A friend of mine has just had a (leaking) 25 year old HW tank replaced -
standard vented HW system gas heated by a secondary coil.

The house is just like mine and on the output of the secondary heating
coil there was a tap like body - neither hers or mine has ever had a
handle and I assume that it is the equivalent of the lock-shield valve
on the rads. It is designed (I assume) to stop the HW tank hogging all
the heat when both HW tank and rads are both demanding heat - but once
set during installation it can be forgotten (in just the same way that
the lock-shields are forgotten).

Anyway as part of the new tank installation this tap has been removed
and not replaced with anything. Is this normal for modern installations
or has there been some sort of drop off?

We wont find out how balanced the system is until much later in the year
and if its wrong I think it would be better to get the installers back
sooner rather than later.

Thanks for any advice

--
Chris

"news" wrote in message
...
A friend of mine has just had a (leaking) 25 year old HW tank replaced -
standard vented HW system gas heated by a secondary coil.

The house is just like mine and on the output of the secondary heating
coil there was a tap like body - neither hers or mine has ever had a
handle and I assume that it is the equivalent of the lock-shield valve on
the rads. It is designed (I assume) to stop the HW tank hogging all the
heat when both HW tank and rads are both demanding heat - but once set
during installation it can be forgotten (in just the same way that the
lock-shields are forgotten).

Anyway as part of the new tank installation this tap has been removed and
not replaced with anything. Is this normal for modern installations or
has there been some sort of drop off?

We wont find out how balanced the system is until much later in the year
and if its wrong I think it would be better to get the installers back
sooner rather than later.

Thanks for any advice

In days of yore, the hot water cylinder was often heated by a separate
gravity/convection circuit that was uncontrolled.

If it is to be part of the pumped system, either it will have to have either
some sort of manual control valve to balance the system
OR more usually
it has a separate circuit controlled by a motorised valve/s
(thermostatically controlled) so that it can be shut off or the entire
boiler output goes to quickly heat the water.
This is a lot more useful and efficient.

If the new tank has no means of balancing/restricting the primary water
flow, you will likely find that most of the primary water goes through the
coil and almost none through the radiators.

On 14/06/2014 06:42, harryagain wrote:
"news" wrote in message
...
A friend of mine has just had a (leaking) 25 year old HW tank replaced -
standard vented HW system gas heated by a secondary coil.

The house is just like mine and on the output of the secondary heating
coil there was a tap like body - neither hers or mine has ever had a
handle and I assume that it is the equivalent of the lock-shield valve on
the rads. It is designed (I assume) to stop the HW tank hogging all the
heat when both HW tank and rads are both demanding heat - but once set
during installation it can be forgotten (in just the same way that the
lock-shields are forgotten).

Anyway as part of the new tank installation this tap has been removed and
not replaced with anything. Is this normal for modern installations or
has there been some sort of drop off?

We wont find out how balanced the system is until much later in the year
and if its wrong I think it would be better to get the installers back
sooner rather than later.

Thanks for any advice

In days of yore, the hot water cylinder was often heated by a separate
gravity/convection circuit that was uncontrolled.

If it is to be part of the pumped system, either it will have to have either
some sort of manual control valve to balance the system
OR more usually
it has a separate circuit controlled by a motorised valve/s
(thermostatically controlled) so that it can be shut off or the entire
boiler output goes to quickly heat the water.
This is a lot more useful and efficient.

If the new tank has no means of balancing/restricting the primary water
flow, you will likely find that most of the primary water goes through the
coil and almost none through the radiators.



Thanks, It does have a three way valve, so I am not worried about when
only the radiators or only HW is calling for heat. However, I suspect
that now if both HW and rads call for heat she will have to wait until
the water is hot and the three way valve shuts off the cylinder until
anything goes into the rads.

This seems like a bit of a retrograde step to my very first house which
had a "Hot water" or "CH" priority system. In this case if set to HW
priority there was no CH until the tank was hot.

--
Chris

In article ,
news writes:
A friend of mine has just had a (leaking) 25 year old HW tank replaced -
standard vented HW system gas heated by a secondary coil.

The house is just like mine and on the output of the secondary heating
coil there was a tap like body - neither hers or mine has ever had a
handle and I assume that it is the equivalent of the lock-shield valve
on the rads. It is designed (I assume) to stop the HW tank hogging all
the heat when both HW tank and rads are both demanding heat - but once
set during installation it can be forgotten (in just the same way that
the lock-shields are forgotten).

Anyway as part of the new tank installation this tap has been removed
and not replaced with anything. Is this normal for modern installations
or has there been some sort of drop off?

Problem with older cylinders is they didn't have many turns in the
coil, so ended up sending the water back without much of the heat
being removed. So yes, they short-circuited the heating system
without dumping much heat into the tank, so boiler output was much
reduced when running both heating and HW.

