24
Fig. no. 13
Position in a boiler room.
6.3
Connection to the hydraulic system
We recommend to design the boilers together with expansion tanks incl. a membrane and the heating
system must be equipped with safety valves. The expansion tank volume calculation based on the water
volume in the system and the conditions for their use are stated in
Č
SN 06 0830.
Filing the heating system with water
Water for filling the boiler and the heating system must be clear and colourless, with no suspended
substances, oils and chemically aggressive substances. Its hardness must correspond to
Č
SN 07 7401 and
in case the water hardness is unsuitable the water must be treated. Even if the water with a higher hardness
is heated several times the salts segregation von the boiler drum walls cannot be prevented. The
precipitation of 1 mm calcite reduces the heat transfer from the metal into the water at the given point
by 10 % and on the top of that it might cause the exchanger disruption – the guarantee becomes invalid.
The heating systems with an open expansion tank make possible a direct contact between the heating water
and the atmosphere. At the period of the heating season the water expanding in the tank absorbs the oxygen
that increases the corrosive effects and at the same time a large volume of water gets evaporated. Only the
water treated to the values shown in the table can be used for refilling.
Recommended water treatment for water boilers and connected closed systems operation
Hardness
mmol/l
1
Ca
2+
mmol/l
0,3
Total Fe + Mn concentration
mg/l
(0,3)*
*) recommended value
After the boiler and heating system have been refilled it is necessary to bleed properly the boiler and
the whole heating system.
At the period of the heating season it is necessary to keep a constant water volume in the system and make
sure that the heating system is vented. The water from the boiler and the heating system must never be
discharged or taken for the use except the emergency cases like repairs etc. The water discharge and refill
increases the corrosion and furring risk. If it is necessary to refill the water in heating system we only refill
a cold boiler in order to prevent the sections rupture.
