Previously, the combustion rate of solid fuel boilers was manually controlled by opening or closing the ash pan door, from where air is supplied to the furnace due to the natural draft of the chimney. Now a special device is doing this - an automatic draft regulator for the boiler. The owner of the house only needs to set the desired temperature of the coolant. The question is how well the thermostat handles its functions and whether it is needed at all.
How the traction control works
The main detail of the air regulator is a mechanical thermocouple placed in a cylindrical body. Through the lever and chain, it controls the rise of the air damper on the ash pan door.
The device is a sealed flask filled with a thermosensitive liquid, expanding greatly when heated. The flask is located inside the case, which is screwed into the sleeve of the boiler’s water jacket and is in contact with the coolant. How the thermostat with a chain drive is arranged is shown in the diagram:
The principle of operation of the automatic draft regulator is based on controlling the flow of air going into the firebox under the influence of the chimney draft. The algorithm looks like this:
- When burning solid fuel and heating the coolant, the fluid inside the element expands and acts on the actuator and lever, overcoming the spring force.
- The lever weakens the chain, the shutter begins to close and reduce the bore. Less air enters the firebox, the combustion process slows down.
- The temperature of the water in the boiler tank decreases, the fluid is compressed and the return spring forces the lever to open the flap again through the chain.
- The cycle is repeated until the wood in the firebox burns out completely, then the spring opens the door as wide as possible.
The adjustment knob at the end of the thermostat serves to limit the stroke of the lever and, accordingly, the air damper. Thus, the limit temperature of the coolant is set.
Reference. In addition to mechanical regulators that are independent of electricity, there is automation for solid fuel boilers with a controller and a blower-fan (or smoke exhaust). The latter supplies air to the furnace at the command of an electronic unit that focuses on the signals of the temperature sensor. Similar automation kits are installed on all pyrolysis and pellet boilers.
Why regulators are needed
Unlike any wood-burning stove, a solid fuel boiler is equipped with a water jacket and cannot be heated to too high a temperature, otherwise the water in it will simply boil. In such cases, the resulting vapor sharply increases the pressure in the system, which causes an explosion. That is, a solid fuel boiler, whose power is manually controlled by the ash pan door, is a source of increased danger.
Note. At the very least, a boiler without any automation can work together with a buffer tank - a heat accumulator, whose volume is correctly calculated. Excessive heat will go there if you did not close the door on time and did not restrict the flow of air into the furnace.
An automatic chimney draft regulator, which you can install yourself on any solid fuel boiler, will supply air instead of you and much better than you. He will react in time to an increase in the temperature of the water in the boiler jacket and will close the air supply to the chamber if the firewood is very hot. Although the inertia will increase the temperature for some time, but in general the heating process will stop.In addition to ensuring safety, the mechanical draft regulator of the boiler helps to solve such issues:
- It does not exceed the temperature of the coolant set by the user. It is not always necessary to accelerate the boiler to 80 ... 90 ° C; in the spring or autumn, 50 ... 60 ° C is quite enough for heating.
- Covering the damper and air supply, the draft regulator increases the duration of the boiler burning from one tab. But we must admit that the conditions for burning fuel are getting worse, and the efficiency of the heater is sharply reduced.
You may argue that any solid fuel heat generators must be connected to the heating system using a safety valve configured for emergency pressure. If the valve overheats, it will work, release the steam and no explosion will occur. So traction controllers seem to be useless. The statement is only partly true, since without automatic equipment the heater will often gain a critical temperature, and after 2-3 operations the valve will flow corny. Yes, and manage the temperature of the water in manual mode is quite difficult.
Instrument selection recommendations
Oddly enough, but on sale you can still find budget models of wood heaters that are not equipped with any automation. Most of them have in the basic configuration only a sleeve mounted inside a water jacket. To automate such a boiler, you will have to buy and install a draft regulator yourself.
Hence the first recommendation: when choosing a heat generator, pay attention to the presence of such a sleeve and an ash pan door that rises up.
To choose the right mechanical regulator, you must adhere to the following recommendations:
- the force developed by the drive (indicated in the product passport) should be sufficient to lift the door;
- select a temperature control range from 60 to 90 ° C;
- make sure that the actuator travel is sufficient to fully open and close the leaf;
- the threaded connection on the housing must correspond to the counterpart in the boiler, usually ¾ ”.
Also pay attention to the location of the sleeve in the boiler body. It can stand on top, front or on the side panel. For the first option, you need to choose a device that can work in a vertical position, for the other two - in a horizontal position. There are traction controllers, for example, Regulus rt3, working in any position and having 2 settings scales.
How to set and adjust the regulator
In most cases, installing a thermostat with your own hands entails emptying the boiler’s water jacket. This will not create a big problem, if the solid fuel boiler is properly connected and the water heating system can be cut off by taps. Otherwise, you will have to drain the entire coolant. After that, the plug is removed from the sleeve, and instead the device is screwed in and the system is again filled with water.
To adjust the draft regulator, you need to light the boiler and follow the instructions:
- Without attaching the chain to the door, open it for air access.
- On the adjusting handle, loosen the screw - lock.
- Set the handle in the position corresponding to the required temperature, for example, 70 ° С.
- Watching the boiler thermometer, attach the chain drive to the valve at the moment when it shows 70 ° C. In this case, the shutter should be ajar only 1-2 mm.
- Tighten the fixing screw.
Attention! It must be ensured that the chain free play does not exceed 1 mm.
Next, you should check the operation of the thermostat in all modes, up to the maximum. It should be borne in mind that some time elapses between the moment the damper closes and the coolant temperature drops and do not rush to reconfigure the device. Solid fuel heat generators tend to lag, because firewood or coal in the firebox cannot go out at once.
Brief conclusions
The need for draft regulators for solid fuel boilers can be concluded: such a primitive automation is better than its complete absence. Yes, mechanical regulators cannot boast of high accuracy, but they will save you from manual control “by eye” and will save firewood with coal. Devices have an undeniable advantage over controllers and fans - non-volatility.