IMM wrote:

"The Natural Philosopher" wrote in message
...

IMM wrote:

No need to as I am brilliant at English and life in general.

"You left out a 'there is', a second 'at', and there is a superfluous
'to' and three commas are missing."


How about a "z"s here and there.

No you are mixing singular and plural here. Also a "Z" on its own does
not form a word in English.

Must try harder.

Yes, really must.

Too true, not a plumber. 10/10

No, a plumber would have a pipe cutter....

He would hae made an ideal Camp
guard at Buchenwald, or Roman Catholic
Priest,


Are you saying both are the same? My oh my!!! This one needs professional
attention.

No, your basic English language comprehension seems to be lacking as
well. The inclusion of "or" would indicate they where alternative
options and not necessarily needing to both be true.

or join the political party that tells the biggest lies,
in the fewest words.


I will never join the Tory party.

Yes, I think you are agreeing with him.


--
Cheers,

John.

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

"John Rumm" wrote in message
...
IMM wrote:

"The Natural Philosopher" wrote in message
...

IMM wrote:

No need to as I am brilliant at English and life in general.

"You left out a 'there is', a second 'at', and there is a superfluous
'to' and three commas are missing."


How about a "z"s here and there.

No you are mixing singular and plural here. Also a "Z" on its own does
not form a word in English.

He doesn't know that.

Must try harder.

Yes, really must.

Too true, not a plumber. 10/10

No, a plumber would have a pipe cutter....

...and not an axe.

or join the political party that tells the biggest lies,
in the fewest words.


I will never join the Tory party.

Yes, I think you are agreeing with him.

Yep.

"The Natural Philosopher" wrote in message
...
IMM wrote:


He would hae made an ideal Camp
guard at Buchenwald, or Roman Catholic
Priest,


Are you saying both are the same? My oh my!!! This one needs
professional
attention.


I know

Have you given your house a haircut yet?

"Phil Addison" wrote in message
...
On Fri, 19 Nov 2004 19:18:27 +0000, "Ed Sirett"
wrote:

In a private e-mail to , on Thurs, 18 Nov 2004
20:43:28 -0000, Tania wrote:

HELLO

I have recently had a combi boiler put in, and whenever the hot tap is
put
on there is a really hot burst of water (too painful to use). It then
goes
cold for a while, then heats up to the temerature I set on the boiler
thermostat. I have two very young children and worry about them
turning on
the hot tap in the loo or bathroom. Has anyone else found a solution
to
this. I asked the engineer who came out to sort out a lighting problem
today, and he said 'other people don't moan about it' which left me
feeling
fed up and no wiser. He did explain to me how it happens several
times,
each more slowly than the last, he was a very rude man! he had no will
to
try and reassure me, but when pushed did say it would be 64 degrees
maximum - so not scalding. Any ideas will be gratefully received.


This is a recognised problem with some combis which are the tube within tube
heat exchanger type. When the heating is running the heat exchanger attains
a high temperature and thus the bit of tapwater within this also reaches
this temperature. When the hot tap is opened this "slug" of very hot water
travels along and passes out of the tap. The boiler runs through its
sequence and fires at the hot water rate which is designed to provide hot
water at the "normal" temperature. The net result is just as described i.e.
a brief pulse of scalding water followed by cooler then normal temperature
hot water. A long length of pipe from boiler to tap will mitigate the
problem but creates an annoying lag in delivery times.
C'est la vie

On Mon, 22 Nov 2004 18:33:03 +0000 (UTC), "John"
wrote:


"Phil Addison" wrote in message
...
On Fri, 19 Nov 2004 19:18:27 +0000, "Ed Sirett"
wrote:

In a private e-mail to , on Thurs, 18 Nov 2004
20:43:28 -0000, Tania wrote:

HELLO

I have recently had a combi boiler put in, and whenever the hot tap is
put
on there is a really hot burst of water (too painful to use). It then
goes
cold for a while, then heats up to the temerature I set on the boiler
thermostat. I have two very young children and worry about them
turning on
the hot tap in the loo or bathroom. Has anyone else found a solution
to
this. I asked the engineer who came out to sort out a lighting problem
today, and he said 'other people don't moan about it' which left me
feeling
fed up and no wiser. He did explain to me how it happens several
times,
each more slowly than the last, he was a very rude man! he had no will
to
try and reassure me, but when pushed did say it would be 64 degrees
maximum - so not scalding. Any ideas will be gratefully received.


