Four of my 7 rads are done in 8mm microbore from a manifold in my hall and the
other 3 rads are fed by 10mm tee'd in to the 22mm before the manifold . As I am
getting a replacement condensing combi boiler and the fitter said 10mm was
preferable to 8 I wondered if cutting the 8mm just after it leaves the manifold
and then replacing it with 10mm would work better or would the couple or three
inches of 8mm still create problems ( if at all) . I had thought all were done
in 10mm and it was only after he left ( thinking they were all 10mm as I was)
that I had a closer look and noticed the difference so lifted a couple of boards
over the manifold and checked what was what .

I don't know why it was done that way ...can you not get 10mm manifolds ?


Stuart

"Stuart" wrote in message
...
Four of my 7 rads are done in 8mm microbore from a manifold in my hall and
the
other 3 rads are fed by 10mm tee'd in to the 22mm before the manifold . As
I am
getting a replacement condensing combi boiler and the fitter said 10mm was
preferable to 8 I wondered if cutting the 8mm just after it leaves the
manifold
and then replacing it with 10mm would work better or would the couple or
three
inches of 8mm still create problems ( if at all) . I had thought all were
done
in 10mm and it was only after he left ( thinking they were all 10mm as I
was)
that I had a closer look and noticed the difference so lifted a couple of
boards
over the manifold and checked what was what .

I don't know why it was done that way ...can you not get 10mm manifolds ?


Stuart

With a condensing boiler, balancing the rads and boiler to have a wide
flow/return temperature differential means smaller bore pipes can be used.
If 8mm was fine before it will be more than fine now.

Your fitter is probably a plumber who are good at drains.

"Stuart" wrote in message
...
Four of my 7 rads are done in 8mm microbore from a manifold in my hall and
the
other 3 rads are fed by 10mm tee'd in to the 22mm before the manifold . As
I am
getting a replacement condensing combi boiler and the fitter said 10mm was
preferable to 8 I wondered if cutting the 8mm just after it leaves the
manifold
and then replacing it with 10mm would work better or would the couple or
three
inches of 8mm still create problems ( if at all) . I had thought all were
done
in 10mm and it was only after he left ( thinking they were all 10mm as I
was)
that I had a closer look and noticed the difference so lifted a couple of
boards
over the manifold and checked what was what .

I don't know why it was done that way ...can you not get 10mm manifolds ?


Stuart



Do your 8mm rads have difficulty maintaining the required temperature? If
not then don't do anything.

Also make sure that your system is properly balanced and the rads are
actually large enough for the room, however if you do decide to change to
10mm then all the connection needs to be enlarged to 10mm.

Peter

On Fri, 15 Dec 2006 23:20:28 -0000, "Doctor Drivel" wrote:


"Stuart" wrote in message
.. .
Four of my 7 rads are done in 8mm microbore from a manifold in my hall and
the
other 3 rads are fed by 10mm tee'd in to the 22mm before the manifold . As
I am
getting a replacement condensing combi boiler and the fitter said 10mm was
preferable to 8 I wondered if cutting the 8mm just after it leaves the
manifold
and then replacing it with 10mm would work better or would the couple or
three
inches of 8mm still create problems ( if at all) . I had thought all were
done
in 10mm and it was only after he left ( thinking they were all 10mm as I
was)
that I had a closer look and noticed the difference so lifted a couple of
boards
over the manifold and checked what was what .

I don't know why it was done that way ...can you not get 10mm manifolds ?


Stuart

With a condensing boiler, balancing the rads and boiler to have a wide
flow/return temperature differential means smaller bore pipes can be used.
If 8mm was fine before it will be more than fine now.

Your fitter is probably a plumber who are good at drains.

Not sure what you mean by that last remark..disregarding the bad
grammar...lol.......the system was fitted years ago and has nothing to do with
the guy who was out today .

