Install Instructions

Page 55
NEOTHERM Residential Boilers
HIGH EFFICIENCY RESIDENTIAL BOILERS
®
This can be a symptom of improper control strategy or
setpoints, or a load distribution problem. The controller in
the Unit includes an anti-short cycle (ASC) function. The
timer for the ASC can be set to delay the boiler start for a
specied time after a call for heat is completed.
11.F Temperature Sensors
High Limit Sensor -
The control uses a dual thermistor sensor to monitor
the Units maximum temperature. The high limit sensor
is installed in the outlet water. A dual thermistor sensor
is used, so that the two temperatures can be monitored
and compared to conrm accuracy. The control will
automatically reduce the ring of the Unit to prevent the
high limit from tripping. The high limit setpoint is factory set
at 195°. However, if desired you can set a lower limit using
the Adjustable High Limit function available from the Quick
Start menu.
Outlet Water Temperature -
The outlet water temperature is sensed by a dual
thermistor sensor, and is limit-rated. The control compares
the two temperature readings to determine accuracy. The
outlet sensor is used as the primary control point for high
limit, temperature operation, and modulation.
Inlet Water Temperature -
The inlet water temperature uses a single thermistor
sensor. The heat exchanger temperature rise (delta T) is
calculated using the inputs from the outlet and inlet sensor
temperatures.
Stack Limit -
The stack temperature is sensed by a dual thermistor
sensor, and is limit-rated. The control compares both of the
temperature readings to determine accuracy. The stack
sensor is used as a limiting feature to avoid excessive
temperatures in the vent.
11.G Diagnostics
Use the Diagnostics to check the status of the sensors and
the digital inputs and outputs. The system also records a
history of lockouts and alarms.
Analog Sensors -
You can use this display to check on operating
temperatures, fan speed, ring rate, etc. (The word
“analog” refers to values that can change continuously
between zero and a higher value.) The values shown here
are “Read Only” – you can’t change them from this display.
Digital Input/Output -
This display shows whether di󰀨erent functions, inputs
and outputs are either on or o󰀨. The functions listed here
include pumps, valves, alarms, etc. The values shown
here are “Read Only” – you can’t change them from this
display.
History -
The system records the most recent lockouts or alerts. (If
there is a current lockout or alert, a note about this will also
appear at the bottom of the Home screen.)
• A “lockout” is a condition that will prevent the unit from
starting or running.
• An “alert” indicates a condition that is not normal. If it
continues, the control system might move to a “lockout,”
or the problem might be corrected.
11.H Error Codes
See Appendix B. on page 68