This is a recognised problem with some combis which are the tube within tube
heat exchanger type. When the heating is running the heat exchanger attains
a high temperature and thus the bit of tapwater within this also reaches
this temperature. When the hot tap is opened this "slug" of very hot water
travels along and passes out of the tap. The boiler runs through its
sequence and fires at the hot water rate which is designed to provide hot
water at the "normal" temperature. The net result is just as described i.e.
a brief pulse of scalding water followed by cooler then normal temperature
hot water. A long length of pipe from boiler to tap will mitigate the
problem but creates an annoying lag in delivery times.
C'est la vie

Thanks Ed and John. So summarizing your replies, Tania should try
turning down the C/H temp if the weather is not too cold. Apart from
that I'm sure telling her it is 'normal' will be of some comfort, so she
can just expect the hot slug and wait for it to drop back to the proper
HW temperature.

I appreciate the explanation of what causes it - and wonder if there is
a safety regulation covering max temp of DHW. Is there a list, or some
easy way of recognising combis that do or don't display this
mis-feature?

I'll be passing the advice onto Tania.

Phil
The uk.d-i-y FAQ is at http://www.diyfaq.org.uk/
Remove NOSPAM from address to email me

"Phil Addison" wrote in message
...
On Mon, 22 Nov 2004 18:33:03 +0000 (UTC), "John"
wrote:


"Phil Addison" wrote in message
...
On Fri, 19 Nov 2004 19:18:27 +0000, "Ed Sirett"
wrote:

In a private e-mail to , on Thurs, 18 Nov 2004
20:43:28 -0000, Tania wrote:

HELLO

I have recently had a combi boiler put in, and whenever the hot tap
is
put
on there is a really hot burst of water (too painful to use). It
then
goes
cold for a while, then heats up to the temerature I set on the
boiler
thermostat. I have two very young children and worry about them
turning on
the hot tap in the loo or bathroom. Has anyone else found a
solution
to
this. I asked the engineer who came out to sort out a lighting
problem
today, and he said 'other people don't moan about it' which left me
feeling
fed up and no wiser. He did explain to me how it happens several
times,
each more slowly than the last, he was a very rude man! he had no
will
to
try and reassure me, but when pushed did say it would be 64 degrees
maximum - so not scalding. Any ideas will be gratefully received.


This is a recognised problem with some combis which are the tube within
tube
heat exchanger type. When the heating is running the heat exchanger
attains
a high temperature and thus the bit of tapwater within this also reaches
this temperature. When the hot tap is opened this "slug" of very hot
water
travels along and passes out of the tap. The boiler runs through its
sequence and fires at the hot water rate which is designed to provide
hot
water at the "normal" temperature. The net result is just as described
i.e.
a brief pulse of scalding water followed by cooler then normal
temperature
hot water. A long length of pipe from boiler to tap will mitigate the
problem but creates an annoying lag in delivery times.
C'est la vie

Thanks Ed and John. So summarizing your replies, Tania should try
turning down the C/H temp if the weather is not too cold. Apart from
that I'm sure telling her it is 'normal' will be of some comfort, so she
can just expect the hot slug and wait for it to drop back to the proper
HW temperature.

I appreciate the explanation of what causes it - and wonder if there is
a safety regulation covering max temp of DHW. Is there a list, or some
easy way of recognising combis that do or don't display this
mis-feature?

I'll be passing the advice onto Tania.

You could put in a secondary circulation loop on the combi and guarantee hot
water instantly at the taps. This would for most of the draw-off time not be
scalding as the pump would slowly circulate the water in the loop and combi
heat exchanger. Have a pipe stat to keep the draw-off temp to around 40C,
so it will not be extracting heat from the combi continuously.

Phil Addison wrote:

I appreciate the explanation of what causes it - and wonder if there is
a safety regulation covering max temp of DHW. Is there a list, or some
easy way of recognising combis that do or don't display this
mis-feature?

My ideal isar has a plate heat exchanger for the HW side, and it does
not demonstrate this behaviour. It also maintains a small (i.e. couple
of litres) store of water that it keeps tempered at the selected HW
output temp to try and provide a more instant and stable temp during
initial demand. Presumably others of similar design would also be free
from the problem.


--
Cheers,

John.