Newer cylinders tend to have larger coils, or even fast heat recovery
where the coil splits into several thinner coils for larger surface
area and higher heat input into the cylinder. So although this will
short out the central heating, it will absorb most of the boiler's
output resulting in a very fast reheat of the tank. The tank stat will
switch back to heating-only before the house starts cooling down.
Some systems nowadays don't even have the mid-position for both heating
and HW - when there's demand from the cylinder, they divert 100% of the
boiler output to a fast recovery coil, which will reheat the cylinder
in minutes, before switching bask to central heating - the radiators
won't even have time to get cold.

OTOH, if the cylinder only has a few turns of the coil, without the
balancing gate valve, it won't work optimally. I don't know if these
cylinders are still available - maybe someone else in the group might?

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

On 14/06/2014 09:54, Andrew Gabriel wrote:


Problem with older cylinders is they didn't have many turns in the
coil, so ended up sending the water back without much of the heat
being removed. So yes, they short-circuited the heating system
without dumping much heat into the tank, so boiler output was much
reduced when running both heating and HW.

Newer cylinders tend to have larger coils, or even fast heat recovery
where the coil splits into several thinner coils for larger surface
area and higher heat input into the cylinder. So although this will
short out the central heating, it will absorb most of the boiler's
output resulting in a very fast reheat of the tank. The tank stat will
switch back to heating-only before the house starts cooling down.
Some systems nowadays don't even have the mid-position for both heating
and HW - when there's demand from the cylinder, they divert 100% of the
boiler output to a fast recovery coil, which will reheat the cylinder
in minutes, before switching bask to central heating - the radiators
won't even have time to get cold.

OTOH, if the cylinder only has a few turns of the coil, without the
balancing gate valve, it won't work optimally. I don't know if these
cylinders are still available - maybe someone else in the group might?


Thanks for that explanation - makes perfect sense.


--
Chris

On Sat, 14 Jun 2014 08:54:56 +0000 (UTC), Andrew Gabriel wrote:

Problem with older cylinders is they didn't have many turns in the
coil, so ended up sending the water back without much of the heat
being removed. So yes, they short-circuited the heating system
without dumping much heat into the tank, so boiler output was much
reduced when running both heating and HW.

If it was a modulating boiler which are a relatively modern
invention. Old boilers are on or off. OK it'll cycle on it's overheat
stat but not until once all the system water is hot enough. That's
not the same as the delta T flow/return not being high enough.

This "tap" may also have been a one way valve to stop gravity
circulation around (part of) the radiators. It's position doesn't
sound right for that though.

We need more detail from the OP, pumps, valves and their location in
the plumbing, control system (stats etc) and when things opearate.

--
Cheers
Dave.

On 14/06/2014 08:32, news wrote:


Thanks, It does have a three way valve, so I am not worried about when
only the radiators or only HW is calling for heat. However, I suspect
that now if both HW and rads call for heat she will have to wait until
the water is hot and the three way valve shuts off the cylinder until
anything goes into the rads.

As others have said, if you're using a fast recovery cylinder which can
absorb the full boiler output, it doesn't take long to heat up.

Also, depending on what timer(s) are being used, it may be possible to
arrange things so that HW and CH are not normally on at the same time.
For example, my HW comes on earlier than the CH each morning - so that
they are not competing.

This seems like a bit of a retrograde step to my very first house which
had a "Hot water" or "CH" priority system. In this case if set to HW
priority there was no CH until the tank was hot.


That would been a W-Plan system with a 3-port diverter (as opposed to
mid-position) valve - which could *only* do one thing at a time. By
default, that would have provided HW priority - I don't think there was
an option for CH priority. A Y-Plan system - with a mid-position valve -
*can* heat both HW and CH at the same time. If the HW *does* hog all the
flow until the cylinder is hot, it's still no worse than a W-Plan.

The problem with fitting a 'balancing' valve to prevent the HW system
from hogging all the flow is that it will also restrict the flow in the
HW-only situation, making it take longer to heat the HW with unnecessary
boiler cycling.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 14/06/2014 08:32, news wrote:
On 14/06/2014 06:42, harryagain wrote:
"news" wrote in message
...
A friend of mine has just had a (leaking) 25 year old HW tank replaced -
standard vented HW system gas heated by a secondary coil.

The house is just like mine and on the output of the secondary heating
coil there was a tap like body - neither hers or mine has ever had a
handle and I assume that it is the equivalent of the lock-shield
valve on
the rads. It is designed (I assume) to stop the HW tank hogging all the
heat when both HW tank and rads are both demanding heat - but once set
during installation it can be forgotten (in just the same way that the
lock-shields are forgotten).

Anyway as part of the new tank installation this tap has been removed
and
not replaced with anything. Is this normal for modern installations or
has there been some sort of drop off?

We wont find out how balanced the system is until much later in the year
and if its wrong I think it would be better to get the installers back
sooner rather than later.

Thanks for any advice

In days of yore, the hot water cylinder was often heated by a separate
gravity/convection circuit that was uncontrolled.

If it is to be part of the pumped system, either it will have to have
either
some sort of manual control valve to balance the system
OR more usually
it has a separate circuit controlled by a motorised valve/s
(thermostatically controlled) so that it can be shut off or the entire
boiler output goes to quickly heat the water.
This is a lot more useful and efficient.

