Vulcan gas 5310052 heater intermittently cuts out. Gets to temp eventually. Removed rear cover to expose control unit. Found that burners come on for about 20 to 30 secs then cut out but fan continues

Check the afc Automatic fan control is shut off too soon .

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

The oven safety valve has to be cranked down for propane.
Get a good fitting wrench and tighten this spud down and open the air shutter on the burner.
This video shows how to tackle a crank down and flip type LP conversion whilst yours might be a bit more fancy it still must be adjusted like any other stove:



If you need further help, reach me via phone at https://www.6ya.com/expert/dan_73bbd84fe1d95b61

Hi Dave, my neighbour has a Vulcan Compact 60 that is doing the same as yours, except the cycle time is even shorter, only four minutes total. The temperature in the house barely rises and never reaches the thermostat setting. Altering the thermostat anticipator does not alter the cycle time. Therefore, as you have found, the fault is not related to the thermostat. The gas technician who inspected the heater said he could see the unit was faulting, but didn't think he could fix it. WTH? To help my friendly neighbour, I have asked numerous experienced techs since and those few who actually seem to know anything have helped me piece together what is probably (I emphasise probably) happening. Current thinking is that the fan is not blowing enough air and the heat exchanger is overheating, which trips the over temp switch (limiter), cutting off the burner. Eventually the fan cools the unit down enough to switch itself off and reset the limiter, then the cycle repeats.
The remedy is to replace the fan or replace the fan bearings, if they have become tight, as is likely the case. It might also be necessary to replace the combination fan/limiter switch, because the contacts are probably arcing due to the extra current drain of the fan with tight bearings (I know this because the arcing causes TV and radio interference to myself and others in the vicinity, which interference ceases when the heater is turned off and resumes when the heater is turned on and had about 20 minutes to heat up). Important: If no action is taken, the heat exchanger can be damaged and/or cracked, especially if the limiter contacts weld closed, which will allow the heater to exceed the limit temperature and probably crack the heat exchanger. This in turn will allow carbon monoxide fumes to enter the house via the ducts. Therefore the problem should be fixed ASAP.
I am currently trying to find someone who understands this heater to the extent described above and therefore has some chance of repairing it correctly. No success as yet, similar to your own experience.
Dave, if you discover anything at all about this fault, please let me know, as I am not going to waste my money on gas techs who are unable to fix the problem because they don't understand the system to the required degree.
Parts can be obtained from many gas supply houses. The one I normally use quoted about $300 for a fan and $150 for a fan/limit switch. This seems too expensive to me. I could get a whole second-hand unit for about $300. Will try to let you know if I make any further discoveries. Anyway, best of luck. Regards, VC60.

Yes. Vulcan heater company is still making heaters. Here is the link. http://www.vulcanelectric.com/

Grainger is a direct seller of Vulcan heaters, so you chould be able to give them a call, explain what you need or giver them a part number and they will be able to get what you need.

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.

Hi it could be a faulty fan control it cuts in on temp rise bring the fan on / and shuts off if the temp gets too high if fan dose not cut in .

Remove power source from the unit. If remote control is installed; remove cover and lift the control wires on the terminal...can be accomplished from either end.

Restore power and see if unit functions normally.

Contact Paloma/Rheem customer (800-432-8373) support and notify them IF you are getting a code "76" error. Rheem has recently extended the warranty on the "Burner Control Assm."; which is your problem. The C4-C8 portion of the error code, is where the unit stops the ignition process...burner fails to light, or gives you intermittent hot water. In either case, contact customer support .

If this helps, please indicate so.
Mike//jzklipper

Remove power source from the unit. If remote control is installed; remove cover and lift the control wires on the terminal...can be accomplished from either end.

Restore power and see if unit functions normally.

Contact Paloma/Rheem customer (800-432-8373) support and notify them IF you are getting a code "76" error. Rheem has recently extended the warranty on the "Burner Control Assm."; which is your problem. The C4-C8 portion of the error code, is where the unit stops the ignition process...burner fails to light, or gives you intermittent hot water. In either case, contact customer support.

If this helps, please indicate so.
Mike//jzklipper

i service these ovens alot and my first guess the t-couple you already replaced.i wouldnt think its the valve.lp burns very dirty as you know,clean out the burner/pilot assmbely and see if this solves it.also take a look at it when its lit and see if the pilot is being pulled to the burner.let me know.also if the unit has a regulator on the back pull the vent plug and clean it up.