On Fri, 15 Dec 2006 23:35:56 GMT, "Peter Andrews"
wrote:


"Stuart" wrote in message
.. .
Four of my 7 rads are done in 8mm microbore from a manifold in my hall and
the
other 3 rads are fed by 10mm tee'd in to the 22mm before the manifold . As
I am
getting a replacement condensing combi boiler and the fitter said 10mm was
preferable to 8 I wondered if cutting the 8mm just after it leaves the
manifold
and then replacing it with 10mm would work better or would the couple or
three
inches of 8mm still create problems ( if at all) . I had thought all were
done
in 10mm and it was only after he left ( thinking they were all 10mm as I
was)
that I had a closer look and noticed the difference so lifted a couple of
boards
over the manifold and checked what was what .

I don't know why it was done that way ...can you not get 10mm manifolds ?


Stuart



Do your 8mm rads have difficulty maintaining the required temperature? If
not then don't do anything.

Also make sure that your system is properly balanced and the rads are
actually large enough for the room, however if you do decide to change to
10mm then all the connection needs to be enlarged to 10mm.

Peter


The present rads work fine other than they are old and really need replacing
with modern ones It's a very old Kingfisher CF60 and a Primatic cylinder setup
....I'll leave it as it is and see how it works ...if necessary the 8mm can be
changed to 10mm later.

Doctor Drivel wrote:

"Stuart" wrote in message
...
Four of my 7 rads are done in 8mm microbore from a manifold in my hall and
the
other 3 rads are fed by 10mm tee'd in to the 22mm before the manifold . As
I am
getting a replacement condensing combi boiler and the fitter said 10mm was
preferable to 8 I wondered if cutting the 8mm just after it leaves the
manifold
and then replacing it with 10mm would work better or would the couple or
three
inches of 8mm still create problems ( if at all) . I had thought all were
done
in 10mm and it was only after he left ( thinking they were all 10mm as I
was)
that I had a closer look and noticed the difference so lifted a couple of
boards
over the manifold and checked what was what .

I don't know why it was done that way ...can you not get 10mm manifolds ?

With a condensing boiler, balancing the rads and boiler to have a wide
flow/return temperature differential means smaller bore pipes can be used.
If 8mm was fine before it will be more than fine now.

There is a small, but significant energy gain on a condenser, by keeping
the temperature difference small.

Stuart wrote:
On Fri, 15 Dec 2006 23:35:56 GMT, "Peter Andrews"
wrote:
"Stuart" wrote in message
.. .

Four of my 7 rads are done in 8mm microbore from a manifold in my hall and
the
other 3 rads are fed by 10mm tee'd in to the 22mm before the manifold . As
I am
getting a replacement condensing combi boiler and the fitter said 10mm was
preferable to 8 I wondered if cutting the 8mm just after it leaves the
manifold
and then replacing it with 10mm would work better or would the couple or
three
inches of 8mm still create problems ( if at all) . I had thought all were
done
in 10mm and it was only after he left ( thinking they were all 10mm as I
was)
that I had a closer look and noticed the difference so lifted a couple of
boards
over the manifold and checked what was what .

I don't know why it was done that way ...can you not get 10mm manifolds ?

Do your 8mm rads have difficulty maintaining the required temperature? If
not then don't do anything.

Also make sure that your system is properly balanced and the rads are
actually large enough for the room, however if you do decide to change to
10mm then all the connection needs to be enlarged to 10mm.

The present rads work fine other than they are old and really need replacing
with modern ones

they work fine but need replacing?

It's a very old Kingfisher CF60 and a Primatic cylinder setup
...I'll leave it as it is and see how it works ...if necessary the 8mm can be
changed to 10mm later.

I doubt a corgi would fit your new boiler without bringing the rest of
the system up to modern spec

I'd look at replacing the manifolds before mucking about with bodges,
but its likely you wont need to change this aspect anyway.


NT

In article ,
Stuart wrote:
The present rads work fine other than they are old and really need
replacing with modern ones

Assuming they are decent quality ones and you've had inhibitor in the
system there's no reason rads should ever need replacing - unless you are
referring to looks.

