Sorted

I've just been up into the loft and airing cupboard and mapped out all the
pipe runs. If you look at this basic diagram.

http://www.diydata.com/planning/cent...ing/boiler.htm

Then my pump would be on the blue line immediately adjacent to the boiler,
pumping into it and then back out into the line that feeds the vent and then
the rads and cylinder. The vent is therefore in the wrong place, before the
rads rather than after them and hence seeing all the pump pressure. Turning
the pump round wouldn't help because then the feed from the bottom of the
loft tank would see this pressure instead thus similarly reducing flow
through the rads.

So at present I only get normal flow because the vent is blocked and the
expansion/feed pipe does any venting required. When I get round to fixing
all the niggles in the system I'll reorganise everything to correct this.

As I say though, whether vented, for the first 15 years here, or unvented
for the last 4 I've always had piping hot rads and hot water and I guess
just the pressure head from the loft tank has sufficed to keep the system
running ok. Black mark to the guy who fitted all this before I moved in I
suppose.
--
Dave Baker
www.pumaracing.co.uk


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