Dear UK-DIY,

I am in the process of replacing my very old gravity fed CH and HW
system. To simplify the job and because of the size of the property, I
have opted to convert to a simple vented fully pumped "Y" plan system
for CH and HW.

I have a semi detached property with just seven radiators and one
bathroom (although adding an on suite shower room at a later date is
not out of the question). The existing setup has more than enough head
to power the one shower without the need for a pump.

I have taken a segmented approach, replacing the radiators last year
and the rest of the system (hot water tank, pipe work conversion to
fully pumped system and new boiler) this year. So far I have replaced
the old copper cylinder with a new Part-L compliant one and am running
all hot water from the immersion heater until the indirect and boiler
installation is completed.

I have installed all the pipe work for the indirect system, including
new pump and three port mid position valve; however I now face a
challenge. In plumbing terms, the house is split into two parts, the
one hundred year old main building, and the newer extension to the
rear. The old part has four radiators connected to a 22mm single pipe
system; the extension has three radiators which are plumbed using a
15mm two pipe flow and return system.

I am planning on having plumber install a Worcester Greenstar 15Ri to
this new setup, but from what I understand condensing boilers rely on
a significant temperature differential between flow and return in
order to modulate properly and that single pipe systems often do not
provide enough of a temperature drop between flow and return.

Because of the age of the house, converting the four radiators in the
two bed rooms and two living areas on the existing single pipe system
to a two pipe flow and return version would be a major challenge
requiring a significant amount of additional work.

I appreciate that the problem with single pipe systems is their lack
of efficiency, however since replacing all the radiators, I used the
heating with just new radiators during the winter and I found that the
radiators on the single pipe section got hot at the same rate and
achieved the same operating temperature as those on the two pipe
system - hence my reluctance to make any changes!

I guess my question is, In order to meet the any new regs and get best
efficiency from my new boiler, am I going to be forced to add another
pipe to the single pipe system to convert the whole thing to a two
pipe system?

Many thanks in advance!

James

On Tue, 24 Jul 2007 02:34:38 -0700, James wrote:

Dear UK-DIY,

I am in the process of replacing my very old gravity fed CH and HW
system. To simplify the job and because of the size of the property, I
have opted to convert to a simple vented fully pumped "Y" plan system
for CH and HW.

I have a semi detached property with just seven radiators and one
bathroom (although adding an on suite shower room at a later date is
not out of the question). The existing setup has more than enough head
to power the one shower without the need for a pump.

I have taken a segmented approach, replacing the radiators last year
and the rest of the system (hot water tank, pipe work conversion to
fully pumped system and new boiler) this year. So far I have replaced
the old copper cylinder with a new Part-L compliant one and am running
all hot water from the immersion heater until the indirect and boiler
installation is completed.

I have installed all the pipe work for the indirect system, including
new pump and three port mid position valve; however I now face a
challenge. In plumbing terms, the house is split into two parts, the
one hundred year old main building, and the newer extension to the
rear. The old part has four radiators connected to a 22mm single pipe
system; the extension has three radiators which are plumbed using a
15mm two pipe flow and return system.

I am planning on having plumber install a Worcester Greenstar 15Ri to
this new setup, but from what I understand condensing boilers rely on
a significant temperature differential between flow and return in
order to modulate properly and that single pipe systems often do not
provide enough of a temperature drop between flow and return.

Because of the age of the house, converting the four radiators in the
two bed rooms and two living areas on the existing single pipe system
to a two pipe flow and return version would be a major challenge
requiring a significant amount of additional work.

I appreciate that the problem with single pipe systems is their lack
of efficiency, however since replacing all the radiators, I used the
heating with just new radiators during the winter and I found that the
radiators on the single pipe section got hot at the same rate and
achieved the same operating temperature as those on the two pipe
system - hence my reluctance to make any changes!

I guess my question is, In order to meet the any new regs and get best
efficiency from my new boiler, am I going to be forced to add another
pipe to the single pipe system to convert the whole thing to a two
pipe system?

The continued use of the single pipe system is not ideal.
However with care about the balancing, thermostatic valve settings and
location of the thermostat it should be possible to make it work, albeit
with some control limitations.










--
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:

The continued use of the single pipe system is not ideal.
However with care about the balancing, thermostatic valve settings and
location of the thermostat it should be possible to make it work, albeit
with some control limitations.

Would you be able to meet the requirement for TRVs on each rad though?

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Jul 25, 1:07 am, John Rumm wrote:
Ed Sirett wrote:
The continued use of the single pipe system is not ideal.
However with care about the balancing, thermostatic valve settings and
location of the thermostat it should be possible to make it work, albeit
with some control limitations.

Would you be able to meet the requirement for TRVs on each rad though?

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Ed, John,

Thanks for your comments, all very much appreciated!

When I replaced the radiators last year, I took the opportunity to put
TRV's on all apart from the two in the main living area (where I
intend to locate the thermostat when its installed). I balanced the
system as best I could and set the TRV's according to the use of each
room.

What I found was that even on the single pipe system all the radiators
worked well (really quite surprisingly well infact - given what I had
heard about single pipe configurations) and all the TRV's seemed to be
working just fine.

