I have a gas boiler and a pretty normal cylinder upstairs in the
hotpress. There is a weird problem in that when I fire it up, the CH
heats up great, but there is no hot water - the cylinder is tepid even
after an hour of running the boiler. Boiler appears to work normally -
heats all the radiators and then maintains the temperature.

There's a thermostatic valve on the hot water pipe going into the
cylinder coil, at the centre of the cylinder, and a regular valve coming
out at the bottom. Hot water is definitely passing through the input
valve as I can feel it piping hot on both sides of the valve, but the
cylinder itself is cold immediately next to where the pipe enters.

The boiler itself is very simple, one pipe goes in and another comes
out. There is no motorized valve, there is only one heating circuit that
does both CH and HW.

Is this kind of problem common or rare ? Are there any tricks that can
be tried before the plumber drains the whole system to try to figure out
what the problem is ?

Regards

GWC

On Sun, 01 Jan 2006 12:30:09 +0000, "Geronimo W. Christ Esq"
wrote:


I have a gas boiler and a pretty normal cylinder upstairs in the
hotpress. There is a weird problem in that when I fire it up, the CH
heats up great, but there is no hot water - the cylinder is tepid even
after an hour of running the boiler. Boiler appears to work normally -
heats all the radiators and then maintains the temperature.

There's a thermostatic valve on the hot water pipe going into the
cylinder coil, at the centre of the cylinder, and a regular valve coming
out at the bottom. Hot water is definitely passing through the input
valve as I can feel it piping hot on both sides of the valve, but the
cylinder itself is cold immediately next to where the pipe enters.

The boiler itself is very simple, one pipe goes in and another comes
out. There is no motorized valve, there is only one heating circuit that
does both CH and HW.

Is this kind of problem common or rare ? Are there any tricks that can
be tried before the plumber drains the whole system to try to figure out
what the problem is ?

Regards

GWC




This is a "gravity" system where the water for the cylinder coil
circulates naturally by convection as the boiler heats it - i.e. the
pump is not involved.

Generally, these systems heat he DHW quite slowly anyway in comparison
to a pumped system. Even so, it should be better than it is.

The valve that you describe is probably for balancing the heat
delivered to the cylinder vs. the CH. Is it fully open?

Otherwise, I would suspect that the coil inside the cylinder is
heavily scaled. Are you in a hard water area?

Another telltale would be that when the boiler is running DHW only,
does it cycle on and off a lot? This would indicate poor transfer of
heat through the cylinder coil. Is the other pipe from the cylinder
back to the boiler also hot?

If this all fits together, then the solution will be to change the
cylinder.

While this is being done, it would make very good sense to use either
a part L1 (this is pretty much the standard nowadays) or a fast
recovery cylinder and to convert to a fully pumped arrangement with
diverter valve.


--

..andy

Andy Hall wrote:

Andy, thanks for that very comprehensive reply.

This is a "gravity" system where the water for the cylinder coil
circulates naturally by convection as the boiler heats it - i.e. the
pump is not involved.

I am not sure that this is the case. The cylinder coil seems to be
connected to the same circuit as the radiators are, and there is of
course a pump there which appears to be working normally.

Generally, these systems heat he DHW quite slowly anyway in comparison
to a pumped system. Even so, it should be better than it is.

I'd expect the cylinder to be full of hot water after an hour or so.
Even if I run it all morning it's still cold. It takes about half an
hour for the gas boiler to finish heating the water in the system.

The valve that you describe is probably for balancing the heat
delivered to the cylinder vs. the CH. Is it fully open?

I think you're right. Yes it's fully open.

Otherwise, I would suspect that the coil inside the cylinder is
heavily scaled. Are you in a hard water area?

This is the interesting thing. The house is only four years old and has
been occupied by the previous owner for two of those (I have just bought
it) so it would be really surprising if the coil was gunked up. Also,
the water is soft - according to a Calgon water testing stick I had to
hand when I checked a few days ago.

Another telltale would be that when the boiler is running DHW only,
does it cycle on and off a lot? This would indicate poor transfer of
heat through the cylinder coil. Is the other pipe from the cylinder
back to the boiler also hot?

The pipe from the cylinder back to the boiler is cold, so this does
indeed suggest that the water is not passing through the cylinder coil.

If this all fits together, then the solution will be to change the
cylinder.

While this is being done, it would make very good sense to use either
a part L1 (this is pretty much the standard nowadays) or a fast
recovery cylinder and to convert to a fully pumped arrangement with
diverter valve.

Thanks, I will keep your comments in mind. The cylinder that is there
seems basic, ie it is not one of the ones covered with spray-on
insulation - there's just a frankly slightly crappy looking jacket - I
was surprised that such a fairly new house would have the less efficient
cylinder, but there you go.

On Sun, 01 Jan 2006 13:34:20 +0000, "Geronimo W. Christ Esq"
wrote:

Andy Hall wrote:

Andy, thanks for that very comprehensive reply.

This is a "gravity" system where the water for the cylinder coil
circulates naturally by convection as the boiler heats it - i.e. the
pump is not involved.

I am not sure that this is the case. The cylinder coil seems to be
connected to the same circuit as the radiators are, and there is of
course a pump there which appears to be working normally.

