I currently have a Y-Plan heating system. The pump and 3-port valve are both
in the airing cuboard with the 3-port valve sitting more or less on top of
the pump. The outlets from the 3-port valve - one to the coil in the
cylinder and the other to the radiators - are horizontal, and are level with
the top indirect coil connection, about half way up the cylinder.

The 3-port valve is showing its age and will soon need replacing. I would
like to convert to an S-Plan system by replacing the 3-port valve with two
2-port valves plus an automatic by-pass. I would also like to insert some
full-bore lever valves to make it easy to isolate each component for
maintenance.

I cannot do this without changing the layout somewhat. There is not enough
horizontal pipe either side of the 3-port valve (to be repaced by a tee) to
insert 2-port valves. So I would like to extend the pipework by a foot or so
above the current level, tee to 2 horizontal branches, and then come down
again vertically with a 2-port valve in each vertical drop. I would, of
course, put a vent pipe with bleed screw at the hightest point.

Can anyone see any problems with this?

TIA.
--
Cheers,
Set Square
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"Set Square" wrote in message
...
I currently have a Y-Plan heating system. The pump and 3-port valve are both
in the airing cuboard with the 3-port valve sitting more or less on top of
the pump. The outlets from the 3-port valve - one to the coil in the
cylinder and the other to the radiators - are horizontal, and are level with
the top indirect coil connection, about half way up the cylinder.

The 3-port valve is showing its age and will soon need replacing. I would
like to convert to an S-Plan system by replacing the 3-port valve with two
2-port valves plus an automatic by-pass. I would also like to insert some
full-bore lever valves to make it easy to isolate each component for
maintenance.

I cannot do this without changing the layout somewhat. There is not enough
horizontal pipe either side of the 3-port valve (to be repaced by a tee) to
insert 2-port valves. So I would like to extend the pipework by a foot or so
above the current level, tee to 2 horizontal branches, and then come down
again vertically with a 2-port valve in each vertical drop. I would, of
course, put a vent pipe with bleed screw at the hightest point.

Can anyone see any problems with this?

TIA.

Cheers,
Set Square


The fed to the coil in the cylinder doesn't really need to enter at the bottom
connector you know, so you could lift the branch from the pump higher and place
the zone valves on two different levels all together. That way you can keep the
branch to the rad' circuit where it is, and only swap round the heating coil so
it runs the other way. One TEE and a couple of elbows would do it.

"Set Square" wrote in message
...
I currently have a Y-Plan heating system. The pump and 3-port valve are
both
in the airing cuboard with the 3-port valve sitting more or less on top of
the pump. The outlets from the 3-port valve - one to the coil in the
cylinder and the other to the radiators - are horizontal, and are level
with
the top indirect coil connection, about half way up the cylinder.

The 3-port valve is showing its age and will soon need replacing. I would
like to convert to an S-Plan system by replacing the 3-port valve with two
2-port valves plus an automatic by-pass. I would also like to insert some
full-bore lever valves to make it easy to isolate each component for
maintenance.

I cannot do this without changing the layout somewhat. There is not enough
horizontal pipe either side of the 3-port valve (to be repaced by a tee)
to
insert 2-port valves. So I would like to extend the pipework by a foot or
so
above the current level, tee to 2 horizontal branches, and then come down
again vertically with a 2-port valve in each vertical drop. I would, of
course, put a vent pipe with bleed screw at the hightest point.

Can anyone see any problems with this?

- Take the flow from the boiler to the top of the airing cuboard and to the
open vent of the F&E tank.
- Tee off at the top of the airing cuopboard and take the pipe down (the
pump must be on this length half wat from the cylinder to the ceiling, as
this reduces pump niose).
- Directly after the tee insert another tee and take this to the cold feed
of the F&E tank.
- The two tees must be close together.
- The feed tee must be nearst to the pump.
- At the end of this downards length have a bend and insert the CH zone
valve.
- Tee off just before the bend and insert the DHW zone valve, then to the
top of the cylidner coil.