--
*What hair colour do they put on the driver's license of a bald man? *

Dave Plowman London SW
To e-mail, change noise into sound.

"Ian Stirling" wrote in message
...
Doctor Drivel wrote:

With a condensing boiler, balancing the rads and boiler to have a wide
flow/return temperature differential means smaller bore pipes can be
used.
If 8mm was fine before it will be more than fine now.

There is a small, but significant energy gain on a condenser, by keeping
the temperature difference small.

That doesn't make sense. What temperature difference exactly? Not "wide
flow/return temperature differential" as correctly stated by DD. Perhaps
you mean keeping a low average flow temperature, in which case 8mm will
suffice perfectly but the radiator output will disappoint.

Jim A

On 15 Dec 2006 19:00:46 -0800, wrote:

Stuart wrote:
On Fri, 15 Dec 2006 23:35:56 GMT, "Peter Andrews"
wrote:
"Stuart" wrote in message
.. .

Four of my 7 rads are done in 8mm microbore from a manifold in my hall and
the
other 3 rads are fed by 10mm tee'd in to the 22mm before the manifold . As
I am
getting a replacement condensing combi boiler and the fitter said 10mm was
preferable to 8 I wondered if cutting the 8mm just after it leaves the
manifold
and then replacing it with 10mm would work better or would the couple or
three
inches of 8mm still create problems ( if at all) . I had thought all were
done
in 10mm and it was only after he left ( thinking they were all 10mm as I
was)
that I had a closer look and noticed the difference so lifted a couple of
boards
over the manifold and checked what was what .

I don't know why it was done that way ...can you not get 10mm manifolds ?

Do your 8mm rads have difficulty maintaining the required temperature? If
not then don't do anything.

Also make sure that your system is properly balanced and the rads are
actually large enough for the room, however if you do decide to change to
10mm then all the connection needs to be enlarged to 10mm.

The present rads work fine other than they are old and really need replacing
with modern ones

they work fine but need replacing?

Why is that causing you a problem . ?.... The rads are about 20+ years old so
are not as modern looking and a bit greyish and have been painted .

On Sat, 16 Dec 2006 09:59:46 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article ,
Stuart wrote:
The present rads work fine other than they are old and really need
replacing with modern ones

Assuming they are decent quality ones and you've had inhibitor in the
system there's no reason rads should ever need replacing - unless you are
referring to looks.

It was looks I was meaning .

On 15 Dec 2006 19:00:46 -0800, wrote:



I doubt a corgi would fit your new boiler without bringing the rest of
the system up to modern spec

Can you explain what you mean having regard to how I described the pesent setup
what I said in my OP.

I'd look at replacing the manifolds before mucking about with bodges,
but its likely you wont need to change this aspect anyway.


I'll leave it as it is and see how it works out .

Jim Alexander wrote:

"Ian Stirling" wrote in message
...
Doctor Drivel wrote:

With a condensing boiler, balancing the rads and boiler to have a wide
flow/return temperature differential means smaller bore pipes can be
used.
If 8mm was fine before it will be more than fine now.

There is a small, but significant energy gain on a condenser, by keeping
the temperature difference small.

That doesn't make sense. What temperature difference exactly? Not "wide
flow/return temperature differential" as correctly stated by DD. Perhaps
you mean keeping a low average flow temperature, in which case 8mm will
suffice perfectly but the radiator output will disappoint.

For a given balanced system, with a given pump, there will be a certain
flow.

The higher the flow, the lower the temperature difference between flow
and return.

Increasing the flow will therefore decrease the temperature of the flow
pipe, marginally, or perhaps not marginally increasing the efficiency of
the condenser, by allowing it to condense more water from the gas
exhaust.

Stuart wrote:
On 15 Dec 2006 19:00:46 -0800, wrote:
Stuart wrote:
On Fri, 15 Dec 2006 23:35:56 GMT, "Peter Andrews"
wrote:
"Stuart" wrote in message
.. .

