Review of Multi-Fuel Stoves some Pointers 2

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Input

From Readers

It has been pointed out to me that my last post perhaps compared two samples of Cast Iron which had quite different life experiences. One from the outside of a stove, and the other sample evident had seen some action.

So I have taken a close up of a casting from the inside of my three year old stove - see the top photo with the position marked. This piece of iron is at the front of the stove and directly above the fire, so it has seen plenty of action and received a lot of heat. I obviously had to clean the soot and debris from the position to make the texture of the iron properly visible.

As you can clearly see from the above close up of the inside casting of the stove, the quality and texture of the cast is, apart from discolouration, of the same nature and texture as that of the outside.

My Blacksmith Anvil has very good quality cast iron, take a good close look at the texture and remember it when looking at stoves. The quality is testified to by the obvious smooth texture of the casting, but much more importantly, by the fact that there has been no signs of wear or burn on the fire exposed parts, or any other part of the stove for that matter, in three years to date.



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Blacksmith Artisan and Inset Stove Design Part 1

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How an Inset Stove

Should Work - part 1

Some concern about the functioning of a friends Blacksmith Artisan inset stove has sparked this series of posts concerning the design, efficiency, and function of inset stoves generally.

Above is a diagram of a typical inset stove. An inset stove is essentially two boxes - one inside the other. 

TWO BOXES

(1) THE INNER OR FIRE BOX

The inner box is the "Fire Box" in which the fire burns. It usually has two air supplies, a primary air supply which allows air to come in underneath the fire, and a secondary air supply which allows air in above the fire. In some designs the secondary air is arranged so as it acts as an air wash to keep the door glass cleaner by wafting the combustion fumes away from the glass.

(2) THE OUTER BOX

The outer casing forms the "Convection Heating System". It is absolutely vital that the air in the "Convection System"  DOES NOT MIX IN ANY WAY with the air used for combustion. If it does mix, at the least it will cause the stove to be very inefficient, and at the worst, it may allow noxious fumes into the room. 

Possible causes which might allow the two air flows to mix are:

(1) a crack in the casing, or 

(2) poorly sealed joints, or 

(3) bad design.

WARNING 

COMBUSTION AIR AND CONVECTION AIR 

SHOULD NOT MIX

The Vital and Distinguishing Part of an Inset Stove

The distinguishing and vital part of an inset stove - and clearly different from a free-standing stove, is the outer "Box" or "convection airway" which causes air to circulate in and around the back, sides, and top of the inner box or "Fire Box" - thus carrying the heat from these surfaces out into the room.. 

Without a properly functioning convection system, an inset stove would be no better than a simple door on a fireplace, as the heat from the back, sides and top of the stove would simply be lost up the chimney..

TWO SEPERATE AIR SYSTEMS

How should the air flow systems work in an "Inset Stove"?  

First point to remember is that there are -  2 -  TWO DISTINCT AIR FLOW SYSTEMS to consider. The FIRST rule is that these two air flows should not mix.

I will write further on this very soon. Look out for the next post on this subject.

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Blacksmith Stove Review Part 4 - Alert -

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Possible Problems with the

Blacksmith Artisan

I have been doing some close up checking of an installed Blacksmith “Artisan” inset stove. I recon that there are fundamental problems with the level of heat output, and with the hot air convection from the back and sides of the stove

There would appear to be no convection of heat from anything other than the exposed front of the stove. How do I come to that conclusion?

In a normal freestanding stove, heat is dispersed from the back, the sides, and the top of the stove. In the Artisan inset, there are no sides, back or top. The only exposed surface is the front.

If the heat from the sides, back and top of the stove is to be used in the house and not dispersed up the chimney, it would have to be gathered, by air convection, from the hot surfaces of the fire box.

One of the Convection Air intake vents seen on the right  side

Looking at the stove, it would appear to have the necessary features for this convection air flow to happen. It has two air intake slots at floor level either side of the frame which roughly 8 x 4 cm.

Hot Air exit grill on top?? - The Air-Wash damper knob on the right?

It has a large grill, in the frame above the door, which runs the full width of the stove. I would assume that this grill is an exit grill for the hot convection air to get into the room.

