Home type furnace manifold probblem.

[rodm1]

I have a York house furnace that sometime when the burner kicks on somehow the orifice at the manifold lights on fire! anyone have a fix for this problem?

http://highperformancehvac.com/Images/gas-furnace-parts.jpg

 

[2LTim]

Rod:
The first of several things to look a would be, is your exhaust fan kicking in and creating a draft for the burner. If that's ok, check the preasure coming out of your gas valve. If it is too high, on initial start-up, the combustion chamber is flooded with gas and backfires which catches the manifold oriface on fire. Your post says "sometime," another possibility for causing intermitent backfires may be improper venting and back preasure caused by wind.
Hope this helps,
Tim

 

[rodm1]

I don't have a exhaust fan on this model. I will see if the venting meats manufacture specs. What kind of presser gage do I need to check with? I'm using LP gas.

 

[Torque1st]

The picture shows an exhaust or induced draft or vent fan.

Some models have screw in orifices in the manifold that can come loose and leak gas which will sometimes ignite.

 

[Vicegrip]

#1. Clean the burners if the gas backs up it will light on the wrong side of the burner at the orifice. The burners most often have a pressed set of slits or holes in them and they get rusty or covered with rust like crud. Good to clean the burners in furnaces that are not acting up too.

#2. Check for cold air down-drafting when the furnace is off.

 

[rodm1]

#1. Clean the burners if the gas backs up it will light on the wrong side of the burner at the orifice. The burners most often have a pressed set of slits or holes in them and they get rusty or covered with rust like crud. Good to clean the burners in furnaces that are not acting up too.

#2. Check for cold air down-drafting when the furnace is off.

The burner is very dirty after I clean it up is there something I can use to prevent the rust again? I can feel slight air movement in the chimney when off.

 

[kbs2244]

Just clean it before every heating season.
Mine has a stainless steel heat exchanger and it is still dirty every year.
To do it right you have to take the thing half apart so you can pull it out to brush and vacum all the passages.