That is it. This is now self venting too and no need for manual air vents
and puim pnoise vastly reduced. More space for maintenance too. Insert the
pressure by-pass valve after the CH zone valve and it must be the last tee
into the boilers return. Sorted.

Use adpters for the pump, not adpters and isolation valves. Put a full bore
valve on:

- The flow just before the pump
- Just after the by-pass valve after the CH zone valve
- Just after the by-pass tee on the return.

Then with 3 valves you can isolate the cylinder, zone valbe, by -pass and
pump.

I would also like to insert some full-bore lever valves to make
it easy to isolate each component for maintenance.

I wouldn't bother. The "wet" part of a 2 port valve is usually pretty
reliable. I wouldn't be convinced that the isolation valves would be any
more so and there are 2 of those to go wrong!

Certainly, the replacement of the wet part of a 2 port valve is sufficiently
infrequently required that a drain down is not an issue.

Christian.

In an earlier contribution to this discussion,
Christian McArdle wrote:

I would also like to insert some full-bore lever valves to make
it easy to isolate each component for maintenance.

I wouldn't bother. The "wet" part of a 2 port valve is usually pretty
reliable. I wouldn't be convinced that the isolation valves would be
any more so and there are 2 of those to go wrong!

Certainly, the replacement of the wet part of a 2 port valve is
sufficiently infrequently required that a drain down is not an issue.

Christian.

Fair enough, but I still want full bore valves either side of the pump
rather than the existing gate valve adapters - so I still need to raise the
level of the tee above that of the existing 3-port valve. Even without
isolation valves, I still can't get 2-port valves on the horizontal pipes
either side of the tee.

So I still need to raise the pipework up higher and then come back down to
the upper inlet on the cylinder (which is about half-way up).

Is this a problem?

Another thing: IMM is telling me that the output from the by-pass valve
needs to last thing tee'd into the boiler return. Is this necessary? It
would be much easier to tee it into the HW return before it disappears under
the floorboards and joins up with the CH return somewhere or other. Is this
a problem - bearing in mind that the by-pass will only operate when both
zone valves are closed, so it can't make water flow backwards round the HW
circuit.
--
Cheers,
Set Square
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In an earlier contribution to this discussion,
BigWallop wrote:

"Set Square" wrote in message
...
I currently have a Y-Plan heating system. The pump and 3-port valve
are both in the airing cuboard with the 3-port valve sitting more or
less on top of the pump. The outlets from the 3-port valve - one to
the coil in the cylinder and the other to the radiators - are
horizontal, and are level with the top indirect coil connection,
about half way up the cylinder.

The 3-port valve is showing its age and will soon need replacing. I
would like to convert to an S-Plan system by replacing the 3-port
valve with two 2-port valves plus an automatic by-pass. I would also
like to insert some full-bore lever valves to make it easy to
isolate each component for maintenance.

I cannot do this without changing the layout somewhat. There is not
enough horizontal pipe either side of the 3-port valve (to be
repaced by a tee) to insert 2-port valves. So I would like to extend
the pipework by a foot or so above the current level, tee to 2
horizontal branches, and then come down again vertically with a
2-port valve in each vertical drop. I would, of course, put a vent
pipe with bleed screw at the hightest point.

Can anyone see any problems with this?

TIA.

Cheers,
Set Square


The feed to the coil in the cylinder doesn't really need to enter at
the bottom connector you know, so you could lift the branch from the
pump higher and place the zone valves on two different levels all
together.

It doesn't! The feed goes into the *top* connection - but this is only half
way up the cylinder. The return comes out of the bottom connection which is
only just above the floor.
--
Cheers,
Set Square
______
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Fair enough, but I still want full bore valves either side of the pump
rather than the existing gate valve adapters -

You can get pump adapters with ball valves instead of gate valves. They
should be considerably more reliable.

Even without isolation valves, I still can't get 2-port valves on the
horizontal pipes either side of the tee.

Go up to the T and then put the valves on the "back down" section. Place a
bleed valve on the top of the loop. It is probably not necessary in use,
though, if sealed pressurised operation is used, as it covers a multitude of
installation sins. However you should still install the valve, in case it
does prove necessary to use it.

Christian.

