On 23/11/2019 14:18, Andrew wrote:
Assuming a heat-only sysem with boiler, pump and
radiators (emitters!!), apart from a thermostat
what controls would be needed other than a timer ?.

I assume that a programmable stat would do the timing
and temp control, so no need for a wiring centre.

Would the boiler provide the power for the pump or
is a relay required ?.

It may depend on the boiler but mine provides the power to the pump
which includes the pump overrun to stop the pump switching off instantly
off the heating demand has been satisfied. The heat exchanger will still
be hot when the burners switch off and if the pump is stopped
immediately at this time the latent heat in the heat exchanger will be
transferred to the non flowing water - hence the need to keep it being
pumped for a while.

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