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What wood should I be using?
DRY. This means a maximum of 25% moisture content but ideally under 18% if possible.
Do not burn any wood which has been treated as this will release poisonous gases and dioxins. Do not use any driftwood as the salt content can cause irreparable damage to the ceramic cylinder and metal components. Younger softwoods and timber which has a higher moisture content will produce a greater volume of creosote and soot than dry, well seasoned hardwood.
Logs should be approximately 100mm - 120mm in diameter by around 300mm - 400mm long for your Pyroclassic IV Fire. Logs should be approximately 100-120 mm in diameter by around 200-250mm long for your Pyroclassic Mini Fire.
Dry wood is a must. To get the heat out of wood the fuel must pass through several stages. Firstly, free water that is not chemically bound with the wood is driven off – even wood at 20% moisture content still has to get rid of 2 litres of water for every 10 kilograms of wood. In the second stage the wood breaks down into the volatile gases, liquids and charcoal. Finally, the charcoal is also gasified, burning with a very short flame close to the char surface that appears to glow. In wood stoves all stages proceed simultaneously.
Wood is the most prolific worldwide, solar embedded, carbon sequestered energy source which is renewable in a human lifetime. It will provide energy when the sun is not shining and the wind is not blowing, when the outside temperature is above or way below freezing and when the electricity is not coming out of that little hole in the wall. If the abundant, worldwide timber resource is managed correctly it is the most sustainable, environmentally safe, renewable, resource we have and it has sustained mankind for centuries, providing us with warmth for the space we live in, warm water to clean with and the ability to cook food.
With the discovery of more energy intensive and easily transportable fossil fuels, wood was relegated to a lowly place in the order of preference and although it is bulky to transport it is the safest as it does not need a specially built pipeline, it won't suddenly explode or cause devastating marine pollution and with almost no refining can be used in its raw state. The closer it is used to the place where it has grown makes this an even more environmentally friendly product.
Most designer wood burners catering to aesthetic demands totally disregard the thermal conductivity of wood. Microscopic examination of wood shows the channels which carry the liquid nutrients up and down the tree; consequently the properties of wood are very different along the grain than across it. Heat moves along the grain about fifteen times faster than across it, therefore, solid wood across the grain does not conduct heat and is an effective insulator meaning it does not readily burn.
When a fire is lit, even by rubbing two sticks together, the gasification process starts and it is the combustion of these gases with air that produce heat which we see as flames and smoke. When heat cannot penetrate wood easily, i.e. across the grain, the volatiles given off are not rich enough nor hot enough to burn efficiently. Efficiency apparently is not a consideration in such panoramic appliances.
This is getting to the really nerdy bit now...
Burning of the volatile gases delivers over 60% of the heat stored in the original log but few heaters can recover the major portion of this heat as the volatiles must be over 600°C and mixed with hot oxygen to burn them. Now these are difficult conditions to meet and here’s why: if the main air supply comes from under or around the burning logs, the glowing char consumes all of the oxygen - it takes only 5cms of glowing char to consume all the available oxygen. At that point, incomplete combustion continues as characterised by increased carbon monoxide and tars which mostly go up the chimney where the unburnt volatiles deposit on the flue walls as a highly flammable, gummy substance known as creosote. It is wrong to introduce cold secondary air above the fuel as it cools the gases below their ignition temperature and now they won’t burn at all. The requirement is to introduce a highly pre-heated but variable volume of air for the different stages of combustion. This is done very efficiently by the secondary air tubes inside the Pyroclassic IV fire.
All fires consume large volumes of air in order to extract the oxygen required to burn their fuel. One kilogram of wood needs 3.7m3 of air to burn completely, although this is only a theoretical minimum for stoichiometric combustion. Such ideal combustion does not exist in real life as only some of the oxygen in that amount of air can be used and therefore 'cool fires' need some 200% - 300% excess air to get the oxygen they need. Therefore some 7 - 10m3 of air per kilogram of wood pass through the firebox cooling the core temperature inside it and cooling air below 600°C , which kills the reaction needed to burn the volatiles. In most fires the air needs of the fire make it work against itself making it inefficient and polluting, the excess air it uses only goes up the chimney with all that gas, tar and particulates. A Pyroclassic IV only uses super-heated air in its secondary burn cycle ensuring there is no cooling of the firebox and no excess air consumed.
