Another 'First'

[Darren]

After about 13 years, this is a first for me.

My question would be is the fan changed; after all a cat III is 'under pressure' while a cat I is 'atmospheric'.

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[hausdok]

Just a wild guess; but a 3-inch vent is consistent in size from the boiler to terminus. so pressure ranges within the vent are probably equal anywhere along its length. However, when you vent into a chimney using a short connector the chimney flue will be far larger, and can vary in size along its length, so the atmospherics would be inconsistent from boiler to terminus.

ONE TEAM - ONE FIGHT!!!

Mike

[Jim Katen]

After about 13 years, this is a first for me.

My question would be is the fan changed; after all a cat III is 'under pressure' while a cat I is 'atmospheric'.

I don't recall having ever seen that either.

There was a thread a few weeks ago regarding an attic-mounted furnace that vented horizontally. I was emphatic about that furnace being a category I unit. Now I wonder.

What make & model is the furnace in that picture?

- Jim Katen, Oregon

[Darren]

It's a Peerless Boiler. Excuse the out of focused spec plate photo.

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The PVC is the gas water heater exhaust.

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[Bill Kibbel]

My question would be is the fan changed; after all a cat III is 'under pressure' while a cat I is 'atmospheric'.

There's no change of fan.

If venting into a chimney, the flue connector dimension is increased to significantly reduce internal pressure. An increaser would be installed on the 3" fan adapter and a 5" vent connector would be installed.