Hi everybody..
A bit of a puzzler that I'm racking my brains over....

I'll set the scene:
My mums heating system (gravity fed with a header tank in the roof space) has three or four rads upstairs , 3 normal and 1 slightly taller towel rad in the bathroom not hugely taller , 4 ft perhaps?

Anyway: It only gets hot at the bottom 1/3 - the usual problem you'd think , bleed it ?
So I open the screw let out a tiny bit of pressurised air, heat rises a bit up the rad (one bar) but no further air (or water)

So I remove the complete nut that houses the bleed screw at top of rad, No sign of water or air 'rush'?

Soooo thinking laterally, I start to fill the rad with a kettle!, several kettles and although the rad is now getting hot close to top , the water never reaches to top of rad ???

and then I hear running water outside the house, on inspection the roof space overflow pipe is letting water out , if I stop with the kettle filling the roofspace overflow eventually stops , so this is kettle water leaving the building!!

What's wrong ?

and how the heck is the rad not filling up when the overflow is obviously above the rad in question?

In article ,
Zaphod2 wrote:

Hi everybody..
A bit of a puzzler that I'm racking my brains over....

I'll set the scene:
My mums heating system (gravity fed with a header tank in the roof
space) has three or four rads upstairs , 3 normal and 1 slightly taller
towel rad in the bathroom not hugely taller , 4 ft perhaps?

Anyway: It only gets hot at the bottom 1/3 - the usual problem you'd
think , bleed it ?
So I open the screw let out a tiny bit of pressurised air, heat rises a
bit up the rad (one bar) but no further air (or water)

So I remove the complete nut that houses the bleed screw at top of rad,
No sign of water or air 'rush'?

Soooo thinking laterally, I start to fill the rad with a kettle!,
several kettles and although the rad is now getting hot close to top ,
the water never reaches to top of rad ???

and then I hear running water _outside_ the house, on inspection the
roof space overflow pipe is letting water out , if I stop with the
kettle filling the roofspace overflow eventually stops , so this is
kettle water leaving the building!!

What's wrong ?

and how the heck is the rad not filling up when the overflow is
obviously above the rad in question?


an air lock in the sustem?

--
From KT24

Using a RISC OS computer running v5.18

Zaphod2 wrote:
Hi everybody..
A bit of a puzzler that I'm racking my brains over....

I'll set the scene:
My mums heating system (gravity fed with a header tank in the roof
space) has three or four rads upstairs , 3 normal and 1 slightly taller
towel rad in the bathroom not hugely taller , 4 ft perhaps?

Anyway: It only gets hot at the bottom 1/3 - the usual problem you'd
think , bleed it ?
So I open the screw let out a tiny bit of pressurised air, heat rises a
bit up the rad (one bar) but no further air (or water)

So I remove the complete nut that houses the bleed screw at top of rad,
No sign of water or air 'rush'?

Soooo thinking laterally, I start to fill the rad with a kettle!,
several kettles and although the rad is now getting hot close to top ,
the water never reaches to top of rad ???

and then I hear running water _outside_ the house, on inspection the
roof space overflow pipe is letting water out , if I stop with the
kettle filling the roofspace overflow eventually stops , so this is
kettle water leaving the building!!

What's wrong ?

and how the heck is the rad not filling up when the overflow is
obviously above the rad in question?





Just a thought, we're you doing it with the pump running? Could I theory
(depending on positioning) have been drawing water and air down into the
rad with bleed valve open. Try again with pump off.

Tim

In message , Zaphod2
wrote


What's wrong ?



Airlock in the pipes supplying the radiator? Turn off all radiators
except the one that has problems to force a water flow through the
problem pipes.

--
Alan
news2009 {at} admac {dot} myzen {dot} co {dot} uk

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 ??

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

Sorry for late reply, *still haven't had chance to re-do this (other jobs have got in the way) and it was bugging me there were probably people that kindly helped wanting to know the result.....

...sooon
I *will get to it and report back

On 09/07/2012 22:44, Zaphod2 wrote:
Sorry for late reply, *still haven't had chance to re-do this (other
jobs have got in the way) and it was bugging me there were probably
people that kindly helped wanting to know the result.....

..sooon
I *will get to it and report back




I had stopped holding my breath :-)


--
Toby...
Remove pants to reply