Date: Mon, 26 Oct 2009
From: "masonryheat" <mheat(at)>
To: mheat(at)
Subject: Fwd:  Re: [MasonryHeaters] Re: dampers


--- In, "Eric Nilsen" <thermas@...> wrote:

I use lock top dampers not the pivoting variety.  I also use only 8" round flue.  Since 8"x 8" dampers are smaller tha 8"x 8" I use 13" x 13" dampers.  I set a short piece (4') of 12" x 12" flue in the chimney cap with the 8" round flue inside, mount the damper to the 12 x 12 flue and seal the space between 8" round flue and 12x 12 flue. This is less costly than buying round flue adaptors.  

I have only had one complaint about freezing in 15+  years and that was on a chimney in a house that was not regularly occupied so that the stove was not in daily use.  My assumption is that regular use of the stove produces enough heat in the flue to prevent freezing between fires.  Top dampers also allow the entire length of chimney inside the house to accumulate and hold some heat, not just up to the level of the in flue damper

 Of the hundred +  top dampers I have installed, 3 or 4 have had cables that broke usually after years of use.  I install a steel cable sleeve  45 degess upward from the face of the masonry into the flue so the cable slides against a relatively smooth non abrasive surface without having to slide against an acute angle. The cable sleeve is a small diameter steel tube slightly less than 1/2" OD , slightly less than 1/4" ID with a steel washer welded on the end at 45 degrees to the shaft that will trim the hole in and rest flat against the masonry . I generally drill the hole for the cable sleeve after the chimney is completed, thread the cable into the flue and get the cable end that will attach to the damper down to the cleanout, drop a line down from the top and pull the cable up.  With the handle end of the cable now hanging out of the hole in the chimney I thread the handle end of the cable through the cable sleeve, put silicon caulk on the sides of the sleeve (not into the hole on the chimney) then slide the cable sleeve into the hole in the chimney and flue allowing the excess silicon that accumulates around the washer to dry before triming it off.  When silicon has set I mount the handle bracket. 

The spiral handle of the cable has a short length of chain from the brass cylinder with the set screw that tightens the handle to the cable to the handle itself.  The damper can be incrementally closed by hooking links in the chain into the bracket before 100% closure

 ----- Original Message -----
  From: skyonic
  Sent: Friday, October 23, 2009
  Subject: [MasonryHeaters] Re: dampers

    i have been getting some advice over this and some negatives i have heard are :

  chimney top dampers are either open or closed, no middle ground
  they tend to freeze and won't open or close
  cable breaks easily

  any truth to these

  --- In, "Eric Nilsen" <thermas@> wrote:
  > I have used chimney top dampers almost exclusively for more than 15 years. They work well and are easier to install than in flue dampers

> ----- Original Message -----
  > From: skyonic
  > To:
  > Sent: Thursday, October 22, 2009 12:43 PM
  > Subject: [MasonryHeaters] dampers
  > i have a 3 year old heater i built myself. When i was building it time and budget were all big issues. Now three years later i need to make some improvements. One big one is my damper, my current damper is basically a sheet of stainless steel that i would pull in and out. The sheet was not in a sleeve and would rub against the mortar, over time the mortar started to erode and now i need a new solution.
  > I have taken apart the part of heater, basically one piece of bluestone that was holding it down. It really may be to late to insert a sleeve type damper, so i'm considering a top damper. The one that fixed to the top of the chimney outside and a stainless cord is dropped down the flue. Do these work well with masonry heaters?
  > thanks for your advice

--- End forwarded message ---