5.5.2 System delivery/return pipes
The sizes of the delivery and return pipes are given for each boiler model in the DIMENSIONS table.
Make sure the system has a sufficient number of vents. Boiler connections must not be stressed by the weight of the system connection
pipes. Therefore the installer must provide for appropriate supports.
5.5.3 condensate discharge
No part of the condensate discharge system must be narrower than the boiler condensate discharge system.
The connection to the drainage system must comply with the current legislation and any local regulations.
To prevent the combustion products from escaping into the boiler room, a trap ensuring a minimum head equal to the firebox pressure
increased by 25 mm must be installed in the condensate discharge path. The connection section between the boiler and trap and between
the trap and drain must have a slope of at least 3° and be such as to prevent any accumulation of condensate.
5.5.4 System filling/draining pipes
For filling and draining the boiler a faucet can be connected to the fitting T5 located at the back (see Fig. 2).
5.5.5 Safety valve and expansion vessel pipes
PreX H 3 cond boilers are suitable for operating with forced water circulation with open or closed expansion vessel. An expansion vessel is
always necessary in order to compensate the increase in water volume due to heating. In the first case, the height of the hydrostatic column
should be at least 3 meters above the boiler casing and be able to contain, between the free water surface in the vessel and the overflow
pipe, the increase in volume of all the water in the system. High and narrow vessels should be preferred in order to expose the smallest
possible water surface to the air, thereby reducing evaporation. In the second case, the capacity of the closed expansion vessel must be
calculated taking into account:
• total volume of water contained in the system
• system maximum operating pressure
• expansion vessel max. working pressure
• expansion vessel initial prefilling pressure
The expansion pipe connects the expansion vessel to the system. This pipe, which will start from the fitting T4 (see Fig. 2), must not have
a shut-off valve. Install on the fitting T4, or on the delivery pipe within 0.5 meters of the starting flange, a safety valve suitable for the boiler
capacity and in accordance with the local and current regulations. It is forbidden to interpose any type of shut-off between the boiler and
the expansion vessel and between the boiler and the safety valves; make sure to use valves adjusted for intervention within the maximum
permitted working pressure.
EN
68
>3°
fig. 10 - condensate discharge
cod. 30902840 - Rev. 00 - 02/2018
PREX H 3 COND