We're having the whole lot stripped out - want one that isn't 30 years
old and badly insulated for the new boiler - and the installer has
suggested a mains pressure cylinder. Apart from anything else the
warranty is longer!

What do the team think?

Andy

On 17/08/15 21:36, Vir Campestris wrote:
We're having the whole lot stripped out - want one that isn't 30 years
old and badly insulated for the new boiler - and the installer has
suggested a mains pressure cylinder. Apart from anything else the
warranty is longer!

What do the team think?

Andy
as long as you put on a water softener, mains pressure is the dogs ********

Until the supply goes off anyway:-)

--
New Socialism consists essentially in being seen to have your heart in
the right place whilst your head is in the clouds and your hand is in
someone else's pocket.

On Monday, 17 August 2015 21:36:39 UTC+1, Vir Campestris wrote:
We're having the whole lot stripped out - want one that isn't 30 years
old and badly insulated for the new boiler - and the installer has
suggested a mains pressure cylinder. Apart from anything else the
warranty is longer!
What do the team think?

Depends on your mains pressure and flow.

On the upside
- no loft tanks
- mains pressure hot water for showers

On the downside
- higher initial cost
- requires annual safety check
- requires tundisk and pressure relief pipework
- may also require pressure regulating valve and pressure relief valve on the cold mains inlet as well

Owain

On 17/08/2015 22:07, wrote:
On Monday, 17 August 2015 21:36:39 UTC+1, Vir Campestris wrote:
We're having the whole lot stripped out - want one that isn't 30 years
old and badly insulated for the new boiler - and the installer has
suggested a mains pressure cylinder. Apart from anything else the
warranty is longer!
What do the team think?

Depends on your mains pressure and flow.

On the upside
- no loft tanks
- mains pressure hot water for showers

On the downside
- higher initial cost
- requires annual safety check
- requires tundisk and pressure relief pipework
- may also require pressure regulating valve and pressure relief valve on the cold mains inlet as well


What does the annual safety check entail?

The Natural Philosopher wrote:
On 17/08/15 21:36, Vir Campestris wrote:
We're having the whole lot stripped out - want one that isn't 30 years
old and badly insulated for the new boiler - and the installer has
suggested a mains pressure cylinder. Apart from anything else the
warranty is longer!

What do the team think?

Andy
as long as you put on a water softener, mains pressure is the dogs ********

Until the supply goes off anyway:-)


My water supply has failed twice in the last 8 months. Corroding pipework.

On 17 Aug 2015, Fredxxx grunted:

On 17/08/2015 22:07, wrote:
On Monday, 17 August 2015 21:36:39 UTC+1, Vir Campestris wrote:
We're having the whole lot stripped out - want one that isn't 30
years old and badly insulated for the new boiler - and the installer
has suggested a mains pressure cylinder. Apart from anything else
the warranty is longer!
What do the team think?

Depends on your mains pressure and flow.

On the upside
- no loft tanks
- mains pressure hot water for showers

On the downside
- higher initial cost
- requires annual safety check

- requires tundisk and pressure relief pipework
- may also require pressure regulating valve and pressure relief
valve on the cold mains inlet as well

The above two items are really just part of the installation though; ie
the higher initial cost. But I suppose could cause issues depending on
the location of the installation.

On the downside I'd add that you might want to consider that if you are
using an existing old CH system, to bear in mind that hitherto it's been
used just at low pressure; will it stand being used at mains pressure,
or might there be a partially corroded weak spot in an old radiator
which will blow in spectacular fashion.

But then again, on the upside, if ever a pressurised system does leak
for whatever reason, there's only a finite volume of water which can be
ejected, compared with an unvented system which would leak forever if
allowed.

Seems to heat up HW very quickly too.

We had one of these systems installed about 12 years ago and I love it,
especially for the showers (nothwithstanding the spectacular leak within
the first week!)

What does the annual safety check entail?

I think mainly eyeballing to check all is working as it should - notably
the safety features - and checking the status of the sacrificial anode
in the tank, if it needs one.

