RC vs M barometric damper

What, if any, are the advantages of the M barometric damper over the RC? It appears that the M type costs about twice as much and the Field literature talks about precise control of draft. Anyone have experience with the M type--or both types?

My oil fired furnace has the type M, My opinion is the RC works fine for coal applications.

http://www.fieldcontrols.com/draftcontrol.php#dctop

I had the RC and converted to the M. Really no difference except the weight setting on the M is alittle more sensitive. Bottom line is use which ever one is least expensive.

I spoke to Field Controls Tech about this. They recommend the M for coal as it has small holes to bleed air to reduce flyash accumulation in the neck if it is a problem. I use an R/C (also rec.) as most do and it works fine, no flyash problem. The M is probably a good choice when you have a very low draft stoker.

IMO, buy a type RC, and a manometer, the money spent should equal an M and you will be able to monitor the performance of your stove.

Of course there is no substitute for performing the required cleaning of fly ash to keep the draft where it needs to be.

Wood'nCoal wrote:My oil fired furnace has the type M, My opinion is the RC works fine for coal applications.

http://www.fieldcontrols.com/draftcontrol.php#dctop

Correction:
My oil furnace has a Field Controls model "DR" which is not painted. It's not shown on their website. Must be a economy model.
I've never seen it move once.
The RC is doing the watusi on the Alaska, I was just watching it. The wind blows, the manometer shows the draft start to rise, the RC opens, the draft goes back to -.025. The wind blows again.........
The Harman RC stays open, just keeps moving to compensate.