"Christian McArdle" wrote in message
. net...
Fair enough, but I still want full bore valves either side of the pump
rather than the existing gate valve adapters -

You can get pump adapters with ball valves instead of gate valves. They
should be considerably more reliable.

I have found that most pump adapters and integrated ball valves can't hack
it. There are some good quality full bore versions around, but are
difficult to get hold of.

"Set Square" wrote in message
...
In an earlier contribution to this discussion,
BigWallop wrote:

"Set Square" wrote in message
...
I currently have a Y-Plan heating system. The pump and 3-port valve
are both in the airing cuboard with the 3-port valve sitting more or
less on top of the pump. The outlets from the 3-port valve - one to
the coil in the cylinder and the other to the radiators - are
horizontal, and are level with the top indirect coil connection,
about half way up the cylinder.

The 3-port valve is showing its age and will soon need replacing. I
would like to convert to an S-Plan system by replacing the 3-port
valve with two 2-port valves plus an automatic by-pass. I would also
like to insert some full-bore lever valves to make it easy to
isolate each component for maintenance.

I cannot do this without changing the layout somewhat. There is not
enough horizontal pipe either side of the 3-port valve (to be
repaced by a tee) to insert 2-port valves. So I would like to extend
the pipework by a foot or so above the current level, tee to 2
horizontal branches, and then come down again vertically with a
2-port valve in each vertical drop. I would, of course, put a vent
pipe with bleed screw at the hightest point.

Can anyone see any problems with this?

TIA.

Cheers,
Set Square


The feed to the coil in the cylinder doesn't really need to enter at
the bottom connector you know, so you could lift the branch from the
pump higher and place the zone valves on two different levels all
together.

It doesn't! The feed goes into the *top* connection - but this is only half
way up the cylinder. The return comes out of the bottom connection which is
only just above the floor.

Cheers,
Set Square


Ah ha !!! With you now. So you really to make a loop that sits behind the hot
water cylinder that will also act a by-pass loop for the whole system as well
then. What orientation is the pump in? If it's standing up on end, with the
inlet and outlet vertical, then you can still take a full loop of 22 mm copper
straight up and make a big loop that sits behind the cylinder. You then take
the indirect coil from a point along the riser pipe from the pump and connect it
to the top most end of the coil the same as it is now.

With another TEE below the one for the water coil, you fit another zone valve
for the central heating loop. One more TEE will take the return from the
by-pass loop behind the cylinder back to the point where the return from the hot
tank is now.

Would that work?

Even without isolation valves, I still can't get 2-port valves on the
horizontal pipes either side of the tee.


Just had another thought. Would it make it easier to install the DHW zone
valve on the cylinder return connection? There's no reason it has to be on
the flow side. Indeed, it will run 5-10C cooler on the return leg. The
radiator valve can still stay on the flow side or also be moved to the
return side provided no radiators have unusual return locations away from
the main trunk.

Christian.

"Christian McArdle" wrote in message
. net...
Even without isolation valves, I still can't get 2-port valves on the
horizontal pipes either side of the tee.


Just had another thought. Would it make it easier to install the DHW zone
valve on the cylinder return connection? There's no reason it has to be on
the flow side. Indeed, it will run 5-10C cooler on the return leg. The
radiator valve can still stay on the flow side or also be moved to the
return side provided no radiators have unusual return locations away from
the main trunk.

Christian.

What the hell are you all on about? Just do what I suggested. Easy, low
pump noises free flow, self venting, easy to isolate all parts in the airing
cupboard, etc.

What the hell are you all on about? Just do what I suggested. Easy, low
pump noises free flow, self venting, easy to isolate all parts in the
airing
cupboard, etc.

Well, your description isn't quite clear. In particular, you don't really
explain where the fill connection goes. You mention a T for the pump before
the T for the feed, but why would another T be needed? I'm hoping you mean
just use the remaining outlet from the previous T for the feed. Perhaps a
diagram would help?

In any case, there is no indication that the F&E tank pipework passes
through this location, or that the system is gravity fed, in which case,
other methods that use the space available may be required.

