brick/type H/ lined or unlined?

[Jeff Merritt]

I have a new 80+ furnace installed into a brick chimney, here is the question, they have removed the top 2/3 of brick chimney and installed a type H chimney, and left the bottom 1/2 ( 12') brick unlined, thoughts please, do you think the bottom half should be lined?, Inspection was in Chicago.

[Patrick Bolliger]

Hey Jeff,
Sounds to me like a problem.

First the size of the chimney ( 7 times rule). Is this a cat 4 condensing unit with pvc exhaust going to the chimney? The idea behind these units is to use what the MFG states is acceptable. If the installer alters that then the MFG will not warranty or repair without $$$$ if H /O claims problems. That's one issue. The next is:

Problems with liners are most likely going to relate to cat 1 negative pressure natural draft units and brick chimneys Acids from products of combustion and chimney size with respect to chimney draw can't pull the gases out hence "eating the mortar" holding the bricks of the chimney. Heating a chimney via the output of the appliance is the factor here so the chimney can work properly.
Check out : http://www.gamanet.org/gama/inforeso...y?OpenDocument

Oversized chimney and low furnace temp (heat) output like a 80 percent unit may not work at all in what you describe..

Got any other details for us on this