Xylem MM 706B Replacement Switch Assembly - Manual (Page 2)

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OFF
ON
STEP 1 - Removal and Replacement of Contacts and Terminal Panels
a. Turn power off to boiler and all controls.
Allow boiler to cool to 80˚F (27˚C) and
reduce the pressure to 0 psi (0 bar).
TOWER TUBE
SWITCH
ASSEMBLY
TERMINAL
CONNECTIONS
SWITCH
COVER
TERMINAL
PANELS
CONDUIT
CONNECTOR
NAMEPLATE
FITTING
HUB
C
A
b. Remove and Replace Switch Assembly
• Remove two screws (A) and lift off
switch cover.
• Identify terminal connections for
rewiring and then disconnect all wires
from terminal panels.
• Remove conduit connector and wires
from the integral fitting hub.
• Remove four hex nuts (B) and carefully
lift switch assembly up and off
tower tube.
• Carefully slide new switch assembly
over tower tube and secure with four
hex nuts (B). Make sure nameplate is
in same position as old unit.
• Remove two screws (A) and lift switch
cover off new unit.
• Install conduit fitting from old unit
with attached wires on switch assembly.
• Reconnect wiring to terminal panel in
exactly the same position as removed.
• Replace switch cover and fasten with
two screws (A).
STEP 2 - Testing
a. Turn on power to boiler and pump circuits.
With the boiler empty, the pump should turn on (5 or 5-M switch models) or the valve open
(7B or 7B-M switch models). The burner should remain off and boiler should begin to fill with water.
b. For Automatic Reset Models
When water level in the gauge glass is approximately 1 3/8” (35mm) above the horizontal cast line,
the burner should turn on.
For Manual Reset Models
When water level in the gauge glass is approximately 1 3/8” (35mm) above the horizontal cast line,
press the manual reset button and the burner should turn on.
c. For 5 or 5-M Switch Models
When water level in the gauge glass is approximately 2 1/8” (54mm) above the horizontal cast line,
the pump should turn off.
For 7B or 7B-M Switch Models
When water level in the gauge glass is approximately 2 11/16” (68mm) above the horizontal cast
line, the valve should be closed.
d. With the water in the boiler at its normal level and burner on, SLOWLY open the blow-down valve
until it is fully open. As the water level in the gauge glass begins to drop, verify that the following
occurs.
For 5 or 5-M Switch Models
When water level drops to approximately 1 1/8” (29mm) above the horizontal cast line, the pump
should turn on.
When water level drops to the horizontal cast line, the burner should turn off.
For 7B or 7B-M Switch Models
As the water level drops, the valve should begin to open.
When the water level drops to approximately 7/8” (22mm) above the horizontal cast line, the valve
should be full open.
When the water level drops to the horizontal cast line, the burner should turn off.
e. Close the blow-down valve after burner turns off and restore water level to normal operating level.
f. Repeat testing procedure several times to ensure proper operation of control.
g. After testing and verification of control operation, the boiler can be returned to service.
– Dimensions shown are typical.
– The following testing procedure is only meant to serve as a verification of proper
operating sequence.
Proceed to Step 2 to Test Control
CAUTION
Immediately turn off all power if the burner turns on with no water in the gauge glass.
Investigate further before continuing procedure.
!
CAUTION
If pump does not turn off or valve close, turn off water supply to boiler. Investigate
further before continuing procedure.
!
There may be more than one source of power to
the boiler.
! CAUTION
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