--
David

On 17/08/2015 23:33, Lobster wrote:
On 17 Aug 2015, Fredxxx grunted:

On 17/08/2015 22:07, wrote:
On Monday, 17 August 2015 21:36:39 UTC+1, Vir Campestris wrote:
We're having the whole lot stripped out - want one that isn't 30
years old and badly insulated for the new boiler - and the installer
has suggested a mains pressure cylinder. Apart from anything else
the warranty is longer!
What do the team think?

Depends on your mains pressure and flow.

On the upside
- no loft tanks
- mains pressure hot water for showers

On the downside
- higher initial cost
- requires annual safety check

- requires tundisk and pressure relief pipework
- may also require pressure regulating valve and pressure relief
valve on the cold mains inlet as well

The above two items are really just part of the installation though; ie
the higher initial cost. But I suppose could cause issues depending on
the location of the installation.

Indeed.

On the downside I'd add that you might want to consider that if you are
using an existing old CH system, to bear in mind that hitherto it's been
used just at low pressure; will it stand being used at mains pressure,
or might there be a partially corroded weak spot in an old radiator
which will blow in spectacular fashion.

I think you are conflating some issues here... the "mains pressure" bit
here is the DHW in the tank and has nothing to do with the primary
heating circuit that the rads are or. That could be a traditional vented
arrangement if you wanted or a modern "sealed system".

The situation you describe may be valid if converting a whole CH system
from vented to sealed.

But then again, on the upside, if ever a pressurised system does leak
for whatever reason, there's only a finite volume of water which can be
ejected, compared with an unvented system which would leak forever if
allowed.

If the DHW leaks, remember its connected to the mains ;-)

--
Cheers,

John.

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

On 17/08/2015 22:23, Fredxxx wrote:
On 17/08/2015 22:07, wrote:
On Monday, 17 August 2015 21:36:39 UTC+1, Vir Campestris wrote:
We're having the whole lot stripped out - want one that isn't 30 years
old and badly insulated for the new boiler - and the installer has
suggested a mains pressure cylinder. Apart from anything else the
warranty is longer!
What do the team think?

Depends on your mains pressure and flow.

On the upside
- no loft tanks
- mains pressure hot water for showers

On the downside
- higher initial cost
- requires annual safety check
- requires tundisk and pressure relief pipework
- may also require pressure regulating valve and pressure relief valve
on the cold mains inlet as well


What does the annual safety check entail?

From:

http://wiki.diyfaq.org.uk/index.php?...requirement s

Regular service and maintenance of unvented systems is vital and should
typically be carried out annually. Maintenance tasks should include:

Cleaning and inspection of the strainer in the cold water supply to the
Pressure Reduction Valve

Inspection of pressure / temperature relief valve and expansion relief
valve

Manual operation of each relief valve to ensure that water flows freely
to the tundish, and that they reseat correctly.

Checking of the pressure in the expansion vessel, and topping up if
required

(it takes me about 10 - 15 mins to do all those on mine)


--
Cheers,

John.

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

On 17/08/2015 21:36, Vir Campestris wrote:

We're having the whole lot stripped out - want one that isn't 30 years
old and badly insulated for the new boiler - and the installer has
suggested a mains pressure cylinder. Apart from anything else the
warranty is longer!

What do the team think?

I personally like them... however, some caveats:

Make sure you have a decent mains flow rate so as to get the best from
them. Basically they can deliver hot water at whatever rate your mains
can supply cold. Also think twice if you are in an area that frequently
gets mains water interruptions.



--
Cheers,

John.

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

On Monday, 17 August 2015 21:36:39 UTC+1, Vir Campestris wrote:
We're having the whole lot stripped out - want one that isn't 30 years
old and badly insulated for the new boiler - and the installer has
suggested a mains pressure cylinder. Apart from anything else the
warranty is longer!

What do the team think?

