281 Issue 1 - Service Manual - BX3
18
5.2 One Flash - Over Heat Condition
Reason Overheat condition
•
This errors will appear whilst an over temperature is current. The overheat switch or flame
rollout circuit is open and measuring a temperature greater than the temperature of the
switch (See chart below).
The heater’s fan will be forced to operate at its predetermined speed for a specific time period.
Supply air over heat and Flame Roll - out
All Brivis BX3 models have a supply air over heat switch located near the supply air discharge
and is activated when the supply air reaches 90°C on the BX326 but on the BX315 and BX320
are activated at 110°C. Also if the flame roll out occurs the switch will interrupt the 24 Volt power
to the gas valve if flame rollout and over heat occurs.
The following will occur.
•
The power supply to the gas valve will be terminated.
•
The fan will operate immediately, if not already operating.
Once the over temperature condition of the switches has cleared and the switch resets (i.e.
switch closes within a specific time), a cool down period will operate for a duration of 120sec.
Then the normal heating cycle can commence again, provided the wall control is still calling for
heat.
Service Check List:
•
Check the temperature rise value of the supply air thermistor and nearest outlet
temperature, over the room temperature (Return air intake temperature). A 47
0
C.
Temperature rise will indicate a true overheat condition.
•
Check there are sufficient outlets open on the duct system.
•
Check the return air filter (if fitted) is sized correctly and is clean.
•
Check that the fan speed is sufficient for the system so that overheating will not result.
•
Check the fan motor is functioning correctly, and is not blocked or obstructed.
•
Check the ducting has not been crushed, damaged or incorrectly sized.
•
Check the return air intake is not subjected to a high temperature from an external source.
•
Check the wire loom and plug connections to the switch are not open circuit, i.e. wire
fallen off switch.
Supply air and Flame roll our switch ratings
Unit
S/Air over heat switch
Flame Roll out switch
BX315
110°C
90°C
BX320
110°C
90°C
BX326
90°C
90°C