OK, so are you saying that there are only two water connections at the
boiler? A "gravity" system has four, with two generally being 28mm
(go to cylinder coil) and two being 22mm for the CH. In that
scenario, you wouldn't have a motorised diverter valve (3 ports) but
might have a zone valve (2 ports) for what is called Honeywell C plan.

If by "connected to the same circuit" you mean that the water is
common between the CH circuit and the cylinder coil and fed from a
small header tank in the loft, then yes that is normal.

If there really aren't any motorised valves, then it implies a
"gravity" system unless there is something very strange.

The test is whether there are two or four water carrying connections
at the boiler. What is the boiler, BTW?


Generally, these systems heat he DHW quite slowly anyway in comparison
to a pumped system. Even so, it should be better than it is.

I'd expect the cylinder to be full of hot water after an hour or so.
Even if I run it all morning it's still cold. It takes about half an
hour for the gas boiler to finish heating the water in the system.

That seems reasonable.


The valve that you describe is probably for balancing the heat
delivered to the cylinder vs. the CH. Is it fully open?

I think you're right. Yes it's fully open.

Otherwise, I would suspect that the coil inside the cylinder is
heavily scaled. Are you in a hard water area?

This is the interesting thing. The house is only four years old and has
been occupied by the previous owner for two of those (I have just bought
it) so it would be really surprising if the coil was gunked up. Also,
the water is soft - according to a Calgon water testing stick I had to
hand when I checked a few days ago.

It would be surprising in that time, but possible in a very hard water
area.


Another telltale would be that when the boiler is running DHW only,
does it cycle on and off a lot? This would indicate poor transfer of
heat through the cylinder coil. Is the other pipe from the cylinder
back to the boiler also hot?

The pipe from the cylinder back to the boiler is cold, so this does
indeed suggest that the water is not passing through the cylinder coil.

Sounds like it is because connection into cylinder is hot, but very
slowly. I'm wondering about that valve near the cylinder.

Are you absolutely *sure* that there is no motorised diverter valve.
The symptoms would happen if you had one and it was stuck in some way.



If this all fits together, then the solution will be to change the
cylinder.

While this is being done, it would make very good sense to use either
a part L1 (this is pretty much the standard nowadays) or a fast
recovery cylinder and to convert to a fully pumped arrangement with
diverter valve.

Thanks, I will keep your comments in mind. The cylinder that is there
seems basic, ie it is not one of the ones covered with spray-on
insulation - there's just a frankly slightly crappy looking jacket - I
was surprised that such a fairly new house would have the less efficient
cylinder, but there you go.


Can you do a sketch of the system in ASCII art and post it or some
photos and put them on a web site somewhere? Specifically around the
cylinder would be interesting.




--

..andy

Andy Hall wrote:

Thanks again, Andy. I'm finding this an instructive conversation.

If there really aren't any motorised valves, then it implies a
"gravity" system unless there is something very strange.

I think it's a strange one There are only two pipes coming out of the
gas boiler (which is a basic Baxi appliance - just a white box with a
thermostat control and some LEDs showing that it is operating).

I do not think there is a motorized valve. I can't see one, and I
imagine if there was one it would require an electrical supply - the
only wired devices that I can see are the pump and the immersion heater.

The pipe from the cylinder back to the boiler is cold, so this does
indeed suggest that the water is not passing through the cylinder coil.

Sounds like it is because connection into cylinder is hot, but very
slowly. I'm wondering about that valve near the cylinder.

Are you absolutely *sure* that there is no motorised diverter valve.
The symptoms would happen if you had one and it was stuck in some way.

It is possible that the valve is stuck, yes. I'm as sure as can be that
there is no motorized valve. There is nothing to control it. The timer
clock on the boiler is very simple, just a rotary dial with little
"notches" all the way round where you can set the ~15min periods you
want it on or off.

Thanks, I will keep your comments in mind. The cylinder that is there
seems basic, ie it is not one of the ones covered with spray-on
insulation - there's just a frankly slightly crappy looking jacket - I
was surprised that such a fairly new house would have the less efficient
cylinder, but there you go.

Can you do a sketch of the system in ASCII art and post it or some
photos and put them on a web site somewhere? Specifically around the
cylinder would be interesting.

Let's try the ASCII art. I will keep it simple. The gas boiler is
downstairs in the kitchen, in a cupboard, and the cylinder is of course
upstairs. The pipes reach up into the bathroom, and under the bathroom
floor to the cylinder. I'm not in the house at the moment so will have
to get photographs if more detail is required.

"TRV" is the thermostatic valve going into the boiler (there is a
sensitive strip running down the centre of the boiler which is connected
by a piece of thin wire to the TRV). "V" is just a regular tap that you
turn on and off. It is currently turned up full. The water is cold on
the pipes either side of V, but piping hot on the pipes either side of
the TRV.

Cylinder

+------- (up to roofspace)
oo
o o
--TRV---o o Hot press
o o
-----V--oooo
=========================
| |
| | two pipes going up
| |
ooo
o o
o o
ooo boiler
|
| gas pipe
|

On Sun, 01 Jan 2006 14:49:25 +0000, "Geronimo W. Christ Esq"
wrote:

Andy Hall wrote:

Thanks again, Andy. I'm finding this an instructive conversation.