Andy

The conventional (old) technology is simpler and works well with minimum maintenance.
The pressurised system needs regular maintenance and there are (expensive) moving parts to go wrong.
Unless your mains incomer is brand new (no scale) there is no guarantees you with get more than a trickle of water to filla bath.

People will tell yoi how marvellous mainpressure hot water systems are but there are lots more parts to go wrong.

There is no need to remove everything.
All you need is a new header tank (if it's a galvanised tank) If plastic it will be OK.
And possibly a new cylinder.

Sounds to me that your plumber is on a work creation scheme or doesn't know anything.
In other words you are being ripped off with unnecessary work and expense. ie you are being advised by a cowboy.
There is never any need for a full scale rip out everything.
Old copper pipe (and cylinders) are much thicker then the new and lasts virtually forever.

On 17/08/15 23:33, Lobster wrote:
On 17 Aug 2015, Fredxxx grunted:

On 17/08/2015 22:07, wrote:
On Monday, 17 August 2015 21:36:39 UTC+1, Vir Campestris wrote:
We're having the whole lot stripped out - want one that isn't 30
years old and badly insulated for the new boiler - and the installer
has suggested a mains pressure cylinder. Apart from anything else
the warranty is longer!
What do the team think?

Depends on your mains pressure and flow.

On the upside
- no loft tanks
- mains pressure hot water for showers

On the downside
- higher initial cost
- requires annual safety check

- requires tundisk and pressure relief pipework
- may also require pressure regulating valve and pressure relief
valve on the cold mains inlet as well

The above two items are really just part of the installation though; ie
the higher initial cost. But I suppose could cause issues depending on
the location of the installation.

On the downside I'd add that you might want to consider that if you are
using an existing old CH system, to bear in mind that hitherto it's been
used just at low pressure; will it stand being used at mains pressure,
or might there be a partially corroded weak spot in an old radiator
which will blow in spectacular fashion.

just shows that you dont inderstand the first thing about it.

The *central heating* is on the primary side and is not pressurised
beyond what you allow it to be - usually 1 bar or so.

Only the DHW and cold water is at mains pressure.


But then again, on the upside, if ever a pressurised system does leak
for whatever reason, there's only a finite volume of water which can be
ejected, compared with an unvented system which would leak forever if
allowed.

Seems to heat up HW very quickly too.

We had one of these systems installed about 12 years ago and I love it,
especially for the showers (nothwithstanding the spectacular leak within
the first week!)

What does the annual safety check entail?

I think mainly eyeballing to check all is working as it should - notably
the safety features - and checking the status of the sacrificial anode
in the tank, if it needs one.



--
New Socialism consists essentially in being seen to have your heart in
the right place whilst your head is in the clouds and your hand is in
someone else's pocket.

On 18/08/2015 09:25, The Natural Philosopher wrote:

The *central heating* is on the primary side and is not pressurised
beyond what you allow it to be - usually 1 bar or so.

Only the DHW and cold water is at mains pressure.

Even that's not quite true as a PRV will be fitted, set to about 3.5
bar. There will be a safety valve after this set to open well before the
safe working pressure in the cylinder is reached (probably ~7 bar). This
may be combined with a temperature limit too depending on the heat
sources feeding the tank. Solar and solid fuel can get bloody hot.

On 18/08/2015 09:39, dennis@home wrote:
On 18/08/2015 09:25, The Natural Philosopher wrote:

The *central heating* is on the primary side and is not pressurised
beyond what you allow it to be - usually 1 bar or so.

Only the DHW and cold water is at mains pressure.

Even that's not quite true as a PRV will be fitted, set to about 3.5
bar. There will be a safety valve after this set to open well before the
safe working pressure in the cylinder is reached (probably ~7 bar). This
may be combined with a temperature limit too depending on the heat
sources feeding the tank. Solar and solid fuel can get bloody hot.

You generally can't use solid fuel for heating unvented cylinders...


--
Cheers,

John.