Finally, the system proposed requires the boiler to have secondary overheat
protection. If this is available, you may as well have combined vent/feed as
well, to eliminate pumping over problems, or better still, convert to sealed
pressurised operation.

Note that if the boiler does not have secondary overheat protection
(normally indicated by suitability for sealed/pressurised operation), then
the proposed control layout must be changed. This is because there needs to
be a direct unvalved connection between the header feed and the boiler
return that does not cross over or combine with the venting arrangements.
This is because the boiler needs a supply of quenching water to prevent it
boiling dry. Rising steam, or an automatic bypass valve would prevent such
supply.

Christian.

In an earlier contribution to this discussion,
Christian McArdle wrote:


In any case, there is no indication that the F&E tank pipework passes
through this location, or that the system is gravity fed, in which
case, other methods that use the space available may be required.

Finally, the system proposed requires the boiler to have secondary
overheat protection. If this is available, you may as well have
combined vent/feed as well, to eliminate pumping over problems, or
better still, convert to sealed pressurised operation.

I decided to post a couple of pictures to make clear what I'm on about!

The first one http://www.mills37.plus.com/cylinder.JPG shows the existing
layout. The flow pipe from the boiler comes up through the floor, with the
flow going up through the pump to the 3-port valve - then left into the top
coil connection and right and down to the radiators. The coil return comes
out of the bottom of the cylinder, through a gate valve for balancing, and
then disappears through the floor under the pump electrics. Somewhere under
the floor, the HW and CH returns merge into a single boiler return pipe.

The system is currently vented, although I may convert it to sealed at some
time. The boiler (Baxi Solo MK I) *is* suitable for sealed operation. The
F&E tank is in the attic directly above the airing cupboard. There is a
single 22mm pipe tee'd into the flow pipe just under the floor and running
across to the LHS of the airing cupboard, where it splits into 2 pipes which
go up the wall to the attic - not visible in the picture - 22mm vent and
15mm fill.

The second picture http://www.mills37.plus.com/cylinder2.JPG is marked up in
red to show the propsed changes, as follows:
* get rid of the 3-port valve and the 2 horizontal pipes either side of it
* extend the pump outlet pipe up higher (probably raising the pump at the
same time to get a full bore valve under it
* run 2 horizontal pipes from the top of the extended flow pipe - one going
down through a 2-port valve to the top coil connection, and the other going
down through another 2-port valve to connect into the CH flow pipe
* fit a vent at the highest point (the top right red bit)
* fit an automatic by-pass valve between the flow pipe above the pump and
the HW return - replacing the existing gate valve with a tee (I can fit a
gate valve on the inlet instead, if needed)

Moving things up like this gives me a lot more room to manoeuvre - including
space for a few full-bore isolation valves to enable component changes
without draining

Are there any glaring gotchas in my proposal?

Thanks for your interest.
--
Cheers,
Set Square
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"Christian McArdle" wrote in message
. net...

What the hell are you all on about?

Just do what I suggested. Easy, low
pump noises free flow, self venting,

easy to isolate all parts in the
airing cupboard, etc.

Well, your description isn't quite clear.

In particular, you don't really
explain where the fill connection goes.

You mention a T for the pump before
the T for the feed, but why would

another T be needed? I'm hoping you mean
just use the remaining outlet from

the previous T for the feed. Perhaps a
diagram would help?



Again:



The boiler is downstairs, the F&E tank in the loft. The flow from the
boiler will go directly to the overflow over the F&E tank.

- In the airing cupboard tee off as high as possible near the ceiling on
this 22mm pipe.
- Bend down to the cylinder beneath.

- Tee off, to top of cylinder coil
- This pipe then enters the 2-way valve.

- a bend from the tee at the cylinder and insert the ch 2-way valve

- half way down the pipe from the top tee to the 3-way valve tee insert the
pump.

You will have a straight run either side of the pump reducing water noises.
Aso, it will make the system self venting. Any air in the DHW coil will
rise up through the 2-way valve past the pump and to the vent. Same with the
CH side.

