Answers to most of the questions we are asked can be found in our operating instructions, which you can access HERE.
If this has not answered your question, here are the answers to others we are frequently asked.
Click on the red heading to open the article.
What type of flue do you recommend?
We recommend a 150mm flue kit for your Pyroclassic Fire.
As we are a carboNZero certified organisation, we are not keen to support the unnecessary freight of bulky flue components great distances when there are comparable products available from reputable manufacturers in your locality. Please speak to your local Pyroclassic agent about the Flue Kit options available to you in your area.
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
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 do I clean the glass?
If the correct quality fuel is burnt in the right manner, the glass should stay relatively clean. The air wash which passes down the inside of the door will scrub off any deposits during the burn cycle. If the glass is becoming dirty then scrunch two pieces of damp newspaper, dip one in cold fire ashes and rub over the inside of glass, use the other to rub over the glass to clean off the dirt. Do this in the morning before rekindling the fire as the glass will be cool enough at this time. To help keep the glass clear and clean if it is becoming dirty then get into the habit of cleaning it regularly as this will maintain the glass and prevent ashes from being fused onto the glass due to intense heat in the firebox.
Why is the door glass small?
Big door glass = big waste of heat
Glass is a very poor insulator, which is not ideal when it comes to wood fires!
The original Pyroclassic fire did not even have a glass as the scientists wanted the fire to be as efficient as possible. Over time, consumers expressed their desire for a window into the fire which has resulted in the glass getting larger with each version.
The Pyroclassic IV has the largest door glass that can be fitted to the front of the fire as the glass retaining strips fit just inside the front opening of the fire chamber.
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 100mm 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.
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.
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.
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.
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.
How do I light my first fire?
1. Soak the reusable fire starters in methylated spirits. Tip: It is also handy to store the fire-lighters in a glass jar filled with methylated spirits.
2. Slide the Turboslide to the far right or far left position. This opens the air hole inside the door and allows air to flow through acting like an old fashioned pair of bellows.
3. Place DRY kindling and a few small logs lengthways in the front of the fire chamber leaving a clear space in front of the air inlet hole.
4. Place a soaked fire starter just under the kindling at the front of the fire chamber and light it. Try to avoid dripping methylated sprirts on to any surface when doing this as it can discolour some hearth materials.
5. Close the door.
6. Once the fire is burning really well and you have a nice bed of hot embers, move the Turboslide to the central position (to cover the air inlet hole), this can be done slowly in several stages if preferred.
7. When opening the door to load more wood, slide the Turboslide to the far left or right open position, and continue as in number 6.
Why is smoke coming from my Pyroclassic fire into my room?
There are a few reasons why this could be happening:
- Negative pressure in the room - this can be caused by a household electric exhaust fan or severe pressure difference in a windstorm. Open a window to equalise the pressure.
- Severe down draft due to surrounding structures, hills, trees or roof layout.
- Most commonly, this is an indication your flue is blocked. Clear the obstruction and investigate the cause. Check the moisture of your wood and make sure you are burning good, dry wood. The flue pipe can block very quickly if you are burning wet or gummy wood. Make sure you are using a reliable chimney sweep as the Pyroclassic is different from other wood fires.
Download down draft troubleshooting info HERE.
What is the ideal operating temperature range of the fire?
There is no ‘max temp’ for a Pyroclassic, the ceramic cylinder has an operating range safe up to 1450 Celsius and the maximum temp wood fuel can burn at is 1100 Celsius in optimum conditions. The door glass will emit heat at approx. 350 Celsius and the top plate typically gets to a maximum of 550-600 Celsius during high fire burn cycles. The fire is designed to withstand and tolerate these temps over and over again with no stress to the unit, there is no welded box to fatigue under expansion in a Pyroclassic and so to answer your question no there is no maximum limit.