Again a very long post with some pictures to try and get as much detail
as possible out there first time.

Some of you may remember my commitment to help a friend overhaul the
heating system on an inherited house, which although used regularly and
kept inhibited at least until the last 3 or 4 years or so has had no
work done other than pump replacement, and inhibitor replenishment since
about 1974.

Indeed this group helped to diagnose non spinning CH pumps last winter
and give me guidance as to how I might replace valves like this
https://www.dropbox.com/s/t5613768cj1hezn/Rad1.jpg?dl=0
with modern TRVs.

(The original thread can still be found on Google Groups
https://groups.google.com/forum/#!searchin/uk.d-i-y/ch$20system$20design%7Csort:date/uk.d-i-y/apuzmBtbWvk/JOQHT5hjAwAJ)

Anyway time has moved on and over the winter the system operated
adequately at maintaining a frost free environment but the response to
demands for increase in temperature could at best be described as
glacial. (Temp increase of 1C or at the most 2C per hour). This has
not bothered the previous owner as in recent years the heating has just
been on for 24 hrs over the winter months.

Now although the pump outputs have been hot, none of the radiators has
got more than lukewarm to the touch, despite the fact that one of the
feed legs to most radiators was hot, (the other pretty much cold).

Suspecting sludge all radiators have been removed, taken outside and
hosed through (there was indeed quite a bit of sludge).

But now we come to the rebuild. When I first asked last autumn from
initial inspection of the system I thought it was S plan with 3 pumps
(DHW, Downstairs Rads and upstairs rads). However from more detailed
inspection, the previous owners notes and a google search what now I
think I have is a *******ised "single pipe system" with three pumps.

I have drawn it out here.
https://www.dropbox.com/s/yn7ac7wk4w...ayout.jpg?dl=0
In the master bedroom and the lounge the original radiators have been
replaced (in 1974) with MUCH larger double panel radiators as shown by
the revised pipe runs.

The downstairs supply pipes are embedded in a solid concrete floor like
this.
https://www.dropbox.com/s/mod6if6hzi...upply.jpg?dl=0
and any thought of changing the pipe runs is probably out of budget and
certainly well beyond my abilities.

The return from downstairs goes up to join the upstairs return before a
common return to the boiler like this.
https://www.dropbox.com/s/k36vmmjljj...eturn.jpg?dl=0

And all of the unmodified original radiators are variations of this
https://www.dropbox.com/s/wl04fyffxc...ginal.jpg?dl=0

Note no lock-shield valve and 3/4 inch valve on one end.

I have flushed out all the radiators and they are all now clean with no
end fittings, there is no sign of serious corrosion on any of them, and
I am ready for the rebuild.

Now the questions start.
I have been googling single pipe systems (completely new to me) and it
seems that although the systems are pumped heat transfer in the rads is
down to gravity (indeed all of the pics I can find show the rads
diagonally connected with the input at the top and output at the bottom).

Although the feed pipe is 1/2 inch the original installer has fitted 3/4
valves and outlet connections.

Do I need to retain 3/4 inch connections? will a 1/2 valve cause too
much of a restriction?

One (quite old) forum I found said that Single pipe systems also seem to
need special (full flow) TRVs (like Danfoss Randall RA-G) which appear
to be about twice the cost of Drayton TRV4 (presumably because of
scarcity) and that a TRV4 had been fitted in a single pipe system and
didn't work. One responder said that he had fitted a Danfoss RAS-C2
successfully in a single pipe system.

Any comments or experiences?

I note that the original installer never fitted any lock-shield valves.
Is this to minimise flow restriction? Would I need to fit lock-shield
valves with TRV?

There is a chance that in the short or medium term the new owner might
want to fit a new boiler. Are current boilers compatible with a single
pipe system?

My plan was to get the radiator side all up and working satisfactorily
and only then consider a boiler replacement,
The minimum work now is to put it all back together as it was (with
either 1/2inch or 3/4inch manual valves - which will actually turn and
not leak :-) ).

