On 11/06/2012 09:01, Zaphod2 wrote:
Thanks for the suggestions so far, I can't re-check any of it 'til next
weekend , but will try the suggestions made.


The pump and boiler had almost certainly been running but idle when I
first opened the bleed, but I did go and set the 'stat on cos I thought
it might bring on some pressure to get some more air at the bleed but it
didn't.
The pump was running when I had the whole nut removed!.

And for information, the pump and boiler are on the ground floor , (this
rad is upstairs).

Thanks in advance for any more ideas

I just don't understand how water can defy gravity and be pushed out in
the roof space overflow rather than coming up to the top in the actual
rad when it was open to the air ??


I think Tim has supplied the only plausible answer, that the pump was
managing to suck water out of the radiator, so if you turn off the
boiler (and wait until the pump stop if there is an over-run), then try
bleeding the radiator (but don't just remove the bleed valve assembly
and assume it won't gush!)

If this results in the radiator filling up, then that solves that question.

If this is the case, I would be mindful to check to see if the system is
pumping over, and also if the expansion pipe that should be over the
expansion tank is above the water line, or under the water (it should
not be in the water, so should be above the overflow outlet).

Your filler valve should also be set to not fill the expansion tank to
just under the overflow, and to keep a reasonable gap to allow for
expansion (Mine is just over half full)

--
Toby...
Remove pants to reply