11
USER’S INFORMATION MANUAL
COMBI BOILERS 99
-
125
-
160
-
199
SEQUENCE OF OPERATION
The Combi boiler operates in a similar way for both a space heating and a
domestic hot water call for heat. When the unit is powered up the controller
enters a self-diagnostic mode, and displays the controller software version in the
main display.
The sequence of operation is as follows:
1. The unit receives a call for heat from a dry contact closure on terminals
X13.1 and X13.2 (24 volts section). The unit can also receive a call forfor
domestic hot water heating from the internal ow sensor, or from a 10KΩ
sensor or aquastat wired to terminals X13.4 and X13.5 (24 volts section).
2. The unit performs a safety check and energizes the fan for a pre-purge
(Service Display = 3).
3. Once the 5-second pre-purge is compete, the unit enters a 5-second trial for
ignition (Service Display = 4). If the unit fails to ignite, the unit will complete
another 5-second pre-purge then 5-second trial for ignition. This is repeated
4 times before a hard lock-out occurs. The Return button must be pressed to
reset the controller and begin another trial for ignition.
4. Once the burner is lit and ame has been proven the unit operates as it is
programmed (Display = for space heating or for domestic hot water).
5. If the unit exceeds its target temperature and there is still a call for heat or
hot water the burner will turn o (integral pump runs unless call is on-demand
DHW). (Service Display = 1)
6. After a space heating call for heat is satised, the unit’s pump will operate for
an adjustable amount of time (Service Display = 0).
7. If the burner is on to maintain the heat exchanger temperature for DHW
Comfort mode (Service Display = 7).
8. If the burner is on for frost protection (Service Display = 9).
MAIN
DISPLAY
LIT
DISPLAY
DESCRIPTION
(blank) - The unit is OFF. Press the space above the Dot for 2
seconds to turn on the unit
.
(blank) (blank) No Call for Heat - Standby
XXX 0 Unit pump running – pump post purge
XXX 1 Unit water temperature exceeds target – unit pump is
energized, call still present
XXX 2 Self-test – When power is applied to the unit the
controller enters a self diagnostic mode for 5 seconds
XXX 3 Fan Pre-purge , and Post-purge
XXX 4 Trial for Ignition and Flame Proving
XXX + Heating – Space Heating
XXX +
Heating – DHW
XXX 7 Burner on for Comfort mode
XXX
9
Freeze Protection mode
Table 2: Operating Display and Service Display Codes.
NOTE
The correct 10KΩ temperature
sensor (or aquastat) must be
used to operate the indirect
water heater properly. If the
incorrect sensor is used
the domestic hot water may
overheat causing serious
injury or death.
NOTE
The unit is equipped with a
Frost Protection feature. This
feature will operate the unit’s
burner to help protect the
unit from freezing. We are
not responsible for damages
to the unit, and/or related
components, nor property
damages that may result from
freezing conditions.
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