To stop the pump sucking in air, take the 15mm cold feed from the F&E tank
and tee it into the pipe from the open vent pipe tee to the pump. Keep it
just before the tee, in other words the two tees together. The pump pulls
down on the cold feed from the F&E tank and open vent, with virtually the
same suction on both

- Self venting.
- Low noise
- no air sucked in.



Draw it out. It is one simple way of preventing air accumulating and
reducing pump noises. The pump will also be above the cylinder and easy to
get at.




Use fixed font.

============ Vent
||
||¦ ¦
||¦ F&E tank ¦
|| -----------
|| ¦¦
|| ¦¦T (cold feed from F&E)
T||===== Horiz. pipe near linen
|| || cupboard ceiling
T = Tee || C||
|| ||
|| C|| Pump in centre of
|| (P ) long straight firmly
|| C|| clipped (C) to wall
|| ||
|| C||
|| ||T
|| ZV====ZV= - To DHW coil flow
|||| (ZV = Z valve)
||||
|| Flow to CH rads
||
From boiler flow
(Combined fill, vent & flow)

"Christian McArdle" wrote in message
. net...
Fair enough, but I still want full bore valves either side of the pump
rather than the existing gate valve adapters -

You can get pump adapters with ball valves instead of gate valves. They
should be considerably more reliable.

Are they ******** - just wait until you try to shut one off after about five
years. 9 out of 10 start leaking water around the spindle. I invariably
replace with gate valve type as they might weep a bit when the pump is
removed but at least a slight weep around the spindle can be dealt with by
nipping up the gland.

Arriving at a pump failure job late afternoon and realising the pump has
ball valve unions seriously depresses me!

* fit an automatic by-pass valve between the flow pipe above the pump and
the HW return - replacing the existing gate valve with a tee (I can fit a
gate valve on the inlet instead, if needed)

Personally, I would use the automatic bypass valve to "short out" the hot
water zone valve. I would also remove the balancing gate valve. Hopefully,
this will give hot water priority and the pump overrun will dump any heat
into the cylinder. This is NOT an appropriate solution on an unvented
cylinder. It should only be considered for gravity cylinders and heat banks.

Christian.

Are they ******** - just wait until you try to shut one off after about
five
years. 9 out of 10 start leaking water around the spindle.

Strange. I've never seen a gate valve type actually work when required,
whilst the ball types have always been fine. A small sample size, I'll grant
you, though...

Christian.

In an earlier contribution to this discussion,
Christian McArdle wrote:

* fit an automatic by-pass valve between the flow pipe above the
pump and the HW return - replacing the existing gate valve with a
tee (I can fit a gate valve on the inlet instead, if needed)

Personally, I would use the automatic bypass valve to "short out" the
hot water zone valve. I would also remove the balancing gate valve.
Hopefully, this will give hot water priority and the pump overrun
will dump any heat into the cylinder. This is NOT an appropriate
solution on an unvented cylinder. It should only be considered for
gravity cylinders and heat banks.

Christian.

Tha't an interesting idea. Dumping a bit of heat into the HW for a few
seconds (during pump over-run) certainly wouldn't do any harm.

Presumably you are referring to unvented *cylinders*? I assume that if I
convert the *primary* circuit to unvented, that wouldn't be a problem?

It's probably a good idea to get rid of the balancing gate valve - in fact,
I'll open it right up now to see what happens. Since I've fitted a
programmable stat on the CH, I generally heat the HW when the CH isn't on,
anyway - so there's no need for any balancing.

Can you see any other problems in what I want to do - with reference to the
pictures mentioned in my earlier post? [
http://www.mills37.plus.com/cylinder.JPG and
http://www.mills37.plus.com/cylinder2.JPG]
--
Cheers,
Set Square
______
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In an earlier contribution to this discussion,
Christian McArdle wrote:

Are they ******** - just wait until you try to shut one off after
about five years. 9 out of 10 start leaking water around the spindle.

Strange. I've never seen a gate valve type actually work when
required, whilst the ball types have always been fine. A small sample
size, I'll grant you, though...

Christian.

