PUMP OVERRUN UNUSUAL SYSTEM

[Mull1000]

Hi,
I have an unusual system in that I have a Rhino boiler in series with a Rayburn connected to my radiators.
I am need to fit an overrun stat as there is no gravity run from the boiler, (there is from the Rayburn) only a pumped system. When the boiler cuts out from the room stat, the pump will stop too. How can I wire it so that the boiler stops but the pump runs on?
I think I may have to fit another pump for run on purposes.
Thanks for your help.

 

[Agile]

So how does the heat escape if there is a power failure?

Tony

 

[picasso]

What is the model of your boiler ?

 

[Mull1000]

Hi,
The heat from the Rayburn is lost into an indirect cylinder by convection (it is vented). With the Rayburn on a low setting this is fine but if it is turned up full you would have to draw off some hot water if the power fails. I have a pipe stat at the cylinder which runs the pump if the water in the cylinder gets too hot.
The heat to the radiators is so poor as the rayburn is only meant to run a towel rail as a heat sink. I picked up a used boiler that has only been used for two years. It is a Rhino FS 50-90 with a Riello RDB burner.
This will be fitted outside as there is no room in the house for it. It will need to be fully pumped and the pipes will need to run down from the boiler to enter the house. The best I can think of is fitting a new pump next to the boiler and using it as the main system pump and wiring the existing pump to only run when powered from overrun stat and the pipe stat next to the cylinder.
I know this is going to be inefficient as the water from the boiler will also circulate through the Rayburn.
Any advice would be appreciated.
Thanks