Outlet Probe; Igniter - A.O. Smith 100 Series Service Handbook

DISPLAYED MESSAGE/CONDITION/INDICATES

Outlet Probe

The Control System has detected an open or shorted
Outlet Temperature Probe circuit.
Important Service Reminder:
When performing any troubleshooting steps outlined in
this manual always consider the wiring and connectors
between components. Perform a close visual inspection
of all wiring and connectors to a given component before
replacing any electrical part or component.
The Control System has detected less than 2.7 AC amps
through the Igniter during the Igniter Warm Up period.
Operational Notes:
The Control System is programed to monitor amperage
through the Igniter during the Igniter Warm Up period and
requires a minimum of 2.7 AC amps before energizing
the 120 VAC Gas Valve for ignition. This is to ensure the
Igniter is hot enough to ensure ignition. See the Sequence
Of Operation on page 45.
Service Notes:
VF Boilers use a hot surface igniter (HSI). Igniters are
wearing parts that will require replacement during the life of
the boiler. The lifespan of an Igniter is directly proportional
to how many times it is energized. Short cycling (repeated
heating cycles of short duration) will increase Igniter
cycles and diminish its lifespan. The most common cause
of short cycling is a low "Setpnt Diff" setting in the User
Settings Menu. The lower the Setpnt Diff setting the more
the boiler will cycle on and off.
The range for the Setpnt Diff is 1° to 50°, the factory
default setting is 3°, see Table 4 on page 23. Dividing the
"Run Mins by the "Heat Cycles" values shown in the Log
& System Info Menu will equal the average minutes per
heating cycle. If the average heating cycle minutes is
less than 10 minutes, considering raising the Setpnt Diff
setting in the User Settings menu to prevent short cycling
and increase the lifespan of the Igniter.
58

Igniter

Servicing should only be performed by a Qualified Service Agent
CHECK/REPAIR
• Check the plug/socket connection at the MCB J7
Socket, see MCB - Section E on page 24. Ensure the
plug/socket pins are in good condition and making
good contact - repair/replace anything worn or
damaged.
• Ensure the wiring between the MCB J7 Socket and
the Outlet Temperature Probe are not pinched and
are continuous - repair/replace anything worn or
damaged.
• Turn power off to the boiler. Unplug the MCB J7
wiring harness plug. Measure and record resistance
between pins 4 and 5 of the J7 plug. If the measured
resistance is less than 317 ohms or greater than
177,000 ohms - replace the Outlet Temperature
Probe.
Service Note:
Resistance from any factory supplied/installed
temperature probe is shown in Table 3 on page 16.
• Call the toll free support phone number on the back
cover of this manual for further assistance if the
problem has not been corrected after performing the
procedures outlined here.
• Check all wiring and connections between pins 1 &
2 of the J18 socket on the MCB (see page 22) and the
Igniter. Repair/replace any worn or damaged wiring
or connectors.
• Closely inspect the pins in the J18 socket/plug for
wear or damage. Ensure the plug and socket are
properly connected and making good contact.
• Ensure there is 120 VAC between pins 1 & 2 of the
J18 socket on the MCB during the Igniter Warm Up
period (blower speed reduces after pre purge cycle is
completed).
• If 120 VAC is not present at the J18 socket during
the Igniter Warm Up period - call the toll free support
phone number on the back cover of this manual for
further assistance.
• Using an AC amp meter, check Igniter amps during
Igniter Warm Up period (blower speed reduces after
pre purge cycle is completed). If amp draw is less
than 3.0 amps replace the Igniter.
• Call the toll free support phone number on the back
cover of this manual for further assistance if the
problem has not been corrected after performing the
procedures outlined here.