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

On 18/08/2015 08:33, harry opened his mouth, primarily it seems to
change feet:

On Monday, 17 August 2015 21:36:39 UTC+1, Vir Campestris wrote:
We're having the whole lot stripped out - want one that isn't 30 years
old and badly insulated for the new boiler - and the installer has
suggested a mains pressure cylinder. Apart from anything else the
warranty is longer!

What do the team think?

Andy

The conventional (old) technology is simpler and works well with minimum maintenance.

It works - how well varies enormously from adequate to feeble.

The pressurised system needs regular maintenance and there are (expensive) moving parts to go wrong.

Not sure what your definition of expensive moving parts are, but one
might argue that a shower pump required to get a decent shower out of a
conventional cylinder would count as one.

Unless your mains incomer is brand new (no scale) there is no guarantees you with get more than a trickle of water to filla bath.

As everyone else has mentioned, a decent flow rate and pressure on the
mains are prerequisites

People will tell yoi how marvellous mainpressure hot water systems are but there are lots more parts to go wrong.

The two statements are unconnected... The second is possibly doubtful.

A conventional system has one valve / moving part in the cold cistern,
and probably a zone valve in the primary of the CH feed. So two in total.

An unvented system has a combined control valve on the inlet (over
pressure, and PRV typically), and a over temp and relief valve on the
side. Plus the expansion vessel. So in all five moving parts in place of
two - hardly "lots"

There is also no cold cistern to overflow, freeze, acquire dead
wildlife, or leak through your ceiling. No need for shower pumps.

There is no need to remove everything.
All you need is a new header tank (if it's a galvanised tank) If plastic it will be OK.
And possibly a new cylinder.

Erm, that pretty much counts as removing everything.

Sounds to me that your plumber is on a work creation scheme or doesn't know anything.

Alternatively, he has seen that there is a decent flow rate available
from the mains, and has recommended a system that will give far better
performance to the customer.

In other words you are being ripped off with unnecessary work and expense. ie you are being advised by a cowboy.

Well when it comes to dodgy advice, you are the master.

There is never any need for a full scale rip out everything.
Old copper pipe (and cylinders) are much thicker

same for usenet posters huh...

then the new and lasts virtually forever.

Until it doesn't - and at 30 years, it will be only a matter of time
before something leaks.

Also (surprisingly) harry seems to have missed the other significant points:

The old cylinder is poorly insulated. Yes this could be improved with a
jacket etc, but it will be difficult to get it to the standard of a
modern cylinder.

Secondly, the old cylinder will have a very low efficiency heat
exchanger. This will result is very slow recovery, and high flow return
temperatures for the boiler - leading to further loss of efficiency
there as well. A modern unvented cylinder will be able to take the
boiler's full output during recovery.



--
Cheers,

John.

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

On 18/08/2015 12:24, John Rumm wrote:

Not sure what your definition of expensive moving parts are, but one
might argue that a shower pump required to get a decent shower out of a
conventional cylinder would count as one.


The shower is downstairs. Upstairs we only have a (brand new!) bath and
basin. The current shower works fine - in fact, it has a pump and we've
turned it off as unnecessary.

Unless your mains incomer is brand new (no scale) there is no
guarantees you with get more than a trickle of water to filla bath.

As everyone else has mentioned, a decent flow rate and pressure on the
mains are prerequisites

People will tell yoi how marvellous mainpressure hot water systems are
but there are lots more parts to go wrong.

The two statements are unconnected... The second is possibly doubtful.

A conventional system has one valve / moving part in the cold cistern,
and probably a zone valve in the primary of the CH feed. So two in total.

An unvented system has a combined control valve on the inlet (over
pressure, and PRV typically), and a over temp and relief valve on the
side. Plus the expansion vessel. So in all five moving parts in place of
two - hardly "lots"

There is also no cold cistern to overflow, freeze, acquire dead
wildlife, or leak through your ceiling. No need for shower pumps.

There is no need to remove everything.
All you need is a new header tank (if it's a galvanised tank) If
plastic it will be OK.
And possibly a new cylinder.

Erm, that pretty much counts as removing everything.

