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1
2
3
smaller section than the inlet of the safety valve or the sum of the inlet sections in case of more valves heading a single pipe.
The discharge piping of the safety valve must be realised in order not to prevent the regular functioning of the valves and
not to cause damages to persons; the discharge must flow immediately near the safety valve and be accessible and visible.
The diameter of the discharge piping must not however be lower than that of the outlet connection of the safety valve. For
diameter of outlet connection it is intended the minimum internal diameter on the valve outlet upstream of the eventual
internal threading.
CLOseD exPANsION VesseL
Warnings: check that the preload of the expansion vessel is set to 1.5 bar.
The vessel maximum exercise pressure must not be lower than the calibration pressure of the safety valve, increased by over
pressures, characteristic of the same valve, bearing in mind the eventual level difference between vessel and valve and the
pressure generated by the functioning of the pump. The capacity of the expansion vessel/s is evaluated depending on the
total system capacity as results from the project. The closed expansion vessels must comply with the dispositions regarding the
planning, manufacturing, evaluation of conformity and use for pressure appliances. Intercepting objects or section decreases
must be inserted/practiced on the connection piping, which can be constituted by system portions. The insertion of a three-way
intercepting valve which allows connection between the vessel and the atmosphere for maintenance operations, is allowed.
Such device must be protected against accidental manoeuvres. The connection pipe must be realised in order not to present
scales or deposits storage points. In case of more heat generators which feed the same system or the same secondary circuit, each
heat generator must be connected directly to the expansion vessel or system expansion vessels unit, altogether dimensioned
for the total volume of water contained in the same system or the same independent circuit. Where it is necessary to separate
the individual heat generator from the expansion vessel or expansion vessels unit, a three-way tap must be applied on the
connection piping between the generator and the vessel, in order to ensure, in every position, the connection of the generator
with the expansion vessel or with the atmosphere. The expansion vessels, the connecting pipes, the bleed pipes and drain pipes
must be protected from freezing, where this phenomenon occurs. The solution used for this purpose is described in the design.
COMMIssIONINg CheCKs
Before connecting the boiler:
a) wash all system piping in order to remove any residues which might compromise the correct functioning of certain system
components (pumps, valves, etc.).
b) check to verify that the flue has adequate draft, is not narrowed and that other appliances do not discharge into the flue.
This is to prevent unexpected power increases. Only after this control can the flue fitting be mounted between the boiler and
the flue. A check of the connections with pre-existing flues is recommended.
AuTOMATIC TherMOsTATIC MIxer VALVe (MANDATOry)
The automatic thermostatic mixing valve finds applications in solid fuel boilers as it prevents cold water return into the exchanger.
Routes 1 and 3 are always open and, together with the pump
installed on the return, they guarantee water circulation
inside the biomass boiler exchanger.
An elevated return temperature, allows efficiency
improvement, reduces formation of combustion product
condensation and prolongs the boiler life span.
Valves on the market have different calibrations. Dal Zotto
advises use of 55°C model with 1" hydraulic connections.
Once the valve calibration temperature is reached,
route 2 is opened and the boiler water goes to the system via
the flow.
Valve sold as an accessory (optional)
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