I would like to upgrade to TRVs but don't want to spend 5 or 6 hundred
pounds on 10 or 11 special new single pipe TRVs if
a) they are not likely to work or
b) they will all need to be ripped out and thrown away if/when the
boiler is replaced.


Any comments/Thoughts/suggestions would be most welcome at this point.


--
Chris B (News)

My first step would be to turn off all rads except one (say nearest to boiler) and see what happens to that rad. I had a similar problem on my sister's system I also worked on as a favour. It is a completely different layout but the cause was a dodgy motorised valve to the heating circuit was getting very little flow. In your case could be the pump is buggered. Also, are you able to adjust the speed on your pump?

If the test shows a perfectly functioning rad, you can then start switching others on one by one. Don't turn them on full though just so they are getting hot.


WRT to the lockshield question other than convenience when removing the rad, given it is a single pipe system, it shouldn't impact the function of the heating system as the valve the other end will be able to reduce the flow through the rad to balance the system.

In article ,
Chris B writes:
Again a very long post with some pictures to try and get as much detail
as possible out there first time.

Some of you may remember my commitment to help a friend overhaul the
heating system on an inherited house, which although used regularly and
kept inhibited at least until the last 3 or 4 years or so has had no
work done other than pump replacement, and inhibitor replenishment since
about 1974.

Indeed this group helped to diagnose non spinning CH pumps last winter
and give me guidance as to how I might replace valves like this
https://www.dropbox.com/s/t5613768cj1hezn/Rad1.jpg?dl=0
with modern TRVs.

(The original thread can still be found on Google Groups
https://groups.google.com/forum/#!searchin/uk.d-i-y/ch$20system$20design%7Csort:date/uk.d-i-y/apuzmBtbWvk/JOQHT5hjAwAJ)

Anyway time has moved on and over the winter the system operated
adequately at maintaining a frost free environment but the response to
demands for increase in temperature could at best be described as
glacial. (Temp increase of 1C or at the most 2C per hour). This has
not bothered the previous owner as in recent years the heating has just
been on for 24 hrs over the winter months.

Most likely, the radiators are undersized compared with a modern
installation, and simply don't have sufficient spare output capacity
to heat up the house from cold quickly.

What's the state of the house insulation? Has it been updated with
things like cavity wall insulation, loft insulation, etc? I would
get that sorted before trying to evaluate if changes are needeed
to the heating system.

Now although the pump outputs have been hot, none of the radiators has
got more than lukewarm to the touch, despite the fact that one of the
feed legs to most radiators was hot, (the other pretty much cold).

Suspecting sludge all radiators have been removed, taken outside and
hosed through (there was indeed quite a bit of sludge).

But now we come to the rebuild. When I first asked last autumn from
initial inspection of the system I thought it was S plan with 3 pumps
(DHW, Downstairs Rads and upstairs rads). However from more detailed
inspection, the previous owners notes and a google search what now I
think I have is a *******ised "single pipe system" with three pumps.

I have drawn it out here.
https://www.dropbox.com/s/yn7ac7wk4w...ayout.jpg?dl=0
In the master bedroom and the lounge the original radiators have been
replaced (in 1974) with MUCH larger double panel radiators as shown by
the revised pipe runs.

That's not a "*******ised" single pipe system - it's a bog standard
single pipe system - actually better than most domestic ones as it's
zoned. There would normally be a flow balancing gate valve in each
of your red limbs, to balance the flow in the pairs of circuits.

The downstairs supply pipes are embedded in a solid concrete floor like
this.
https://www.dropbox.com/s/mod6if6hzi...upply.jpg?dl=0
and any thought of changing the pipe runs is probably out of budget and
certainly well beyond my abilities.

The return from downstairs goes up to join the upstairs return before a
common return to the boiler like this.
https://www.dropbox.com/s/k36vmmjljj...eturn.jpg?dl=0

That looks like one of the flow balancing gate valves, although
I would expect one on each of the single pipe circuits.

And all of the unmodified original radiators are variations of this
https://www.dropbox.com/s/wl04fyffxc...ginal.jpg?dl=0

Note no lock-shield valve and 3/4 inch valve on one end.

