© 2013
400_D - 09/13
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Symptom
Look For...
Corrective Action
LCD display is off
Fuse holder
Control power supply has a 24 V (ac) fuse which if blown, requires
replacement.
Power to control
Use electrical meter to measure 24 V (ac) voltage on input power R and C
terminals.
No central
heating
Burner symbol on
LCD
If the burner symbol is on the LCD, there is a problem with the boiler. Ensure
the boiler aquastat manual limit is reset to the on position.
WWSD symbol on
LCD
Warm Weather Shut Down (WWSD) is an energy saving feature that prevents
central heating during the summer. Ensure the outdoor temperature reading
is accurate and replace outdoor sensor if necessary. WWSD setting can be
increased if heating is required.
Boil Calls on LCD
If there are no Boil Calls, there are no thermostats calling for heat.
DHW Call on LCD
During DHW tank heating, the central heating may not be heated.
System in AWAY
During AWAY, the thermostats operate at a lower temperature. Locate a ‘User
Switch’ and set to Normal to resume heating.
“MIN” shown
together with boiler
target or boiler
supply on LCD
Boiler is operating below the boiler minimum setting.
No DHW tank
heating
DHW Call on LCD
If a DHW call is present, the control is aware that the DHW tank requires heat.
DHW tank reading
Ensure the DHW tank temperature is accurate and replace if necessary.
Burner symbol on
LCD
If the burner symbol is on the LCD, there is a problem with the boiler. Ensure
the boiler aquastat manual limit is reset to the on position.
DHW pump symbol
on LCD
If the DHW pump symbol is on, check to ensure the DHW pump is in operation
by checking for pump vibration or voltage on the pump wiring terminals.
DHW pump in
operation
If DHW pump and boiler are operating, the system may require the boiler system
pump to operate to heat the DHW tank. Ensure the DHW Mode setting is set
correctly.
Single zone over
heating
LCD shows zone on
Thermostats have a differential of +/- 1.5°F of the temperature setting. Due to
the display rounding numbers up, heating can appear on when the temperature
is 2°F above the setting. This is normal operation.
LCD shows zone off
Ensure zone valve terminals measure 0 V (ac). Measuring 0 V (ac) indicates
mechanical zone valve may have failed in open position. Measuring 24 V (ac)
indicates control relay may have failed.
Single zone under
heating
LCD shows zone on
Ensure zone valve terminals measure 24 V (ac). Measuring 24 V (ac) indicates
mechanical zone valve may have failed in closed position. Measuring 0 V (ac)
indicates control relay may have failed.
LCD shows zone off
Check for calls
Frequently Asked Questions
