Xylem MM 413F User Manual
Replacement Head Mechanism
!
With Switch Assembly:
93-HD, 94-HD
93-M-HD, 94-M-HD
93-7B-HD, 94-7B-HD
93-7B-M-HD, 94-7B-M-HD
Without Switch Assembly:
93-HDLS 94-HDLS
Replacement head mechanisms can be
installed without disturbing existing equalizing
connections or disassembly of components,
making repair simple and easy.
Head Mechanism
with Switch Assembly
INSTRUCTION MANUAL
MM-413F
Head Mechanism
without Switch Assembly
WARNING
N
UTIO
CA
G
IN
RN
A
W
• 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 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.
• 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 blow down, connect a drain pipe to the control
opening to avoid exposure to steam discharge.
• To prevent a fire, do not exceed the switch contact rating.
Failure to follow this warning could cause property damage, personal injury or death.
2
Electrical Ratings
Models with 5 or 5-M Switch
Switch Ratings
Burner Valve
120 VAC
345 VA 0 - 135 ohms @ 24 VAC
240 VAC
Models with 7B or 7B-M Switch
Approximate
Distance Above
Cast Line Differential
Setting In. (mm) In. (mm)
Pump Off 23/16 (56) 11/16 (27)
Pump On 11/8 (29)
Burner On 13/8 (35) 13/8 (35)
Burner Off 0
Switch Settings
Values are ±
1
/8 " (3mm)
NOTE: Due to the slower operation of some
motorized valves, complete valve opening or
closing may occur at slightly different
levels than indicated above.
Models with 5 or 5-M Switches
Approximate
Distance Above
Cast Line Differential
Setting In. (mm) In. (mm)
Valve Full 23/16 (56) 11/16 (27)
Closed
Valve Full
7
/8 (22)
Open
Burner On 13/8 (35) 13/8 (35)
Burner Off 0
Models with 7B or 7B-M Switches
OPERATION
Maximum Pressure:
Series 93/193: 150 psi (10.5 kg/cm
2
)
Series 94/194: 250 psi (17.6kg/cm
2
)
PUMP
OFF
BURNER
OFF
BURNER
CUT-OFF LEVEL
AT CAST LINE
2
3
/16"
(56mm)
PUMP OFF
PUMP ON
(27mm)
1
1
/16"
BURNER
“CUT-OFF LEVEL”
AT CAST LINE
BURNER OFF
(35mm)
BURNER ON
1
3
/8"
BURNER
“CUT-OFF LEVEL”
AT CAST LINE
BURNER OFF
(35mm)
BURNER ON
1
3
/8"
MOTORIZED
VALV E
CLOSED
BURNER
OFF
BURNER
CUT-OFF LEVEL
AT CAST LINE
2
3
/16"
(56mm)
MOTORIZED
VALV E
CLOSED
MOTORIZED
VALV E
OPEN
(27mm)
1
1
/16"
Pump and Burner Switch Contact Ratings
Voltage Pilot Duty Only
120 VAC
345 VA
240 VAC
3
OFF
ON
STEP 1 - Preparation
INSTALLATION –
TOOLS NEEDED:
One (1) flathead screw driver, one (1) scraper and
one (1) 9/16" socket box or open end wrench.
a. Turn power off to boiler and all controls.
FLOAT
CHAMBER
b. Allow boiler to cool to 80˚F (27˚C) and
reduce pressure to 0 psi (0 bar).
Drain water in boiler to a level that is
below the float chamber.
There may be more than one source of power to
the boiler.
!
CAUTION
TOWER TUBE
SWITCH
ASSEMBLY
SWITCH
COVER
TERMINAL
PANELS
CONDUIT
CONNECTOR
FITTING
HUB
B
A
a. Disconnect and Remove Wires.
For Replacement Heads with Switches
(-HD Models)
• Remove two screws (A) and lift off switch
cover.
• Identify terminal connections for rewiring
and then disconnect all wires from
terminal panels.
• Remove conduit connection and wires
from integral fitting hub.
For Replacement Heads without Switches
(-HDLS Models)
• Remove four hex nuts (B) and carefully lift
switch assembly up and off tower tube.
STEP 2 - Head Removal
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