281 Issue 1 - Service Manual - BX3
1
1.0 HEATER OPERATION
This section provides an overview of the operation of the BX3 series heaters. It is vital that an
understanding of how BX3 series heaters, and their components, operate in order to service the
BX3 Series heater effectively and efficiently.
1.1 Operation Overview
The Brivis BX3 series is a 3 Star range suited for internal installations on Natural Gas only.
The BX3 series heater has a combustion system consisting of a fixed speed combustion fan and
direct spark ignition module. The gas valve is on/off only i.e. not modulating and the rate is set
for each model. Once the combustion fan pressure switch validates the system pressure is
correct the normal start up sequence will begin, refer below.
Upon power up the HCDSI24 -1 control board shall perform a system check and allow all of its
inputs and outputs to settle. The HCDSI24-1 initiates an ignition cycle upon receiving a call for
heat from an external thermostat.
The following will occur:
• The micro-controller shall check that the external flame safety guard is operational. As the
flame circuit is earth referenced, additional checks are made to detect an earth
disconnect.
• The control board will do a safety check and make sure the pressure switch circuit is
open.
• The unit then energises the combustion fan motor, and verifies that the pressure switch
closes. The unit will operate for the pre-purge time before continuing to the safety time.
• The unit shall simultaneously energise the spark igniter and gas valve with the intention to
light the main gas burner. The igniter shall be energised for at most the duration of the
safety time or until a valid flame signal is detected which ever occurs first. Safety time
shall cause the gas valve and combustion fan to remain energised for the duration of the
call for heat.
• 20 seconds after the warm up period the control board will then power the main supply air
fan to its set speed.
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