Also, both my pump gate valves started leaking because the fibre washers
between the body and the works crumbled (not the gland round the shaft) -
and could only be addressed by dismantling the valves, rather defeating the
object of the things!
--
Cheers,
Set Square
______
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Tha't an interesting idea. Dumping a bit of heat into the HW for a few
seconds (during pump over-run) certainly wouldn't do any harm.

There is one disadvantage I can think of, though. You could possibly
overheat the water if all the TRVs are set low and the ABV starts to open. I
don't know if this would cause much of a problem in a cylinder. It would
cause none in a heat bank, as the water is supposed to be kept hot and it is
water that would have passed through anyway.

Presumably you are referring to unvented *cylinders*? I assume that if I
convert the *primary* circuit to unvented, that wouldn't be a problem?

Yes, an unvented cylinder. The primary can be sealed pressurised.

Christian.

"Christian McArdle" wrote in message
. net...
Tha't an interesting idea. Dumping a bit of heat into the HW for a few
seconds (during pump over-run) certainly wouldn't do any harm.

There is one disadvantage I can think of, though. You could possibly
overheat the water if all the TRVs are set low and the ABV starts to open.
I
don't know if this would cause much of a problem in a cylinder. It would
cause none in a heat bank, as the water is supposed to be kept hot and it
is
water that would have passed through anyway.

Presumably you are referring to
unvented *cylinders*? I assume that if I
convert the *primary* circuit to unvented, that wouldn't be a problem?

Yes, an unvented cylinder. The primary can be sealed pressurised.

Having an auto by-pass dumping heat into a cylinder is a no, no, unless. the
cylinder has a boiler high temp cut off and a hot water draw-off blending
valve. Without these, water in the cylidner may get to scalding level and
the cylinder will may get to boiler flow temperature (not a problem if a
blending valve is used).

Without these, water in the cylidner may get to scalding level and
the cylinder will may get to boiler flow temperature (not a problem if a
blending valve is used).

Yes, that's why I would suggest the heat bank might be more suitable for it.
These are typically fitted with blending valves or other systems of
temperature control.

Christian.

In an earlier contribution to this discussion,
IMM wrote:


Having an auto by-pass dumping heat into a cylinder is a no, no,
unless. the cylinder has a boiler high temp cut off and a hot water
draw-off blending valve. Without these, water in the cylidner may
get to scalding level and the cylinder will may get to boiler flow
temperature (not a problem if a blending valve is used).

[So what happens if you have gravity primary circulation in the HW circuit
(with no zone valve and tank stat to convert them to C-Plan systems) - as a
great number of systems still do?]


Back to the main subject, if I can't dump the bypass into the cylinder,
what's wrong with dumping it into the HW return before it merges with the CH
return, as per
http://www.mills37.plus.com/cylinder2.JPG ?
--
Cheers,
Set Square
______
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[So what happens if you have gravity primary circulation in the HW circuit
(with no zone valve and tank stat to convert them to C-Plan systems) - as
a
great number of systems still do?]

All such systems and even fully pumped systems without cyldiner thermostats
are indeed dangerous.

Christian.

In an earlier contribution to this discussion,
Christian McArdle wrote:

[So what happens if you have gravity primary circulation in the HW
circuit (with no zone valve and tank stat to convert them to C-Plan
systems) - as a great number of systems still do?]

All such systems and even fully pumped systems without cyldiner
thermostats are indeed dangerous.

Christian.


Agreed, but there are lot of them about - as evidenced by many of the
questions in this NG!

When I had one in my previous house, I at least had a Cytrol valve (a bit
like a TRV) in the gravity return, to stop the flow when the HW was hot
enough. [Only problem was that the flow would occasionally decide to go the
other way round - whereupon the Cyltrol found itself on the *input* side of
the cylinder - and I got no hot water!]
--
Cheers,
Set Square
______
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"Set Square" wrote in message
...
In an earlier contribution to this discussion,
Christian McArdle wrote:

[So what happens if you have gravity primary circulation in the HW
circuit (with no zone valve and tank stat to convert them to C-Plan
systems) - as a great number of systems still do?]

All such systems and even fully pumped systems without cyldiner
thermostats are indeed dangerous.

Christian.

