Have 3 pitco commercial deep fryers. Getting flames up the back flue in first fryer.

The burner flames must be BLUE. Yellow flames will produce soot. Sounds like the burner orifice size needs to be checked.

Flames coming out of the exhaust can be caused by several things.
The fryer could be set up for natural gas and it is installed on a propane system. The fryer can be leaking oil near the burner tube and the oil is burning causing excess flame. There could be grease buildup in the flue in the back of the fryer from people hanging the baskets in the wrong place.

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.

Hi Dan.
Check if the fire tubes are clean, exhust system must be operating well during fryer operation. There should be no fresh air directed at the flue stack of the fryer, only exhaust.
Regards.

Hi there.
You should inspect the fire tubes, it is a tunnel under the fry tank where the burner flames suppose to travel to heat up the oil. Your fire tubes may be clogged with soot or carbon that's why flames cannot go thru the fire tubes. Fire tubes must be free of soot or carbon deposits.
Soot build up on fire tubes can be prevented by keeping the gas pressure at standard as much as possible, low gas pressure produce yellow flame or poor flame quality and in turn will produce soot.
Also, make sure that no air or ventilation is directed towards the flue riser, otherwise, the same will result, flames rolling back towards the door.
Regards.

There may be soot/ carbon build up inside the fire tubes that's why flame crawl all the way to flue. Also check if your fryer receives the right gas pressure and type as rated on the nameplate.

As high as the flue stack and it should be made of stainless steel.

You have to dismantle the back panel to have access in cleaning the flue. Soot formation or carbon build up on fryers are due to low operating gas pressure. When the fryer receives lower than the nameplate rating gas pressure, the flame on burners will be of poor quality (yellow flame) which will in turn produce soot/ carbon.

check burners and chambers for soot build up. Check gas regulator valve