Whilst I fully understand its not ideal, the work required to put in
the second pipe is a major job to do properly, I have very old walls
and plaster which i'm really not keen to chase out in order to put in
new pipework (i'm not looking to create a bigger problem than I
already have!)

Ed, when you mention control limitations - what are you thinking ? are
you considering the inability to implement any zoning ?

Thanks again

James.

In article .com,
James writes:
Ed, John,

Thanks for your comments, all very much appreciated!

When I replaced the radiators last year, I took the opportunity to put
TRV's on all apart from the two in the main living area (where I
intend to locate the thermostat when its installed). I balanced the
system as best I could and set the TRV's according to the use of each
room.

What I found was that even on the single pipe system all the radiators
worked well (really quite surprisingly well infact - given what I had
heard about single pipe configurations) and all the TRV's seemed to be
working just fine.

What you heard about single pipe systems was probably wrong.
Mostly it is based on a lack of understanding of how they
work because they aren't installed or taught today. There
is nothing fundamentally wrong with them. They are more
difficult to calculate and setup in the first place, but
yours was probably installed back in the days when heating
engineers did still know how to do that.

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

On Wed, 25 Jul 2007 01:24:28 -0700, James wrote:

On Jul 25, 1:07 am, John Rumm wrote:
Ed Sirett wrote:
The continued use of the single pipe system is not ideal.
However with care about the balancing, thermostatic valve settings and
location of the thermostat it should be possible to make it work, albeit
with some control limitations.

Would you be able to meet the requirement for TRVs on each rad though?

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Ed, John,

Thanks for your comments, all very much appreciated!

When I replaced the radiators last year, I took the opportunity to put
TRV's on all apart from the two in the main living area (where I
intend to locate the thermostat when its installed). I balanced the
system as best I could and set the TRV's according to the use of each
room.

What I found was that even on the single pipe system all the radiators
worked well (really quite surprisingly well infact - given what I had
heard about single pipe configurations) and all the TRV's seemed to be
working just fine.

Whilst I fully understand its not ideal, the work required to put in
the second pipe is a major job to do properly, I have very old walls
and plaster which i'm really not keen to chase out in order to put in
new pipework (i'm not looking to create a bigger problem than I
already have!)

Ed, when you mention control limitations - what are you thinking ? are
you considering the inability to implement any zoning ?

Not so much that. Of course the single pipe run cannot be subdivided but
the TRVs will make it more controlled.

I was thinking that there may be issues with balancing the single pipe
against the two pipe stuff. It all depends on the layout.

You can think of the single pipe part as a large single big radiator
(which happens to have parts in several rooms). It has a larger
flow/return temp differential which is great with a condensing boiler.

Does the living room have any additional sources of heat? (fireplace or
large southerly facing window?) In which case it may not be the best place
for the over all heating thermostat.

--
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

On Jul 25, 7:42 pm, Ed Sirett wrote:
On Wed, 25 Jul 2007 01:24:28 -0700, James wrote:
On Jul 25, 1:07 am, John Rumm wrote:
Ed Sirett wrote:
The continued use of the single pipe system is not ideal.
However with care about the balancing, thermostatic valve settings and
location of the thermostat it should be possible to make it work, albeit
with some control limitations.

Would you be able to meet the requirement for TRVs on each rad though?

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Ed, John,

Thanks for your comments, all very much appreciated!

When I replaced the radiators last year, I took the opportunity to put
TRV's on all apart from the two in the main living area (where I
intend to locate the thermostat when its installed). I balanced the
system as best I could and set the TRV's according to the use of each
room.

What I found was that even on the single pipe system all the radiators
worked well (really quite surprisingly well infact - given what I had
heard about single pipe configurations) and all the TRV's seemed to be
working just fine.

Whilst I fully understand its not ideal, the work required to put in
the second pipe is a major job to do properly, I have very old walls
and plaster which i'm really not keen to chase out in order to put in
new pipework (i'm not looking to create a bigger problem than I
already have!)

Ed, when you mention control limitations - what are you thinking ? are
you considering the inability to implement any zoning ?

Not so much that. Of course the single pipe run cannot be subdivided but
the TRVs will make it more controlled.

I was thinking that there may be issues with balancing the single pipe
against the two pipe stuff. It all depends on the layout.

You can think of the single pipe part as a large single big radiator
(which happens to have parts in several rooms). It has a larger
flow/return temp differential which is great with a condensing boiler.

Does the living room have any additional sources of heat? (fireplace or
large southerly facing window?) In which case it may not be the best place
for the over all heating thermostat.

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

Ed, Andrew,

Thanks again for the very useful information.

The living area has two radiators (neither of which have been fitted
with TRV's) and is quite a large open area. It has an open fireplace
which we use in the winter at one end.

I am planning on purchasing a wireless thermostat and timer (probably
the Honeywell CMT927) which has an optional table top stand to sit on
a bookcase or shelf. In this way, I can move the device around to find
the best location and then if necessary mount it permanently.

As a result of your advice, I have a much better understanding of the
single pipe system now and feel confident in bringing it up with
whoever I find to fit the boiler.

James