Burning wood scientifically is done very effectively by the Pyroclassic IV freestanding woodburning fire but even the cleanest and most efficient woodburning stove needs logs which are as dry as possible to give the best output from your fuel. Check the moisture content of your wood when you buy it and then let nature do the hard work for you. Stack it off the ground in an open sided, roofed store to allow plenty of air flow around it for as long as possible or at least until the moisture content is below 20%. It’s then ready to be used in your Pyroclassic fire to give you a nice warm house right through winter in the most efficient and cleanest way possible.
What do I do if one of my side panels are shaking/rattling when the fire is going?
Because of the panels being interchangeable and not permanently fixed to the fire there is a small chance that occasionally a panel may rattle slightly in its channel, this is due to the small gap between the coloured panel and the channel which allows the panel to move ever so slightly.
If this occurs then it can be remedied by removing the panel and putting a slight curve across the panel (you are only wanting to add a total of around 1mm - 2mm of curve) by flexing it from top to bottom. The easiest way to do this is to lie the panel half on a flat surface and apply weight to the bottom section on the surface and also to the top section hanging off the side. This will create a slight curve in the panel. Please note: You shouldn't bend it far enough to crease the panel or have any visible curve to it. This very small relief in the panel will mean that it sits tighter against both sides of the inside of the channel section and eliminates the rattle.
What is a load limiter?
Along the top of the fire chamber is a load limiter, which is designed to restrict the operator from overloading it. This will burn off in approximately 3-7 years depending on frequency of use. The load limiter does not need replacing but the airtubes will.
Can I use a heat transfer kit?
The simple answer is yes.
The thing with heat transfer kits is they work well with excess heat. The Pyroclassic IV produces a different kind of heat than your traditional 'black box' style wood fire. The black box fires spit out heat almost instantly as long as you keep refueling it regularly so will therefore provide you with excess heat which is why heat transfer kits are useful for these kind of fires. The Pyro on the other hand takes longer to heat up but once up to temperature retains this heat like a kiln and gives off a lovely, warm more consistent heat with less fuel needed once the cylindrical ceramic fire chamber is hot.
Many Pyro customers find this as the biggest advantage of a Pyro and have it going for 2-3 months solid during winter. However, it won't necessarily provide lots of excess heat for use in a transfer system. Our recommendation is to install the Pyro first before the transfer system as you may likely find you don't require one.
It is worth noting that in newer homes which have much better seals around doors and windows these kits can cause a negative pressure to build up in the room the fire is in as all the air is being sucked out. This results in the fire being starved of air and in some cases has even caused smoke from the starving fire being drawn back into the room. This same effect can also be caused by powerful range hoods and other fan forced systems in newer, more airtight housing.
If you are building a very airtight home, we recommend you put in an air vent, approximately the size of a fire brick. The Pyroclassic IV needs 3.6 cubic metres of air per kilogram of wood to operate effectively.
How does the Pyroclassic IV burn overnight?
The overnight burn ability of the Pyroclassic IV is 100% dependent on the quality and size of fuel you put in it.
You will need to have a good ember bed established, then add 2 or 3 dry hardwood logs (preferably Kanuka) measuring approximately 400mm long by 120mm thick into the fire box. Allow the flames to establish on the front ends of the logs and then ensure the turboslide is fully closed meaning the air flow into the fire is controlled by the fire itself. The further back in the fire chamber you have the fire the longer it will burn for.
Remember, you need to add a kilo of fuel for every hour burn time required. If you follow these instructions you should have some hot embers left in the back of the fire chamber in the morning ready to be brought forward to establish another fire.