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

In article ,
John Rumm wrote:
You could put in a secondary circulation loop on the combi and
guarantee hot water instantly at the taps. This would for most of the
draw-off time not be scalding as the pump would slowly circulate the
water in the loop and combi heat exchanger. Have a pipe stat to keep
the draw-off temp to around 40C, so it will not be extracting heat
from the combi continuously.

Works well enough with a stored water system, but how are you going to
do it on a combi?

I *think* he means having a heating loop for the water off the central
heating side.

Any bodge rather than do the job properly.

--
*Why do the two "sanction"s (noun and verb) mean opposites?*

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

"John Rumm" wrote in message
...
IMM wrote:

You could put in a secondary circulation loop on the combi and guarantee
hot
water instantly at the taps. This would for most of the draw-off time
not be
scalding as the pump would slowly circulate the water in the loop and
combi
heat exchanger. Have a pipe stat to keep the draw-off temp to around
40C,
so it will not be extracting heat from the combi continuously.

Works well enough with a stored water system, but how are you going to
do it on a combi?

The same way as it is implemented on a heat bank or thermal store, using a
couple of check valves and a pump. The pump has to be big enough to activate
the burner, or better, the combi operates on a very low minimum mains
pressure. water. Best have a length of 28mm about 1 foot long, or two in
parallel, as the mains enters the combi. This acts as a hot water store
preventing the cold spot as the burner proves itself. The secondary loop
must be insulated. The pump must be on the return of the loop, but not in
the cold mains path. i.e., mains in to combi, check valve, tee (return from
loop), check valve in loop as it meets the tee, from tee to combi have a
28mm section, or two in parallel (this acts as a hot store that feeds into
the combi to prevent the cold spot), pipe stat, set to 45C after pump but
before loop check valve. Voila.

"Dave Plowman (News)" wrote in message
...
In article ,
John Rumm wrote:
You could put in a secondary circulation loop on the combi and
guarantee hot water instantly at the taps. This would for most of the
draw-off time not be scalding as the pump would slowly circulate the
water in the loop and combi heat exchanger. Have a pipe stat to keep
the draw-off temp to around 40C, so it will not be extracting heat
from the combi continuously.

Works well enough with a stored water system, but how are you going to
do it on a combi?

I *think*

Don't think, you are not up to it.

On Tue, 23 Nov 2004 01:20:11 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article ,
John Rumm wrote:
You could put in a secondary circulation loop on the combi and
guarantee hot water instantly at the taps. This would for most of the
draw-off time not be scalding as the pump would slowly circulate the
water in the loop and combi heat exchanger. Have a pipe stat to keep
the draw-off temp to around 40C, so it will not be extracting heat
from the combi continuously.

Works well enough with a stored water system, but how are you going to
do it on a combi?

I *think* he means having a heating loop for the water off the central
heating side.

Any bodge rather than do the job properly.

Hmmm... I thought he meant take a pipe back from the tap to the source
and keep pumping it round the loop, as can be done with a stored DHW
system. But with mains pressure hot water from a combi??? Errr, nope!

Phil
The uk.d-i-y FAQ is at http://www.diyfaq.org.uk/
Remove NOSPAM from address to email me

"Phil Addison" wrote in message
...
On Tue, 23 Nov 2004 01:20:11 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article ,
John Rumm wrote:
You could put in a secondary circulation loop on the combi and
guarantee hot water instantly at the taps. This would for most of
the
draw-off time not be scalding as the pump would slowly circulate the
water in the loop and combi heat exchanger. Have a pipe stat to
keep
the draw-off temp to around 40C, so it will not be extracting heat
from the combi continuously.

Works well enough with a stored water system, but how are you going to
do it on a combi?

I *think* he means having a heating loop for the water off the central
heating side.

Any bodge rather than do the job properly.

Hmmm... I thought he meant take a pipe back from the tap to the source
and keep pumping it round the loop, as can be done with a stored DHW
system. But with mains pressure hot water from a combi??? Errr, nope!

Err. yep. Similar to how it is done on a thermal store or heat bank. I
implemeted on a Microgenus.

IMM wrote:

gosh, an IMM post that is actualy plausible and did not mention politics
or insult anyone once - well done!

