On 13/06/2021 13:53, John Rumm wrote:
On 13/06/2021 10:07, Roger Mills wrote:
On 12/06/2021 22:41, Fredxx wrote:


Some heat only boilers don't have a pump over-run facility. The Baxi
EcoBlue is an example.




Fair enough if it can cope with the flow stopping as soon as the flame
stops. But, in any case, the OP was talking about using a system
boiler, which included a pump inside the casing.

S-Plan+ with a single pump is easy enough - many system boilers have an
internal bypass valve, and so can cope with occluded flow. The control
systems are also usually clever enough to overrun the pump and keep the
required valves open for long enough after the flame is extinguished.



Fair enough. But I was replying to another poster who had suggested
keeping the existing 2 circuit pipework with a pump in each circuit.
Using a system boiler in such a setup would be a challenge!
--
Cheers,
Roger