ETA Woodchip
ETA HACK 35 - 130 
Technical Details 


Automatic adjustment to fuel type
What fuel will you be using to operate your boiler? Today it may be spruce wood chips direct from the forest, but tomorrow your local furniture factory may supply you with very dry hardwood waste as fuel. This is no problem for an ETA boiler!

With the help of the lambda probe, the regulator in the ETA HACK measures the flue gas oxygen and adjusts the input of fuel as well as the air intake
for combustion depending on the energy density of the wood currently being burnt.

Industry standard
Rough industrial standard wood chips from a sawmill can also be handled without any difficulty. The feeder screw has a diameter that allows for pieces up to 5 cm square (G50) to be conveyed smoothly into the boiler. The auger through is designed so that there is space on top of the screw to carry extra long pieces with a length of up to 12 cm and a cross-section up to 5 cm in diameter.

The pitch of the conveyor screw increases progressively along the length of the enclosed through, loosening and separating the chips as they progress. This ensures that the flow of fuel is both smooth and quiet.


An air tight, single chamber, rotary valve installed in ETA’s wood chip boilers, sets new standards of safety. In contrast to conventional fire protection flaps, this single-chamber wheel design means that it can never be in a position which allows a direct connection between the fuel store and the combustion area. No furnace gas can enter the fuel feeder and prematurely ignite the wood chips. This is the most reliable possible protection against burn-back.

The single-chamber rotary valve has been newly developed by ETA to handle wood chips up to G50 in size. Excessively long pieces of wood are cut as they enter the chamber with a toughened, and replaceable, blade. Only a small minimal amount of power is needed to drive both the stoker screw and the one-chamber rotary valve, so you have maximum safety with low electricity costs


The types of worm gearboxes which are often found in conveyor screws achieve a level of efficiency of around 65%. The component gears used in ETA’s wood chip feeder systems are top quality helical gears which work with 95% efficiency. These gears, combined with the progressive screw, can lead to a reduction in electricity consumption of more than 30%.

The new 220 volt single phase wood chip boiler released by ETA in late Autumn 2007 allows for greater flexibility in installation location and means that rotary converters will no longer be required on sites where 3 phase power is not available


The amount of electricity required by the motor is constantly monitored and so any blockages or resistance that builds up in the feeder screw is immediately registered. This triggers the screw to briefly run in reverse. This backwards movement is repeated up to three times which releases any pieces of wood or small stones jammed in the screw. The fuel feed can then proceed unhindered. When the feeder screw is running in reverse, the agitator on the bunker floor is automatically taken out of gear. With the agitator in neutral, all the power from the motor is directed towards dealing with the obstruction in the feeder screw.


A boiler always works most efficiently when it is clean – and stays clean – throughout the heating season. And so, any automatic wood- burning heating system must provide for automatic ash removal throughout the system: from the grate to the heat- exchanger.

Turbulators keep the heat exchangers tubes clear through a daily cleaning process and the fire grate is regularly tilted to empty ash and debris build up. Two conveyor screws, driven by a single motor, carry the ash from the collection bin under the grate and also the fly ash from the heat exchangers, to the main ash bin. This can then simply be removed from the front of the boiler.

There are no narrow sections in the ash channels so it is not possible for stones or nails to block them


Within a refractory-lined furnace, the wood flame is mixed with the turbulent secondary air. This guarantees that the fire burns cleanly with a high combustion temperature even when fed wood chips containing up to 40% moisture content

Without having to pass through any corners or narrow points the chips are pushed on to the grate sideways. At pre-determined intervals, depending on the heat output level at which the boiler is set, and when combustion is complete, the grate is tilted to 90° in order to remove ash and any foreign bodies from the burning areas. The tilting grate allows users to burn fuel that contains stones, debris and even nails without any related problems

The fire can be regulated between minimum and maximum settings. To satisfy moderate heating needs during autumn and spring, interrupting the burning process controls the heat output. Because incomplete combustion would lead to a build-up of soot in the boiler and flue, the fuel is therefore allowed to burn fully down before the interval. After burning off, the primary and secondary air-flaps are closed, and there is no air flow through the boiler and so no waste heat passes up the chimney.