That's correct for a single pipe system.

I have flushed out all the radiators and they are all now clean with no
end fittings, there is no sign of serious corrosion on any of them, and
I am ready for the rebuild.

Now the questions start.
I have been googling single pipe systems (completely new to me) and it
seems that although the systems are pumped heat transfer in the rads is
down to gravity (indeed all of the pics I can find show the rads
diagonally connected with the input at the top and output at the bottom).

This is a common misunderstanding, and I've seen it stated here too.
Yours are *not* gravity fed - they are pumped. The radiator is a
big fat pipe, and has much less flow resistance than the much thinner
pipe across the bottom. The flow splits according to the inverse of
the two path flow resistances.

Although the feed pipe is 1/2 inch the original installer has fitted 3/4
valves and outlet connections.

Radiators of that age will often have 3/4 or even 1" connections.
This is because they might have been used in gravity systems which
require larger pipes. However, the pressure across a radiator in a
single pipe system is much lower, so you want to avoid any additional
flow restrictions.

Do I need to retain 3/4 inch connections? will a 1/2 valve cause too
much of a restriction?

My parents' single pipe system has 1/2" valves, but internally they
are like traditional stop cocks and probably have much less resistance
than a modern radiator valve. If you change to 1/2", you might want
to look at the internal design for one with least flow restriction.

One (quite old) forum I found said that Single pipe systems also seem to
need special (full flow) TRVs (like Danfoss Randall RA-G) which appear
to be about twice the cost of Drayton TRV4 (presumably because of
scarcity) and that a TRV4 had been fitted in a single pipe system and
didn't work. One responder said that he had fitted a Danfoss RAS-C2
successfully in a single pipe system.

Any comments or experiences?

I have tried TRV4 on single pipe system, and its flow resistance is
too high to get full power from a large radiator. If you fit TRV's,
you might have problems if you don't use full flow ones. You can fit
a TRV4 anywhere in the single pipe (except the section between ends
of the same radiator) and it will then control all the radiators in
that branch. However, be careful to check the boiler doesn't need a
bypass circuit (the original boiler won't, but if it's been replaced,
a newer one might).

I note that the original installer never fitted any lock-shield valves.
Is this to minimise flow restriction? Would I need to fit lock-shield
valves with TRV?

Single pipe systems never had lockshield valves because they weren't
necessary (flow resistance could be an issue, but they weren't required
at all in the design). The balancing is done per single pipe circuit,
and not per radiator. Back in those days, systems were designed much
more accurately than they are today, with each raditor sized for the
power it needs to give off and the drop in temperature of its feed
depending how far along the circuit it is and power drawn off by the
radiators before it.

There is a chance that in the short or medium term the new owner might
want to fit a new boiler. Are current boilers compatible with a single
pipe system?

Yes, but you would have to stop the installer putting unsuitable
TRVs on all the rads. You would not be able to make the system
quite as efficient as a modern installation, but the improvement in
boiler efficiency even without replacing the radiator circuit will
be well worth having.

My plan was to get the radiator side all up and working satisfactorily
and only then consider a boiler replacement,
The minimum work now is to put it all back together as it was (with
either 1/2inch or 3/4inch manual valves - which will actually turn and
not leak :-) ).

I would like to upgrade to TRVs but don't want to spend 5 or 6 hundred
pounds on 10 or 11 special new single pipe TRVs if
a) they are not likely to work or
b) they will all need to be ripped out and thrown away if/when the
boiler is replaced.

Try one. The largest radiator will be the most challenging.
But based on my experience, I would not be overly hopeful.

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

On 14/05/2018 10:08, Andrew Gabriel wrote:
In article ,
Chris B writes:


What's the state of the house insulation? Has it been updated with
things like cavity wall insulation, loft insulation, etc? I would
get that sorted before trying to evaluate if changes are needeed
to the heating system.

Oh yes, Double Glazing, CWI and loads of loft insulation.


