Monday, January 30, 2012

Hamco Blacksmith Mulberry Performance of Inset Stoves


Inset Stoves 
are they
Correctly Rated?

Just received this comment letter from Marie:

Marie 1:05 PM (1 hour ago)
Marie has left a new comment on your post "New Inset Multi Fuel Stove from Hamco":

Hi, We installed this Hamco Inset stove and were so disappointed with the output we have now taken it out and put back in our previous Stanley "Oisin" free standing stove. The Stanley gives double the output but doesn't look half as good unfortunately. Our room is 14x18ft and our chimney does have a strong draw due to our windy location -don't know whether that means we can't have success with any insert stove or what. Would love to know if Inserts should still work well when you have strong chimney draw? 

Poor Heat from Inset Stoves

In a fairly recent post pertaining to poor efficiency questions in the Blacksmith Artisan,

I was coming to the conclusion that the UK rating agency which I think is called "Gastec" is somehow incorrectly over-rating the output to room of at least some of the inset stoves it is testing.

In all fairness to Blacksmith, with whom I have taken up the issue of low efficiency of their "Artisan", I now am beginning to think that most if not ALL inset stoves out there carry a rating some 25 to 33% higher than they actually should.

This is not through the fault of the manufacturer or vendor, I also suspect that it is not through any active fault of the rating agency either. I am starting to think that the problem may arise from the way in which the heat output is assessed.

If the rating for an inset stove, with its dual heat output sections, was fully and properly assessed, I believe that there should be two heat output figures issued. (1) The radiant and convected heat from the exposed surfaces of the stove, and (2) the convection heat output from the convection chamber.

On the other hand, if the heat output is rated by subtracting the flue losses from the total, which would be valid for a simple free standing stove,  but would not give a true rating at all in the case of an inset stove.

Chimneys and Inset Stoves

If the chimney worked OK with the freestanding Stanley, then, it should be OK with the inset stove. Usually the problems arise from insufficient draught. Excess draught will cause the fire to burn too brightly. Insufficient draught, and you will get smoking and sluggish burn.

To round up, I would suggest to anyone considering an inset stove, to take the current rating system and subtract say 25% to 30% when considering the heat they require.

So an inset with a rating of 6Kw you would best consider it to have an actual output of closer to 4Kw.


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