If there really aren't any motorised valves, then it implies a
"gravity" system unless there is something very strange.

I think it's a strange one There are only two pipes coming out of the
gas boiler (which is a basic Baxi appliance - just a white box with a
thermostat control and some LEDs showing that it is operating).

I do not think there is a motorized valve. I can't see one, and I
imagine if there was one it would require an electrical supply - the
only wired devices that I can see are the pump and the immersion heater.

It may not be near the cylinder. Can you find the point where the CH
part of the circuit splits from the feed to the coil?

Could be under a floor?



The pipe from the cylinder back to the boiler is cold, so this does
indeed suggest that the water is not passing through the cylinder coil.

Sounds like it is because connection into cylinder is hot, but very
slowly. I'm wondering about that valve near the cylinder.

Are you absolutely *sure* that there is no motorised diverter valve.
The symptoms would happen if you had one and it was stuck in some way.

It is possible that the valve is stuck, yes. I'm as sure as can be that
there is no motorized valve. There is nothing to control it. The timer
clock on the boiler is very simple, just a rotary dial with little
"notches" all the way round where you can set the ~15min periods you
want it on or off.

Thanks, I will keep your comments in mind. The cylinder that is there
seems basic, ie it is not one of the ones covered with spray-on
insulation - there's just a frankly slightly crappy looking jacket - I
was surprised that such a fairly new house would have the less efficient
cylinder, but there you go.

Can you do a sketch of the system in ASCII art and post it or some
photos and put them on a web site somewhere? Specifically around the
cylinder would be interesting.

Let's try the ASCII art. I will keep it simple. The gas boiler is
downstairs in the kitchen, in a cupboard, and the cylinder is of course
upstairs. The pipes reach up into the bathroom, and under the bathroom
floor to the cylinder. I'm not in the house at the moment so will have
to get photographs if more detail is required.

"TRV" is the thermostatic valve going into the boiler (there is a
sensitive strip running down the centre of the boiler which is connected
by a piece of thin wire to the TRV). "V" is just a regular tap that you
turn on and off. It is currently turned up full. The water is cold on
the pipes either side of V, but piping hot on the pipes either side of
the TRV.

This "TRV" is an interesting one - especially as it connects directly
to the boiler. Can you describe in more detail - shape, make?
It sounds as though the boiler controls it is some way, but without
more detail of it and the actual model of boiler, hard to say. Photos
of the cylinder area would be a help.


Do you know where the pump is? Inside the boiler?





Cylinder

+------- (up to roofspace)
oo
o o
--TRV---o o Hot press
o o
-----V--oooo
=========================
| |
| | two pipes going up
| |
ooo
o o
o o
ooo boiler
|
| gas pipe
|

--

..andy

In an earlier contribution to this discussion,
Geronimo W. Christ Esq wrote:

I have a gas boiler and a pretty normal cylinder upstairs in the
hotpress. There is a weird problem in that when I fire it up, the CH
heats up great, but there is no hot water - the cylinder is tepid even
after an hour of running the boiler. Boiler appears to work normally -
heats all the radiators and then maintains the temperature.

There's a thermostatic valve on the hot water pipe going into the
cylinder coil, at the centre of the cylinder, and a regular valve
coming out at the bottom. Hot water is definitely passing through the
input valve as I can feel it piping hot on both sides of the valve,
but the cylinder itself is cold immediately next to where the pipe
enters.
The boiler itself is very simple, one pipe goes in and another comes
out. There is no motorized valve, there is only one heating circuit
that does both CH and HW.

Is this kind of problem common or rare ? Are there any tricks that can
be tried before the plumber drains the whole system to try to figure
out what the problem is ?

Regards

GWC

From reading the other posts in this thread, I'd say that you have a
conventional boiler with a very *unconventional* hot water system!

It seems to have been established that the coil in the HW cylinder is
connected in parallel with the CH radiators and is, in effect, just another
radiator.

Has it ever worked properly since you've been in the house? The thought
occurs to me that the TRV on the cylinder may be one intended for a
radiator, and having a remote sensor which is supposed to sense room
temperature. If so, even with the valve on max, it will close when the
sensed temperature reaches the upper 20's degC. So if it is strapped to the
cylinder, it will close when the HW gets to 25-30 degrees - which is no use
to man or beast!

To test this theory, either pull the sensor away from the cylinder so that
it's just sensing air temperature, or remove the head from the TRV. If the
hot water then gets hot, you'll know that the TRV is the problem.

One thing I don't understand: You said that the pipe going back to the
boiler from the cylinder was cold. But from your description of the system,
this pipe is shared by the central heating system (presumably connected
under the floor somewhere) - so I would expect the return pipe to be hot -
certainly at the boiler end - whenever the radiators are hot, regardless of
what's happening to the cylinder. Am I missing something?
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

Set Square wrote:

From reading the other posts in this thread, I'd say that you have a
conventional boiler with a very *unconventional* hot water system!

Thanks for your reply. I think this type of system has been installed as
standard in the 30-odd houses in the development built around here at
this time, just outside Belfast. It could be a (Northern?) Irish thing
Although, the fact that thermostatic valves are available for this
kind of application suggests that this method of heating the water is at
least practiced by more than a few people locally. I sounds like it's
just a cheapo way of heating a small-ish house.

