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What chimney sweeps can you recommend to clean the flue?
It would be great if we could keep an up to date national register of all the good chimney sweeps around the country but as you can imagine this is a somewhat transient profession and so a call through the good old yellow pages and an ask around some friends is usually the best course of action to get a sweep.
It is always worth asking them if they have done any local Pyroclassic fires before and if so can they tell you where so you can ask the homeowner how it went, any doubts and we are always happy to give some tips to proactive chimney sweeps.
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 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.
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 do I remove the ash from my Pyroclassic?
Remove the ash when the fire chamber is relatively cool. Use the Pyroclassic curved shovel to slowly empty the fire chamber. Ash almost always contains some hot ember.
Never use a vacuum cleaner. Obtain a metal (non-combustible) ash container with a lid. Store outside on concrete or bare ground.
Pot ash can be great for your garden if your soils are acidic, use only ash from a cooled fire which used good quality wood.
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.
I would like to move my existing wood fire to another location within the same house?
An existing burner that is moved within a house is considered to be a newly installed burner, so it must meet the woodburner standards in the National Environmental Standards for Air Quality. You may also need a building consent.
See more information at http://www.mfe.govt.nz/air/national-environmental-standards-air-quality
What is the best type of wood to use?
A number of things should be considered when using wood for heating. An understanding of the various types of wood fuel that is available including its advantages and limitations, and it is essential to know how to light and maintain a good fire.
Wood fuel ranges from soft woods like pine, to hardwoods like manuka. But whatever wood is chosen, the key to a successful fire is to ensure the fuel is as 'Dry', or as 'Seasoned', as possible.
Green wood can hold up to its own weight in moisture and sap and it takes time to get rid of this.
While surface water does not really matter because that will evaporate quickly, it is important to reduce the sap levels within the cell structure of the wood itself. Softwoods will season quite quickly, in about 6 to 12 months, but it can take for 18 months to 2 years for hardwoods such as Manuka to dry to an acceptable level.
Most woods make suitable fuel, pine is common and good its high resin content and loose cellular structure means it burns faster than some others, so be prepared to make more trips to the wood shed. Macarocarpa and gum are also excellent fuels although marcarocarpa tends to spit and spark more than a lot of other fuels and in some appliances this may cause servicing problems because of fly ash.
It is suggested avoiding native timber for fuel, unless it becomes available through demolition or natural attrition. Manuka though, is considered a nuisance timber in some areas of New Zealand, and could be used for fuel. It is indeed good fuel - provided it is dry - but remember, drying Manuka will take a long time.
If you knock two pieces of seemingly dry wood together if it "rings" rather than "thuds" it is likely to be dry, regular use of a moisture meter will ensure you know just how dry your wood fuel is. However simply because a piece of wood is dry on the outside, it doesn't mean that it is dry enough to burn. Conversely, even if the outside is wet, if it is seasoned properly, it will often burn beautifully. The drier the wood, the cleaner the burn, the less likely is creosote formation and unburnt smoke being exhausted from the flue.
Place a piece of timber on a good fire base if three sides are burning within 15 minutes, the fuel can be considered to be "dry."
How should I store my wood?
Gathering and stacking wood in the open air over the summer period is advantageous because the warmth of the sun and good air circulation will automatically evaporate some of the sap. When the wood gets wet from seasonal rain, the rain water replaces sap and because water is more quickly evaporated, the fuel dries faster.
Split larger logs, so that the largest surface area of the internal wood is exposed to the atmosphere, stack the wood loosely, on bearers, with the ends facing a prevailing wind, cover with a plastic sheet on a light frame to create a warmhouse effect, with the sides open to the prevailing breeze so it can flow freely through your stack.
Do not use it until it is fully seasoned, do not stack rotten wood - it has very little useful heat in it and leave the bark on split wood - it helps to provide natural protection from rain.
Why did I have a Flue Fire?
Your flue fire has been caused by a build-up of unburnt gases that have cooled and solidified in your flue pipes that have then collected more unburnt solids slowly building up until you have then had a high fire situation that has ignited this very combustible fuel deposits which can then burn at temps up to 2000 degrees potentially causing structural damage to the flue pipes themselves. This build up has most likely occurred due to either poor fuel quality resulting in poor combustion and/or due to continuous low heat fires which don’t allow complete secondary combustion thus allowing these particles to exit the fire without being converted to heat.