S-Plan on a Glow-worm BBU

[Donkmeister]

I'm planning on moving the cylinder and cold water cistern in my house to allow another project to go ahead... Doing this would also be an ideal time to convert my system from a Y-plan to an S-plan.

How can I determine, for certain, whether my boiler has a pump overrun? I don't have the instructions for the boiler, but there is no control to adjust overrun. The programmer is a Honeywell ST699B, I have the instructions for this but it too mentions nothing about pump overrun.

If I do need a bypass circuit, is it best to just use pipe, or install a radiator? Is there a valve that would let the boiler just dump the waste heat into the hot cylinder, or would that require a twin-coil cylinder?

I'm weighing this up against having a combi put in with S-plan - I need to do some flow and pressure measurements to check if a combi is even an option, but I suspect it is too low and I need to stick with tanks. The BBU would eventually be replaced with a system boiler in the kitchen, we would like to wait until we've saved up.

 

[namsag]

Pretty certain no glowworm BBU had pump overruns so you dont have to take that into consideration.

But a bypass was not only for boilers with overruns . Bypass is also there if the microswitches in motorised valve stick and keep the boiler and pump on and for when trvs start to shut down .
Auto bypass just after the pump and before the valves into the return is sufficient for a BBU no need to have a rad etc as it