1980's Furnace with Partially Lit Burner

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  #1  
Old 01-31-19, 09:11 PM
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1980's Furnace with Partially Lit Burner

Hi All,

I've got a furnace which is running on half it's capacity right now, since only one of two burners are working properly. It's a mid 80's model. Things I've done:

Removed the burner (big long cast iron piece with slits) and cleaned it throughly.
Cleaned the manifold outlet making sure the little hole was free from debris.
Turned off furnace and pilot light and restarted the whole thing.
Adjusted the air intake to achieve a nice blue flame on the working burner.
Banged along the manifold (without damaging it) to try free any clogs.
Adjusted the gas value (by a quarter turn) slightly to see if it made any difference - it did not so I adjusted it back.
Cleaned inside the furnace with a Shopvac.

Right now the second burner as the gas flows from the manifold doesn't appear to be getting enough gas. The first burner works fine as you can see from the photos. The second burner only has a tiny amount of flame.

It's minus -22C (or -7.6F) outside - so the house is getting chilly! Any help appreciated.

Many Thanks.

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Last edited by PJmax; 01-31-19 at 09:48 PM. Reason: resized/reoriented pictures
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  #2  
Old 01-31-19, 09:51 PM
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Welcome to the forums.

Remember...... older furnaces need their heat exchangers examined for rust thru and cracks.

Take the burner back out and clean the gas orifices.
They are usually brass, are attached to the gas manifold and are inside the air shutter area.
 
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Old 02-01-19, 03:02 AM
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As PJ said, take the burner's out, flush them with water and let it dry. Remove the brass orfices and make sure they are clean (no spider web or anything to clog), Reinstall the orfices and the burners. Check the operation. Note; the right burner flame does not look right either. While the burners are out carefully inspect the flue area above the burners for integrity. No cracks , holes, heavy rust accumulation, all the way up to the flue connection. Check the flue pipe to the chimney and the chimney also for restrictions or debris. Have the gas company or someone check the gas pressure in your home. If you can, check the gas meter flow. (1) cu. ft. per minute of gas useage while the furnace is operating = 60,000 btu/hr approximate gas input. If you can't get this problem solved or you feel that it is too complicated call for professional help to keep you and your family safe.
 
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Old 02-01-19, 08:32 AM
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Despite giving both the burners and the orifices a good clean yesterday, it turned out the blockage was is the gas manifold further up the pipe. A can of compressed air later and it's all running nicely now.

Many Thanks All!
 
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Old 02-01-19, 02:13 PM
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That is a tribute to what spiders can do. They climb in and build very strong webs that can stop gas and airflow. Good job cleaning. Don't forget to have the heat exchanger checked.
 
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