I'm contemplating setting up a recirculating system for the hot water
in my bungalow.

The HW cylinder, (OSO Pressurised Stainless Steel, heated by nearby
Oil Boiler on a separate zone) which I would want to retain, is in the
attached garage, and the Kitchen is about 40m away. That's a lot of
pipe to empty down the drain every time you want a hot sink, it also
takes a long time.

But finding information on how to do it is a big problem, can anyone
point me to a good information source?

I'm guessing a well insulated pipe run with a bronze pump in the return
switched by a pipe thermostat at the highest/furthest point is the
idea, but connected how to the cylinder? Feed from the top and return
to the bottom with cold feed tee-ed in somehow. Check valve in the
circuit and another on the cold feed?

Does anyone have any experience of actually doing one? Advice?

If I could get the waste down then a meter makes sense (high rateable
value, 2 people).

Thanks,
R.

Does anyone have any experience of actually doing one? *Advice?

Not done one. Treloar on Plumbing has one-paragraph on it, basically
saying non-corrosive pump on pipe returning from furthest point, with
connection back to top-third of cylinder to prevent cooler water in
bottom of cylinder mixing.

As far as controlling the pump, a flow switch on the cold inlet to the
cylinder would seem the way to do it. Available in the Farnell
catalogue.

On Feb 18, 11:11*am, " wrote:
Does anyone have any experience of actually doing one? *Advice?

Not done one. Treloar on Plumbing has one-paragraph on it, basically
saying non-corrosive pump on pipe returning from furthest point, with
connection back to top-third of cylinder to prevent cooler water in
bottom of cylinder mixing.

As far as controlling the pump, a flow switch on the cold inlet to the
cylinder would seem the way to do it. Available in the Farnell
catalogue.

That won't work, you need circulation before anyone turns the tap on.
Run it on a 24hr timer with a pipe thermostat.


NT

On Feb 17, 5:53*pm, TheOldFellow wrote:
I'm contemplating setting up a recirculating system for the hot water
in my bungalow.

The HW cylinder, (OSO Pressurised Stainless Steel, heated by nearby
Oil Boiler on a separate zone) which I would want to retain, is in the
attached garage, and the Kitchen is about 40m away. That's a lot of
pipe to empty down the drain every time you want a hot sink, it also
takes a long time.

But finding information on how to do it is a big problem, can anyone
point me to a good information source?

I'm guessing a well insulated pipe run with a bronze pump in the return
switched by a pipe thermostat at the highest/furthest point is the
idea, but connected how to the cylinder? *Feed from the top and return
to the bottom with cold feed tee-ed in somehow. *Check valve in the
circuit and another on the cold feed?

Does anyone have any experience of actually doing one? *Advice?

If I could get the waste down then a meter makes sense (high rateable
value, 2 people).

Thanks,
R.

I've also not done it, although am planning to.

Grundfos do a range of pumps specifically for the purpose:
http://net.grundfos.com/doc/webnet/i...family-houses/

They're low power designed to run constantly, although a timer so they
only run during the likely usage periods cuts cost.

A

On Thu, 18 Feb 2010 03:11:35 -0800 (PST)
" wrote:


Does anyone have any experience of actually doing one? Â*Advice?

Not done one. Treloar on Plumbing has one-paragraph on it, basically
saying non-corrosive pump on pipe returning from furthest point, with
connection back to top-third of cylinder to prevent cooler water in
bottom of cylinder mixing.

As far as controlling the pump, a flow switch on the cold inlet to the
cylinder would seem the way to do it. Available in the Farnell
catalogue.

Thanks for that. I've just discovered my OSO cylinder has a special
'Secondary Return' tapping, for exactly this purpose. It's
about half way up the cylinder, so that lines up with what you say.
And it's very encouraging that the cylinder manufacturer planned for
it, and even has a diagram in the installation instructions (page 16):

http://www.osoho****er.com/uk/pdf/20...ion_manual.pdf

I don't understand the flow-switch idea, the plan is to maintain hot
water at the furthest point, not to assist the flow of the 40 meters of
cold when a tap is opened. It has to be a thermostat and timer I
think, with possibly a push switch to override the timer.

R.

That won't work, you need circulation before anyone turns the tap on.
Run it on a 24hr timer with a pipe thermostat.


I've just done a back-of-an-envelope calculation, and you're quite
right.

