5
THERM 90 KD.A
1.2.3 General description
The gas condensing boiler THERM 90 KD.A consists from support frame, which houses all operating elements of the boiler.
Upper part of the boiler houses compact stainless condensing element Sermeta, which integrates combustion chamber with
burner and double-chamber vertically stacked stainless exchanger. Housing of the condensing elements is also made from
stainless material, which ensures high temperature resistance and lifetime of the element. The heat transfer surfaces of the
heat exchangers are formed by the round-shaped tube sheets, which must be protected against dirt deposition from the
heating system. Due to this reason the heating system must be fitted with filtering and decanting device at inlet of the return-
water to the boiler (such as spiro-valve). Temperature sensors are located at the input and output collector of heating water
on the element. Removable front burner wall of the element is made from the aluminium alloy, is fitted with two electrodes
(burning and ionizing), tube burner an shaped piping for supply of the gas-air mixture.
The gas-air mixture ratio is prepared by compact assembly of pre-mix fan, mixer and gas valve. The mixture is created by
the mixer in conjunction with the special gas valve. It consists of a gas pressure regulator, two solenoid blocking valves and
ratio regulation of the output volume of gas with elements for mechanical setting. Adjustment of synchronism of the ratio
regulation is possible only with special device (flue gas analyser). The whole system operates so that the volume of added
gas is directly proportional to the volume of air through the mixer delivered with the ventilator. Therefore it can be stated
that the output on the boiler depends on the volume of the air flow for combustion.
As a result, the revolutions of the ventilator are fluently controlled within a wide range which ensures the high output range
of the boiler. The air is supplied into the ventilator is through the shaped piping from the connection system.
Condensate from the condensing element, flue gas exhaustion piping and air inlet is discharged by the hoses to the siphon,
from which the condensate is passed outside the boiler.
Supply of the combustion air, incl. forced extraction of the flue gases, is ensured usually by the coaxial piping, which passes
horizontally through the perimeter wall or vertically
through the roof structure to the free area. It is
necessary to install the piping to prevent (due to the
low temperatures of burnt gases) the possibility of
the freezing of the exhaust terminal. Vertical piping
must terminate at the roof chimney, horizontal with
a slight slope into the exhaust from the boiler.
Power saving transfer pump Wilo ensuring flowing
of water through the boiler is installed at the inlet of
the return water. Sufficient flow and pressure of the
heating water are monitored by the flow and pressure
switch. In addition, the boiler is fitted with the safety
valve for the boiler overpressure protection. Further,
the boiler can be supplemented with suitable motor-
driven three-way valve for splitting of functions of
the hot water heating and warming of the heating
system.
The control panel is completely plastic. The controls
are located at the front side. The integrated single-
plate automatic HDIMS20-TH20 contains electronic
circuits for ignition of burner and for microprocessor
control of the boiler operations.