Now although the pump outputs have been hot, none of the radiators has
got more than lukewarm to the touch, despite the fact that one of the
feed legs to most radiators was hot, (the other pretty much cold).

Suspecting sludge all radiators have been removed, taken outside and
hosed through (there was indeed quite a bit of sludge).

But now we come to the rebuild. When I first asked last autumn from
initial inspection of the system I thought it was S plan with 3 pumps
(DHW, Downstairs Rads and upstairs rads). However from more detailed
inspection, the previous owners notes and a google search what now I
think I have is a *******ised "single pipe system" with three pumps.

I have drawn it out here.
https://www.dropbox.com/s/yn7ac7wk4w...ayout.jpg?dl=0
In the master bedroom and the lounge the original radiators have been
replaced (in 1974) with MUCH larger double panel radiators as shown by
the revised pipe runs.

That's not a "*******ised" single pipe system - it's a bog standard
single pipe system - actually better than most domestic ones as it's
zoned. There would normally be a flow balancing gate valve in each
of your red limbs, to balance the flow in the pairs of circuits.

The downstairs supply pipes are embedded in a solid concrete floor like
this.
https://www.dropbox.com/s/mod6if6hzi...upply.jpg?dl=0
and any thought of changing the pipe runs is probably out of budget and
certainly well beyond my abilities.

The return from downstairs goes up to join the upstairs return before a
common return to the boiler like this.
https://www.dropbox.com/s/k36vmmjljj...eturn.jpg?dl=0

That looks like one of the flow balancing gate valves, although
I would expect one on each of the single pipe circuits.

And all of the unmodified original radiators are variations of this
https://www.dropbox.com/s/wl04fyffxc...ginal.jpg?dl=0

Note no lock-shield valve and 3/4 inch valve on one end.

That's correct for a single pipe system.

I have flushed out all the radiators and they are all now clean with no
end fittings, there is no sign of serious corrosion on any of them, and
I am ready for the rebuild.

Now the questions start.
I have been googling single pipe systems (completely new to me) and it
seems that although the systems are pumped heat transfer in the rads is
down to gravity (indeed all of the pics I can find show the rads
diagonally connected with the input at the top and output at the bottom).

This is a common misunderstanding, and I've seen it stated here too.
Yours are *not* gravity fed - they are pumped. The radiator is a
big fat pipe, and has much less flow resistance than the much thinner
pipe across the bottom. The flow splits according to the inverse of
the two path flow resistances.

Although the feed pipe is 1/2 inch the original installer has fitted 3/4
valves and outlet connections.

Radiators of that age will often have 3/4 or even 1" connections.
This is because they might have been used in gravity systems which
require larger pipes. However, the pressure across a radiator in a
single pipe system is much lower, so you want to avoid any additional
flow restrictions.

Do I need to retain 3/4 inch connections? will a 1/2 valve cause too
much of a restriction?

My parents' single pipe system has 1/2" valves, but internally they
are like traditional stop cocks and probably have much less resistance
than a modern radiator valve. If you change to 1/2", you might want
to look at the internal design for one with least flow restriction.

One (quite old) forum I found said that Single pipe systems also seem to
need special (full flow) TRVs (like Danfoss Randall RA-G) which appear
to be about twice the cost of Drayton TRV4 (presumably because of
scarcity) and that a TRV4 had been fitted in a single pipe system and
didn't work. One responder said that he had fitted a Danfoss RAS-C2
successfully in a single pipe system.

Any comments or experiences?

I have tried TRV4 on single pipe system, and its flow resistance is
too high to get full power from a large radiator. If you fit TRV's,
you might have problems if you don't use full flow ones. You can fit
a TRV4 anywhere in the single pipe (except the section between ends
of the same radiator) and it will then control all the radiators in
that branch. However, be careful to check the boiler doesn't need a
bypass circuit (the original boiler won't, but if it's been replaced,
a newer one might).

I note that the original installer never fitted any lock-shield valves.
Is this to minimise flow restriction? Would I need to fit lock-shield
valves with TRV?

