I have a Vulcan ducted gas heater 902. because polit tube is blocked so I used a wire go through the tube from the flame end. after that the flame is getting much big and can not be stayed . Can it be fixed? how? Cheers

The thermocouple which senses the flame has probably failed or it could be a poor pilot flame (Dirty or partially blocked injector) Get a licensed gas Tech to service it if this hasn't been done previously.

Hi Vulcan Bonaire,

Is this a ducted gas heater or a free standing gas heater???

Hi there. Flames rolling back instead of shooting inside the fire tubes can be a result of clogged fire tubes or air entering the flue, also check if there are objects blocking the flue. Regards.

you can remove the pilot assembly and blow air thru it and then run a small piece of wire thru it
At the same time wipe the thermocouple end that you took out real good up and down on your jeans .That end has lead on it and that can become corroded so it does not get a good signal
clean the other end with a real fine sandpaper or a new not wet brillo pad

Check your exhaust, see if its clogged or blocked, clean the flame sensors, I that does not work, then your gas valve is starting to go bad, there is a cap on it if you take the cap off you can turn the gas flow down a little bit,

What size is the orifice? Are you using LPG or CNG? What pressure is the regulator set to?

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

Possibly a bad thermocouple or whatever is sensing the flame. If its a flame rod you can clean it with steel wool. Let me know what you find.

Simply clean out the jet tube with a fine wire, the sound you hear is the gas blowing by the irregular edges, and swirling and not mixing and producing sound waves, (Bit like a flute) So, you need to clean the tube right out, and smooth off the end again, & sorta "Countersink", Flame the end too, at the end.use a very fine needle file, and make it look like new, that will sort your problem out. Then adjust so you have a good gas flow. Also check out it isn't blocked too.

Thank you for posting your question here on Fixya.com.

Along the manifold there will be several gas ports feeding gas into the burner tray tubes. The tubes are the narrow steel tubes that extend under the heater from the gas line. We use a piece of #12 solid wire and run it in and out of the tubes from under the manifold. Spiders like nesting in the tubes and their silk blocks the gas flow. Once the gas migrates over from further away from the pilot you get the 'whoosh' of ignition. As you clean the tubes and recheck the heater be sure you pay attention to the flame color. Anywhere you see orange flames above a tube you need to shut down and then clean the tube. Orange flame means poor combustion and needs to be fixed to prevent sooting.

If this answer does not fix your problem, please comment with additional details prior to rating the answer. Positive feedback is appreciated once your problem is solved!

John