HI S

Spamlet wrote:
"Adrian" wrote in message
...
HI All

I've not used float-type auto air vents before - so I may be doing
something wrong - expert advice welcomed !

Regular readers may recall the saga of my heatpump system - which was
causing the CH header tank to regularly overflow. This was finally sorted
by bleeding trapped air out of the heat store.

Systems looks like a conventional CH boiler - except that the 'boiler' is
a heatpump, and the return from radiator and DHW circuits passes through a
200 litre, heavily insulated copper 'heat-store' before it goes back to
the heatpump. When the heat pump switches off the system circulates water
from the store through the DHW / CH until it's cooled sufficiently.

Anyway....

The whole thing's piped up in copper / pex - the circulating pump has a
little brass float-type auto air vent on the highest point of the
circuit - but the feed to the top of the heat store had no such vent.

The only way to bleed the air from the heat store was to slacken off the
compression fitting at the top of the store and wait while the air finds
its way out - necessitates leaning over the store and applying lateral
pressure to the pex pipe to slightly unseat the pipe - a slow and
uncomfortable process!

So - I bought another auto air vent and fitted it as close as possible to
the feed into the heat store - confidently expecting it to vent air ..
automatically ....

Trouble is - it doesn't grr
It's still necessary to do the 'lean over the heat store for a hour at a
time to let the air out'....

So - what don;t I understand about using these auto air vents ?
It's fitted pretty much at the high point of the circuit - certainly on a
level with the union into the heat store. Fitted into a 3/4" x 3/4" x
female threaded 'tee' - with the air valve fitted vertical and into the
threaded part of the tee...

Any ideas please ??

TIA
Adrian

Perhaps the air is getting into the tank (ie, as bubbles) faster than it can
go up the vent tube.


Hmm - possibly

Only when the water stops circulating will the bubbles
rise to the top. So really you need the vent in the high point of the tank
itself.

That would be ideal - but it seems that the manufacturers of the tank
didn't think of that g

You can also put it on an extended tube to maximise the volume of
air in the tube instead of in the tank: but obviously you can't go higher
than the header tank, or the float won't float.

I'd thought of that - maybe fabricate a nice little 'J-shaped' piece of
copper tube that could connect to the tank inlet, then have a 'tee' so
that the valve can sit a few inches above the tank inlet - and the
return from the heating can come in the short leg of the tee...


We have a float bleed on our ch and it can be tricky to set it up so that
the float doesn't get stuck. Ours has a tyre valve like nipple at the top
which you can depress from the outside to jiggle the float and bleed the air
manually from time to time to make sure it is topped right up. It's very
like an old carburettor float chamber; that one used to have to tickle to
get it to fill right up.

Ah - that takes me back - BSA 350 single - a right pig to start!

Both of these valves have a removable cap on the top - but the odd ting
is that when you remove the cap from the one that's on the heat store
and slide a piece of tin wire down to depress the float there's only a
tiny amount of air that escapes - while loosening the union on the tank
itself allows air out, and you can hear the water trickling inside the
tank.

When I got it sorted the last time (before I drained everything down to
add a proper drain cock and this air-valve) I managed to get it to the
point where the circulating water was silent in the tank - but it took a
couple of hours with the union slackened off and 'jiggling' the pex pipe
to get the air to come out - I was hoping to 'automate' the process!

Before anybody asks g - yes - the air is coming _out_ rather than 'in'
- soap solution blows bubbles when wiped around the loosened union.

Thanks
Adrian