Problem changing 1-pipe CH system to 2-pipe system
 

Hi.



I'm trying to change my central heating pipework from an old (I guess 30-ish
years) one-pipe system to a two-pipe system. A new boiler in the kitchen
will eventually replace the old back boiler, but for the time being I want
to run the new pipework with the old boiler/pump.



The old system had a total of about 4m of 22mm pipe with 8mm pipes T-eed off
and some 8mm manifolds. The new pipes consist of 2 x 11m 'spines' of 22mm,
plus about 20m of 15mm T-ees. There are new lockshield valves and TRVs
except for the hall rad which has 2 lockshield valves. My new flow and
return pipes are connected to the pump.



The problem is it doesn't work! I've got all valves fully open - the hall
rad heats up a bit but the other rads hardly get any hot water.



My only theory is that the old pump (which is a Grundfos UPS Selectric
15-50, on setting '3') can't cope with the extra resistance of the new
pipework. Alternatively, and highly possible, is that I'm doing something
very stupid.



Suggestions on how to diagnose/fix this will be gratefully received.



Steve

Problem changing 1-pipe CH system to 2-pipe system
 

On Fri, 14 Nov 2008 23:13:01 +0000, Steve wrote:

I'm trying to change my central heating pipework from an old (I guess
30-ish years) one-pipe system to a two-pipe system. A new boiler in the
kitchen will eventually replace the old back boiler, but for the time
being I want to run the new pipework with the old boiler/pump.



The old system had a total of about 4m of 22mm pipe with 8mm pipes T-eed
off and some 8mm manifolds.

This sounds very, very unlike a one-pipe system. Are you saying it was
like this (ASCII art pre)

--------
| |
| |===== . . . . . . .
| | . (rest of system omitted)
| boiler | 22mm .
| |=====+=+==========.
| | | |
-------- | | 8mm
| |
-------
| rad |
-------

rather than this:


--------
| |
| |=======+==. . . . .
| | | . (rest of system omitted)
| boiler | | 22mm .
| |=====+=|==========.
| | | |
-------- | | 8mm
| |
-------
| rad |
-------

??


Suggestions on how to diagnose/fix this will be gratefully received.

Need to be clear on exactly what it is to start with.



--
YAPH http://yaph.co.uk

Bob the builder / it'll cost 'yer
Bob the builder / loadsa dosh

Problem changing 1-pipe CH system to 2-pipe system
 

In an earlier contribution to this discussion,
Steve wrote:

Hi.



I'm trying to change my central heating pipework from an old (I guess
30-ish years) one-pipe system to a two-pipe system. A new boiler in
the kitchen will eventually replace the old back boiler, but for the
time being I want to run the new pipework with the old boiler/pump.



The old system had a total of about 4m of 22mm pipe with 8mm pipes
T-eed off and some 8mm manifolds. The new pipes consist of 2 x 11m
'spines' of 22mm, plus about 20m of 15mm T-ees. There are new
lockshield valves and TRVs except for the hall rad which has 2
lockshield valves. My new flow and return pipes are connected to the
pump.


The problem is it doesn't work! I've got all valves fully open - the
hall rad heats up a bit but the other rads hardly get any hot water.



My only theory is that the old pump (which is a Grundfos UPS Selectric
15-50, on setting '3') can't cope with the extra resistance of the new
pipework. Alternatively, and highly possible, is that I'm doing
something very stupid.



Suggestions on how to diagnose/fix this will be gratefully received.



Steve


Please explain what you mean by "My new flow and return pipes are connected
to the pump".

It that is literally true, the pump will simply circulate water round the
rads without it ever going through the boiler! The sequence should be: Hot
water comes out of the boiler, through the pump into the flow pipe, through
the various rads - connected in parallel - to the return pipe and thence
back to the boiler.

Can you draw a diagram of your system and put it on-line, and post a link
here, so that we can get a better idea of what it looks like? [Hand-drawn
and scanned will do if you can't easily produce a diagram on your computer].
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

Problem changing 1-pipe CH system to 2-pipe system
 

"YAPH" wrote in message
...
On Fri, 14 Nov 2008 23:13:01 +0000, Steve wrote:

I'm trying to change my central heating pipework from an old (I guess
30-ish years) one-pipe system to a two-pipe system. A new boiler in the
kitchen will eventually replace the old back boiler, but for the time
being I want to run the new pipework with the old boiler/pump.



The old system had a total of about 4m of 22mm pipe with 8mm pipes T-eed
off and some 8mm manifolds.

This sounds very, very unlike a one-pipe system. Are you saying it was
like this (ASCII art pre)

--------
| |
| |===== . . . . . . .
| | . (rest of system omitted)
| boiler | 22mm .
| |=====+=+==========.
| | | |
-------- | | 8mm
| |
-------
| rad |
-------

rather than this:


--------
| |
| |=======+==. . . . .
| | | . (rest of system omitted)
| boiler | | 22mm .
| |=====+=|==========.
| | | |
-------- | | 8mm
| |
-------
| rad |
-------

??


