High Carbon Monoxide

[walker]

What would cause high carbon monoxide levels in a mid-efficiency furnace (800PPM) ?? I was working on one today and took a reading and it was really high and I didn't know what the cause of this could be.

Any insight would be great, thanks in advance.

[Admin]

I would check the manifold gas pressure and lower it if required.  An overfired furnace can create up to 4500 PPM.  A small adjustment can lower this down to 20 PPM.

What kind of furnace were you working on?

[walker]

It was a keeprite, I did check the manifold and it was running at 3.5"w.c.

Can any other issues cause high CO?

[Admin]

Make sure the burners are in good shape and clean.  Does the flame look good?

Those furnaces have had alot of heat exchanger failure so I'd look for cracks.

[walker]

I did a camera and visual inspection of the heat exchanger, and everything looked good, that's why I'm puzzled as to the high reading, flame was good as well.

[slo-115]

There were some tough years with those icp products. If possible cut a inspection door in the hot air plenum and check for "poped" heat exchanger rings. Sometimes if you pull the blower fan you can find those rivet rings laying down there

[harshal]

FOUND TODAY POPPED RING IN THE ICP.M-CUG5075BFA2.WAS ALMOST 20 YRS OLD MID.SOMETIMES U CAN FIND THE POPPED RING THROUGH THE LIMIT HOLE/OTHERWISE I OPEN UP THE PLENUM AND CHK FOR ALL THE PASSES UPTO BOTTOM .BCOA THEY ARE MORE LIKELY TO POOPED UP BCOZ OF HIGH HEAT OR CLOSE TO BURNER AREA I MID FURNACE.THE HIGH CO COULD BE RESULT OF PARTIALLY BLOCKAGE IN COLLECTOR BOX/I WOULD OPEN UP N VACCUM IT OUT N REPLACE THE GASKET IF REQ.