The present rads work fine other than they are old and really need replacing
with modern ones

they work fine but need replacing?

Why is that causing you a problem . ?

Its not, theyre your rads not mine. I was just guessing it might not be
true, since such statements usually arent. And you seem to have
confirmed that.


.... The rads are about 20+ years old so
are not as modern looking and a bit greyish and have been painted .

Ah well, if theyve been painted you do need new ones.


NT

"Ian Stirling" wrote in message
...
Jim Alexander wrote:

"Ian Stirling" wrote in message
...
Doctor Drivel wrote:

With a condensing boiler, balancing the rads and boiler to have a wide
flow/return temperature differential means smaller bore pipes can be
used.
If 8mm was fine before it will be more than fine now.

There is a small, but significant energy gain on a condenser, by keeping
the temperature difference small.

That doesn't make sense. What temperature difference exactly? Not "wide
flow/return temperature differential" as correctly stated by DD.
Perhaps
you mean keeping a low average flow temperature, in which case 8mm will
suffice perfectly but the radiator output will disappoint.

For a given balanced system, with a given pump, there will be a certain
flow.

The higher the flow, the lower the temperature difference between flow
and return.

Increasing the flow will therefore decrease the temperature of the flow
pipe, marginally, or perhaps not marginally increasing the efficiency of
the condenser, by allowing it to condense more water from the gas
exhaust.

From the Mohammed el Fayed book of central heating that. For your low
temperature difference system you would need to set the boiler flow
temperature at a temperature others would achieve on the return with a wide
differential temperature setup (the norm). As I said, listen to DD on this
one.

Jim A

On 2006-12-16 15:06:19 +0000, Ian Stirling said:

Jim Alexander wrote:

"Ian Stirling" wrote in message
...
Doctor Drivel wrote:

With a condensing boiler, balancing the rads and boiler to have a wide
flow/return temperature differential means smaller bore pipes can be used.
If 8mm was fine before it will be more than fine now.

There is a small, but significant energy gain on a condenser, by keeping
the temperature difference small.

That doesn't make sense. What temperature difference exactly? Not
"wide flow/return temperature differential" as correctly stated by DD.
Perhaps you mean keeping a low average flow temperature, in which case
8mm will suffice perfectly but the radiator output will disappoint.

For a given balanced system, with a given pump, there will be a certain
flow.

The higher the flow, the lower the temperature difference between flow
and return.

Increasing the flow will therefore decrease the temperature of the flow
pipe, marginally, or perhaps not marginally increasing the efficiency of
the condenser, by allowing it to condense more water from the gas
exhaust.

That would assume that the boiler is not measuring flow and return
temperatures and adjusting burn rate
accordingly (modulating).

Condensing boiler efficiency is dependent much more on the return
temperature - not so much the flow.
In a design for a new system, the normal choices are 70 degree flow and
50 degree return and sufficient radiator capacity, using those
temperatures to meet the heat loss under conditions of -3 degrees
outside.
At higher outside temperatures, both temperatures can be lower than this.

This is an area where people become confused. On the face of it, a
larger temperature drop implies greater release of heat coupled with
the appeal of a lower return temperature and hence greater efficiency.
The flaw is in missing the point that if this is achieved by reducing
flow rate, there is less heat transfer anyway.

This is based on the simple formula of heat transfer being proportional
to temperature rise or fall multiplied by the mass of water and by a
constant.

Since the objective is to deliver an adequate amount of heat to
compensate for heat losses, a boiler should ideally control the pump
speed and the burn rate. However, most just control the burn rate by
a simple measure of temperatures and the pump runs on a constant
setting.

The main limitation is the maximum temperature drop that the heat
exchanger can sustain. This is a physical limit and is generally
around 12-15 degrees for a conventional boiler, 20-25 for a condensing
one.

