I have a Vulcan Ultra 21E ceiling ducted unit
The LED flashing fault is no 8 which is a gas interruption.
The unit fan runs, ignition starts full flame and gas flows for about 2 secs then shuts down
Just been thru a similar problem with my Climate Technologies Vulcan High Efficiency Ducted Gas heater which in this case is installed under the house. This heater is about 7 years old and I have previously (2 years back) refurbished the controller by replacing the main power supply electrolytic filter capacitors.
I also had a communication problem with the Touch pad Thermostat which in the end required replacing the entire touch pad as one of it's voltage regulators had gone intermittent (Touch pads are available on E-Bay). To operate the heater while the touch pad was out of commission I installed a manual switch between the heat contacts on the heater controller. Closing the switch causes the heater to permanently run if it has no thermostat. Once communication with the touch panel was restored we were able to try and find the intermittent heater fault.
Again I have been getting Fault Code 08 "Gas Interruption" however the heater was lighting OK and then going out after about a minute or so. In the end I found 2 distinct heater faults.
Fault 1 was the flame sensor where the weld between the wire and flame probe rod had broken but it was still touching. This meant it was sensing Flame OK and then later would go open with expansion as the temperature rose. I fixed this by replacing the Flame Probe with a new one sourced from Reece HVAC.
At this point I celebrated thinking it was fixed!
Fault 2 after the flame sensor issue was cleared the fault still persisted but slightly less often.
The heater was cycling 3 times to get going and then locking out, requiring a reset from the touch thermostat or heater controller board. Sometimes the heater would achieve a onging burn for a long period, and other times just locking out after 3 tries.
Careful observation of the flame, through the observation holes after it lit, showed correct flame sensing but as soon as the nominal 65C duct temperature was reached the combustion fan (modulates) throttles back too far and the flame goes out, the flame sensor switches off and gas valve is then closed. The pressure differential across the burner manafold controls the Gas flow rate so if the combustion fan goes too slow the flame goes out due to lack of gas.
On the control board there is a potentiometer marked "MIN GAS RATE" this needs to be tweaked clockwise until the burner remains lit when the nominal 60-65C duct temperature is reached. Don't turn it up too far or the heater may not throttle back enough and end up going out on overheat.
Once a stable flame is achieved when throttled, try the heater in the economy mode which uses a lower recirculating fan speed and check the flame still remains lit. My problem was most obvious in the Econ mode.
Hope this helps someone else - It took me over a year to solve this one. NeilP
Aug 21, 2011 |