The same way as it is implemented on a heat bank or thermal store, using a
couple of check valves and a pump. The pump has to be big enough to activate
the burner, or better, the combi operates on a very low minimum mains
pressure. water. Best have a length of 28mm about 1 foot long, or two in
parallel, as the mains enters the combi. This acts as a hot water store
preventing the cold spot as the burner proves itself. The secondary loop
must be insulated. The pump must be on the return of the loop, but not in
the cold mains path. i.e., mains in to combi, check valve, tee (return from
loop), check valve in loop as it meets the tee, from tee to combi have a
28mm section, or two in parallel (this acts as a hot store that feeds into
the combi to prevent the cold spot), pipe stat, set to 45C after pump but
before loop check valve. Voila.

I presume you need to set the pipe stat to below the minimum stat
temperature that can be selected for HW from the front panel of the
boiler, otherwise you could end up unable to meet the demand from the
stat if someone turns the boiler stat right down?

How do you ensure that you don't enter a deadlock situation where the
water temp in the secondary return is close to target, but the pipe stat
demand is still on, however the boiler refuses to fire since the delta
required is below its minimum modulation setting?

It strikes me you also have a conflicting requirement he The 28mm
pipe "hot store" would have a higher thermal mass than the bulk of the
secondary loop, and hence would cool slower unless you reduce its
lagging (in comparison with the rest of the loop) such that its
temperature decay approximates that of the rest of the loop. However you
need to maintain enough hysteresis in this control loop to prevent
firing the boiler for HW too often (and hence diverting the boiler from
the CH on a regular basis). Perhaps a simple programmer would be of use
to disable the loop during the night or other times when HW is unlikely
to be needed.



--
Cheers,

John.

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

"John Rumm" wrote in message
...
IMM wrote:

gosh, an IMM post that is
actualy plausible

All my posts are 110% plausible. Your low intekingence would not see that
though. Sad but tue.

and did not mention politics

I don't mention politics. When I do it is pure wisdom.

or insult anyone once

I never insult being the perfect gentleman. I make observations.

- well done!

Thank you.

The same way as it is implemented
on a heat bank or thermal store, using a
couple of check valves and a pump.
The pump has to be big enough to activate
the burner, or better, the combi operates
on a very low minimum mains
pressure. water. Best have a length
of 28mm about 1 foot long, or two in
parallel, as the mains enters the combi.
This acts as a hot water store
preventing the cold spot as the burner
proves itself. The secondary loop
must be insulated. The pump must
be on the return of the loop, but not in
the cold mains path. i.e., mains in to
combi, check valve, tee (return from
loop), check valve in loop as it meets
the tee, from tee to combi have a
28mm section, or two in parallel
(this acts as a hot store that feeds into
the combi to prevent the cold spot),
pipe stat, set to 45C after pump but
before loop check valve. Voila.

I presume you need to set the
pipe stat to below the minimum stat
temperature that can be selected
for HW from the front panel of the
boiler, otherwise you could end up
unable to meet the demand from the
stat if someone turns the boiler stat right down?

yep.

How do you ensure that you don't enter a deadlock situation where the
water temp in the secondary return is close to target, but the pipe stat
demand is still on, however the boiler refuses to fire since the delta
required is below its minimum modulation setting?

A combi modulates on temperature. When it nears the setpoint is modulates
down and switches off on reaching setpoint. Not an issue.

It strikes me you also have a conflicting
requirement he The 28mm
pipe "hot store" would have a higher
thermal mass than the bulk of the
secondary loop,

May have a higher mass, depending on the length of the secondary loop.

and hence would cool slower
unless you reduce its
lagging (in comparison with the rest
of the loop) such that its
temperature decay approximates that
of the rest of the loop.

This 28mm pipe(s) would be in the cold water main line just before the
combi. This stored hot water is pushed into the combi by the incoming cold
mains. it makes up for the cold lag in the burner proving cycle.

However you need to maintain enough
hysteresis in this control loop to prevent
firing the boiler for HW too often (and
hence diverting the boiler from
the CH on a regular basis).

Depending on where the pipe stat is fitted. Too close to the tee with the
cold water mains may mean heat is convected off.

Perhaps a simple programmer would be of use
to disable the loop during the night or
other times when HW is unlikely
to be needed.

A time clock is essential on all secondary loops. The heat loss on this
loop would be no more than any other loop on any other type of system.

IMM wrote:

All my posts are 110% plausible. Your low intekingence would not see that
though. Sad but tue.