As a point of caution you should never insert a fresh log which is too large or placed in the fire too late to ensure a flaming combustion, doing this will cook the wood fuel on the remaining embers releasing unburnt volatile gases into the combustion chamber which will eventually reach a point of ignition, this can result in a sizable explosion inside the fire chamber and may cause damage to the unit.
What are the ceramic chips/divots in my cylinder? Is it normal?
These are exposed air blisters and are completely normal. The blisters are a result of small air pockets getting trapped just at the edge of the surface in our castings. Depending on how much air is trapped inside these, they sometimes erupt and take a piece of the ceramic off. These will not affect the performance of the fire at all.
There is over 35mm of thickness to the cylinder, and this is then wrapped in a thick insulating blanket and a complete steel band to ensure that nothing can escape from the cylinder walls.
When and how should I clean the flue?
Pyroclassic Fires are renowned for burning very cleanly when dry fuel is used but you should still always clean your flue once a year. This is often a requirement for many insurance companies.
Keeping your flue pipes clean will help eliminate the risk of a flue fire. Your flue is also a great indication of how your wood fuel is performing. If the pipes are clean then the wood is good, if the pipes are filling up with carbon, creosote and tar deposits then you may need to revisit the operating instructions and refresh yourself with how to create a cleaner burning fire.
The easiest way to clean the flue is by placing a deep baking tray or similar under the base of the flue and sweep the flue down into this, this stops all the debris from falling into the top chamber and requiring vacuuming out. Sweeping the flue into the top chamber is never a good idea as it can restrict the flow of gasses from the primary fire chamber and cause your fire to perform poorly.
To clean the top chamber and wetback, you will need to remove the top plate (it just lifts off) and clean out the top chamber of soot and creosote. Take care not to remove any of the Kaowool lining during cleaning and ensure that the gasket is all intact before replacing the top plate. Support the flue with a frame made of wood so you can easily remove the top plate.
The build-up around the wetback is best removed by hand. The wetback can be knocked out of alignment if it is moved when the creosote is being cleaned off so be careful as this can cause the constant rise to be knocked out of alignment and can result in water hammer developing in the system.
What are the clearances for a Pyroclassic IV installed on a mini raised woodbin?
You can download the installation clearances for installing a Pyroclassic IV on a mini raised woodbin HERE.
How can I test if I am getting a good heat output from my Pyroclassic fire?
As you will note in the operating instructions for the Pyroclassic IV, the fire will not give its full performance for the first few uses until the unit has fully cured and heat tempered.
A couple of quick checks to measure the approximate output levels is to hold your hand 10cm off the centre of the top plate when the fire is running. If you can’t keep it there for 5 seconds then the fire is cranking along. If you can between 5 - 10 seconds then the unit is performing well in its expected typical output range. If you can hold it there for more than 10 seconds then you can probably hold it there indefinitely and so depending on the heat required you could load a fresh fuel charge in and begin the cycle again.
The side panels are also a good indicator of when a Pyroclassic is fully heat cycled. If the bottom back corner of the side panel is warmer than skin temp then the whole cylinder is hot, if it’s not warmer than your hand then it is still warming up.
Why are there cracks and deterioration in my Pyroclassic cylinder?
This is a natural way to relieve built-up stress in refractories. It has no effect on operation, performance or useful life of the unit. The firebox is an arch structure, the most stable and permanent construction known. These cracks will develop over time and is nothing to worry about.
Due to it being cast as a one piece cylinder it goes through some expansion and contraction every time it is heat cycled. This is just the cylinder relieving its inert tension and results in a variety of different levels of cracking.
These cracks and blisters can slowly grow over time due to erosion through use. If you do not like the appearance of the cylinder when cracks appear, you can purchase veneering cement which can be mixed to a toothpaste like consistency and inserted into the cracked areas.
The story goes that the two original designers each had a Pyro and one touched up his cylinder every year and the other never touched his...25 years later both fires were still working albeit one was looked in better looking condition internally than the other!
25 year-old Pyroclassic II Cylinder