The layout, suitable for medium/large systems, can be divided into 2 zones:

Boiler and heating system zone

This consists of:

·       Boiler capable of running even when the flow rate is zero, sized according to the nominal power of the system

·       Water treatment devices (dirt separator and deaerator) for the protection of generators and, more generally, all system components

·       Charging unit with pressure reducing valve and backflow preventer

·       638 series diverter valve for managing “technical” water between the solar panels and the boiler

·       Mixing valves complete with special control unit for flow temperature management

Layouts suitable for medium/large systems. The boiler should be sized according to the nominal power of the system. This solution is generally used in systems with heat interface units, i.e. with zone outlets able to provide both heating and domestic hot water production.
The boiler should feature set point regulation (60 to 65 °C): the temperature which should be used to size the heat interface units to enable both heating and domestic hot water production.
The heat stored in the tank is used with the aid of the 2 three-way diverter valves, as follows:

1.    If the temperature of the tank exceeds that of the system return but not the required flow temperature, the system return is made to pass through both the solar tank and the boiler;

2.    If the temperature of the tank exceeds that of the required flow temperature, the system return is only made to pass through the solar tank and not the boiler.

Solar panels zone

This consists of:

·       Flat manifold or vacuum pipe type solar panels

·       A circulation unit for solar thermal systems with pump and shut-off, control, expansion and safety equipment

·       A solar circuit control unit with corresponding temperature probes

·       A solar type tank for the production and storage of “technical” water

The solar thermal system helps to reduce the amount of energy consumed by the boiler. When the relevant solar regulator programme is selected, the return circuit passes through the solar water storage if specific conditions arise; otherwise it is diverted to the boiler. If, on the other hand, the solar water storage temperature is greater than the flow temperature, the boiler can be by-passed.

The solar circuit must be regulated so that it is activated only when:

1.    The temperature of the solar panels probe by some degree exceeds (generally 5 to 8 °C), the temperature of the probe installed at the base of the tank;

2.    The temperature of the probe installed at the top of the tank does not exceed the maximum safety temperature.

If necessary, or if required by current legislation relating to water hardness, the heating system water must be suitably treated.

Note:
The control, expansion and safety equipment must be of appropriate size to reflect the heating capacity and specific characteristics of the system, in accordance with applicable laws and regulations.