This system is evidently a novelty to many of the esteemed uk.d-i-y
contributors, so I will post up some pictures during this week.

It seems to have been established that the coil in the HW cylinder is
connected in parallel with the CH radiators and is, in effect, just another
radiator.

That's correct.

Has it ever worked properly since you've been in the house?

No, and I'm a bit peeved about that. The transaction was completed a few
weeks ago. Since the house was basically new I did not get a full survey
done on it, which would probably have uncovered the issue before now. I
didn't try the HW, assuming (foolishly) that it worked because the CH
seemed to work perfectly. I have been meaning to try to get in touch
with the sellers to find out if there is a known problem with it, but I
probably don't have much recourse with them unfortunately. I guess you
can tell I'm an FTB.

The thought
occurs to me that the TRV on the cylinder may be one intended for a
radiator, and having a remote sensor which is supposed to sense room
temperature. If so, even with the valve on max, it will close when the
sensed temperature reaches the upper 20's degC. So if it is strapped to the
cylinder, it will close when the HW gets to 25-30 degrees - which is no use
to man or beast!

No, it is definitely a "proper" thermostatic valve intended for this
application. It has temperature markings all the way up to 90 AFAIK (not
just numbers 1-5ish that you normally see on radiator valves). Previous
posters have suggested that it may not be opening all the way, although
I did move it to it's fully-open position.

To test this theory, either pull the sensor away from the cylinder so that
it's just sensing air temperature, or remove the head from the TRV. If the
hot water then gets hot, you'll know that the TRV is the problem.

Thanks for that tip. I will try that.

One thing I don't understand: You said that the pipe going back to the
boiler from the cylinder was cold. But from your description of the system,
this pipe is shared by the central heating system (presumably connected
under the floor somewhere) - so I would expect the return pipe to be hot -
certainly at the boiler end - whenever the radiators are hot, regardless of
what's happening to the cylinder. Am I missing something?

This is probably an important clue. The return pipe coming out of the
bottom of the cylinder gets to a T junction a short distance away which
I guess is the main return for the whole system. The water flowing
through the top line (as opposed to the leg) of the "T" is very warm but
not as warm as the flow pipe - which sounds like what you would expect.
However, the leg of the "T" which comes from the cylinder is stone cold.
I guess that is because the cold water is just sitting there without
moving through the coil.

Once again, thanks to everyone who has replied. This has been an
interesting discussion.

In an earlier contribution to this discussion,
Geronimo W. Christ Esq wrote:


No, it is definitely a "proper" thermostatic valve intended for this
application. It has temperature markings all the way up to 90 AFAIK

Are you sure it's 90 degC and not 90 degF?!

If it *is* the proper one for the job, it may just be stuck. As someone else
has suggested, remove the thermostatic head from the valve and check that
the pin moves down when you press on the end and comes up again when you
release it. If it's stuck down it would explain your problem. Tapping the
side of the valve with a metal object (spanner etc.) may free it.


This is probably an important clue. The return pipe coming out of the
bottom of the cylinder gets to a T junction a short distance away
which I guess is the main return for the whole system. The water
flowing through the top line (as opposed to the leg) of the "T" is
very warm but not as warm as the flow pipe - which sounds like what
you would expect. However, the leg of the "T" which comes from the
cylinder is stone cold. I guess that is because the cold water is
just sitting there without moving through the coil.

Ah, that explains it. I got the impression earlier that the return pipe was
cold all the way to the boiler - but now realise that it's not.

You've not mentioned a room thermostat. I assume there isn't one?
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

Set Square wrote:

No, it is definitely a "proper" thermostatic valve intended for this
application. It has temperature markings all the way up to 90 AFAIK

Are you sure it's 90 degC and not 90 degF?!

Irritatingly, the thermo does not say. I'd assumed it would be C.

If it *is* the proper one for the job, it may just be stuck. As someone else
has suggested, remove the thermostatic head from the valve and check that
the pin moves down when you press on the end and comes up again when you
release it. If it's stuck down it would explain your problem. Tapping the
side of the valve with a metal object (spanner etc.) may free it.

Yup, I plan to do that the next time I am in the place.

This is probably an important clue. The return pipe coming out of the
bottom of the cylinder gets to a T junction a short distance away
which I guess is the main return for the whole system. The water
flowing through the top line (as opposed to the leg) of the "T" is
very warm but not as warm as the flow pipe - which sounds like what
you would expect. However, the leg of the "T" which comes from the
cylinder is stone cold. I guess that is because the cold water is
just sitting there without moving through the coil.

Ah, that explains it. I got the impression earlier that the return pipe was
cold all the way to the boiler - but now realise that it's not.

That's it. The thing works very well for heating the radiators - they
heat up nice and quick so the flow/return loop definitely appears to be
in tip-top order. We just need to figure out what's up with the cylinder
coil.

You've not mentioned a room thermostat. I assume there isn't one?

Nope, no thermostat. TBH, I've seldom if ever seen them in any houses in
Northern Ireland. Oil is popular here, which is probably because there
was no natural gas network up until around ten years ago, and the OFCH
systems installed almost universally tend to be boilers in an outhouse
with a three-port valve allowing separate control of HW and CH.