Here is the dilemma: 

Air is drawn into both of the intake slots - I checked this with a sheet of paper held near the slots, and sure enough, there is a good flow of air which sucks the paper onto the opening.

In the course of things, you would expect this air flow to be heated around the sides and back of the stove and then to exit as hot air through the slotted vent at the top, wouldn’t you?

But here lies the core of the problem. Instead of an outflow of hot air from the upper grills, air is being sucked in causing a cooling effect. I checked this simply by placing a length of tissue across the top of the grill - it is clearly being sucked in - instead of being gently blown out by the hot air convection.

The airwash damper does not affect the air flow - nor should it - it should have a seperate air way.  So where is all of this air from the room going? What is this telling us?

What appears to be happening is that air is being sucked in both at the top grill, where hot air should be coming out,  and at the bottom air intake slots. This air is effectively cooling the front of the stove and reducing the heat from the one radiant surface.

Poor Heat Output from this stove

The manufacturer rates the stove output at 5 Kw. I have no means of measuring this in any scientific way - but let me say this much, it is well under 3 Kw of heat when compared to a 3 Kw electric heater.

Now, I am hoping that this case might be just a one off problem, and hopefully it does not represent a problem of poor design.

Contacted Blacksmith Stoves

I contacted Blacksmith and had a callback from one of their senior reps. however, he could not directly answer the technical questions, did not seem to understand the principle of the convection process, or of the need for the combustion air and convection air to be completely separate. I was left no wiser by the call.

I have asked for some technical diagrams of the Artisan stove which might clearly show the layout of the airways. I am hoping to have these early next week, and that they will clarify things a bit.

If the convection airways are incorrectly designed and unable to gather heat properly from the back and sides of the firebox, the efficiency of this stove could be no greater than 30% to 40% rather than the 70% claimed. The heat output to the room based on what I experienced is no-where remotely close to the 5 Kw quoted.

I will also request a copy of the independent labs test results, especially the details of the criteria used to determining mean output and fuel to room transfer efficiency.

Best Wait and See

We, that is myself and the owners of the Artisan stoves, will await some technical clarification and assistance, and detailed diagrams and instructions, and I will inform this blog of the outcome.

In the meantime - Caveat Emptor (buyer beware) applies. Personally, if I were considering a purchase or installation of the Blacksmith “Artisan” stove, I would postpone until the design, heat output, and efficiency can be fully assessed.

I will post information as it becomes available.


ADDENDUM:
Added 11th January 2012

I have since received a copy of the standards certification cert of the Artisan stove along with a set of technical drawings showing an exploded view of the stove from the people at Blacksmith. It all looks 100% kosher. As far as I can tell from the drawings, all the bits are there and in the right places.

I acknowledge that I have only closely observed one installation and that any inefficiencies may well be associated only with this one stove and installation.


The bottom line however, as far as this one installation goes, is that the output of this stove is substantially less than a similar size of stove, the Blacksmith  "Anvil", which I have no hesitation in recommending.  I would however put the output of heat from the inset "Artisan" as somewhat disappointing.

I would also point out that I have not so far been able to compare the Artisan inset against similar stoves by different manufacturers.

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Multi-Fuel Stove Tips & Tricks part 1 of 4

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Multi-Fuel Stove 

Tips & Tricks 

for economy and efficiency

part 1 of 4

1.    The Stove Itself.

If you don’t have a well-designed stove in good condition - you simply won’t get good heat output or fuel efficiency.

Apart from superficially looking nice and pretty, a stove must have certain well-designed and properly functioning technical features in order to work efficiently and have a reasonable working life.

Fire Grates.

The fire grate/s should be cast in high chromium iron in order to sustain high temperatures without burning out and warping. Check this carefully before you buy any stove, or you could find yourself replacing the grates after a couple of years, this is especially true if you use smokeless coals which can burn at very high temperatures. The grates are quite an expensive part of a stove. They are complex in shape and come in several parts. This is because they are usually remotely activated by an external lever to move them in order to shake down excess ash from the fire.

The Importance of Air.

