Unical ELLPREX Series, Installation, Use And Servicing Instruction

12

2.4 - CONNECTION TO THE

CHIMNEY

The chimney has a foundamental importance for
the good operation of the boiler.
Due to the low temperature of the smokes
during the intermittent opera tion, it is necessary
that the chimney is perfectly impermeable to
the condensate of the combustion products and
manufactured with corrosion resistant materials.
The different connections must be sealed with

an approved boiler putty so that the inlet of fresh
air, with consequent increase  of the possibility
of condensate formation, is avoided.
Furthermore the possible condensate or rain
water comming from the chimney must be
avoided from entering the smoke chamber of
the boiler.
As far as the cross section and the high of the
chimney is concerned, it is necessary to make
reference to the local and national rules in force.

In the flue pipe, between the boiler and the
chimney, convenient sampling points for
smoke temperature and combustion products
analysis must be provided.

2.5 - WATER CONNECTIONS

2.5.1 - FEEDING WATER QUALITY

- The chemical-physical characteristics of

the C.H. system and reinstatement water
are foundamental for the good operation
and safety of the boiler.

- Among the inconvenients caused by the

bad quality of the feeding water the most
frequent and serious is the scaling of the
heat exchange surfaces.

- Less frequent, but also dangerous, is the

corrosion of the water side surfaces of all
the circuit.

- It is well known that the lime, due to its very

low thermal conductivity, reduces the heat

transfer so that also a scaling of a few
millimeters produces very dangerous
localized overheating.
1mm of lime reduces the heat transfer from
metal to water by 10%.
It is suggested to make a water treatement
in the following cases:

A- high hardness of the water available on site

(higher than 20°f).

B- very large C.H. systems.
C- large quantities of reinstatement water due

to water leaks.

D- subsequent fillings of the system due to

maintenance works.

E- mixing of different metals in the CH circuit.

For the  treatment of filling water it is suggested to
address them self to specialized firms.
The same firms are able to provide for the
descaling of the boilers.
Every C.H. system needs reinstatements of
water, du to evaporation, small or large water
leaks or for maintenance works.
It is, therefor, necessary to be able to evaluate
the entity of the reinstatement water to avoid
inconvenients due to untreated water.
For that reason it is suggested to fit, in the
feeding line to the boiler, a water meter for small
capacities.

2.5.2 - C.H. FLOW AND RETURN

CONNECTIONS

The dimensions of flow and return connections
are shown, for each boiler model, in the table
DIMENSIONS.
Before connecting  the boiler to the C.H.

system, this one has to be throughly cleaned.
Make sure in the system there is a sufficient
number of air venter.
When connecting flow and return pipes avoid to
create mechanical stress onto the boiler flanges.
The boiler is not made to support the piping of

the C.H. system, which needs dedicated
supports.
Once the complete C.H. system is finished,
check for water leaks all the connections.

2.5.3 - CONNECTION OF FILLING

AND DRAIN TAP

For the filling and drain of the boiler a dedicated
tap can be connected to the point T4, which is
in rear part of the boiler.

2.5.4 - CONNECTION OF THE

PRESSURE RELIEF VALVE

Fit onto the point T3 or onto the supply pipe,
within 0.5m from the flow flange, a pressure
relief valve properly dimensioned for the  boiler

capacity and in conformity with the local rules in
force.
It is forbidden to put any gate valve between
the boiler and the pressure relief valve.
The maximum working pressure of the boiler is

6 bar; the pressure relief valve has to be
selected accordingly.

2.5.5 - CONNECTION OF THE

EXPANSION PIPE AND VESSEL

An expansion vessel is always necessary, to
compensate the water volume increase due
to the heating.
The ELLPREX boilers are suitable for fully
pumped systems, which can be open vented
or sealed.
In the 1

st 

case the height of the hydrostatic

column must be, at least, 3m above the boiler

casing and the capacity of the expansion
cistern shall be able to contain, between the
water surface and the overflow pipe, the volume
increase of all the water of the C.H. system.
Preference shall be given to high and narrow
cisterns, to expose to the air a surface as small
as possible, thus reducing the water evaporation.
In the 2

nd

 case the vessel capacity has to be

calculated taking into consideration:
- The total volume of the water contained in

the system. The maximum working pressure
of the system (see setting of PRV).

- The maximum working pressure of the

expansion vessel.

- The initial preloading of the expansion vessel.
- The maximum working temperature of the

boiler (the maximum setting of the
thermostat fitted onto the panel board is
90 °C; under this aspect it it suggested to
consider 100 °C.