Assuming all 80m (of the 40m there and 40m back pipe run the OP
mentions) needs to be cleared, and it's 22mm throughout - thats 121
litres to clear. If pump performance is similar to a CH circulator
(around 0.3 l/s) - that comes out as 6-7 minutes to clear!

I was thinking the heat loss from the pipe would make it essential to
be demand-only.

TheOldFellow wrote:
I'm contemplating setting up a recirculating system for the hot water
in my bungalow.

The HW cylinder, (OSO Pressurised Stainless Steel, heated by nearby
Oil Boiler on a separate zone) which I would want to retain, is in the
attached garage, and the Kitchen is about 40m away. That's a lot of
pipe to empty down the drain every time you want a hot sink, it also
takes a long time.

Possibly counter intuative but have you considered smaller bore pipework?
You've got a pressurised cylinder so 10mm shouldn't be a problem and maybe
even 8mm would work satisfactorily. That would cut down the dead space a
lot.

I hasten to add I have no experience of doing this but on the continent is
seems to be the norm to use much smaller bore pipework that we use here and
the flow has always struck me as being perfectly adequate for sinks.

Tim

On 18 Feb, 11:11, " wrote:

As far as controlling the pump, a flow switch on the cold inlet to the
cylinder would seem the way to do it.

Temp on the pump inlet is, AFAIK, more usual. There's also a yard or
two of uninsulated pipe here, so that the thermostat cools down more
quickly than the water in the pipes to the taps. The pump is run to
keep the entire system at reduced pressure, i.e. immediately before
the cylinder return.

The return pipe can be pretty small (I've seen 10mm on a big install)
as it doesn't need any appreciable flowrate - if you're in a hurry,
the taps were open anyway. This also helps the pump return cool faster
than the tap feed.

Treloar also notes that the return to the cylinder should enter 2/3rd
up, so that you're not trying to circulate the entire cylinder volume,
including any stratified cold water at the bottom of it.

In principle it might be nice to have a way to stop the pump if a
tap's open (so that the pump isn't stealing flowrate when you need
it), but that would need an extra pressure-drop sensor that was also
insensitive to the pump's demands, otherwise the whole system would
start oscillating. I can't imagine you'd add a recirculation system to
any system that already had such a demand sensor, otherwise you'd be
firing up a combi continuously etc.

wrote in message
...

That won't work, you need circulation before anyone turns the tap on.
Run it on a 24hr timer with a pipe thermostat.


I've just done a back-of-an-envelope calculation, and you're quite
right.

Assuming all 80m (of the 40m there and 40m back pipe run the OP
mentions) needs to be cleared, and it's 22mm throughout - thats 121
litres to clear. If pump performance is similar to a CH circulator
(around 0.3 l/s) - that comes out as 6-7 minutes to clear!

I was thinking the heat loss from the pipe would make it essential to
be demand-only.

If the tap is used frequently then adding lots of insulation will help.
You will want lots if its re-circulating so you may as well try it first.

On Thu, 18 Feb 2010 12:44:32 -0000
"Tim" wrote:

TheOldFellow wrote:
I'm contemplating setting up a recirculating system for the hot water
in my bungalow.

The HW cylinder, (OSO Pressurised Stainless Steel, heated by nearby
Oil Boiler on a separate zone) which I would want to retain, is in the
attached garage, and the Kitchen is about 40m away. That's a lot of
pipe to empty down the drain every time you want a hot sink, it also
takes a long time.

Possibly counter intuative but have you considered smaller bore pipework?
You've got a pressurised cylinder so 10mm shouldn't be a problem and maybe
even 8mm would work satisfactorily. That would cut down the dead space a
lot.

I hasten to add I have no experience of doing this but on the continent is
seems to be the norm to use much smaller bore pipework that we use here and
the flow has always struck me as being perfectly adequate for sinks.

Tim


Good idea, especially from the bathroom ( 1/3rd way) to the kitchen.
Certainly for the return as others have said.

R.

I don't understand the flow-switch idea...

As others have pointed out, it would be far too slow to do it that
way.

In article , Tim
writes
TheOldFellow wrote:
I'm contemplating setting up a recirculating system for the hot water
in my bungalow.

The HW cylinder, (OSO Pressurised Stainless Steel, heated by nearby
Oil Boiler on a separate zone) which I would want to retain, is in the
attached garage, and the Kitchen is about 40m away. That's a lot of
pipe to empty down the drain every time you want a hot sink, it also
takes a long time.