In which case, are you aware there is another poster on this group using
the name IMM? Alas his posts frequently make no sense at all. You should
track this scoundrel down and remonstrate with him.

How do you ensure that you don't enter a deadlock situation where the
water temp in the secondary return is close to target, but the pipe stat
demand is still on, however the boiler refuses to fire since the delta
required is below its minimum modulation setting?


A combi modulates on temperature. When it nears the setpoint is modulates
down and switches off on reaching setpoint. Not an issue.

You may be right, however you may not. This is something that will vary
with boiler types and instalation details.

You have an inherent difficulty in that you have two separate (i.e an
outer and an inner) closed loop control systems, but your outer loop is
operating with no a priori knowledge of the characteristics of the inner
loop.

As you can demonstrate with many boilers, if you run a hot tap slowly,
the boiler can turn off the burner because the heating load is too small
and it is unable to modulate low enough to not exceed the preset
temperature. This is not much of an issue with a tap - you either turn
it off or turn it on more. With the feedback loop you describe, I can
see that you could arrive at the same situation. Pipe stat set at 45
degrees, water return currently at 43, and boiler stat set at 50
degrees. Boiler unable to fire because at minimum burner power it would
cause a temp delta of more than 7 degrees.

In some cases it will work fine, others can be tweeked, some may not
work. You still run the risk that the outer loop "hogs" the boiler and
deprives the CH. Much depends on the sophistication of the control
system implemented in the boilers software. If it is a simple first
order "error following" feedback loop, then your system will be fine
(and given the simplicity of implementing this type of control, I am
sure many do). If it is a more sophisticated second order control
system, then you may have a problem.

It strikes me you also have a conflicting
requirement he The 28mm
pipe "hot store" would have a higher
thermal mass than the bulk of the
secondary loop,


May have a higher mass, depending on the length of the secondary loop.

In fact my terminology above was insufficiently precise... the thermal
mass is not so much the issue as the thermal inertia. Yes, the secondary
loop may have the greater mass, but its mass to surface area ratio
(given consistent insulation) will influence the rate of heat loss.

and hence would cool slower
unless you reduce its
lagging (in comparison with the rest
of the loop) such that its
temperature decay approximates that
of the rest of the loop.


This 28mm pipe(s) would be in the cold water main line just before the
combi. This stored hot water is pushed into the combi by the incoming cold
mains. it makes up for the cold lag in the burner proving cycle.

Yup, follow that, not sure how it relates to the issue I mention above
however.

This store of water could also be counter productive if the boiler also
implements its own store for exactly the same purpose.

The heat loss on this
loop would be no more than any other loop on any other type of system.

True, but not relevant. In the most typical loop (i.e. the CH) you are
not that interested in pipe temperature - only room temp.

--
Cheers,

John.

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

On Mon, 22 Nov 2004 19:30:53 +0000, Phil Addison wrote:

On Mon, 22 Nov 2004 18:33:03 +0000 (UTC), "John"
wrote:


"Phil Addison" wrote in message
...
On Fri, 19 Nov 2004 19:18:27 +0000, "Ed Sirett"
wrote:

In a private e-mail to , on Thurs, 18 Nov 2004
20:43:28 -0000, Tania wrote:

HELLO

I have recently had a combi boiler put in, and whenever the hot tap is
put
on there is a really hot burst of water (too painful to use). It then
goes
cold for a while, then heats up to the temerature I set on the boiler
thermostat. I have two very young children and worry about them
turning on
the hot tap in the loo or bathroom. Has anyone else found a solution
to
this. I asked the engineer who came out to sort out a lighting problem
today, and he said 'other people don't moan about it' which left me
feeling
fed up and no wiser. He did explain to me how it happens several
times,
each more slowly than the last, he was a very rude man! he had no will
to
try and reassure me, but when pushed did say it would be 64 degrees
maximum - so not scalding. Any ideas will be gratefully received.


This is a recognised problem with some combis which are the tube within tube
heat exchanger type. When the heating is running the heat exchanger attains
a high temperature and thus the bit of tapwater within this also reaches
this temperature. When the hot tap is opened this "slug" of very hot water
travels along and passes out of the tap. The boiler runs through its
sequence and fires at the hot water rate which is designed to provide hot
water at the "normal" temperature. The net result is just as described i.e.
a brief pulse of scalding water followed by cooler then normal temperature
hot water. A long length of pipe from boiler to tap will mitigate the
problem but creates an annoying lag in delivery times.
C'est la vie

Thanks Ed and John. So summarizing your replies, Tania should try
turning down the C/H temp if the weather is not too cold. Apart from
that I'm sure telling her it is 'normal' will be of some comfort, so she
can just expect the hot slug and wait for it to drop back to the proper
HW temperature.

