Bleeding cast iron radiators

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No...@m.here.please

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Aug 23, 2008, 6:36:14 PM8/23/08
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Hi,

I've just fitted a couple of cast iron radiators, picture of which can be
seen here - http://img292.imageshack.us/img292/8771/dsc00222ax9.jpg.

They warm up OK but only the bottom half of the radiators. I'm guessing
there's air at the top which is causing the problem. However, the only
valve fitted is a few inches above the outlet (you can see it sticking out
on the picture). There's no valve at the top of the radiator.

Is this normal? Is hot air gathering at the top causing them not to heat
up? If I open the valve, then water just comes out.

Cheers,

Steve.


RW

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Aug 24, 2008, 4:25:52 AM8/24/08
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<No...@m.here.please> wrote in message
news:eda444466a296c31b7ee66f2d766a2b8@localhost...


IANAP......But.....Perhaps you lay the rad on its side and fill with the
bleed hole open to expel air then mount upright


Tim Downie

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Aug 24, 2008, 4:49:54 AM8/24/08
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No...@m.here.please wrote:
> Hi,
>
> I've just fitted a couple of cast iron radiators, picture of which
> can be seen here -
> http://img292.imageshack.us/img292/8771/dsc00222ax9.jpg.
>
> They warm up OK but only the bottom half of the radiators. I'm
> guessing there's air at the top which is causing the problem.
> However, the only valve fitted is a few inches above the outlet (you
> can see it sticking out on the picture). There's no valve at the top
> of the radiator.

Very weird. Never seen a radiator, cast iron or otherwise without a bleed
valve at the top. Are you quite sure that there isn't a recessed square
screw (perhaps buried in layers of paint) at one end of the radiator?

If not, I would suggest that your best bet is to contact the sellers and ask
them how you're supposed to bleed them. Without a bleed screw, they're not
fit for purpose.

Tim


No...@m.here.please

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Aug 24, 2008, 5:21:25 AM8/24/08
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On Sun, 24 Aug 2008, Tim Downie wrote:

> No...@m.here.please wrote:
> > Hi,
> >
> > I've just fitted a couple of cast iron radiators, picture of which
> > can be seen here -
> > http://img292.imageshack.us/img292/8771/dsc00222ax9.jpg.
> >
> > They warm up OK but only the bottom half of the radiators. I'm
> > guessing there's air at the top which is causing the problem.
> > However, the only valve fitted is a few inches above the outlet (you
> > can see it sticking out on the picture). There's no valve at the top
> > of the radiator.
>
> Very weird. Never seen a radiator, cast iron or otherwise without a bleed
> valve at the top. Are you quite sure that there isn't a recessed square
> screw (perhaps buried in layers of paint) at one end of the radiator?

Well, there is a notch which looks like it's there to take a flat bladed
screwdriver (you can see it at the top in the centre of the circular
piece). It has one on each end. It might be for the tie rid, that said
there's a seperate tie rod underneath.

> If not, I would suggest that your best bet is to contact the sellers and ask
> them how you're supposed to bleed them. Without a bleed screw, they're not
> fit for purpose.

I bought them secondhand a few years ago, so no comeback I'm afraid.

How does the water flow through these? Is it a common feed at the bottom?
Or does it flow up and down the first section which then feeds the next
one?

Steve.

Andrew Gabriel

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Aug 24, 2008, 7:49:21 AM8/24/08
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In article <fe74a695d631e84cbc056d45dff376ba@localhost>,

Not sure if you're saying they only have one connection?
If so, they were steam radiators, which also explains why
no bleed valve. (There was an automatic vent to let air out
each time the steam system started up, like you get on a
pressure cooker, which could be what that low down valve
was originally for.)

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Bob Minchin

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Aug 24, 2008, 10:19:26 AM8/24/08
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Not too difficult to drill and tap for a bleed nipple.
Some are threaded 1/8 BSPT (which is about 3/8" od). This thread is
quite fine (28 tpi) and will give a decent few turns into relatively
thin materials.


Bob

Bob Martin

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Aug 25, 2008, 3:59:06 AM8/25/08
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My house still has cast-iron radiators, probably installed around 1940.
They are connected as 5 vertical pairs (ie from the loft to the bedroom rad then down to
a downstairs rad then back to the boiler). Only the downstairs one of each
pair has a bleed screw. I don't know why it works - to me it would make more
sense if the upstairs one was the bleedable one - but it does.

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