Any stove should essentially be an airtight box, so having good door seals and well-jointed sections etc. is of the essence. A stove should have precise controls on both the primary and secondary air inlets. It is the mixture of fuel and air that causes combustion. Control the air and you control the level of combustion.

The Primary Air Inlet.

The primary air inlet or control is the one underneath the firebox that allows air to come up under and permeate through the burning fuel. This is the most important control to regulate the rate of burn. It should be capable of controlling the air supply to the fire in a quick and accurate way.

With some fuels, especially smokeless coals, it can be almost closed down completely. This will give slow burn and will keep the stove going for up to 9 hours or so over night or while you are at work. Slow constant heat 24 - 7 will keep a house very comfortable and stop fluctuations in temperature. When a house cools down, it can take up to half a day or more to get it fully warm again.

It takes a bit of practice to get the right settings. Basically, open the primary air right up when lighting a fire, as the fire gets going, begin to turn down the air. When the fire is good and hot further reduce the air until the fire starts to dim down. At that point gradually - over a few minutes - open the valve a fraction at a time, until you reach a point of burn that you require.

Secondary Air Inlet.

The secondary air inlet allows an air supply in above the burning fuel in order to allow burn-off of the gasses released from the fuel. I personally do not ever open this inlet, as I use mainly smokeless coal which tends to glow rather than create a flame. Opening the secondary air supply, where gasses don’t need to be flame burned, can reduce the efficiency of the burn. When wood is burned, the secondary air supply needs to be opened a crack in order to get full and proper combustion of the gasses released.

Subsequent posts on this subject will be spaced out over a few weeks - so keep a look out for them.

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Solid Fuel Stove Review

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My New Stove
Blacksmith "Anvil" Review
part 1
ADDENDUM December 2015
(5years on and the stove is still in perfect order - I am well pleased with it)

I have been preaching the gospel of stoves, along with fireplace doors, for some time as a means of increasing the nations energy efficiency. My perspective has widened a little because I have installed both a fireplace door and a new stove. Today I am making a first assessment of the new stoves performance.

My name sake, SEAI (Sustainable Energy Authority of Ireland), in their great wisdom, have seen fit not to back simple methods of energy efficiency like stoves with any sort of grant aid. You know - that may be a good thing - coz they would probably just have attracted the cowboys to the scene and hyped the price of stoves.

Anyway what I am writing about is my own new stove. I replaced an old solid-fuel range in my kitchen about two months ago with a lovely little stove.


A Review of my New Stove

My stove is from Irish supplier Blacksmith Stoves (look it up) and is the "Anvil" non boiler model. It is rated at 6 Kw output or 21,000 BTU, and as having an efficiency of up to 80%.

It is cast in solid cast iron and thoughtfully designed by people who would seem to know stoves and combustion. I have seen several pretty looking stoves with badly designed technical features. To date I am well pleased with the design of this stove.

The single door closes and seals very well, with a well designed simple lock and insulated handle. The grates are good and heavy, and the ash box is very easy to lift out for emptying with the supplied handle.

I can vouch for the stoves heat output -  it is easily capable of putting out the rated 6Kw when fired up with smokeless coal. The problem, for us, is keeping the output down and steady, as the room can become like a sauna all too quickly. With some practice it is possible to get an even 2 or 3 Kw output.

Fuel

The stove happily burns just about anything you put into it. We have burned peat, different woods and smokeless coal, all giving good results. The smokeless coal puts out much more heat than the other fuels, if you want to push the stoves output than this is the fuel to go for.

It has a very precise air control, once you learn how to adjust it properly - takes a little practice. The ashes are easily removed and cleaning is a breeze.

I have found smokeless formed type coals are by far the best fuel to use. With this type of coal, it is possible for the stove to burn over night for up to 10 hours, and to give a reasonable heat output all through the night. All this on a couple of shovels of smokeless fuel. In the morning, open up the air vent and add some fuel and away she goes. In fact, the stove has not gone out in two whole months!!!

Cost

We paid €400 euro for this great little stove and consider it very good value for the money. I would recommend it, in the right settings, as efficient, multi-fuel tolerant, good value, easy to adjust and to clean, and easy to get 8 hours continuous burn overnight. I have seen other similar stoves in use but I much prefer this one.

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