Inlet Probe - A.O. Smith 100 Series Service Handbook

DISPLAYED MESSAGE/CONDITION/INDICATES

Inlet Probe

The Control System has detected an open or shorted Inlet
Temperature Probe when the Inlet Temperature Probe is
configured as the Controlling Probe. See The Controlling
Probe on page 7 and MCB - Section D on page 23. The
Control System will declare a fault condition and lock
out in this condition displaying the "Inlet Probe" Error
Message on the UIM's LCD.
If the Inlet Temperature Probe is not configured as the
Controlling Probe and the Inlet Temperature Probe circuit
is open or shorted, the boiler will continue to operate. In
this condition the UIM's LCD display will show dashed
lines (-----) in place of the Inlet temperature reading
when the Inlet Temperature Probe circuit is open and will
display the word "Short" when the circuit is shorted. See
the illustrations below.
Out l et
- I nl et
= D el t a T
Ta nk
Out l et
- I nl et
= D el t a T
Ta nk
Installation Notes:
Each VF Boiler is fired and the optimal combustion
is set before leaving the factory. The Inlet Probe is
configured as the Controlling Probe at the factory during
this process. The Inlet Probe MUST NOT be configured
as the Controlling Probe when the boiler is installed. All
VF Boilers are supplied from the factory with a Remote
Temperature Probe to be installed in a storage tank
on domestic water applications or in the return loop in
hydronic heating systems. The Remote Temperature
Probe MUST BE configured as the Controlling Probe on
all applications, see the The Controlling Probe on page 7
and the SW1 dipswitch information on page 23.
With the boiler properly configured and installed the "Inlet
Probe" Error Message should never be displayed.
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.
56
14 0 ° F
------
5 0° F
11 5° F < <<<
14 0 ° F
Sh o rt
------
11 5° F < <<<
Servicing should only be performed by a Qualified Service Agent
CHECK/REPAIR
• Check the plug/socket connection at the MCB J8
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 J8 Socket and
the Inlet Temperature Probe are not pinched and
are continuous - repair/replace anything worn or
damaged.
• Turn power off to the boiler. Unplug the MCB J8
wiring harness plug. Measure and record resistance
between pins 2 and 5 of the J8 plug. If the measured
resistance is less than 317 ohms or greater than
177,000 ohms - replace the Inlet 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.