Small radiators + electronic valves

18/07/2026

Installations with low-water-content radiators

+ underfloor heating with electronic mixing valves

Installation with mixed zones:

• radiators with 2-port zone valves (low flow rate)

• underfloor heating with electronic mixing valves

Connection to a boiler that can be fitted with a zone control unit

BOILER: To begin with, let us consider boilers that can be connected to a zone control unit. The boiler may heat domestic hot water either instantaneously or via a cylinder, and may have a sealed or an open combustion chamber. The boiler does not need to be fitted with a by-pass (Immergas fits this device as standard on the vast majority of its boiler models).

ZONES: The system can be divided into a maximum of three zones. One zone can be controlled by the CAR or Super CAR remote control. The radiator zone supplied through a zone valve must always be the first one (No. 1 – that is, the one upstream of the low loss header). In zones with radiant surfaces (e.g. underfloor heating), the zone circulation pumps are installed at the inlet to the zone, with the mixing valve upstream of the pump. The "common" port of the mixing valve is connected to the suction side of the pump. The underfloor heating safety thermostats must have their contact wired in series with the corresponding room thermostat contacts.

Controllers that manage the underfloor heating zones must have a "volt-free" contact for connection to the zone control unit (the room thermostat is normally connected here), so that the outputs of the zone control unit can be used to power the underfloor heating circulation pumps.

Installation with mixed zones:

• radiators with 2-port zone valves (low flow rate)

• underfloor heating with electronic mixing valves

Connection to a boiler WITHOUT provision for a zone control unit

BOILER: This layout can be used for boilers that are not designed for connection to a zone control unit.

ZONES: With this layout the system can be divided into an unlimited number of zones, but none of them can be controlled by the CAR or Super CAR remote control. The radiator zone supplied through a zone valve must always be the first one (No. 1 – that is, the one upstream of the low loss header). The zone pumps or valves can be powered through the corresponding room thermostats even when the boiler is set to summer mode or to domestic hot water (DHW) priority. This has no adverse effect on boiler operation, but it is nevertheless advisable to switch off the external pumps during summer mode.

In zones with radiant surfaces (e.g. underfloor heating), the zone circulation pumps are installed at the inlet to the zone, with the mixing valve upstream of the pump. The “common“ port of the mixing valve is connected to the suction side of the pump. The contact of the underfloor heating safety thermostat must be wired in series with the contact of the corresponding room thermostat. Controllers that manage the underfloor heating zones must have a "volt-free" contact for connection to the relay box.

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