On Feb 6, 11:55*pm, rog wrote:
On 6 Feb, 20:35, " wrote:





Why not put in a mains pressure tank *you won't need expension tanks?

Not with a solid fuel appliance - these must have an unpressurised
circuit, as there's no way to shut them down once fired up. They must
also rely on gravity circulation (in case of a power cut).

Caveat - I've never fitted a solid fuel rayburn - only a modern
pressure-jet oil burner. However solid fuel was one of the options I
considered and I had a good think abut how I'd route it in my own
place, and nosed about at other installations.

For your f&e, your routing sounds ok to me. But the main boiler to hw
tank in 28mm - I'd take great care to ensure you follow the Rayburn
installation instructions exactly, to ensure that you have excellent
gravity circulation. Both pipes slope upwards all the way, minimum
number of bends, heat-leak radiator etc. Otherwise you may for
evermore be plagued by kettling/knocking in your boiler.

Thanks for your reply, another query is as the rads ( fitted with
thermostatic valves ) and heat sink rad are all in the upper storey,
do I need a circulation pump at all; in a previous house with s/f
rayburn the u/s rads were operating ok when pump off, obviously d/s
rads not.- Hide quoted text -

- Show quoted text -

It depends on the layout. Basically speaking the vertical distance of
the extremity of the system needs to be twice the the horizontal
distance between heat source and radiator/cylinder to work well.
There needs to be a vertical column of pipe right next to the heat
source to power it all up. Pipe diameters need to be around twice the
norm for pumped circuits. ie you ideally need radiator with 3/4"
connections. These are available but at a price. Your radiators need
to be twice as big too.
It all can be done, I did it a while back, all in steel pipe. I twas
OK but took a lot longer. Any pump cannot be in series, it would stop
it from working, too much resisitance.. The pump needs to be in a
little bypass loop with a full way valve on the main pipe run that is
closed when the pump is runningPopintless really if the thing works on
gravity.. (There would still need to be a separate gravity safety
circuit in this case.)
Don't even think about thermostatic valves or even angle valves on
the radiators, you need full way straight pattern valves. All to keep
resistance down.