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Frequently Asked Questions (2 of 2)
Symptom
Look For...
Burner symbol on
LCD
WWSD symbol on
LCD
Mix or Boil Calls on
No central
LCD
heating
DHW Call on LCD
System in AWAY
"MIN" shown
together with boiler
target or boiler
supply on LCD
Boiler short
Burner symbol
cycling
cycling on and off
LCD shows zone on
Single zone over
heating
LCD shows zone off
Single zone under
LCD shows zone on
heating
LCD shows zone off
Job Record
Item
OUTDOOR DESIGN
MIX DESIGN
MIX TYPE
MIX MOTOR
BOILER TYPE
BOILER DESIGN
BOILER MINIMUM
BOILER MOTOR
MINIMUM MODULATION
MODULATION DELAY
Corrective Action
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.
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.
If there are no Mix or Boil Calls, there are no thermostats calling for heat.
During DHW tank heating, the central heating may not be heated.
During AWAY, the thermostats operate at a lower temperature. Locate a 'User
Switch' and set to Normal to resume heating.
Boiler is operating below the boiler minimum setting and the mixing valve is
closed or the mix injection pump is operating at low speed. The mixing device
will operate normally once the boiler warms up.
Mixing using variable speed injection pumps requires the balancing valve to
be set correctly. Lack of head pressure can lead the injection pump speed to
ramp up and down.
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.
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.
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.
Check for calls
Setting
Item
FLUSHING
WWSD OCCUPIED
WWSD UNOCCUPIED
DHW MODE
DHW EXCHANGE
DHW OCCUPIED
DHW UNOCCUPIED
SETPOINT
UNITS
31 of 32
Setting
© 2016
402_D - 05/16
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