Agreed, but there are lot of them about - as evidenced by many of the
questions in this NG!

illegal on new systems.

In an earlier contribution to this discussion,
IMM wrote:

"Set Square" wrote in message
...
In an earlier contribution to this discussion,
Christian McArdle wrote:

[So what happens if you have gravity primary circulation in the HW
circuit (with no zone valve and tank stat to convert them to C-Plan
systems) - as a great number of systems still do?]

All such systems and even fully pumped systems without cyldiner
thermostats are indeed dangerous.

Christian.

Agreed, but there are lot of them about - as evidenced by many of the
questions in this NG!

illegal on new systems.


Yes - but on the basis of thermal efficiency rather than safety.
--
Cheers,
Set Square
______
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"Set Square" wrote in message
...
In an earlier contribution to this discussion,
IMM wrote:

"Set Square" wrote in message
...
In an earlier contribution to this discussion,
Christian McArdle wrote:

[So what happens if you have gravity primary circulation in the HW
circuit (with no zone valve and tank stat to convert them to C-Plan
systems) - as a great number of systems still do?]

All such systems and even fully pumped systems without cyldiner
thermostats are indeed dangerous.

Christian.

Agreed, but there are lot of them about - as evidenced by many of the
questions in this NG!

illegal on new systems.

Yes - but on the basis of thermal efficiency rather than safety.

I believe safety was factored into their decision.

In an earlier contribution to this discussion,
IMM wrote:

All such systems and even fully pumped systems without cyldiner
thermostats are indeed dangerous.

Agreed, but there are lot of them about - as evidenced by many of
the questions in this NG!

illegal on new systems.

Yes - but on the basis of thermal efficiency rather than safety.

I believe safety was factored into their decision.

Do you know of any legislation which explicitly forbids gravity systems
running at boiler temperature? As far as I am aware, such systems would be
implicitly - but not explicitly - outlawed simply because they fail to meet
the boiler interlock requirement. My understanding is that boiler interlocks
are only required on fuel efficiency grounds.
--
Cheers,
Set Square
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"Set Square" wrote in message
...
In an earlier contribution to this discussion,
IMM wrote:

All such systems and even fully pumped systems without cyldiner
thermostats are indeed dangerous.

Agreed, but there are lot of them about - as evidenced by many of
the questions in this NG!

illegal on new systems.

Yes - but on the basis of thermal efficiency rather than safety.

I believe safety was factored into their decision.

Do you know of any legislation which explicitly forbids gravity systems
running at boiler temperature? As far as I am aware, such systems would be
implicitly - but not explicitly - outlawed simply because they fail to
meet
the boiler interlock requirement. My understanding is that boiler
interlocks
are only required on fuel efficiency grounds.

Having a boiler interlock there is another level of temperature control and
safety.

Yes - but on the basis of thermal efficiency rather than safety.

That is certainly my understanding too. However, there are rumours of a
safety requirement coming in as well, which will mandate TMVs on the output
of conventional cylinders, bringing the temperature down to some ridiculous
level like 40C, which effectively bans hot baths and prevents the topping up
of the BS tepid bath with hot water to extend its life.

Christian.

"Christian McArdle" wrote in message
. net...
Yes - but on the basis of thermal efficiency rather than safety.

That is certainly my understanding too. However, there are rumours of a
safety requirement coming in as well, which will mandate TMVs on the
output
of conventional cylinders, bringing the temperature down to some
ridiculous
level like 40C,

user adjustable.

"Set Square" wrote in message
...
In an earlier contribution to this discussion,

SNIP

Do you know of any legislation which explicitly forbids gravity systems
running at boiler temperature? As far as I am aware, such systems would be
implicitly - but not explicitly - outlawed simply because they fail to
meet
the boiler interlock requirement. My understanding is that boiler
interlocks
are only required on fuel efficiency grounds.

Despite having "plan" systems installed I very often find cylinder stats
wound right up so as to be ineffective. Asking the householder often elicits
the reply "we like our hot water to be really hot".
Makes all this well meaning efficiency legislation totally useless doesn't
it?

You can please some of the people some of the
time...................................