Suggestions on how to diagnose/fix this will be gratefully received.

Need to be clear on exactly what it is to start with.


I described it badly - the old system matches your first diagram, the supply
and return to each rad are from adjacent T-ees on the same section of 22m
pipe.

My new layout matches your second diagram.

Cheers

Steve

Problem changing 1-pipe CH system to 2-pipe system
 

"Roger Mills" wrote in message
...
In an earlier contribution to this discussion,
Steve wrote:

Hi.
I'm trying to change my central heating pipework from an old (I guess
Please explain what you mean by "My new flow and return pipes are
connected to the pump".

It that is literally true, the pump will simply circulate water round the
rads without it ever going through the boiler! The sequence should be: Hot
water comes out of the boiler, through the pump into the flow pipe,
through the various rads - connected in parallel - to the return pipe and
thence back to the boiler.

Of course, you are right. My description was wrong and the new layout is as
you describe: boiler - pump - supply-pipe - inlets on radiator;
outlets on radiator - return pipe - boiler

Can you draw a diagram of your system and put it on-line, and post a link
here, so that we can get a better idea of what it looks like? [Hand-drawn
and scanned will do if you can't easily produce a diagram on your
computer].
--
The diagrams in the previous post from YAPH correctly shows my before and
after layouts. However I'll see if I can put more specific diagrams
on-line. (I can draw diagrams in Word or Paintbox easily, but I'm shaky
about putting them online, so this could take a while!).

Cheers

Steve

Problem changing 1-pipe CH system to 2-pipe system
 

"Steve" wrote in message
...


The problem is it doesn't work! I've got all valves fully open - the hall
rad heats up a bit but the other rads hardly get any hot water.


Don't you need to partly close the lockshield valves on the radiators that
heat so as to force the water through the others?


See http://www.diyfaq.org.uk/plumbing/rad-balance.html

Other thoughts are blockage and air lock!


--
Michael Chare

Problem changing 1-pipe CH system to 2-pipe system
 

Steve wrote:

My only theory is that the old pump (which is a Grundfos UPS Selectric
15-50, on setting '3') can't cope with the extra resistance of the new
pipework. Alternatively, and highly possible, is that I'm doing something
very stupid.

If the pump is as old as the system it could be struggling to do
anything. Or you just have a real awkward air-lock somewhere. Even in
the pump it's self ?
IIRC old pumps didn't have any method of bleeding apart from loosening
the fixings. Might be worth a go.

Pete

Problem changing 1-pipe CH system to 2-pipe system
 

"Michael Chare" wrote in message
...
"Steve" wrote in message
...


The problem is it doesn't work! I've got all valves fully open - the
hall rad heats up a bit but the other rads hardly get any hot water.


Don't you need to partly close the lockshield valves on the radiators that
heat so as to force the water through the others?


See http://www.diyfaq.org.uk/plumbing/rad-balance.html

Other thoughts are blockage and air lock!

Thanks Michael. I'll try it - but in the old system, all rads got pretty
hot. With my new arrangement the hall radiator just gets warm (not hot) and
the others are stone cold. So its doesn't sound like a balancing thing.
Cheers
Steve

Problem changing 1-pipe CH system to 2-pipe system
 

"www.GymRatZ.co.uk" wrote in
message ...
Steve wrote:

My only theory is that the old pump (which is a Grundfos UPS Selectric
15-50, on setting '3') can't cope with the extra resistance of the new
pipework. Alternatively, and highly possible, is that I'm doing
something
very stupid.

If the pump is as old as the system it could be struggling to do
anything. Or you just have a real awkward air-lock somewhere. Even in
the pump it's self ?
IIRC old pumps didn't have any method of bleeding apart from loosening
the fixings. Might be worth a go.

Pete
Thanks Pete. The pump appears to be relatively modern (currently available
on sale) so the original one was probably replaced a few years ago (I've
been in the bungalow about 3 years). Yes - air lock or blockage sounds
possible. I'll probably have to drain/refill.
Cheers
Steve

Problem changing 1-pipe CH system to 2-pipe system
 

"Steve" wrote in message
...
Hi.



I'm trying to change my central heating pipework from an old (I guess
30-ish years) one-pipe system to a two-pipe system. A new boiler in the
kitchen
..
clipped
..
For those interested, here are diagrams of the old and new systems

http://s409.photobucket.com/albums/p...ent=newsys.jpg
http://s409.photobucket.com/albums/p...ent=oldsys.jpg
Cheers
Steve

Problem changing 1-pipe CH system to 2-pipe system
 

In an earlier contribution to this discussion,
Steve wrote:

"Steve" wrote in message
...
Hi.