On 16 Dec 2006 07:18:01 -0800, wrote:

Stuart wrote:
On 15 Dec 2006 19:00:46 -0800, wrote:
Stuart wrote:
On Fri, 15 Dec 2006 23:35:56 GMT, "Peter Andrews"
wrote:
"Stuart" wrote in message
.. .

The present rads work fine other than they are old and really need replacing
with modern ones

they work fine but need replacing?

Why is that causing you a problem . ?

Its not, theyre your rads not mine. I was just guessing it might not be
true, since such statements usually arent. And you seem to have
confirmed that.


I wasn't meaning they need replacing because there is something wrong with them
working .I was meaning they need ( in the widest use of that word) because they
don't look particularly good compared to a brand new shiny one .

On Sat, 16 Dec 2006 15:41:27 GMT, "Jim Alexander"
wrote:

As I said, listen to DD on this
one.

But to do that means removing him from my kill file


--

"Stuart" wrote in message
...
On Fri, 15 Dec 2006 23:20:28 -0000, "Doctor Drivel"
wrote:


"Stuart" wrote in message
. ..
Four of my 7 rads are done in 8mm microbore from a manifold in my hall
and
the
other 3 rads are fed by 10mm tee'd in to the 22mm before the manifold .
As
I am
getting a replacement condensing combi boiler and the fitter said 10mm
was
preferable to 8 I wondered if cutting the 8mm just after it leaves the
manifold
and then replacing it with 10mm would work better or would the couple or
three
inches of 8mm still create problems ( if at all) . I had thought all
were
done
in 10mm and it was only after he left ( thinking they were all 10mm as I
was)
that I had a closer look and noticed the difference so lifted a couple
of
boards
over the manifold and checked what was what .

I don't know why it was done that way ...can you not get 10mm manifolds
?


Stuart

With a condensing boiler, balancing the rads and boiler to have a wide
flow/return temperature differential means smaller bore pipes can be used.
If 8mm was fine before it will be more than fine now.

Your fitter is probably a plumber who are good at drains.

Not sure what you mean by that last remark..disregarding the bad
grammar..

Perfect grammar.

.lol.......the system was fitted years ago and has nothing to do with
the guy who was out today .

read again.

"Matt" wrote in message
...
On Sat, 16 Dec 2006 15:41:27 GMT, "Jim Alexander"
wrote:

As I said, listen to DD on this
one.

But to do that means removing him from my kill file

Lord Hall, please keep me in your kill file.

On Sat, 16 Dec 2006 23:55:59 -0000, "Doctor Drivel" wrote:




With a condensing boiler, balancing the rads and boiler to have a wide
flow/return temperature differential means smaller bore pipes can be used.
If 8mm was fine before it will be more than fine now.

Your fitter is probably a plumber who are good at drains.

Not sure what you mean by that last remark..disregarding the bad
grammar..

Perfect grammar.
What you said was "Your fitter is probably a plumber who are good at drains."


Well if you think that is perfect grammar maybe you should go back to college .





.lol.......the system was fitted years ago and has nothing to do with
the guy who was out today .

read again.

I have an I have no idea WTF you are talking about . Maybe you would care to
explain as I am not a mind reader.
..

"Stuart" wrote in message
...
On Sat, 16 Dec 2006 23:55:59 -0000, "Doctor Drivel"
wrote:




With a condensing boiler, balancing the rads and boiler to have a wide
flow/return temperature differential means smaller bore pipes can be
used.
If 8mm was fine before it will be more than fine now.

Your fitter is probably a plumber who are good at drains.

Not sure what you mean by that last remark..disregarding the bad
grammar..

Perfect grammar.
What you said was "Your fitter is probably a plumber who are good at
drains."


Well if you think that is perfect grammar maybe you should go back to
college .

That is totally and utterly perfect in every way.

I have an I have no idea WTF you are talking about .

They learn some grammar.

