In an earlier contribution to this discussion,
Malcolm Reeves wrote:


How does a bypass remove residual heat? For that the pump has to run
so you need pump overrun not bypass. However, you may need a bypass
and pump overrun to cover the situation of all rads with TRVs (which
you shouldn't have) and needing to get rid of some heat (to the pipe
work presumably).

By providing a flow path for the water when the pump is over-running and all
the TRVs and/or zone valves are shut. The residual heat is actually
dissipated by the pipework as the water flows round the by-pass circuit. If
the residual heat can't be carried away from the boiler, the boiler
temperature continues to rise to the point where its overheat stat trips -
which requires manual resetting.

--
Cheers,
Set Square
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