FAQ

1. Can heating furnaces be installed in a closed system?
Most UNIWEX models are designed for open- system operation. However, they can be used in a closed system if all the requirements of Polish regulations are met. We suggest using a plate heat exchanger or a cooling coil. They will allow you to use the system in an open system, and behind the exchanger or coil in a closed system.

2. When do explosions in the furnace occur?
Explosions in furnaces are not a common occurrence, but they can occur when a furnace has been incorrectly sized for the floor space, or the wrong furnace controller parameters have been set. An explosion can also occur if cold water is violently poured into a furnace with boiling water (for example, to lower the temperature).

However, most often this problem occurs when the ignition temperature of the flue gases is higher than the temperature of the entire furnace. Their concentration increases significantly, so if the fan is then turned back on, the gases can suddenly ignite, causing an explosion.
Lack of heat collection, irregular frequency of blowdown cycles, improper fireplace draught, and throttled thermostatic valves on heat consumers can also become the cause. High quality fuel is also of great importance, as it significantly affects the behavior of equipment and the lack of regular furnace cleaning.

3. Why take care of the furnace and clean it regularly?
Heating furnaces, like any other installation, require regular maintenance and cleaning. The use of different types of fuels - even the best quality ones - leaves the walls of the unit contaminated with soot. This significantly reduces heat recovery, as the sludge coating insulates the water jacket from the flue gas. Even a small deposit on the walls can reduce the efficiency of the furnace by several percent, raising the temperature by up to 100°C. The inferior performance of the device is associated with an increase in the amount of fuel consumed, as well as shorter service life. Backflow of flue gases into the room, caused by the weakening of the contaminated chimney draught, is also a major problem.

4. What to do when water boils in the furnace?
When the water boils, lower the temperature of the entire unit. However, under no circumstances should cold water be violently poured into it, as an explosion may occur. Instead, it is better to open the cleanout opening behind the burner, or close the air supply to the combustion chamber. You can also scoop out the rest of the fuel in the furnace and close the flap through which air is drawn in (for a furnace with a blower, this is the shutter on the fan).

5. What is the thickness of the sheet metal from which the furnace is made?
Both the outer and inner shells of the furnace are made of certified furnace sheet 8 mm thick.

6. I intend to buy a furnace with automatic fuel feeding - what type of feeder should I choose?
The most common choice is a screw feeder, which is much smaller than a piston feeder. The investment in heating furnaces with a screw feeder is much lower, but it involves feeding fuel of excellent quality. The reciprocating feeder works in cyclic mode - feeding the fuel, a few seconds of pause intended for its afterburning and again feeding the next batch. The piston feeder is designed for dirty, diverse, and wet (up to 50%) fuel.

7. What is the required moisture content of the wood to be burned?
UNIWEX furnaces, especially those in the COMFORT CLASSIC line, can use wood with a moisture content of up to 50%, but the ideal value is a maximum of 20%.

It is important to remember that the highest combustion efficiency is only possible with wood with minimal moisture content. Water vapor in the flue gas adversely affects the entire system, shortening its life.

8. What are the consequences of using fuel that is too wet?
Fuel that is too wet can permanently damage central heating furnaces. Therefore, the use of fuel with a moisture content of more than 50% means that damage to the furnace is not covered by the warranty. In addition, damp wood reduces the power of the device, thus reducing its efficiency, which is associated with higher fuel consumption.

Moisture accelerates the operation of the feeders, and thus their wear. It also lowers the temperature of the hearth and flue gases and increases the pollution of the flue. There is also much more ash and smoke.

9. What should I do when my furnace starts to smoke through the door?
This problem occurs at the very beginning of furnace operation, when the flue pipes are still soggy and cold. An increased amount of smoke begins to enter through the charge and pre-burner doors, and a dark liquid begins to appear on the furnace itself. However, do not be alarmed, this phenomenon is natural and subsides after a maximum of two days.