If the new tank has no means of balancing/restricting the primary water
flow, you will likely find that most of the primary water goes through
the
coil and almost none through the radiators.



Thanks, It does have a three way valve, so I am not worried about when
only the radiators or only HW is calling for heat. However, I suspect
that now if both HW and rads call for heat she will have to wait until
the water is hot and the three way valve shuts off the cylinder until
anything goes into the rads.

This seems like a bit of a retrograde step to my very first house which
had a "Hot water" or "CH" priority system. In this case if set to HW
priority there was no CH until the tank was hot.

One consideration to keep in mind is that modern part L compliant
cylinders will have a much higher power heat exchanger than old
cylinders. On many old ones the maximum transfer rate was often limited
to less than 5kW, so you needed some load from the rads to prevent the
boiler cycling endlessly during a cylinder reheat. A modern one may be
able to sink 15kW or more, and hence the need to provide additional load
is no longer there, and you can get a much faster reheat (in fact, you
can reheat fast enough to match a smallish demand (e.g. a shower) in
real time, giving combi style "unlimited" hot water.


--
Cheers,

John.

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

On 14/06/2014 09:54, Andrew Gabriel wrote:

Newer cylinders tend to have larger coils, or even fast heat recovery
where the coil splits into several thinner coils for larger surface
area and higher heat input into the cylinder. So although this will
short out the central heating, it will absorb most of the boiler's
output resulting in a very fast reheat of the tank. The tank stat will
switch back to heating-only before the house starts cooling down.
Some systems nowadays don't even have the mid-position for both heating
and HW - when there's demand from the cylinder, they divert 100% of the
boiler output to a fast recovery coil, which will reheat the cylinder
in minutes, before switching bask to central heating - the radiators
won't even have time to get cold.

On mine it does one or the other, even though its S+ plan and has
multiple two port valves, so in theory could run the DHW in parallel
with other zones. That's because it runs a much higher flow temperature
for the cylinder reheat than it runs for the (weather compensated) rad
zones.

OTOH, if the cylinder only has a few turns of the coil, without the
balancing gate valve, it won't work optimally. I don't know if these
cylinders are still available - maybe someone else in the group might?

I would expect most stuff would be part L compliant now...?


--
Cheers,

John.

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

On 14/06/2014 10:56, Dave Liquorice wrote:
On Sat, 14 Jun 2014 08:54:56 +0000 (UTC), Andrew Gabriel wrote:

Problem with older cylinders is they didn't have many turns in the
coil, so ended up sending the water back without much of the heat
being removed. So yes, they short-circuited the heating system
without dumping much heat into the tank, so boiler output was much
reduced when running both heating and HW.

If it was a modulating boiler which are a relatively modern
invention. Old boilers are on or off. OK it'll cycle on it's overheat
stat but not until once all the system water is hot enough. That's
not the same as the delta T flow/return not being high enough.

This "tap" may also have been a one way valve to stop gravity
circulation around (part of) the radiators. It's position doesn't
sound right for that though.

We need more detail from the OP, pumps, valves and their location in
the plumbing, control system (stats etc) and when things opearate.


It is a fully pumped system, with a mid position valve just down stream
of the pump from where there is a split to HW/CH. Thermostats on the HW
, ambient Air and most radiators. Separately programmable HW and CH
timing cycles. Two year old modulating condensing boiler.

Unless this changes replies radically I think I have enough helpful
advice from the group about the design of modern HW tanks that we can
rest easy that there has not been a drop off.

Thanks to all.

--
Chris

Well I'd get the installers back, no point I guess wondering what could work/not work I suppose. Mind you they might charge a lot ? Well if they do might be easier getting some prices in from some other firms.

That's what I did and I was amazed at how much I'd ended-up saving when I'd used STL Heating. Just goes to show it's best to shop around!

5 posts today in this group from this spammer for STL -
"amazed at how much I'd ended-up saving "
"blog that someone made"
"rang some local North West based firms"

- I smell a rat.

On 15/06/2014 02:28, John Rumm wrote:


One consideration to keep in mind is that modern part L compliant
cylinders will have a much higher power heat exchanger than old
cylinders. On many old ones the maximum transfer rate was often limited
to less than 5kW, so you needed some load from the rads to prevent the
boiler cycling endlessly during a cylinder reheat. A modern one may be
able to sink 15kW or more, and hence the need to provide additional load
is no longer there, and you can get a much faster reheat (in fact, you
can reheat fast enough to match a smallish demand (e.g. a shower) in
real time, giving combi style "unlimited" hot water.



That's an interesting perspective which, of course, makes a lot of
sense. Being on the verge of dealing with my DHW (I have been for a
while but it's really going to happen soon), it's a current area of
interest and the heat transfer rate could be a significant factor in
choosing one cylinder over another and perhaps a factor in deciding on
what size to get (although I suspect that 'enough to fill the bath' is a
good rule of thumb) .
Very few suppliers seem to quote a figure for heat exchange, however,
and instead give reheat times or just say "it's good, 'onest guv", if
anything. Similarly, I couldn't find a specific minimum performance in
part L, though I'm sure there should be and I could easily be looking at
the wrong document.