On 22/05/16 23:01, Tim Lamb wrote:
In message , John
Rumm writes
My thinking is to take the pipe under the wall and return through or
over the Posi- joist. Hence lots of places where a length of pipe is
able to trap air.

For a unvented (i.e. pressurised) primary heating circuit, air traps
are not really much of an issue. It may make it slight harder to drain
down completely, but filling is usually straight forward, even if you
do have to do a second round of bleeding and topping up once the
system is running.

This what I was hoping to read:-)

Plenty of compressed air on farm so I could blow it out if needed.

I've not seen a Speedfit manifold but I guess you can manually close off
all the circuits and fill them one at a time on full pump pressure.

You are normally filling from mains pressure - so that soon displaces
the air IME.

Just back from Suffolk! The underfloor heating pipes were all laid on
top of insulation and not routed through or over joists.

I asked how they attached the flooring and learned the chipboard was
glued at the half lap and simply laid on top of the slotted in heating
pipes!

I've heard of chip over insulation (free floating) with solid concrete
underneath - but not over joists.