No Veito unit feeds or backs up a solar system on its own. There are two installation types that can both be correct — which one you have changes the outcome.
Correct installation — they work together
Before it enters the house, the hot water coming from the solar system must be passed through a
thermostatic (NIKS) mixing valve and limited to
no more than 50 °C . This protects the unit from the high inlet temperatures that can occur in summer. In winter, when the solar system does not heat enough (e.g. 30 °C), the Veito unit tops the incoming lukewarm water up to the temperature you want. With this installation the two systems can stay together.
Wrong installation — a bypass forms
If there is no mixing valve and
both systems are left with their valves open there is a
bypass forms in the pipework: the hot water circulates without passing through the unit, and because the unit sees no flow it never switches on. In that case
the valve of the system you are not using at that moment must be closed — either the solar system, or the storage heater, or your Veito unit is open.
How do I tell?
Close the unit's water valve; with the valve closed no water should come out of the hot tap. If it keeps running, there is a bypass in the pipework. For the detailed test and the fix, see
our bypass guide .