Geronimo W. Christ Esq wrote:

this time, just outside Belfast. It could be a (Northern?) Irish thing
Although, the fact that thermostatic valves are available for this
kind of application suggests that this method of heating the water is at
least practiced by more than a few people locally. I sounds like it's
just a cheapo way of heating a small-ish house.

There is a legit use for the things to regulate the maximum temp of the
HW on gravity circulated systems (i.e. older boilers with two sets of
feed/return pipes and no pump involved in the HW part).

Has it ever worked properly since you've been in the house?


No, and I'm a bit peeved about that. The transaction was completed a few
weeks ago. Since the house was basically new I did not get a full survey
done on it, which would probably have uncovered the issue before now. I

I think you may be overestimating most surveys ;-)

This is probably an important clue. The return pipe coming out of the
bottom of the cylinder gets to a T junction a short distance away which
I guess is the main return for the whole system. The water flowing
through the top line (as opposed to the leg) of the "T" is very warm but
not as warm as the flow pipe - which sounds like what you would expect.
However, the leg of the "T" which comes from the cylinder is stone cold.
I guess that is because the cold water is just sitting there without
moving through the coil.

yup sounds that way... still at least you can see where to stick your
three port valve! ;-)


--
Cheers,

John.

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

On Mon, 02 Jan 2006 01:19:46 +0000, John Rumm
wrote:

Geronimo W. Christ Esq wrote:

this time, just outside Belfast. It could be a (Northern?) Irish thing
Although, the fact that thermostatic valves are available for this
kind of application suggests that this method of heating the water is at
least practiced by more than a few people locally. I sounds like it's
just a cheapo way of heating a small-ish house.

There is a legit use for the things to regulate the maximum temp of the
HW on gravity circulated systems (i.e. older boilers with two sets of
feed/return pipes and no pump involved in the HW part).


But not on a system using a Primatic cylinder which is what I have and
that causes the DHW to be extremely hot when the CH has been on for
some time as it is just now in this weather



Stuart





Shift THELEVER to reply.

Set Square wrote:

From reading the other posts in this thread, I'd say that you have a
conventional boiler with a very *unconventional* hot water system!

I have been carefully reading the FAQ entry about combination boilers.

I assume I am right in believing that all of the hot water sources (bath
tap, shower, and kitchen hw tap) are fed off a specific water circuit
coming from the cylinder. If so, am I right in saying that provided the
existing plumbing is up to scratch, installing a combi would simply be a
matter of removing the existing boiler, cylinder and loft apparatus, and
running a flow/return from the combi's secondary heat exchanger into the
circuit formerly supplied by the cylinder, and leaving the existing CH
circuit pretty much as-is ?

That way I would not have to replace the timeclock or any of the
electronics, and I've only two extra pipes to install (and a few to
remove) - sounds like slightly less bother (but more expense) than
installing a three-port valve and controlling electronics. The diagram
suggests that the three-port valve in a combi system is built into the
boiler unit. It is something I think I will consider in the medium term.

I like the concept of a combi - it sounds very efficient. And, I imagine
that the current boilers are also condensers so they have an extra level
of efficiency that way as well.

On Tue, 03 Jan 2006 00:20:03 +0000, "Geronimo W. Christ Esq"
wrote:

Set Square wrote:

From reading the other posts in this thread, I'd say that you have a
conventional boiler with a very *unconventional* hot water system!

I have been carefully reading the FAQ entry about combination boilers.

I assume I am right in believing that all of the hot water sources (bath
tap, shower, and kitchen hw tap) are fed off a specific water circuit
coming from the cylinder. If so, am I right in saying that provided the
existing plumbing is up to scratch, installing a combi would simply be a
matter of removing the existing boiler, cylinder and loft apparatus, and
running a flow/return from the combi's secondary heat exchanger into the
circuit formerly supplied by the cylinder, and leaving the existing CH
circuit pretty much as-is ?

That way I would not have to replace the timeclock or any of the
electronics, and I've only two extra pipes to install (and a few to
remove) - sounds like slightly less bother (but more expense) than
installing a three-port valve and controlling electronics. The diagram
suggests that the three-port valve in a combi system is built into the
boiler unit. It is something I think I will consider in the medium term.

I like the concept of a combi - it sounds very efficient. And, I imagine
that the current boilers are also condensers so they have an extra level
of efficiency that way as well.


It may be ideal for your situation considering size and type of house

However, do consider the usual warnings:


- Is the mains cold supply adequate? Measure at the cold tap in the
kitchen. If less than about 20 litres/min, it may well be inadequate
for a mains fed system.

- Take a careful look at HW production rate. The quoted figures of
flow for a 35 degree rise in temperature approximate to what you will
get in total at a shower or into a bath in the winter. Some of the
smaller combis deliver 11-13 litres/min. Are you OK with that for a
shower considering that stored systems can deliver 2-3 times that?
Same for baths. Are you OK with 10-15 mins bath filling time?

You can get larger combis of 15-20 lpm, but they are physically large.
Do you have the space? Note that the rating is not important in the
CH context. If the boiler seems large, it doesn't matter because it
will modulate down to the needed rate.

On the other hand, you may well find the gain in space where the
cylinder and roof tanks are to be very appealing. The important
thing is to do some basic checks and make sure that you select
carefully.

