Two barometric dampers or one larger one?

Dave M

My 32-foot tall interior chimney has a bit too much draft. The Fields documents recommend a 7-inch draft regulator on a 6-inch flue if the chimney is greater than 16 feet high. Trying to decide between a 7-inch damper vs adding a second 6-inch damper. What is the neatest way install a 7-inch damper in a 6-inch smoke pipe? Current setup is Peerless WBV-04 oil boiler with a single 6-inch damper. Can’t get the over fire draft down to -.02. Peerless recommends -.01 to -.02. Best it gets is -.03 to -.04. Have two draft gauges, the big MZF and the pocket version, both Bacharach.

STEVEusaPA

Just buy a 7". Install like any add on where you cut into a regular 6" flue pipe, make the bazillion notches, cut your fingers 3 times.
I wouldn't go 2 draft regulators. I tried that with mine, didn't work.
Actually I went with the 'neutral pressure point adjuster' technique that I learned from George in the best book on oil burners:
Advanced Residential Oilburners by George Lanthier

Steamhead

I've done it both ways, but agree with @STEVEusaPA that you should just use a 7" and enlarge the hole in the smoke pipe to match. Assemble the collar to the smoke pipe first then mark where the new opening will be, to avoid making it too big.

EBEBRATT-Ed

I agree install the 7" damper and do not use a tee. If the damper runs nearly wide open and has trouble controlling then you can add the "neutral pressur point adjuster"

Dave M

Alright then. I agree. A single 7-inch damper it shall be. Thanks all. And happy Holidays!

hot_rod

I received some info on this brand, being imported by this company back in NJ. A really nice quality, tight sealing unit.

Steamhead

I believe that's the same company that makes the TigerLoop.

And much of the info in the last two screenshots could be right out of one of the old Audel oil burner books by Frank Graham, or one of Firedragon's more recent ones. Excellent info.