On Sun, 17 Dec 2006 12:24:34 -0000, "Doctor Drivel" wrote:


"Stuart" wrote in message
.. .
On Sat, 16 Dec 2006 23:55:59 -0000, "Doctor Drivel"
wrote:




With a condensing boiler, balancing the rads and boiler to have a wide
flow/return temperature differential means smaller bore pipes can be
used.
If 8mm was fine before it will be more than fine now.

Your fitter is probably a plumber who are good at drains.

Not sure what you mean by that last remark..disregarding the bad
grammar..

Perfect grammar.
What you said was "Your fitter is probably a plumber who are good at
drains."


Well if you think that is perfect grammar maybe you should go back to
college .

That is totally and utterly perfect in every way.

I have an I have no idea WTF you are talking about .

They learn some grammar.


" THEY learn some grammar" ?

Can I have some of what you are on please ?

"Stuart" wrote in message
...
On Sun, 17 Dec 2006 12:24:34 -0000, "Doctor Drivel"
wrote:


"Stuart" wrote in message
. ..
On Sat, 16 Dec 2006 23:55:59 -0000, "Doctor Drivel"
wrote:




With a condensing boiler, balancing the rads and boiler to have a wide
flow/return temperature differential means smaller bore pipes can be
used.
If 8mm was fine before it will be more than fine now.

Your fitter is probably a plumber who are good at drains.

Not sure what you mean by that last remark..disregarding the bad
grammar..

Perfect grammar.
What you said was "Your fitter is probably a plumber who are good at
drains."


Well if you think that is perfect grammar maybe you should go back to
college .

That is totally and utterly perfect in every way.

I have an I have no idea WTF you are talking about .

They learn some grammar.


" THEY learn some grammar" ?

That's what I said diddle I.

On Fri, 15 Dec 2006 22:11:11 +0000, Stuart wrote:

Four of my 7 rads are done in 8mm microbore from a manifold in my hall and the
other 3 rads are fed by 10mm tee'd in to the 22mm before the manifold . As I am
getting a replacement condensing combi boiler and the fitter said 10mm was
preferable to 8 I wondered if cutting the 8mm just after it leaves the manifold
and then replacing it with 10mm would work better or would the couple or three
inches of 8mm still create problems ( if at all) . I had thought all were done
in 10mm and it was only after he left ( thinking they were all 10mm as I was)
that I had a closer look and noticed the difference so lifted a couple of boards
over the manifold and checked what was what .

I don't know why it was done that way ...can you not get 10mm manifolds ?


Looking at the other posts it would appear that you have been introduced
to a range of replies.

Provided:
1) The existing system, when it worked, worked well enough to heat all
the radiators enough to heat the house properly.
&
2) There is absolutely no hint of sludge or scale in the existing circuit

then keeping the existing 8mm and 10mm pipes will be a good choice.

Obviously 8mm pipework is even more prone blockage than larger sizes but
isn't automatically a problem.

The existing system worked on the basis that the difference between the
flow and return temperatures would be somewhat more than a system using
larger pipes. This is all to the good when using a condensing boiler.




--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

On Sun, 17 Dec 2006 19:15:29 +0000 (UTC), Ed Sirett
wrote:

On Fri, 15 Dec 2006 22:11:11 +0000, Stuart wrote:

Four of my 7 rads are done in 8mm microbore from a manifold in my hall and the
other 3 rads are fed by 10mm tee'd in to the 22mm before the manifold . As I am
getting a replacement condensing combi boiler and the fitter said 10mm was
preferable to 8 I wondered if cutting the 8mm just after it leaves the manifold
and then replacing it with 10mm would work better or would the couple or three
inches of 8mm still create problems ( if at all) . I had thought all were done
in 10mm and it was only after he left ( thinking they were all 10mm as I was)
that I had a closer look and noticed the difference so lifted a couple of boards
over the manifold and checked what was what .

I don't know why it was done that way ...can you not get 10mm manifolds ?


Looking at the other posts it would appear that you have been introduced
to a range of replies.