In terms of the hookup, you have described what's involved well. It
may also be necessary to upgrade the gas supply from the meter since
combis normally require at least a 22mm supply pipe.





--

..andy

On Tue, 03 Jan 2006 00:52:44 +0000, Andy Hall
wrote:

On Tue, 03 Jan 2006 00:20:03 +0000, "Geronimo W. Christ Esq"
wrote:

Set Square wrote:

From reading the other posts in this thread, I'd say that you have a
conventional boiler with a very *unconventional* hot water system!

I have been carefully reading the FAQ entry about combination boilers.

I assume I am right in believing that all of the hot water sources (bath
tap, shower, and kitchen hw tap) are fed off a specific water circuit
coming from the cylinder. If so, am I right in saying that provided the
existing plumbing is up to scratch, installing a combi would simply be a
matter of removing the existing boiler, cylinder and loft apparatus, and
running a flow/return from the combi's secondary heat exchanger into the
circuit formerly supplied by the cylinder, and leaving the existing CH
circuit pretty much as-is ?

That way I would not have to replace the timeclock or any of the
electronics, and I've only two extra pipes to install (and a few to
remove) - sounds like slightly less bother (but more expense) than
installing a three-port valve and controlling electronics. The diagram
suggests that the three-port valve in a combi system is built into the
boiler unit. It is something I think I will consider in the medium term.

I like the concept of a combi - it sounds very efficient. And, I imagine
that the current boilers are also condensers so they have an extra level
of efficiency that way as well.


It may be ideal for your situation considering size and type of house

However, do consider the usual warnings:


- Is the mains cold supply adequate? Measure at the cold tap in the
kitchen. If less than about 20 litres/min, it may well be inadequate
for a mains fed system.

- Take a careful look at HW production rate. The quoted figures of
flow for a 35 degree rise in temperature approximate to what you will
get in total at a shower or into a bath in the winter. Some of the
smaller combis deliver 11-13 litres/min. Are you OK with that for a
shower considering that stored systems can deliver 2-3 times that?
Same for baths. Are you OK with 10-15 mins bath filling time?

You can get larger combis of 15-20 lpm, but they are physically large.
Do you have the space? Note that the rating is not important in the
CH context. If the boiler seems large, it doesn't matter because it
will modulate down to the needed rate.

On the other hand, you may well find the gain in space where the
cylinder and roof tanks are to be very appealing. The important
thing is to do some basic checks and make sure that you select
carefully.

In terms of the hookup, you have described what's involved well. It
may also be necessary to upgrade the gas supply from the meter since
combis normally require at least a 22mm supply pipe.





I have a floor standing Kingfisher ( very old one ) ,10mm piping and
rads with TRV's and a Primatic cylinder a few years ago i had a BG guy
out and he said that the rads and piping and TRV's wouldn't stand up
to it if I got a combi boiler fitted because of the pressure .I
questioned what he was saying as i couldnt see how these fittings
could fail but he was insistent ...I didnt get anyhting changed and
the boiler has lasted ever since altho' has probably cost me loads in
gas costs ..
Was he right in what he said .??





Stuart





Shift THELEVER to reply.

Stuart wrote:

I have a floor standing Kingfisher ( very old one ) ,10mm piping and
rads with TRV's and a Primatic cylinder a few years ago i had a BG guy
out and he said that the rads and piping and TRV's wouldn't stand up
to it if I got a combi boiler fitted because of the pressure .I
questioned what he was saying as i couldnt see how these fittings
could fail but he was insistent ...I didnt get anyhting changed and
the boiler has lasted ever since altho' has probably cost me loads in
gas costs ..

Was he right in what he said .??

Possibly partially right for some situations! (that got enough get out
clauses in it? ;-)

Pipework and TRVs are usually fine at pressure (just think about you
mains water pipes etc).

Rads are also usually fine unless on the last legs - in which case the
pressure change may push them over the edge and you will get pinhole
leaks. However if this is the case they were due to do it anyway - you
just accelerated the process by a few months. For a system treated with
corrosian inhibitor on a regular basis this ought not happen anyway.

Old lockshield valves may weep when the pressure is increased. Having
said that there is no guarentee they will (the ones on my system were
fine when I converted it to sealed operation)

--
Cheers,

John.

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

In an earlier contribution to this discussion,
Geronimo W. Christ Esq wrote:

Set Square wrote:

From reading the other posts in this thread, I'd say that you have a
conventional boiler with a very *unconventional* hot water system!

I have been carefully reading the FAQ entry about combination boilers.

I assume I am right in believing that all of the hot water sources
(bath tap, shower, and kitchen hw tap) are fed off a specific water
circuit coming from the cylinder. If so, am I right in saying that
provided the existing plumbing is up to scratch, installing a combi
would simply be a matter of removing the existing boiler, cylinder
and loft apparatus, and running a flow/return from the combi's
secondary heat exchanger into the circuit formerly supplied by the
cylinder, and leaving the existing CH circuit pretty much as-is ?

I rather fear that that would result in throwing out the baby with the
bathwater!

It would be a relatively small job to add proper controls to your existing
system - so why throw away a perfectly good boiler.

