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indication
Condition
Possible Cause
Limit String Status
Limit String Status
i
Air Proving Switch
Limits
Flow Switch
Limit String
Fault
The Limit String Status screen shows the safety limit status. A contact icon, either “open” or
“closed”, graphically represents each safety limit. The “closed” contact icon is steady; the “open”
contact icon is blinking. For example, the screen shown to the left illustrates a “closed” Limit
contact and an “open’ Flow Switch and Air Proving Switch Limit contacts.
NOTE: Since the limit string items are wired in series, all limits downstream of the “open” limit will
also appear on the screen as “open” (blinking) icons regardless of whether or not they are actually
open. The Air Proving Switch is wired independent to all other limits. The Air Proving Switch is
only required to be closed during boiler pre-purge. It is normal for it to be open during run mode.
Sensor Status
Sensor Fault
The Sensor Status screen shows the status of all sensors. Possible states include:
None: Feature requiring this sensor has not been selected.
Normal: Sensor is working normally.
Shorted: Sensor is shorted or is defective.
Open: There is a break in the wiring between the Control and the sensor or the
sensor is defective
Out of Range: Sensor is defective or is being subjected to electrical noise.
Unreliable: Sensor is defective or is being subjected to electrical noise.
When a sensor fails “opened” or “shorted” the value is changed to reverse video
(background black and value white) “024” or “768” respectively to indicate that there is
a fault with the sensor.
Rate Limit
Rate Limit
The following messages appear when the firing rate is limited or reduced to help avoid
a lockout or save energy.
Refer to Hard Lockout section for corrective actions
- High Stack Temperature Limit
- High Supply Temperature Limit
- High Differential Temperature Limit
The following messages appear as part of normal start and stop sequences:
- Minimum Modulation (normal start/stop sequence)
- Low Fire Hold Rate: Low fire hold rate is a normal start-up rate hold used to help
ensure system temperature feedback prior to release to modulation. Low Fire
Hold Time may be adjusted. Refer to the “Changing Adjustable Parameters”,
Paragraph F, for additional information.
- Maximum Expected Heat Rate: Maximum Expected Heat Rate limit is a normal
start-up rate hold used to save energy. This limit helps reduce extra cycles
and save energy. Boiler is free to modulate up to the sum of the active zones and
domestic hot water expected heat rates. Each zone heat rate is adjustable and
may be modified under the modulation menu. Refer to the “Changing Adjustable
Parameters”, Paragraph F, for additional information.
EMS Status
Energy
Management
System Fault
The Energy Management System (EMS) fault screen provides input fault status. When
an input is shown as “Not Selected” it is not required for this application or has not yet
been selected. These options are selected under the “Energy Management” Adjust
mode menu.
Modbus Input Failure If a modus input is selected and out of range or not present
a “535” value is shown reverse video (background black and
value white). To fix the problem check the input source and
check that the input is properly connected.
4-20mA Input Failure Failure status for the 4-20mA input is the same as shown
under Sensor Fault.
E. Active Fault Screen Faults
II. Troubleshooting
(continued)