Provided:
1) The existing system, when it worked, worked well enough to heat all
the radiators enough to heat the house properly.
&
2) There is absolutely no hint of sludge or scale in the existing circuit

then keeping the existing 8mm and 10mm pipes will be a good choice.

Obviously 8mm pipework is even more prone blockage than larger sizes but
isn't automatically a problem.

The existing system worked on the basis that the difference between the
flow and return temperatures would be somewhat more than a system using
larger pipes. This is all to the good when using a condensing boiler.


Thx Ed ...I'll get the new boiler fitted and see how it goes ..

Stuart .

"Ed Sirett" wrote in message
...
On Fri, 15 Dec 2006 22:11:11 +0000, Stuart wrote:

Four of my 7 rads are done in 8mm microbore from a manifold in my hall
and the
other 3 rads are fed by 10mm tee'd in to the 22mm before the manifold .
As I am
getting a replacement condensing combi boiler and the fitter said 10mm
was
preferable to 8 I wondered if cutting the 8mm just after it leaves the
manifold
and then replacing it with 10mm would work better or would the couple or
three
inches of 8mm still create problems ( if at all) . I had thought all
were done
in 10mm and it was only after he left ( thinking they were all 10mm as I
was)
that I had a closer look and noticed the difference so lifted a couple of
boards
over the manifold and checked what was what .

I don't know why it was done that way ...can you not get 10mm manifolds ?


Looking at the other posts it would appear that you have been introduced
to a range of replies.

Provided:
1) The existing system, when it worked, worked well enough to heat all
the radiators enough to heat the house properly.
&
2) There is absolutely no hint of sludge or scale in the existing circuit

then keeping the existing 8mm and 10mm pipes will be a good choice.

Obviously 8mm pipework is even more prone blockage than larger sizes but
isn't automatically a problem.

The existing system worked on the basis
that the difference between the
flow and return temperatures would be
somewhat more than a system using
larger pipes.

It didn't. It worked on a temp differential of 10C or 11C like any other
system at the time, no matter how big the pipes.

Dave Plowman (News) wrote:
In article ,
Stuart wrote:
The present rads work fine other than they are old and really need
replacing with modern ones

Assuming they are decent quality ones and you've had inhibitor in the
system ...

Which there shouldn't be on a primatic system and this means the pipes
often do clog up more than other systems.

On Mon, 18 Dec 2006 09:57:42 +0000, Doctor Drivel wrote:

"Ed Sirett" wrote in message
...
On Fri, 15 Dec 2006 22:11:11 +0000, Stuart wrote:

Four of my 7 rads are done in 8mm microbore from a manifold in my hall
and the
other 3 rads are fed by 10mm tee'd in to the 22mm before the manifold .
As I am
getting a replacement condensing combi boiler and the fitter said 10mm
was
preferable to 8 I wondered if cutting the 8mm just after it leaves the
manifold
and then replacing it with 10mm would work better or would the couple or
three
inches of 8mm still create problems ( if at all) . I had thought all
were done
in 10mm and it was only after he left ( thinking they were all 10mm as I
was)
that I had a closer look and noticed the difference so lifted a couple of
boards
over the manifold and checked what was what .

I don't know why it was done that way ...can you not get 10mm manifolds ?


Looking at the other posts it would appear that you have been introduced
to a range of replies.

Provided:
1) The existing system, when it worked, worked well enough to heat all
the radiators enough to heat the house properly.
&
2) There is absolutely no hint of sludge or scale in the existing circuit

then keeping the existing 8mm and 10mm pipes will be a good choice.

Obviously 8mm pipework is even more prone blockage than larger sizes but
isn't automatically a problem.

The existing system worked on the basis
that the difference between the
flow and return temperatures would be
somewhat more than a system using
larger pipes.

It didn't. It worked on a temp differential of 10C or 11C like any other
system at the time, no matter how big the pipes.