What you suggest would work provided you have an adequate cold water supply
*and* adequate gas supply (the required power output of a combi is
determined by its "instant" water heating capacity - and is generally
greater than that of a conventional boiler - sized on its space heating
capacity - so it needs a fat gas pipe). But be aware that many people prefer
the concept of stored hot water for fast bath filling etc.

You're going to be looking at a couple of grand for changing the boiler -
whereas you can get a suitable control pack - which would transform your
system - for as little as 60 quid. See http://tinyurl.com/9vdrj as an
example. I think I would personally spend a bit more than this and go for an
S-Plan system with two 2-port valves rather than a single 3-port valve, and
I would use a programmable room stat. Even so, we're talking less than 200
quid.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

Geronimo W. Christ Esq wrote:

There's a thermostatic valve on the hot water pipe going into the
cylinder coil, at the centre of the cylinder, and a regular valve coming
out at the bottom. Hot water is definitely passing through the input
valve as I can feel it piping hot on both sides of the valve, but the
cylinder itself is cold immediately next to where the pipe enters.

Some of the replies yesterday suggested that the thermostatic valve that
we've discussed (recalling that the cylinder coil looks like just
another radiator from the point of view of the system) could be jammed.

I went in for a look. The valve is a Pegler Belmont, this one :

http://tinyurl.com/ayssx

I gave it a few sharp but controlled taps with the heating running, but
this did not achieve anything. Then, I found that the plastic head could
be removed by unscrewing the metal nut at the base, seen in the picture
at the above URL. This exposed what looked like another nut (loose
enough to be turned by hand) with a hole in the centre. A pin was
visible, but the pin was depressed a short distance (a mm or two) below
the top of the nut. I wasn't courageous enough to mess with it (don't
want water everywhere) so I'm going to get a plumber to check it.

Does this sound like it is seized up ? I guess there is about 25-30cm of
22mm copper pipe between the thermostatic valve and then cylinder body.
All of that heats up fairly quickly when the boiler is on - around as
quickly as the bathroom radiators do (all other rads are off).

In an earlier contribution to this discussion,
Geronimo W. Christ Esq wrote:


I went in for a look. The valve is a Pegler Belmont, this one :

http://tinyurl.com/ayssx

I gave it a few sharp but controlled taps with the heating running,
but this did not achieve anything. Then, I found that the plastic
head could be removed by unscrewing the metal nut at the base, seen
in the picture at the above URL. This exposed what looked like
another nut (loose enough to be turned by hand) with a hole in the
centre. A pin was visible, but the pin was depressed a short distance
(a mm or two) below the top of the nut. Does this sound like it is seized
up ?

Very probably. Looking at the underside of the head, can you see what pushes
on the pin? Is it small enough in diameter to go down the hole in the nut to
reach the pin? If not, the pin definitely shouldn't be that low. If the
actuator *does* go inside the nut, can you move the pin down more by
pressing on it with a pin punch or similar? Does it come up again when you
stop pushing?
Can you persuade the pin to pop up by tapping the side of the valve? [Hold a
large hammer against side of the valve, and tap the other side with a small
hammer]


I guess there is about 25-30cm
of 22mm copper pipe between the thermostatic valve and then cylinder
body. All of that heats up fairly quickly when the boiler is on -
around as quickly as the bathroom radiators do (all other rads are
off).

It's probably just getting hot due to conduction in the copper pipe rather
than gue to water flowing through it.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

On Mon, 2 Jan 2006 17:03:46 -0000, "Set Square"
wrote:

In an earlier contribution to this discussion,
Geronimo W. Christ Esq wrote:


I went in for a look. The valve is a Pegler Belmont, this one :

http://tinyurl.com/ayssx

I gave it a few sharp but controlled taps with the heating running,
but this did not achieve anything. Then, I found that the plastic
head could be removed by unscrewing the metal nut at the base, seen
in the picture at the above URL. This exposed what looked like
another nut (loose enough to be turned by hand) with a hole in the
centre. A pin was visible, but the pin was depressed a short distance
(a mm or two) below the top of the nut. Does this sound like it is seized
up ?

Very probably. Looking at the underside of the head, can you see what pushes
on the pin? Is it small enough in diameter to go down the hole in the nut to
reach the pin? If not, the pin definitely shouldn't be that low. If the
actuator *does* go inside the nut, can you move the pin down more by
pressing on it with a pin punch or similar? Does it come up again when you
stop pushing?
Can you persuade the pin to pop up by tapping the side of the valve? [Hold a
large hammer against side of the valve, and tap the other side with a small
hammer]


It does sound as if the pin is jammed "down" so the valve is shut and
preventing the flow of water through it .....If the pin cannot be
persuaded to return to the "up" position then replacement of the
valve should sort the problem .




Stuart





Shift THELEVER to reply.

Stuart wrote:

It does sound as if the pin is jammed "down" so the valve is shut and
preventing the flow of water through it .....If the pin cannot be
persuaded to return to the "up" position then replacement of the
valve should sort the problem .

Thanks very much, Stuart. I've replied to John Rumm with more detail,
but I will be mentioning the likely fault to the plumber so that he can
start his investigation there.

Set Square wrote:

Very probably. Looking at the underside of the head, can you see what pushes
on the pin? Is it small enough in diameter to go down the hole in the nut to
reach the pin? If not, the pin definitely shouldn't be that low. If the
actuator *does* go inside the nut, can you move the pin down more by
pressing on it with a pin punch or similar? Does it come up again when you
stop pushing?