Possibly counter intuative but have you considered smaller bore pipework?
You've got a pressurised cylinder so 10mm shouldn't be a problem and maybe
even 8mm would work satisfactorily. That would cut down the dead space a
lot.

From experience, 10 & 8mm cause a disproportionate restriction on flow,
even at mains pressures, for 40m I'd say 15mm is borderline but worth a
try.
--
fred
BBC3, ITV2/3/4, channels going to the DOGs

On Wed, 17 Feb 2010 17:53:29 +0000
TheOldFellow wrote:

I'm contemplating setting up a recirculating system for the hot water
in my bungalow.

The HW cylinder, (OSO Pressurised Stainless Steel, heated by nearby
Oil Boiler on a separate zone) which I would want to retain, is in the
attached garage, and the Kitchen is about 40m away. That's a lot of
pipe to empty down the drain every time you want a hot sink, it also
takes a long time.

But finding information on how to do it is a big problem, can anyone
point me to a good information source?

I'm guessing a well insulated pipe run with a bronze pump in the return
switched by a pipe thermostat at the highest/furthest point is the
idea, but connected how to the cylinder? Feed from the top and return
to the bottom with cold feed tee-ed in somehow. Check valve in the
circuit and another on the cold feed?

Does anyone have any experience of actually doing one? Advice?

If I could get the waste down then a meter makes sense (high rateable
value, 2 people).

Thanks,
R.



To reply to my own. SWMBO has suggested another idea, a simple push
button demand system. Button in the kitchen, calls a relay which
starts the pump, thermostat cancels the relay when hot water reaches
the kitchen. Saves 100l of water every time, but doesn't save any time.

By the way Dom's calculation of 6-7 minutes is wrong, it's only the
40M that needs to clear, and at the moment it's more like 3-4 minutes,
much of the pipe is 15mm. But he's right about the heat loss meaning
it should be demand only, no matter how thick ( say 25mm ) I lag the
pipe - actually I was thinking of putting the bulk of the pipe in a box
of foil celotex 120mm. All the runs are in the loft, so there it's all
loss, no heating gain, but on the other hand room for thick insulation.

R.

On Feb 18, 1:29*pm, Andy Dingley wrote:
On 18 Feb, 11:11, " wrote:

As far as controlling the pump, a flow switch on the cold inlet to the
cylinder would seem the way to do it.

Temp on the pump inlet is, AFAIK, more usual. There's also a yard or
two of uninsulated pipe here, so that the thermostat cools down more
quickly than the water in the pipes to the taps. The pump is run to
keep the entire system at reduced pressure, i.e. immediately before
the cylinder return.

The return pipe can be pretty small (I've seen 10mm on a big install)
as it doesn't need any appreciable flowrate - if you're in a hurry,
the taps were open anyway. This also helps the pump return cool faster
than the tap feed.

Treloar also notes that the return to the cylinder should enter 2/3rd
up, so that you're not trying to circulate the entire cylinder volume,
including any stratified cold water at the bottom of it.

In principle it might be nice to have a way to stop the pump if a
tap's open (so that the pump isn't stealing flowrate when you need
it), but that would need an extra pressure-drop sensor that was also
insensitive to the pump's demands, otherwise the whole system would
start oscillating. I can't imagine you'd add a recirculation system to
any system that already had such a demand sensor, otherwise you'd be
firing up a combi continuously etc.

The thermostat would maximise the tap flow if its mounted at the tap
end on the main pipe. Once the water delivery point is hot, the pump
stops, and any water use keeps the pipe hot.
.... I also haven't done this though.


NT

On Feb 18, 3:57*pm, fred wrote:
In article , Tim
writesTheOldFellow wrote:
I'm contemplating setting up a recirculating system for the hot water
in my bungalow.

The HW cylinder, (OSO Pressurised Stainless Steel, heated by nearby
Oil Boiler on a separate zone) which I would want to retain, is in the
attached garage, and the Kitchen is about 40m away. That's a lot of
pipe to empty down the drain every time you want a hot sink, it also
takes a long time.

Possibly counter intuative but have you considered smaller bore pipework?
You've got a pressurised cylinder so 10mm shouldn't be a problem and maybe
even 8mm would work satisfactorily. *That would cut down the dead space a
lot.

