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1. Circulation system - open or closed?
In case You have an open circulation system, You have to mount an open expansion vessel
at the highest point of the installation. The vessel should be chosen according to the
total amount of water
that the central heating system contains (approximately 5% of the total
amount). An example of the vessel mounting scheme is shown above.
If You have a closed
circulation system, You can use our boilers as well. In this system a closed
pressurised expansion vessel is used (approximately 12% of the total
amount). The installation always needs to be secured by using
one or two safety
valves. We recommend a 1,5bar safety valve bar for boilers up to 65 kW, and a 2 bar for boilers above 65kW.
To protect the boiler and the closed installation from boiling there is a need to
install a cooling device. There are two solutions:
a) Cooling circuit with an One-way valve (cools down the whole installation when the temperature rises above 97 centigrades Celsius).
In some boilers, such a cooling circuit is built-in into the
boiler,
e.g. Atmos, Orlan Super.
In some boilers it is available for an extra fee:
Dakon
Dor , Ogniwo 12,6-20kW.
In other
steel boilers and in all cast-iron boilers you need to mount a cooling circuit as an
additional
element. Do not forget to order the cooling loop together with the One-way thermal release valve e.g. Danfoss BVTS, Watts STS-20.
b) Two-way thermal release valve e.g. Regulus DBV-1, Syr 5067 or Caleffi 544 (pours cold water into the water
return and
releases hot water from the hot water supply at the same time). This solution is used mainly for bigger boilers, e.g.
with a power
above 50kW, because in these cases an external cooling loop might not be enough
for cooling down the boiler. It is important that the sensor of this valve is in
contact with the moving hot water from the hot water supply so that it really
switches on at 95-97 degrees Celsius.
2. Equipment
To guarantee the correct fuel burning boilers are equipped with an automatic
aeration device:
Draught regulator – mechanically lifts up the lower air inlet door
depending on wanted temperature,
Ventilator – blows air into the combustion chamber, it is used with a
steering.
These additional devices are sometimes already included in the Price, sometimes
they must be bought separately. If You click on a boiler, than scroll down to
the bottom of the product description, there You find the available options.
3. Boiler with an automatic fuel supplier
If you like comfort and can afford it, a boiler with an automatic fuel supply is
a good solution. Such a boiler has very often a retort burner which is
feeded with the essential amount of fuel needed to achieve the required water
temperature. The aeration is processed automatically, so the exhaust gases are
clean. All you have to do is filling the hopper (in average every 3–10 days). The hopper
can be mounted on the right or on the left side of the boiler depending on the
needs. These boilers are used also in summer for domestic hot water heating. For
burning coal 5–25 mm screw feeders are used, whilst for fine coal are used
piston ones.
4. Mixing valves
You can use a three-way mixing valve. It is mounted at the return. Its function
is to protect the boiler from corrosion and tar formation by heating up water
returning to it. The three-way mixing valve can be regulated manually or it can
be a thermostatic one. A thermostatic three-way mixing valve works automatically.
Ports 1 and 3 are always open, which allows circulation in boiler network as
well as a higher return temperature to the network. Port 2 opens with increase
of water temperature. See photo below:
Another option is a four-way mixing valve. It protects the boiler as well as the
former one. Additionally, it can keep a lower temperature in radiators at the
same time. Such a four-way valve leads some of the hot water exiting the boiler
to the boiler again. This heating up of the return water protects the boiler
from low temperature corrosion and prolongs the boiler exploitation. The same
quantity of water returning from radiators the mixing valve leads again to them.
This enables the boiler to work with the suggested temperature at least 60oC and
keeping of a lower temperature in the radiators at the same time.
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