8
possible vertical way between expansion tank and boiler. If the circulation pump is installed on return line,
and the head of pump at maximum speed is "h", the vertical distance (h) given in above scheme must be
achieved within the system design (h, being the vertical distance between the top radiator of the circuit and
bottom level of open expansion tank). If h is not achieved in such system, there will be air suction on
radiators at highest level of circuit. In this case, the pump must be installed on delivery line from boiler.
A hydrometer must be installed on the delivery line to monitor the pressure level and to check if there is any
leakage. The hydrometer should be purchased separately, and should be installed at the same level with
the boiler outlet. A by-pass line should be installed between inlet and outlet connections of circulation pump
in order to allow maximum water delivery when circulation pump is switched off and there is fuel fired in
boiler, particularly during sudden electricity cuts off.
NOTICE
The optional safety heat exchanger kit is highly recommended to be used with the boiler, even in
the case of open vented systems to protect the boiler and the whole heating circuit against
excessive heat accumulation. For installation of this kit, please refer to the next section.
NOTICE
When water temperature in hydraulic circuit is relatively low, particularly when solid fuel is just fired,
it is normal for water vapour in flue gases to condense. Condensation rarely creates a problem for
the boiler, as it will stop when boiler becomes hot. However, the boiler should not be operated in
fully condensing mode. When you open loading door, if chamber walls are wet, it means that there
is condensation in flue gases. Continuous condensation does not only create massive tarrs on
combustion chamber heating surfaces, but also has little effect on boiler lifetime. We will
recommend you to follow one of the following methods to control condensation rate in the boiler:
1. You can install a thermostatic three way mixing valve between delivery and return line of the
boiler as described in above circuit scheme. Here, three way valve should preferably be set to 40
o
C. Then, water will by-pass directly between delivery and return of the boiler, until the return water
temperature reaches up to 40
o
C.
2. You can control circulation pump by means of a thermostat that can be attached delivery or
return of the boiler. If thermostat is on the return line, it should be set to 40
o
C, if it is on the delivery
side, set to 55 - 60
o
C. As the pump will not start unless water temperature rise up to the set value,
boiler warms faster, and condensation mode is minimized.
5.3. Design parameters for open expansion tank
Expansion tank protects hydraulic circuit from
excessive temperatures by allowing free volume
for expanding water and keeping the water
pressure from exceeding the static pressure.
Expansion tank may be built in rectangular prism
or cylindrical shape, may be installed in horizontal
or vertical position in the system. Safety lines
between boiler and expansion tank should be
installed by an increasing slope up to tank.
Following scheme shows the maximum vertical
distances between safety lines and boiler:
The size of expansion tank can easily be calculated regarding the total expanding water contained in whole
system. If the total volume of water in the system is V
s
; the volume of expansion tank should be:
Vg= 8.Vs / 100 (in litres)
SV: Delivery safety line
SR: Return safety line