Single pipe systems never had lockshield valves because they weren't
necessary (flow resistance could be an issue, but they weren't required
at all in the design). The balancing is done per single pipe circuit,
and not per radiator. Back in those days, systems were designed much
more accurately than they are today, with each raditor sized for the
power it needs to give off and the drop in temperature of its feed
depending how far along the circuit it is and power drawn off by the
radiators before it.

There is a chance that in the short or medium term the new owner might
want to fit a new boiler. Are current boilers compatible with a single
pipe system?

Yes, but you would have to stop the installer putting unsuitable
TRVs on all the rads. You would not be able to make the system
quite as efficient as a modern installation, but the improvement in
boiler efficiency even without replacing the radiator circuit will
be well worth having.

My plan was to get the radiator side all up and working satisfactorily
and only then consider a boiler replacement,
The minimum work now is to put it all back together as it was (with
either 1/2inch or 3/4inch manual valves - which will actually turn and
not leak :-) ).

I would like to upgrade to TRVs but don't want to spend 5 or 6 hundred
pounds on 10 or 11 special new single pipe TRVs if
a) they are not likely to work or
b) they will all need to be ripped out and thrown away if/when the
boiler is replaced.

Try one. The largest radiator will be the most challenging.
But based on my experience, I would not be overly hopeful.


Thanks for those comments, most informative and I don't feel quite so
daunted now.


--
Chris B (News)

On Monday, 14 May 2018 07:44:17 UTC+1, Chris B wrote:

Again a very long post with some pictures to try and get as much detail
as possible out there first time.

Some of you may remember my commitment to help a friend overhaul the
heating system on an inherited house, which although used regularly and
kept inhibited at least until the last 3 or 4 years or so has had no
work done other than pump replacement, and inhibitor replenishment since
about 1974.

Indeed this group helped to diagnose non spinning CH pumps last winter
and give me guidance as to how I might replace valves like this
https://www.dropbox.com/s/t5613768cj1hezn/Rad1.jpg?dl=0
with modern TRVs.

(The original thread can still be found on Google Groups
https://groups.google.com/forum/#!searchin/uk.d-i-y/ch$20system$20design%7Csort:date/uk.d-i-y/apuzmBtbWvk/JOQHT5hjAwAJ)

Anyway time has moved on and over the winter the system operated
adequately at maintaining a frost free environment but the response to
demands for increase in temperature could at best be described as
glacial. (Temp increase of 1C or at the most 2C per hour). This has
not bothered the previous owner as in recent years the heating has just
been on for 24 hrs over the winter months.

Now although the pump outputs have been hot, none of the radiators has
got more than lukewarm to the touch, despite the fact that one of the
feed legs to most radiators was hot, (the other pretty much cold).

Suspecting sludge all radiators have been removed, taken outside and
hosed through (there was indeed quite a bit of sludge).

OK, let's clarify some basics.
1. Your flow rate through the rads is inadequate. The last thing you need to do is reduce that further by adding LSVs or reducing the size of fittings..
2. Since the flow rate is so abysmal tht even the 1st rad doesn't get hot, there are a few immediate suspects
a) pump has clogged vanes and is barely pumping. CH pumps are openable & vanes clean outable.
b) you've almost certainly got serious sludging elsewhere in the system. There are therefore 2 things you really do need: a magnetic filter and cleaning chemical. Since it's so bad I'd run it with cleaner in for a lot more than a week. Some cleaners can be kept in a long time, some can't.

Your dropbox files are mostly not readable, being all of in inch in size. Put them somewhere sensible.


But now we come to the rebuild. When I first asked last autumn from
initial inspection of the system I thought it was S plan with 3 pumps
(DHW, Downstairs Rads and upstairs rads). However from more detailed
inspection, the previous owners notes and a google search what now I
think I have is a *******ised "single pipe system" with three pumps.

I have drawn it out here.
https://www.dropbox.com/s/yn7ac7wk4w...ayout.jpg?dl=0
In the master bedroom and the lounge the original radiators have been
replaced (in 1974) with MUCH larger double panel radiators as shown by
the revised pipe runs.

