor Switch Rating
(Amperes)
Voltage Full Load Locked Rotor
120 VAC
240 VAC
7.2
3.6
43.2
21.6
Pilot Duty
120 VA at
120 or 240 VAC
NOTE: 11MV is rated at 24VA @ 24 VAC to 120 VAC
!
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 electrical shock, turn off the electrical power before making
electrical connections.
• The low water cut-off switch 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.
• 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 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 serious personal injury from steam and hot water make sure
there is a discharge line from the blow down valve to a proper place of
disposal.
• To prevent a fire, do not use this low water cut-off to switch currents over
7.2A, 1/3 HP at 120 VAC or 3.6A, 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.
MM-705B
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OPERATION - 11 AND 11MV
The No. 11 switch contains two (2) single pole single
throw switches to control a water feeder and the low
water cut-off. The low water cut-off switch is between
terminals marked "1" and "2". The switch at terminals
"3" and "4" can be used to control a McDonnell &
Miller electric water feeder or a low water alarm. The
No. 11MV has the same switch arrangement as the
No. 11. This switch has special contacts for the low
water cut-off terminals "1" and "2" for use on millivoltpotential gas valve control systems or 24VAC burners. Some millivolt systems have terminals on the
gas valve marked "L1" and "L2" which can be utilized
for wiring a limit switch. Others have both thermostat
and pressure control in series; if so, simply wire this
pair of terminals in series with them. A second switch
(at "3" and "4") can be used on 24 volt circuits only
for an alarm or electric feeder control.
SCHEMATIC OF TWIN SWITCH
INTERNAL OPERATION
10
30
02
10
30
0
10
30
02
NORMAL
WATER LEVEL
04
FEEDER OR
ALARM
OPERATING LEVEL
2
04
LOW WATER
CUT-OFF
OPERATING LEVEL
04
MILLIVOLT/LOW VOLTAGE SYSTEM
120V or 24V BURNER AND FEEDER WIRING
MILLIVOLT
GENERATOR/
TRANSFORMER
TO BURNER
NEUTRAL WIRE
TO BURNER
HOT WIRE
10
30
SAFETY
SWITCH
JUMPER
SAFETY
SWITCH
02
10
30
02
04
04
ELECTRIC
FEEDER
OR ALARM
ELECTRIC
FEEDER
OR ALARM
24 VOLT
TRANSFORMER
OPERATION - 11M
The No. 11M is a SPDT switch with a latching
mechanism. Terminal "2" is the common. At
normal water level, a circuit through terminal
"1" is closed. It latches open in a low water
condition.
Depressing the manual reset button unlatches
the mechanism after normal water level has
been restored to the control. Terminal "4" provides a contact only for an alarm at low water
and is NOT intended for use with an electric
feeder.
1
2
3
4
!
Do not electrically connect water feeder
to a No. 11M. This model includes a
manual reset feature, failure to follow
this caution could result in boiler
flooding and property damage.
NORMAL WATER LEVEL
2
3
4
RESET
BUTTON
NEUTRAL
BURNER
RESET
BUTTON
1
CAUTION
LOW WATER CUT-OFF
ALARM LEVEL
1
2
3
4
RESET
BUTTON
HOT
TRANSFORMER
(OPTIONAL)
ALARM
MM-705B
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INSTALLATION/REPLACEMENT PROCEDURE
Turn off boiler power. Allow boiler to cool to
room temperature. Using a flatblade screwdriver, remove the terminal cover (B). Tag
and remove wiring from terminals. Remove
screws (D) and housing (C). Remove four
(4) switch mounting screws (E) and old
switch (F). Install new switch, "TOP" notch
up and being certain to align "U-shaped"
F
notch of switch rocker on float mechanism
roller (J). Secure switch on bracket (H) with
screws (E). Reassemble housing (C) with
screws (D). Reconnect wiring as tagged to
proper terminals and reassemble terminal
cover (B) with screw (A). Restore power to
boiler and test through several cycles.
E
D
J
D
H
E
Conduit housing is movable into any one of
four positions. Remove two screws (D) and
rotate to desired position. NOTE: 11M cannot
be rotated out of "TOP" position due to reset
button orientation requirement.
A
B
C
TOP
LEFT
1
3
BOTTOM
TOP
2
4
RIGHT
MM-705B
7/31/07
12:54 PM
Page 1
McDonnell & Miller
MAINTENANCE
SCHEDULE:
• Blow down weekly during heating season.
• Check all wiring for brittle or worn insulation.
Replace control every 10 years.
Follow ASME Boiler and Pressure
Vessel Code - Section VI Paragraph
7.07G. It states that the controls
should be dismantled annually by
qualified personnel, to the extent
necessary to insure freedom from
obstructions and proper functioning of
the working parts.
TROUBLESHOOTING
Problem:
1. Control does not turn burner off on low water.
2. Control does not turn electric feeder off.
Cause: Contacts may be fused from overload.
Test: With a continuity meter or ohm meter check if both
circuits open as the rocker is moved through its operating
range.
Solution: Replace the switch if either circuit remains closed
through the test. Refer to the installation / replacement
procedure.
If the switch functions normally off of the control, inspect the float and
interior chamber condition for obstructions and debris, especially
around the bellows area and at the gauge glass end.
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