I appreciate the explanation of what causes it - and wonder if there is
a safety regulation covering max temp of DHW. Is there a list, or some
easy way of recognising combis that do or don't display this
mis-feature?


There are regulation covering maximum HW temperature but they don't (yet)
apply to normal domestic dwellings.

I doubt there has been a list of suspects made with this problem.
Pott. Lynx
Saunier Duval
Ferroli
Fer
Vaillant Turbomax+

It can also occur where the 2ndary heater exchanger is also used a CH
bypass circuit.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html

"John Rumm" wrote in message
...

SNIP


This 28mm pipe(s) would be in the cold water main line just before the
combi. This stored hot water is pushed into the combi by the incoming
cold
mains. it makes up for the cold lag in the burner proving cycle.

Yup, follow that, not sure how it relates to the issue I mention above
however.

This store of water could also be counter productive if the boiler also
implements its own store for exactly the same purpose.

The heat loss on this
loop would be no more than any other loop on any other type of system.

True, but not relevant. In the most typical loop (i.e. the CH) you are not
that interested in pipe temperature - only room temp.

--
Cheers,

John.



Since many combis operate the hot water function to the exclusion of the
heating function any of this ilk will become useless for heating duty whilst
the hot water recirculating loop is running

"John" wrote in message
...

"John Rumm" wrote in message
...

SNIP


This 28mm pipe(s) would be in the cold water main line just before the
combi. This stored hot water is pushed into the combi by the incoming
cold
mains. it makes up for the cold lag in the burner proving cycle.

Yup, follow that, not sure how it relates to the issue I mention above
however.

This store of water could also be counter productive if the boiler also
implements its own store for exactly the same purpose.

The heat loss on this
loop would be no more than any other loop on any other type of system.

True, but not relevant. In the most typical loop (i.e. the CH) you are
not
that interested in pipe temperature - only room temp.

--
Cheers,

John.

Since many combis operate the hot water function to the exclusion of the
heating function any of this ilk will become useless for heating duty
whilst
the hot water recirculating loop is running

Go away...you don't say....

The loop will run for a matter of a few minutes as it heats up the loop and
the pipe stat will cut the pump out when the loop is up top temp. It is not
a continuous pumping operation. The pump also charges up the pre-heater
28mm pipes.

Works wonderfully.

On Tue, 23 Nov 2004 23:02:55 -0000, "IMM" wrote:


The loop will run for a matter of a few minutes as it heats up the loop and
the pipe stat will cut the pump out when the loop is up top temp. It is not
a continuous pumping operation. The pump also charges up the pre-heater
28mm pipes.

Hi,

If it's just to stop the slug of very hot water, another way would be
to split the HW from the combi into two branches, a short one and a
long one.

As the slug of hot water comes out of the boiler, half goes through
each branch. The half going through the shorter branch would be mixed
with cooler water coming the longer branch. Then as this half comes to
an end, the half coming through the longer branch would mix with
cooler water coming through the shorter branch.

Needs no valves, pumps and thermostats, and can be easily retrofitted
into existing pipework.

cheers,
Pete.


Works wonderfully.

"Pete C" wrote in message
news
On Tue, 23 Nov 2004 23:02:55 -0000, "IMM" wrote:


The loop will run for a matter of a few minutes as it heats up the loop
and
the pipe stat will cut the pump out when the loop is up top temp. It is
not
a continuous pumping operation. The pump also charges up the pre-heater
28mm pipes.

Hi,

If it's just to stop the slug of very hot water, another way would be
to split the HW from the combi into two branches, a short one and a
long one.

As the slug of hot water comes out of the boiler, half goes through
each branch. The half going through the shorter branch would be mixed
with cooler water coming the longer branch. Then as this half comes to
an end, the half coming through the longer branch would mix with
cooler water coming through the shorter branch.

Needs no valves, pumps and thermostats, and can be easily retrofitted
into existing pipework.

Or fit a blending valve and guaranteed set temperatures