[Vass]

Ok, I'm replacing/re-routing the CH pipes around the house after the
builders have move staircases etc
So whats the guidelines for pipes to rads?
is it 22mm supply, with 15mm tails to the rads?
I'm bringing a couple of pipes from the bedroom floor down the wall in the
lounge
to a rad under the window, so can these be 15 all the way down and accross
to the rad
with just 22 in the joist space?
TIA
--
Vass
'06 R1, '90 CBR1000F
www.doubleyolk.co.uk
www.haylinglegends.co.uk

[Roger Mills]

In an earlier contribution to this discussion,
Vass wrote:

Ok, I'm replacing/re-routing the CH pipes around the house after the
builders have move staircases etc
So whats the guidelines for pipes to rads?
is it 22mm supply, with 15mm tails to the rads?
I'm bringing a couple of pipes from the bedroom floor down the wall
in the lounge
to a rad under the window, so can these be 15 all the way down and
accross to the rad
with just 22 in the joist space?
TIA

It depends on the size of the rad(s) in the lounge, and whether there are
any upstairs rads connected to the same 15mm leg. The general rule of thumb
is that 15mm pipe will support rads up to a total of about 6kW.
--
Cheers,
Roger
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[TheScullster]

"Roger Mills" wrote

It depends on the size of the rad(s) in the lounge, and whether there are
any upstairs rads connected to the same 15mm leg. The general rule of
thumb is that 15mm pipe will support rads up to a total of about 6kW.
--
From experience I would only use that rule of thumb for single large rads or
2 rads back to back not far from the 22mm main.
Personally I would run 22mm close to rad take offs and only use long
convoluted 15mm runs where there was no realistic alternative.

Phil

[Vass]

"TheScullster" wrote in message
. uk...

"Roger Mills" wrote

It depends on the size of the rad(s) in the lounge, and whether there are
any upstairs rads connected to the same 15mm leg. The general rule of
thumb is that 15mm pipe will support rads up to a total of about 6kW.
--
From experience I would only use that rule of thumb for single large rads
or 2 rads back to back not far from the 22mm main.
Personally I would run 22mm close to rad take offs and only use long
convoluted 15mm runs where there was no realistic alternative.

i need 9000 btu's in the lounge diner
was going to fit a vertical in the dining area and a larger
std rad under the window in the lounge
22's all round then
Ta
--
Vass

[nospam[_2_]]

On Mon, 17 Sep 2007 13:47:01 +0100, "TheScullster"
wrote:

It depends on the size of the rad(s) in the lounge, and whether there are
any upstairs rads connected to the same 15mm leg. The general rule of
thumb is that 15mm pipe will support rads up to a total of about 6kW.
--
From experience I would only use that rule of thumb for single large rads or
2 rads back to back not far from the 22mm main.
Personally I would run 22mm close to rad take offs and only use long
convoluted 15mm runs where there was no realistic alternative.


I don't know the answer but in our house it's all 15mm. The house was
built in the 1970s and the pipework has minimal insulation. In fact
the pipes are just beneath the floorboards, which means there is no
room for me to retrofit any insulation (unless anyone has any ideas?
help please!)

Despite this we are warm enough and it can get too warm at times. Of
course we will have a totally different boiler and radiators than you
so what works for us many not work as well for you.

If I were doing it I think I would use 22mm under the floorboards and
use 15mm for the "spurs" to the radiators. If you are dropping pipes
just to go to one rad. I would just use 15mm for the visible section.
At least you could use chrome pipe to make it look prettier. I think
visible 22mm would not be aesthetically pleasing. Of course, if these
pipes run to other rads, it becomes a different story.

Is the 22mm overkill? After all, don't some rads use even smaller
pipes than 15mm? I bought a 15mm rad valve recently (tool station) and
was surprised that the bore in the valve was so small: less than 5mm I
would guess. So wouldn't running 22 to it would be redundant because
the bottle neck is at the valve? OTOH I would think it better to be
overspecified and have reserve in your system rather than run it to
its limit.

[Vass[_2_]]

"nospam" wrote in message
...
On Mon, 17 Sep 2007 13:47:01 +0100, "TheScullster"
wrote:

Is the 22mm overkill? After all, don't some rads use even smaller
pipes than 15mm? I bought a 15mm rad valve recently (tool station) and
was surprised that the bore in the valve was so small: less than 5mm I
would guess. So wouldn't running 22 to it would be redundant because
the bottle neck is at the valve? OTOH I would think it better to be
overspecified and have reserve in your system rather than run it to
its limit.

all thoughts I've had so far, but the 60's house I have used to have
microbore and that worked fine
so 15mm to the single rad from 22 in the ceiling seems enough for the
5000btu rad
thanks for the input.
--
Vass

[Mark Williams]

nospam writes:

Is the 22mm overkill? After all, don't some rads use even smaller
pipes than 15mm? I bought a 15mm rad valve recently (tool station)
and was surprised that the bore in the valve was so small: less than
5mm I would guess. So wouldn't running 22 to it would be redundant
because the bottle neck is at the valve? OTOH I would think it
better to be overspecified and have reserve in your system rather
than run it to its limit.

Tubes which are too big have at least one downside: having to wait a
longer than necessary time for the hot water to make its way to the
most distant radiator(s) when the heating starts.

URL:http://www.cda.org.uk/megab2/build/pub-150-copper-tubes-in-domestic-heating-systems.pdf
gives more detail about optimising the diameter of each part of the
system than the `guidelines' the OP asked for, but IMO it's well worth
doing.

--
Mark