Supply trunk reducer - how to replace?

Old 12-10-20, 03:49 PM
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Supply trunk reducer - how to replace?

I have a 12" round main trunk that is reduced to 8" about 6 feet from the furnace. The 8" is taken from a hole in the end cap on the 12" main. I guess those are called shortway reducers. The 8" trunk is about 1" off center. I can feel warm air coming out of the vents connected to the 8" pipe, but there is no force. Those connected to the 12" main do send air out with some force. I am thinking this is due to the hole in the cap eccentric reducer because the air hits a 3" wall on the cap..

I am thinking of replacing this shortway reducer with a proper tapering reducer, with a 1" off center. These reducers have 2" collars and a 4' tapered mid section. So, I need to cut the 8" to make a 4" gap between the two trunk sections, right? I can push the 8" aside to put the collar on the 12" main. How do I insert the other end of the reducer into the 8" trunk? Do I have to dismantle the entire 8" trunk? Would appreciate your thoughts. Thank you.


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