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With the probe wire removed, check the probes and
contactors in the following manner:
1. With an ohmmeter, check the probe at wire
connection and shell. There should be no
resistance present when the boiler is empty. If
resistance is present, remove and clean the
probes. Also check for a cracked insulator, then
reinstall probes and check. You should read
continuity between the probes and shell only
when the boiler shell is full
of water.
2. Check low level and differential contactors. With
a voltmeter, check across terminals 1 & 2. Meter
should read 115 V. Across terminals 9 & 10, you
should read 350 V. Using a jumper wire, jump
terminals 9 & 10. Contactor should engage. If
contactor does not engage, replace contactor.
3. Remove sensing probe. First remove the bolted
cover over the sensor cluster. Then remove the
wire from the probe and unscrew the probe with a
wrench. Be careful to note the location of each
probe and the number of the wire connected to it.
Incorrectly connected wires will cause the controls
to malfunction.
4. Clean probe thoroughly, removing ALL deposits
from the insulator. Do not use an abrasive on the
insulator; use a soft cloth.
5. Inspect through the probe socket for the presence
of water. Water must drain from the probe
housing. If in doubt, pour water into the housing
and observe that it drains quickly. If the housing
fails to drain, remove the housing or housing
cover and clean the interior mechanically.
Water Level Gauge Assembly
Close the valve at the top and at the bottom of the
gauge assembly. Unscrew the packing nuts at the top
and bottom of the glass tube. Slide the glass tube up
until the bottom of the tube is clear of the fitting. When
reinstalling the tube, use new sealing washers. Do
not overtighten the packing nuts; it could break the
gauge glass. Check that both top and bottom valves
are fully open.
Pressure Switches
WARNING: DISCONNECT ELECTRICAL POWER
SUPPLY BEFORE REMOVING BOILER CONTROL
BOX COVER.
There are two pressure switches located inside the
boiler control box. One pressure switch is the cycling
or primary control; the other is the high limit control.
They are identical switches, differing only in their
settings. Each one is identified by a label attached to
the switch case. The labels show the proper setting
for:
Cycling Switch: Off at 10 psi and on at 8 psi
High Limit Switch: Off at 15 psi and on at 6 psi
There are two square head slotted adjustment screws
which project through the top of the switch case and
a dial with pointers that indicate the approximate
setting. The adjustment screw directly above the dial
changes both the cut-out (off) and the cut-in (on)
points. Set it first to give the proper OFF setting.
Turning the screw clockwise increases the pressure.
Then set the second adjustment screw to give the
proper ON setting.
To check the wiring, remove the switch cover (held in
place by one captive screw). If wiring is correct and
an adjustment of the setting does not correct the
problem, replace the control. DO NOT attempt to
disassemble the switch or its operating mechanism.
High Limit Thermostat
Remove thermostat and inspect flat surface of
thermostat for corrosion or rust. Replace if rusted.
Clean thermostat mounting and thermostat surfaces
before remounting or replacing. A good metal-to-
metal contact is essential for proper functioning of the
thermostat. This service must be performed at least
once a year.
On gas boilers, the high limit thermostat is located on
the face of the boiler close to the sight glass on the
right. For access, remove the approximately 2" x 2"
metal cover placed over the thermostat.