The loft tanks are plastic. A bit sludgy, but plastic. They're also
under thatch which should help protect from frost.

snip

The old cylinder is poorly insulated. Yes this could be improved with a
jacket etc, but it will be difficult to get it to the standard of a
modern cylinder.

Secondly, the old cylinder will have a very low efficiency heat
exchanger. This will result is very slow recovery, and high flow return
temperatures for the boiler - leading to further loss of efficiency
there as well. A modern unvented cylinder will be able to take the
boiler's full output during recovery.

OK, thanks everyone. I've raised my concern over the downstairs bathroom
radiator - it has a large blister which might be full of water. But WTH
that's on a solid quarry tiled floor.

Andy

On 18/08/2015 21:05, Vir Campestris wrote:
On 18/08/2015 12:24, John Rumm wrote:

Not sure what your definition of expensive moving parts are, but one
might argue that a shower pump required to get a decent shower out of a
conventional cylinder would count as one.


The shower is downstairs. Upstairs we only have a (brand new!) bath and
basin. The current shower works fine - in fact, it has a pump and we've
turned it off as unnecessary.

Unless your mains incomer is brand new (no scale) there is no
guarantees you with get more than a trickle of water to filla bath.

As everyone else has mentioned, a decent flow rate and pressure on the
mains are prerequisites

People will tell yoi how marvellous mainpressure hot water systems are
but there are lots more parts to go wrong.

The two statements are unconnected... The second is possibly doubtful.

A conventional system has one valve / moving part in the cold cistern,
and probably a zone valve in the primary of the CH feed. So two in total.

An unvented system has a combined control valve on the inlet (over
pressure, and PRV typically), and a over temp and relief valve on the
side. Plus the expansion vessel. So in all five moving parts in place of
two - hardly "lots"

There is also no cold cistern to overflow, freeze, acquire dead
wildlife, or leak through your ceiling. No need for shower pumps.

There is no need to remove everything.
All you need is a new header tank (if it's a galvanised tank) If
plastic it will be OK.
And possibly a new cylinder.

Erm, that pretty much counts as removing everything.

The loft tanks are plastic. A bit sludgy, but plastic. They're also
under thatch which should help protect from frost.

snip

The old cylinder is poorly insulated. Yes this could be improved with a
jacket etc, but it will be difficult to get it to the standard of a
modern cylinder.

Secondly, the old cylinder will have a very low efficiency heat
exchanger. This will result is very slow recovery, and high flow return
temperatures for the boiler - leading to further loss of efficiency
there as well. A modern unvented cylinder will be able to take the
boiler's full output during recovery.

OK, thanks everyone. I've raised my concern over the downstairs bathroom
radiator - it has a large blister which might be full of water. But WTH
that's on a solid quarry tiled floor.

Its a bit unclear from your original post if you are also converting
your CH primary side from vented to sealed (i.e. typically with a new
boiler).

If so, then yes you may in theory get failures of stuff that was on its
last legs anyway - but in general, problems are rare. (I have converted
several vented systems to sealed operation and not had a problem so far).


--
Cheers,

John.

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

On 18/08/2015 21:05, Vir Campestris wrote:

snip

OK, thanks everyone. I've raised my concern over the downstairs bathroom
radiator - it has a large blister which might be full of water. But WTH
that's on a solid quarry tiled floor.

My experience is that water in one room will often spread into another,
and at the most inconvenient time possible.

Personally I would examine the blister a bit more and replace if
necessary at the same time as your other work.

On 19/08/2015 23:40, Fredxxx wrote:
On 18/08/2015 21:05, Vir Campestris wrote:

snip

OK, thanks everyone. I've raised my concern over the downstairs bathroom
radiator - it has a large blister which might be full of water. But WTH
that's on a solid quarry tiled floor.

My experience is that water in one room will often spread into another,
and at the most inconvenient time possible.

Personally I would examine the blister a bit more and replace if
necessary at the same time as your other work.

The right time to do it is when he has the system drained. If it's full
of water it'll drop a teacup full on the floor, and that will be it.

Andy