The downstairs supply pipes are embedded in a solid concrete floor like
this.
https://www.dropbox.com/s/mod6if6hzi...upply.jpg?dl=0
and any thought of changing the pipe runs is probably out of budget and
certainly well beyond my abilities.

The return from downstairs goes up to join the upstairs return before a
common return to the boiler like this.
https://www.dropbox.com/s/k36vmmjljj...eturn.jpg?dl=0

And all of the unmodified original radiators are variations of this
https://www.dropbox.com/s/wl04fyffxc...ginal.jpg?dl=0

Note no lock-shield valve and 3/4 inch valve on one end.

I have flushed out all the radiators and they are all now clean with no
end fittings, there is no sign of serious corrosion on any of them, and
I am ready for the rebuild.

Now the questions start.
I have been googling single pipe systems (completely new to me) and it
seems that although the systems are pumped heat transfer in the rads is
down to gravity (indeed all of the pics I can find show the rads
diagonally connected with the input at the top and output at the bottom).

well, yes and no. With all rads in any CH system if the water goes in & out at the bottom, the movement of hot water up to the top is mainly by gravity. This is of no consequence.


Although the feed pipe is 1/2 inch the original installer has fitted 3/4
valves and outlet connections.

Do I need to retain 3/4 inch connections? will a 1/2 valve cause too
much of a restriction?

reducing size will make it even worse than now.
If your valves are faulty, some can be repacked to stop dribbles.

One (quite old) forum I found said that Single pipe systems also seem to
need special (full flow) TRVs (like Danfoss Randall RA-G) which appear
to be about twice the cost of Drayton TRV4 (presumably because of
scarcity) and that a TRV4 had been fitted in a single pipe system and
didn't work. One responder said that he had fitted a Danfoss RAS-C2
successfully in a single pipe system.

Any comments or experiences?

'ang on. Do the rads have a bypass pipe across them? If they do, TRVs would work sort-of but would worse the flow a lot, making the system not work. If there's no shorting pipe, a TRV anywhere in the run would affect flow to all rads and thus be counterproductive. In short I would not fit TRVs to the current system. TRVs to be frank are overrated. It's not difficult to get perfectly good performance without them, and they do NOT give thermostatic control of room temp, as people often fondly imagine.


I note that the original installer never fitted any lock-shield valves.
Is this to minimise flow restriction? Would I need to fit lock-shield
valves with TRV?

LSVs just prevent gross misadjustment. They aren't necessary. And once again, do you really want to turn your water flow down further? If not, forget adding LSVs.


There is a chance that in the short or medium term the new owner might
want to fit a new boiler. Are current boilers compatible with a single
pipe system?

yes. Whether a boiler re[pacement will trigger an insistence from an installer on replumbing the rads or adding TRVs I can't say. If it's diyed then that won't apply.


My plan was to get the radiator side all up and working satisfactorily
and only then consider a boiler replacement,
The minimum work now is to put it all back together as it was (with
either 1/2inch or 3/4inch manual valves - which will actually turn and
not leak :-) ).

I would like to upgrade to TRVs but don't want to spend 5 or 6 hundred
pounds on 10 or 11 special new single pipe TRVs if
a) they are not likely to work or
b) they will all need to be ripped out and thrown away if/when the
boiler is replaced.

I don't think I would. You won't see much advantage from TRVs if you balance the system, which isn't hard. I think you need to get it working first. For now I'd let the setup run 24/7, it won't make much diffrence to heating bill.

Any comments/Thoughts/suggestions would be most welcome at this point.


NT

On 14/05/2018 19:39, wrote:


OK, let's clarify some basics.
1. Your flow rate through the rads is inadequate. The last thing you need to do is reduce that further by adding LSVs or reducing the size of fittings.
OK

2. Since the flow rate is so abysmal tht even the 1st rad doesn't get hot, there are a few immediate suspects
a) pump has clogged vanes and is barely pumping. CH pumps are openable & vanes clean outable.
Will have a look into this

b) you've almost certainly got serious sludging elsewhere in the system. There are therefore 2 things you really do need: a magnetic filter and cleaning chemical. Since it's so bad I'd run it with cleaner in for a lot more than a week. Some cleaners can be kept in a long time, some can't.
OK


Your dropbox files are mostly not readable, being all of in inch in size. Put them somewhere sensible.