Inasmuch any domestic system is 'designed' rather than estimated (usually
quite well) then microbore systems have a larger difference between flow
and return temperatures than systems using 22& 15mm.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

"Ed Sirett" wrote in message
...
On Mon, 18 Dec 2006 09:57:42 +0000, Doctor Drivel wrote:

"Ed Sirett" wrote in message
...
On Fri, 15 Dec 2006 22:11:11 +0000, Stuart wrote:

Four of my 7 rads are done in 8mm microbore from a manifold in my hall
and the
other 3 rads are fed by 10mm tee'd in to the 22mm before the manifold .
As I am
getting a replacement condensing combi boiler and the fitter said 10mm
was
preferable to 8 I wondered if cutting the 8mm just after it leaves the
manifold
and then replacing it with 10mm would work better or would the couple
or
three
inches of 8mm still create problems ( if at all) . I had thought all
were done
in 10mm and it was only after he left ( thinking they were all 10mm as
I
was)
that I had a closer look and noticed the difference so lifted a couple
of
boards
over the manifold and checked what was what .

I don't know why it was done that way ...can you not get 10mm manifolds
?


Looking at the other posts it would appear that you have been introduced
to a range of replies.

Provided:
1) The existing system, when it worked, worked well enough to heat all
the radiators enough to heat the house properly.
&
2) There is absolutely no hint of sludge or scale in the existing
circuit

then keeping the existing 8mm and 10mm pipes will be a good choice.

Obviously 8mm pipework is even more prone blockage than larger sizes but
isn't automatically a problem.

The existing system worked on the basis
that the difference between the
flow and return temperatures would be
somewhat more than a system using
larger pipes.

It didn't. It worked on a temp differential of 10C or 11C like any other
system at the time, no matter how big the pipes.

Inasmuch any domestic system is 'designed' rather than estimated (usually
quite well) then microbore systems have a larger difference between flow
and return temperatures than systems using 22& 15mm.

Only if it was not sized right.

On Mon, 18 Dec 2006 22:16:20 +0000 (UTC), Ed Sirett
wrote:

On Mon, 18 Dec 2006 09:57:42 +0000, Doctor Drivel wrote:

"Ed Sirett" wrote in message
...
On Fri, 15 Dec 2006 22:11:11 +0000, Stuart wrote:

Four of my 7 rads are done in 8mm microbore from a manifold in my hall
and the
other 3 rads are fed by 10mm tee'd in to the 22mm before the manifold .
As I am
getting a replacement condensing combi boiler and the fitter said 10mm
was
preferable to 8 I wondered if cutting the 8mm just after it leaves the
manifold
and then replacing it with 10mm would work better or would the couple or
three
inches of 8mm still create problems ( if at all) . I had thought all
were done
in 10mm and it was only after he left ( thinking they were all 10mm as I
was)
that I had a closer look and noticed the difference so lifted a couple of
boards
over the manifold and checked what was what .

I don't know why it was done that way ...can you not get 10mm manifolds ?


Looking at the other posts it would appear that you have been introduced
to a range of replies.

Provided:
1) The existing system, when it worked, worked well enough to heat all
the radiators enough to heat the house properly.
&
2) There is absolutely no hint of sludge or scale in the existing circuit

then keeping the existing 8mm and 10mm pipes will be a good choice.

Obviously 8mm pipework is even more prone blockage than larger sizes but
isn't automatically a problem.

The existing system worked on the basis
that the difference between the
flow and return temperatures would be
somewhat more than a system using
larger pipes.

It didn't. It worked on a temp differential of 10C or 11C like any other
system at the time, no matter how big the pipes.

Inasmuch any domestic system is 'designed' rather than estimated (usually
quite well) then microbore systems have a larger difference between flow
and return temperatures than systems using 22& 15mm.

I'm a bit confused by references to different sized pipes here . Do you mean the
two pipes to and from each rad are different sizes( I'm presuming you don't mean
that) or,as in my case different rads have different sized pipes( 8mm or 10mm)
connecting them to the 22 mm F+R ( either from tees or from a manifold) ?