Boiler Control Instruction & Operation Manual
Page
52
of
68
Trouble- Shooting
Limit String
The Limit String Status screen shows the safety limit status. A contact icon, either
“ON” or “OFF”, graphically
represents each safety limit. The
“ON” contact icon with normal text; the “OFF” contact icon is shown in red. “ON”
means that the contact is closed and there is no issue. An
“OFF” limit means the contact is open and the limit is not
“made”.
Limit String Status screen (Figure 23) shows boiler limits in order, 120 Vac positive to neutral. W hen a limit is
“OFF”, all other contacts below (or “downstream”) that limit will also show as “OFF”. When troubleshooting,
the first
Limit in the string of
“OFF” Limits is the contact to inspect.
“ON” limits indicating the limits are
closed.
Figure 23:
Limit String Status
“OFF” limits indicating the limits are
open. In this case the contact at A6
(ILK) Thermal Fuse Limit is open. The
status of limits downstream is
unknown.
NOTE
: Some Limits cycle normally based on the function of the boiler. For example, the Low Air Pressure limit will
cycle to
“OFF” after the boiler post purge is complete. The “Help” icon only indicates a fault (flashes) when the limit
string is not behaving normally.
