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RATIONAL SCC – 202G COMBI OVEN 2014 NAT GAS
This oven has given head aches, here is a brief history
Heat exchangers have been replaced in a kit along with burners and igniters, adjusted the max blower speed to the lowest settings according to a rational rep, did that and great no backfiring on one oven but on another the backfiring is present even after adjusting blower fan speed for max, first oven backfires heavily in steam mode like a modified supra that spits flames about a foot high, I can tell it has gas just by seeing flame come out the exhaust, and in hot air it backfires within an hour of running but it sure does not backfire as much as steam when you try and start it up. The other oven just does not function on steam mode and goes to a reset gas immediately after trying to turn on but hot air works just fine. Both hot bottom and top air flue gas analysis readings inside the board are 5.75uA and the steam flue gas analysis reads 0.0uA with the blower motor running and rpms showing. Ultimately all igniters are gapped right, electrode on each unit are gapped right, work to which I tested before installing and are brand new to top it off. It was giving me a code 33-1 at first so we got 2 new automatic ignition controllers. The gas screw for the steam mode gas valve is at 3.5mm tried adjusting them both to get a ball park but nothing. After installing new ignition boxes on both top and bottom it gave me a 34.4 internal data communication defective on the one that does nothing for steam after getting many gas reset codes and the one that backfires gives a 34.8. This has been a very very invested job and it does not help much when rational is very hard to get a hold of let alone try and break down what is actually going on im sure the gas valve works on both since 1 backfires fire and the other one I can literally smell the gas come out the exhaust can anybody point me in the right direction as a young tech
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1 Reply
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is this an SCC WE oven? How is incoming gas pressure static, and the drop when hot air burners fire up?
I have never seen a steam burner backfire or even have delayed igntion, thats why I ask about gas pressure as you are having problems with all the burners .
Backfiring issues on hot air heat exchangers on scc we units can sometimes be solved with a modified burner.
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