The tried-and-tested induced draught technique (i.e. without a combustion air fan) commonly used when burning wood logs and pellets are also applied by ETA to burning wood chips. A quiet expulsion fan at the exit point of the boiler keeps the pressure in the boiler low, thus ensuring high operational safety and no risk of flash-back. The air-tight one-chamber rotary valve means that a usual combustion air fan is not necessary. The air required is drawn in through the regulated primary and secondary air flaps as a result of the vacuum within the boiler.
Of course, a system with an induced draught fan and no ignition fan operates with less electricity - the ETA HACK needs only 76 watts. And this already low consumption is improved even further because of the speed regulator.

After stopping the furnace for just a short while, the refractory-lined chamber still remain hot enough for any new fuel which is fed in to be spontaneously ignited by remaining embers. It is only necessary to start the ignition fans if the fire has been out for a longer period of time.

However, feedback from the lambda sensor and the exhaust temperature ensure that the fans are switched off, in order to save electricity, as soon as the fire has caught hold

The wood chip heating systems from ETA can be adapted to all types of chimneys. The induced draught fan fits into small diameter

chimneys. The speed regulator controlling the draught and the continuously regulated flaps controlling the input of the combustion air mean that no draught limiters are needed in the chimney. By setting the exhaust temperature, condensation is avoided in the brick-lined chimney and, modern stack design, this exploits the benefits of the low temperature serviceability

The regulation of an ETA heating system is convenient and cost efficient throughout – from the function of the furnace, to the warmth supplied by the radiators or under-floor heating in your home. Solar panels can also be integrated, allowing the system to be regulated as a whole.
There’s no need to worry about with complex electronics. Once the settings for the boiler have put in, information about its current status is given in the four-line text display panel. If you want to change the heating time settings, an easy-to-follow information text takes you through the procedure.

The various individual heating circuits can easily be adjusted. The desired room temperature can be set using a remote control, and the systems can also be switched from day-time to night-time

The reliability of operation of ETA systems is ensured by comprehensive measurement and feedback of information about the status of all components and functions of the system (speed of induced draft fan, position of air flaps, oxygen level in the chimney flue, flue temperatures and water temperatures).
If a large stone or similar object blocks the fuel supply screw, instructions on how to quickly deal with the problem are given on the display panel.

If there is a lack of air, complete combustion cannot take place. Whereas, if there is too much air, the warmth produced by the boiler is not fully utilized, too much of the warmth being produced simply passes up the chimney as wasted exhaust gas and the efficiency is reduced.

The lambda control regulates the primary and secondary air depending on the type of fuel currently being burnt in order to achieve a high degree of efficiency.

If a number of properties are connected to one central heating system or if the boiler is located in a separate building – the ETA HACK is equipped with a “bus” regulator to manage this.


The heating circuits and hot water tanks in the external buildings are connected via a CAN-bus to the boiler control. In this way, the readings from all parts of the installation are constantly available so that the total heating needs and consequently the regulation of the furnace can be controlled

A Perfect Fit with the ETA “Building Block” system
The well thought out building block system keeps construction time down and makes it possible to assemble a very flexible feed system from a number of standard components.

Boiler will be supplied with a stoking mechanism on either the right or left hand side of the boiler main body.  On the side opposite the feed system there are no parts requiring maintenance which means that the boiler can be placed up against a wall to save space.

The conveyor screw links distances of up to 8 meters.  The connection between the conveyor screws is a 1 3/8” splined shaft, commonly used on drive shafts in agricultural machinery. Conveyor casings are connected by bolted flanges. This makes installation simpler by avoiding the need to cut and weld. By replacing or adding sections of conveyor screw (standard lengths in multiples of 12.5cm) it is easy to adjust the overall length of the feeding screw.

Fuel Feed

A floor agitator is the most effective way to move fuel from the fuel bunker to the boiler through the conveyor screw. Again ETA’s building block approach to installation of your heating system means that various sizes of sprung blade agitators are available – agitator diameters range from 1.5 to 6.0 meters.


A charge screw conveyor with a diameter of 250mm and a transport capacity of 30 m3/h, makes it possible to feed fuel into otherwise inaccessible cellar areas.

The ETA range of fuel storage equipment also covers special needs and includes an hydraulic scraper floor for large fuel bunkers, a rotating pivot auger screw for high silos as well as link and inclined screw conveyors to overcome differences in height


By using a globe joint at the connection point between the feeding screw and the single chamber rotary valve. The gradient and angle can be varied up and down and from left to right giving greater flexibility for boiler positioning