Don't know what is going on there I have tried them from unsigned in
Firefox, Opera and Maxthon browsers and they look ok in all of those on
my PC and tablet. The photos were uploaded at approx 4000 by 2000 pixels
and the layout diag 2000 by 1500



But now we come to the rebuild. When I first asked last autumn from
initial inspection of the system I thought it was S plan with 3 pumps
(DHW, Downstairs Rads and upstairs rads). However from more detailed
inspection, the previous owners notes and a google search what now I
think I have is a *******ised "single pipe system" with three pumps.

I have drawn it out here.
https://www.dropbox.com/s/yn7ac7wk4w...ayout.jpg?dl=0
In the master bedroom and the lounge the original radiators have been
replaced (in 1974) with MUCH larger double panel radiators as shown by
the revised pipe runs.

The downstairs supply pipes are embedded in a solid concrete floor like
this.
https://www.dropbox.com/s/mod6if6hzi...upply.jpg?dl=0
and any thought of changing the pipe runs is probably out of budget and
certainly well beyond my abilities.

The return from downstairs goes up to join the upstairs return before a
common return to the boiler like this.
https://www.dropbox.com/s/k36vmmjljj...eturn.jpg?dl=0

And all of the unmodified original radiators are variations of this
https://www.dropbox.com/s/wl04fyffxc...ginal.jpg?dl=0

Note no lock-shield valve and 3/4 inch valve on one end.

I have flushed out all the radiators and they are all now clean with no
end fittings, there is no sign of serious corrosion on any of them, and
I am ready for the rebuild.

Now the questions start.
I have been googling single pipe systems (completely new to me) and it
seems that although the systems are pumped heat transfer in the rads is
down to gravity (indeed all of the pics I can find show the rads
diagonally connected with the input at the top and output at the bottom).

well, yes and no. With all rads in any CH system if the water goes in & out at the bottom, the movement of hot water up to the top is mainly by gravity. This is of no consequence.


Although the feed pipe is 1/2 inch the original installer has fitted 3/4
valves and outlet connections.

Do I need to retain 3/4 inch connections? will a 1/2 valve cause too
much of a restriction?

reducing size will make it even worse than now.
If your valves are faulty, some can be repacked to stop dribbles.
Ok rather than looking to fit new 1/2 inch valves I will look to clean
out and overhaul the existing ones, at least as a first step to getting
the system going.


One (quite old) forum I found said that Single pipe systems also seem to
need special (full flow) TRVs (like Danfoss Randall RA-G) which appear
to be about twice the cost of Drayton TRV4 (presumably because of
scarcity) and that a TRV4 had been fitted in a single pipe system and
didn't work. One responder said that he had fitted a Danfoss RAS-C2
successfully in a single pipe system.

Any comments or experiences?

'ang on. Do the rads have a bypass pipe across them?
The grd floor pipes are buried in the solid floor by I am 99% sure that
yes they have a bypass pipe.

If they do, TRVs would work sort-of but would worse the flow a lot,
making the system not work. If there's no shorting pipe, a TRV anywhere
in the run would affect flow to all rads and thus be counterproductive.
As would also closing the manual valve?

In short I would not fit TRVs to the current system. TRVs to be frank
are overrated. It's not difficult to get perfectly good performance
without them, and they do NOT give thermostatic control of room temp, as
people often fondly imagine.
OK



I note that the original installer never fitted any lock-shield valves.
Is this to minimise flow restriction? Would I need to fit lock-shield
valves with TRV?