*From experience, 10 & 8mm cause a disproportionate restriction on flow,
even at mains pressures, for 40m I'd say 15mm is borderline but worth a
try.


I was wondering about a tirck to get round this.

Ideally, I could just run a 10mm to the basin (fast to heat up, but
low pressure) and 22mm to the shower (slower to get hot, but high
pressure) , but that would mean taking up the bathroom floor.

So, how about using a thermostatic mixer and running both a a 22mm and
a 10mm hot supply from boiler to bathroom. The two would split at the
boiler and join again at the bathroom with the 10mm going in to the
'hot' inlet of the thermostatic mixer and the 22mm going in to the
'cold' inlet (even though it will carry hot water).

When you first turn on the tap your get hot through the 10mm only
(thermostat senses outlet too cold so shuts off the 22mm inlet) so it
arrives fast but at reduced pressure. Then once the hot water arrives
in the 10mm the thermostatic mixer mixes cold from the 22mm.
Eventually the 22mm runs hot as well and you have high pressure hot.

So, you'd get hot water quickly (but at lower pressure) at first and
then hot water at high pressure.

Has anyone ever done this?



Robert

On 18 Feb, 16:09, NT wrote:

The thermostat would maximise the tap flow if its mounted at the tap
end on the main pipe. Once the water delivery point is hot, the pump
stops, and any water use keeps the pipe hot.

That's a nice idea, as it limits the pumping to the minimum needed,
but in practice I would suspect that it depends on how near the pipe
runs are. You have to run this long extra pipe (the tap is by
definition far, or else we wouldn't be bothering), but are probably
unlikely to run an extra cable.

It's worth doing this though - the point isn't to save pump energy
(small) or noise at night (use a time switch), but to reduce heat
losses from the pipework.

In article
,
RobertL writes
On Feb 18, 3:57*pm, fred wrote:

*From experience, 10 & 8mm cause a disproportionate restriction on flow,
even at mains pressures, for 40m I'd say 15mm is borderline but worth a
try.

I was wondering about a tirck to get round this.

Ideally, I could just run a 10mm to the basin (fast to heat up, but
low pressure) and 22mm to the shower (slower to get hot, but high
pressure) , but that would mean taking up the bathroom floor.

So, how about using a thermostatic mixer and running both a a 22mm and
a 10mm hot supply from boiler to bathroom. The two would split at the
boiler and join again at the bathroom with the 10mm going in to the
'hot' inlet of the thermostatic mixer and the 22mm going in to the
'cold' inlet (even though it will carry hot water).

When you first turn on the tap your get hot through the 10mm only
(thermostat senses outlet too cold so shuts off the 22mm inlet) so it
arrives fast but at reduced pressure. Then once the hot water arrives
in the 10mm the thermostatic mixer mixes cold from the 22mm.
Eventually the 22mm runs hot as well and you have high pressure hot.

So, you'd get hot water quickly (but at lower pressure) at first and
then hot water at high pressure.

Nice try but the disproportionately higher frictional losses on the
smaller pipe would mean that the 22mm pipe would go hot before the 10mm.

The pipe volume varies with the square of the radius but the frictional
losses go up disproportionately, at something like another power or 2
higher than the inverse ratio of the area so the 10mm pipe would not
'empty' first.

I tried 10mm as an experiment on a 10m run with a 3bar head and it was
useless, barely a trickle of flow.
--
fred
BBC3, ITV2/3/4, channels going to the DOGs

In an earlier contribution to this discussion, Andy Dingley
wrote:
On 18 Feb, 11:11, " wrote:


In principle it might be nice to have a way to stop the pump if a
tap's open (so that the pump isn't stealing flowrate when you need
it), but that would need an extra pressure-drop sensor that was also
insensitive to the pump's demands, otherwise the whole system would
start oscillating.

At first, I thought that's what Dom's suggested flow switch on the cold
inlet was for - but he was actually suggesting something different.

*However*, if you had a flow switch on the cold feed which switched the pump
*off* when flow was detected, that should have the desired effect. With no
taps open, there's be circulation only - but as soon as you opened a tap,
there would flow in the cold feed, and the pump would stop - preventing it
from detracting from the flow to the tap.
--
Cheers,
Roger
_______
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

TheOldFellow wrote:
On Wed, 17 Feb 2010 17:53:29 +0000
TheOldFellow wrote:

I'm contemplating setting up a recirculating system for the hot water
in my bungalow.