10. Can water be allowed into the system while the furnace is running?
Under no circumstances should water be topped up throughout the system while the device is operating. This can cause the entire system to unseal, thus causing permanent damage. Water can only be added when the furnace is at a standstill. In addition, if a leak in the system is noticed, it should be sealed. Failure to do so can cause scale formation, which will also permanently damage the device.

11. How often should the furnace be cleaned?
Central Heating furnaces should be cleaned regularly, but the frequency depends on the quality of the fuel used, the power of the device, as well as the load with which it operates. Also of great importance is the floor space in which the installation is located, as well as how it is used.

We suggest cleaning the exchangers when the deposit on the surface walls is 2 mm. This means cleaning every few to several weeks - depending on the factors mentioned above. After a few years of operation, the furnace should also be cleaned from the inside of any scale that has formed, using solutions designed for this purpose.

12. What happens to the furnace if the electricity is turned off?
Temporary power outage: the controller will resume the operation of the system when the power is turned on, without any consequences. No additional steps are required.

Prolonged power outage: the furnace firing process should be carried out again. If the flame from the furnace enters the feeder, the safety valve will eliminate any danger. It is also worth considering the possibility that there will still be embers in the hearth after a long break. It is then necessary to first turn on the exhaust fan, and then resume the operation of the system. To avoid overheating, it is also important to ensure that the furnace power is taken away.

13. What is the most suitable water for the furnace?
According to the Polish standard PN-85/C- 04601, in terms of the quality of water for replenishing circuits, water should be distinguished by the following parameters:

• pH value ≤ 8.5,
• total hardness ≤ 0.02 mva1/1 (0.056 degree GH),
• dissolved oxygen ≤ 0.03 mg/l,
• sulfites ≤ 3 mg/l.

14. What standards should the furnace room meet?
Central heating furnace room must meet the requirements described in PN-87/B-02411. It covers such issues as, among others, the location of the furnace room and the components included in it. First of all, the system should include supply ventilation in the form of a duct with a cross section of not less than 50% of the chimney cross section. At the same time, it must not be smaller than the dimensions of 21 x 21 cm. It should be located directly under the ceiling of the room with a cross section of not less than 25% of the chimney cross section (not less than 14 x 14 cm). The exhaust opening and the supply opening should be located on opposite walls.

The furnace room itself should be centrally located in relation to the rooms to be heated. Made of noncombustible material, the front door must open to the outside of the room. According to the standard, the furnace should be connected to a system that has an underflow pump or a three- or four-way valve.

15. What fuels can UNIWEX furnaces burn?
Depending on the model of the central heating furnace. UNIWEX can burn a variety of fuels. This includes shredded particleboard, MDF and HDF, sawdust, fruit stones, chunk and forest wood, wood chips, pellets, briquettes, among others. We encourage you to read the full list.

It is worth noting that garbage made of, for example, plastics should not be burned. They not only damage the device, but also harm the environment. We also describe the most common problems associated with the operation of furnaces, along with potential causes and solutions:

1. There is a noticeable smell of smoke:

• Leaky flue/smoke ducts - clean or reseal the system (you can raise the chimney, or use an artificial exhaust),
• Leaky connection on the flanges - apply new gaskets and seal the entrance to the furnace with fireproof mortar,
• Leaky fuel tank - close the tank to the clamps (you can replace the gasket),
• damaged lining - repair or make a new one,
• improper draft in the chimney - clean or seal the system,
• Under-pressurized side door - adjust and press the door (you can replace the seal).

2. Steam is emitted in the furnace:

• temperature limiter does not work - check if the sensor is properly connected, it can be replaced,
• temperature sensor does not work - check its installation, connection and response by bridging it.

3. The furnace does not reach the desired temperature:

• Excess secondary air - close the dampers that regulate its supply to the chamber,
• defective controller interfering with the combustion process - replace or adjust the controller by a service technician,
• too much draught - regulate it through the flap in the furnace flue.

4. Fire retreat into the sawdust container:

• Faulty feeder - determine and remove the fault,
• Defective sensor with fire valve - replace,
• no voltage for a long time - expel the fuel from the tank and extinguish the fire.

If you have additional questions that we have not covered in the list above, we encourage you to use our contact form.