Fireplace Efficiency Issues
Lars Helbro
A Heater Builder from Denmark, Comments

From: "Lars Helbro"
To: "Jim Buckley"
Subject: Comments to your page.
Date: Thu, 18 Nov 1999

Hej again Jim

I found this at your "site" - your discussions with Norbert, and i couldnt help comment it:

Now, is it fair? Is it real world? I think so based on the way the appliances are actually used. From my own observation here in Washington, where it's often not very cold - just damp and chilly - it's the stoves that pollute the whole valley, smoldering away all day at low burn. If they had a heater or a fireplace they would only fire it briefly once or twice a day. I don't think most people would allow a fireplace to smolder like that and Paul says it's flat out impossible to reduce the burn rate that much unless you have an airtight door and cut the air supply way down.

I totally agree with you in this matter! In the spring and autum we have exactly the same problem here ind DK. Back in 1987 the Danish institut of tecnologi made several tests on stoves in "the field" (in real peoples home,- and with the owners to do the firejob as they where used to). The results where best for the old untight stoves, and not worth mentioning for the rest. I think, that the people in DTI was very tired of testing tight stoves under unrealistic conditions (conditions where you dont care if the output is totally in mismatch with the normally need for heat in the house).

More anecdotal observation - the chimney fires of the 1970's and 80's were clearly caused by European-style air tight stoves operated incorrectly.  I remember us all bragging about how long our Jotul or Morso would keep a fire and I remember all the chimney fires. This is not an anecdote in DK - it is more like a national sport! God dam it! Fireplaces and leaky old pot belly stoves never used to lead to that many creosote fires. exactly as proved by the folks from DTI. Creosote means poor combustion and means particulate and other emissions were probably high. I don't think it's difficult to understand that open fireplaces burn inherently cleaner than stoves. Me neather.

Back in the 80's, I used my influens on the goverment to make them look upon the pollution from stoves and boilers. The manufactors then became busy, and made there own (voluntary) testing procedure - the DS-standard, and then the goverment vent to slep again - of course. This standard claims low pollution and high efficiency, but still dosnt worry about the output of heat,- and furthermore, some of the new stoves that fullfill the DS-standard need more draft in the chimny than nature normally can prowide, so not mutch have changest here. By the way - the danish authoritys still, after 10 years,- dosnt really approve masonry heaters as a reality. The tigth damper between the heater and the chimney is still illegal, but due to my testings absolutely nessesary,- so i have to quote an old danish poet who said: "In Denmark everything is forbidden, unless you really want to do it", so I'll keep on building my illegal heaters.

As for my tipi fires - I don't think it makes any difference except in the first few minutes after starting or adding new logs. It does help to keep the steam and volatile gases that pour out of the ends of the logs at first in the fire. My Rumfords will pass any test Walter's will, tipi fire or not, partly because Walter doesn't understand or maybe doesn't trust the venturi and doesn't make his throat opening small enough. Rumfords will perform better than regular fireplaces because they are taller and we delay turbulent mixing and cooling of the products of combustion with dilution air because of the laminar flow under the airfoil throat. I figure we keep the gases hot about four times longer than in a low fireplace with a slanty back and turbulence right behind the lintel right over the fire.

As for the pollution from an open fire, I think that it is important for the user to get heat from your fire, and as little smoke as possibel to the laundry (and your valley), but if pollution from bad burning (clean) wood was an global disarster, i dont think that God would have invented thunder and ligtning and thereby once in a while, a burning forrest. I think, that the most inportant thing we can do, is to make fireplaces, heaters, what ever,- that is difficult to misuse. It must be better to gain an efficienci of 70% that esily can be achived by ordinary users, than a stove that might reach 80% if you are very clever and carefull.

I learn mutch reading yours and Norberts "sites", so i hope that i can provide you with a little of what we have found out her in DK since the golden age af Morso and Jotul.


P.s. As you said to Norbert: "if this goes to far - let me know"

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