LSVs just prevent gross misadjustment. They aren't necessary. And once again, do you really want to turn your water flow down further? If not, forget adding LSVs.
OK



There is a chance that in the short or medium term the new owner might
want to fit a new boiler. Are current boilers compatible with a single
pipe system?

yes. Whether a boiler re[pacement will trigger an insistence from an installer on replumbing the rads or adding TRVs I can't say. If it's diyed then that won't apply.



My plan was to get the radiator side all up and working satisfactorily
and only then consider a boiler replacement,
The minimum work now is to put it all back together as it was (with
either 1/2inch or 3/4inch manual valves - which will actually turn and
not leak :-) ).

I would like to upgrade to TRVs but don't want to spend 5 or 6 hundred
pounds on 10 or 11 special new single pipe TRVs if
a) they are not likely to work or
b) they will all need to be ripped out and thrown away if/when the
boiler is replaced.

I don't think I would. You won't see much advantage from TRVs if you balance the system, which isn't hard. I think you need to get it working first. For now I'd let the setup run 24/7, it won't make much diffrence to heating bill.

Many thanks for your input. I will look to getting the system "much
improved" at minimal expense by cleaning and overhauling the existing
valves (if poss), cleaning the pumps, reassembly with existing bits and
run with a cleaner. Then decide where we go from there.

Much appreciate your comments.


Any comments/Thoughts/suggestions would be most welcome at this point.


NT



--
Chris B (News)

On Monday, 14 May 2018 21:09:21 UTC+1, Chris B wrote:
On 14/05/2018 19:39, tabbypurr wrote:


just a few more bits of input...

2. Since the flow rate is so abysmal tht even the 1st rad doesn't get hot, there are a few immediate suspects
a) pump has clogged vanes and is barely pumping. CH pumps are openable & vanes clean outable.
Will have a look into this

http://wiki.diyfaq.org.uk/index.php/...ng_pump_repair



'ang on. Do the rads have a bypass pipe across them?
The grd floor pipes are buried in the solid floor by I am 99% sure that
yes they have a bypass pipe.

If they do, TRVs would work sort-of but would worse the flow a lot,
making the system not work. If there's no shorting pipe, a TRV anywhere
in the run would affect flow to all rads and thus be counterproductive.
As would also closing the manual valve?

closing the manual valve on a rad will tell you for sure if there's a shorting pipe. If there isn't, the whole run will go cold, so I presume there is..


For now I'd let the setup run 24/7, it won't make much diffrence to heating bill.

If a house runs at 20C in the day & drops to 18-19C at night, that's 19-19.5C average. So the heatloss & gas consumption for a system on 24/7 is (for 0C outdoors) around 20/19-19.5 as much, ie 2.5 - 5% more.


Many thanks for your input. I will look to getting the system "much
improved" at minimal expense by cleaning and overhauling the existing
valves (if poss), cleaning the pumps, reassembly with existing bits and
run with a cleaner. Then decide where we go from there.

Much appreciate your comments.

Last system I cleaned had no detectable heat output on one rad, and the rad had been removed & flushed. With cleaner in it didn't respond for a while, but after I forget, maybe 2 weeks, it finally cleared & soon ran ok.

And you can tell what the water flow rate is by feeling the pipe when the boiler fires. The slug of hot water should move along at a practical pace, if it hardly gets anywhere you've got near zero flow. I daresay it's possible the hot primary water is going some place else, like through the DHW coil instead, pipe feeling should give you more idea what's going on.


NT

On Mon, 14 May 2018 11:39:34 -0700 (PDT)
wrote:

Your dropbox files are mostly not readable, being all of in inch in
size. Put them somewhere sensible.

They're displaying just fine here in a couple of browsers: Dropbox
scales them to mostly fill a browser window.

On 15/05/2018 19:15, Rob Morley wrote:
On Mon, 14 May 2018 11:39:34 -0700 (PDT)
wrote:

Your dropbox files are mostly not readable, being all of in inch in
size. Put them somewhere sensible.

They're displaying just fine here in a couple of browsers: Dropbox
scales them to mostly fill a browser window.

Thanks, appreciate the feedback from a machine that is no way connected
with the one they were uploaded from.

--
Chris B (News)