I will need to examine it again. I take it by messing around with the
valve I'm not likely to start a leak (unless I hit the pipe too hard and
snap it) ?

As far as I can tell, the actuator does not go inside the nut hole, it
is a flat spring loaded surface.

Can you persuade the pin to pop up by tapping the side of the valve? [Hold a
large hammer against side of the valve, and tap the other side with a small
hammer]

Will try that, thanks.

of 22mm copper pipe between the thermostatic valve and then cylinder
body. All of that heats up fairly quickly when the boiler is on -
around as quickly as the bathroom radiators do (all other rads are
off).

It's probably just getting hot due to conduction in the copper pipe rather
than gue to water flowing through it.

Okay.

Certainly we seem to be close to a solution here - many thanks to all
who have replied. The plumber will be looking at this on Wednesday (if I
can't get the pin to pop out before then) so I will pass on the details
of the likely fault.

Geronimo W. Christ Esq wrote:

I gave it a few sharp but controlled taps with the heating running, but
this did not achieve anything. Then, I found that the plastic head could
be removed by unscrewing the metal nut at the base, seen in the picture
at the above URL. This exposed what looked like another nut (loose

Try hitting it again with the head removed...

enough to be turned by hand) with a hole in the centre. A pin was
visible, but the pin was depressed a short distance (a mm or two) below
the top of the nut. I wasn't courageous enough to mess with it (don't
want water everywhere) so I'm going to get a plumber to check it.

Does this sound like it is seized up ?

Yes...

I have not seen inside one of these particular TRVs, but on all the ones
I have seen, the pin should stick up. The action of the TRV head is to
progressively push down on the pin, causing the water flow to cease. A
quick look at the bit you took off ought to confirm how it works. If the
head looks like it has a flat surface or small recess that the pin
should push against, then the pin ought to be "up" (and hence the valve
"full on") when the head is removed.


--
Cheers,

John.

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

John Rumm wrote:

I gave it a few sharp but controlled taps with the heating running,
but this did not achieve anything. Then, I found that the plastic head
could be removed by unscrewing the metal nut at the base, seen in the
picture at the above URL. This exposed what looked like another nut
(loose

Try hitting it again with the head removed...

Thanks for the reply. I might work up the courage to give that a shot
next time I'm in the house, which should be very soon. When I did
clatter it, I hit around the bottom of the valve and not the plastic head.

enough to be turned by hand) with a hole in the centre. A pin was
visible, but the pin was depressed a short distance (a mm or two)
below the top of the nut. I wasn't courageous enough to mess with it
(don't want water everywhere) so I'm going to get a plumber to check it.

Does this sound like it is seized up ?

Yes...

I have not seen inside one of these particular TRVs, but on all the ones
I have seen, the pin should stick up. The action of the TRV head is to
progressively push down on the pin, causing the water flow to cease. A
quick look at the bit you took off ought to confirm how it works. If the
head looks like it has a flat surface or small recess that the pin
should push against, then the pin ought to be "up" (and hence the valve
"full on") when the head is removed.

I looked at the inside of the head; it has a black round section with a
flat surface as you have said (there is no recess though) which is
spring-loaded. It definitely would not be possible for the black section
to physically contact the pin at this point. I am wondering, though, how
the pin managed to get below the surface of the nut with the hole, going
by the way this apparently works I'd expect it to get stuck level with
the nut rather than below it.

I'm a bit disturbed by the way the nut with the hole containing the pin
seems to swivel around freely; I was able to twist it by hand. I am
guessing this allows the valve always be open by a minimum or maximum
amount at all times, with the pin then adjusting that as appropriate.

Geronimo W. Christ Esq wrote:

Try hitting it again with the head removed...


Thanks for the reply. I might work up the courage to give that a shot
next time I'm in the house, which should be very soon. When I did
clatter it, I hit around the bottom of the valve and not the plastic head.

You are only after shock effect here - i.e. tapping the the end of a
spanner / small hammer. You are not trying to bend the pipe over! ;-)


--
Cheers,

John.

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

In message , John
Rumm writes
Geronimo W. Christ Esq wrote:

Try hitting it again with the head removed...
Thanks for the reply. I might work up the courage to give that a
shot next time I'm in the house, which should be very soon. When I
did clatter it, I hit around the bottom of the valve and not the
plastic head.

You are only after shock effect here - i.e. tapping the the end of a
spanner / small hammer. You are not trying to bend the pipe over! ;-)

What I do is to lay the flat of a spanner on the pin and just keep on
tapping it wirra 'ammer until it springs out again

--
geoff

In article ,
Geronimo W. Christ Esq wrote:
Then, I found that the plastic head could
be removed by unscrewing the metal nut at the base, seen in the picture
at the above URL. This exposed what looked like another nut (loose
enough to be turned by hand) with a hole in the centre. A pin was
visible, but the pin was depressed a short distance (a mm or two) below
the top of the nut. I wasn't courageous enough to mess with it (don't
want water everywhere) so I'm going to get a plumber to check it.

On all the TRVs I've seen, the pin is spring loaded to the up position. It
should be possible to push it down by hand and it should spring up again.

--
*What am I? Flypaper for freaks!?

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