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HEATING BOILERS: Astra G-120E
5. INSTALLATION
• ACCUMULATION TANK
These solid fuel boilers are intended to be fully loaded during the operation; the most efficient mode of their exploitation is at the
nominal or maximum heat output. It is advisable to install an accumulation tank of sufficient size in their proximity, which could
accumulate the excessive heat. If the boiler is operated without the accumulation tank, its lifetime can be shortened because, in
such a case, a relatively low temperature of the outflowing water is maintained in the boiler (65-70°C). Therefore, the temperature
of the water returning to the boiler from the heating system is as low as 55-60°C. More water vapour condenses in the boiler at such
operating temperatures, more tar accumulates on the internal walls of the boiler and metal corrosion intensifies. When operating
the boiler with an accumulation tank, it is possible and advisable to maintain constantly maximum temperature of outflowing and
returning water, respectively 85°C and 70°C, then condensation of water vapour and metal corrosion will be significantly lower.
Recommended capacity of the accumulation tank is approximately 50 litres per 1 kW of nominal power of boiler:
Boiler model
Astra G-120E
Required volume of the accumulation tank, litres
5500
• DESCRIPTION OF THE EMERGENCY COOLING SYSTEM DIAGRAM
The boiler is to be operated only with an emergency cooling system installed!
A thermostatic safety temperature limiter 95°C valve (Fig. 4) protects
the boiler form the overheating. If the water temperature in the boiler
exceeds 95°C, the valve automatically opens the flow of cold water from
the public water supply network through the cooling serpentine, where
it absorbs the excessive heat energy and flows out into the sewage.
The sensor of the valve with the external thread ½” is screwed onto the
socket on the rear wall of the boiler.
Technical data of the thermostatic safety valve are the following:
Opening temperature - 95°C; Maximum operating temperature-
110°C; Operating pressure - 10 bar; Bulb of the sensor - L=142 mm,
external thread ½“.
The emergency cooling system protecting the boiler
from overheating cannot be used for heating domestic water.
• DESCRIPTION OF THE HOUSE HEATING SYSTEM
SCHEME
The house heating system with an accumulation tank could be
divided functionally into two circles: heat production and heat
consumption. Both circles operate independently and interact in the
accumulation tank. The heat production circle consists of a boiler, Laddomat 21 thermostatic mixing unit with a circulation
pump installed in it, expansion vessel, fittings and accumulation tank. The intended use of this circle is to charge the
accumulation tank only. To charge the tank, the boiler could operate on its maximum heat output and outflowing water
temperature 85°C. That mode of boiler operation is optimal for the boiler and combustion process itself.
The heat consumption circle uses the heat accumulated in the tank. The circle consists of a room thermostat or a programmed
1
5
3
2
4
Fig. 4 Connection diagram of the emergency cooling
system
1. To sewage; 2. Thermostatic safety temperature limiter 95°C
valve; 3. Filter; 4. Water from public water supply, pressure 2-6
bar, temperature 12°C; 5. Sensor of the thermostatic safety
temperature limiter 95°C valve.