I'm trying to change my central heating pipework from an old (I guess
30-ish years) one-pipe system to a two-pipe system. A new boiler in
the kitchen
.
clipped
.
For those interested, here are diagrams of the old and new systems

http://s409.photobucket.com/albums/p...ent=newsys.jpg
http://s409.photobucket.com/albums/p...ent=oldsys.jpg
Cheers
Steve

The new system *should* work ok. Your diagram doesn't show how it gets
filled and vented though. Presumably there is a small fill and expansion
tank in the attic? Is there water in the tank - i.e. ball valve not seized
up? Are there any taps in the fill pipe between tank and system and, if so,
are they open?

Your problem sounds to me like an air lock. You need to make sure that
*both* the flow and return pipe to each rad are full of water. Any trapped
air could prevent hot water from flowing through the rad. So you need to do
a thorough bleeding - just waiting for water rather than air to come out of
the bleed screw may not be enough. At each rad, bleed each pipe in turn - by
bleeding with one valve closed and then swapping to the other valve. In each
case bleed at least a litre of water out of each side - that should make
sure that there's no air in the pipes.

Have you already tried turning all rads except one (each in turn) off, and
running the pump at its highest speed? That will *sometimes* shift trapped
air, and get things moving.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

Problem changing 1-pipe CH system to 2-pipe system
 

On Sat, 15 Nov 2008 00:57:24 +0000, Steve wrote:

I described it badly - the old system matches your first diagram, the
supply and return to each rad are from adjacent T-ees on the same
section of 22m pipe.

My new layout matches your second diagram.

Then you did indeed have a 1-pipe system. I've never seen one implemented
in 22mm + 8/10mm microbore as you describe. Did it ever work? It sounds
like incompetence rather than design :-)

(I note you show the pipes to the rads as 15mm on the diagram you posted
but you said they were 8mm in your original post. Also you show a break in
the loop of 22mm so the flow and return legs are separate: this would have
resulted in the entire system flow going through the middle-right-most rad
in your pictu I take it that wasn't how it was.)

Your new system as per the diagram you posted is correct. As others have
said, assuming the pump is running and there aren't other blockages in the
system (e.g. a Y-line filter?) it could be air-locked. How far is the
heat getting along the pipes. And are you sure? - double check! - that the
pipework is actually connected up as you think it is.


--
YAPH http://yaph.co.uk

Never believe anyone who claims to be a liar

Problem changing 1-pipe CH system to 2-pipe system
 

"Roger Mills" wrote in message
...
In an earlier contribution to this discussion,
Steve wrote:

"Steve" wrote in message
...
Hi.



I'm trying to change my central heating pipework from an old (I guess
30-ish years) one-pipe system to a two-pipe system. A new boiler in
the kitchen
.
clipped
..
..
Your problem sounds to me like an air lock. You need to make sure that
*both* the flow and return pipe to each rad are full of water. Any trapped
air could prevent hot water from flowing through the rad. So you need to
do a thorough bleeding - just waiting for water rather than air to come
out of the bleed screw may not be enough. At each rad, bleed each pipe in
turn - by bleeding with one valve closed and then swapping to the other
valve. In each case bleed at least a litre of water out of each side -
that should make sure that there's no air in the pipes.

Have you already tried turning all rads except one (each in turn) off, and
running the pump at its highest speed? That will *sometimes* shift trapped
air, and get things moving.
--
Cheers,
Roger
______

Many thank Roger. Problem cured! I closed all rads except one, put pump on
max and thoroughly bled the rad with alternate valves closed. as suggested.
The first rad I tried solved it.
I had of course already bled the system (yesterday) but obviously didn't do
it thoroughly enough.

Many thanks again

Steve

Problem changing 1-pipe CH system to 2-pipe system
 

"Roger Mills" wrote in message
...
In an earlier contribution to this discussion,
Steve wrote:

"Steve" wrote in message
...
Hi.



I'm trying to change my central heating pipework from an old (I guess
30-ish years) one-pipe system to a two-pipe system. A new boiler in
the kitchen
.
clipped
..
..
.. The new system *should* work ok. Your diagram doesn't show how it gets
filled and vented though. Presumably there is a small fill and expansion
tank in the attic? Is there water in the tank - i.e. ball valve not seized
up? Are there any taps in the fill pipe between tank and system and, if
so, are they open?

Your problem sounds to me like an air lock. You need to make sure that
*both* the flow and return pipe to each rad are full of water. Any trapped
air could prevent hot water from flowing through the rad. So you need to
do a thorough bleeding - just waiting for water rather than air to come
out of the bleed screw may not be enough. At each rad, bleed each pipe in
turn - by bleeding with one valve closed and then swapping to the other
valve. In each case bleed at least a litre of water out of each side -
that should make sure that there's no air in the pipes.

Have you already tried turning all rads except one (each in turn) off, and
running the pump at its highest speed? That will *sometimes* shift trapped
air, and get things moving.
--
Cheers,
Roger

Problem solved! As suggested, with pump on max I closed all rads but one
and bled it with one valve at a time closed, Problem fixed after first
radiator. Must have been an airlock.

Many many thanks

Steve