The HW cylinder, (OSO Pressurised Stainless Steel, heated by nearby
Oil Boiler on a separate zone) which I would want to retain, is in
the attached garage, and the Kitchen is about 40m away. That's a lot
of pipe to empty down the drain every time you want a hot sink, it
also takes a long time.

But finding information on how to do it is a big problem, can anyone
point me to a good information source?

I'm guessing a well insulated pipe run with a bronze pump in the
return switched by a pipe thermostat at the highest/furthest point
is the idea, but connected how to the cylinder? Feed from the top
and return to the bottom with cold feed tee-ed in somehow. Check
valve in the circuit and another on the cold feed?

Does anyone have any experience of actually doing one? Advice?

If I could get the waste down then a meter makes sense (high rateable
value, 2 people).

Thanks,
R.



To reply to my own. SWMBO has suggested another idea, a simple push
button demand system.

Just what I was going to suggest. It seems wasteful (& pointless) to keep
water circulating once HW has reached your kitchen sink. The tricky bit it
getting the pump to know in advance when you're going to want hot water. ;-)

Button in the kitchen, calls a relay which
starts the pump, thermostat cancels the relay when hot water reaches
the kitchen. Saves 100l of water every time, but doesn't save any
time.

Perhaps you could trigger it with a wireless doorbell type switch? Then you
could stick it in your pocket and trigger it on you way to the kitchen.
Possibly a silly idea but you could have a few buttons so that you could
have his & hers buttons as well as a few fixed ones.

On 18 Feb, 23:20, "Tim" wrote:

Perhaps you could trigger it with a wireless doorbell type switch? *Then you
could stick it in your pocket and trigger it on you way to the kitchen.

PIR occupancy sensor over the sink

On Feb 19, 1:12*am, Andy Dingley wrote:
On 18 Feb, 23:20, "Tim" wrote:

Perhaps you could trigger it with a wireless doorbell type switch? *Then you
could stick it in your pocket and trigger it on you way to the kitchen.

PIR occupancy sensor over the sink

exactly. One in bathroom, one in kitchen, so the pump only runs when
someone comes into the room. But is it worth it?

NT

NT wrote:
On Feb 19, 1:12 am, Andy Dingley wrote:
On 18 Feb, 23:20, "Tim" wrote:

Perhaps you could trigger it with a wireless doorbell type switch?
Then you could stick it in your pocket and trigger it on you way to
the kitchen.

PIR occupancy sensor over the sink

exactly. One in bathroom, one in kitchen, so the pump only runs when
someone comes into the room. But is it worth it?

I think I go into my kitchen far more often than I run the HW so a room PIR
would be a bit wasteful. If it was just over the sink, it wouldn't save you
any time, just water.

As to "is it worth it?" almost certainly not but who cares? ;-)

Tim

On Feb 18, 5:56*pm, fred wrote:
In article
,
RobertL writes



On Feb 18, 3:57*pm, fred wrote:

*From experience, 10 & 8mm cause a disproportionate restriction on flow,
even at mains pressures, for 40m I'd say 15mm is borderline but worth a
try.

I was wondering about a tirck to get round this.

Ideally, I could just run a 10mm to the basin (fast to heat up, but
low pressure) *and 22mm to the shower (slower to get hot, but high
pressure) , but that would mean taking up the bathroom floor.

So, how about using a thermostatic mixer and running both a a 22mm and
a 10mm hot supply from boiler to bathroom. *The two would split at the
boiler and join again at the bathroom with the 10mm going in to the
'hot' inlet of the thermostatic mixer and the 22mm going in to the
'cold' inlet (even though it will carry hot water).

When you first turn on the tap your get hot through the 10mm only
(thermostat senses outlet too cold so shuts off the 22mm inlet) so it
arrives fast but at reduced pressure. *Then once the hot water arrives
in the 10mm the thermostatic mixer mixes cold from the 22mm.
Eventually the 22mm runs hot as well and you have high pressure hot.

So, you'd get hot water quickly (but at lower pressure) at first and
then hot water at high pressure.

Nice try but the disproportionately higher frictional losses on the
smaller pipe would mean that the 22mm pipe would go hot before the 10mm.

Ah, but there would be no flow in the 22mm becuase the thermostatic
mixer woudl shut it off until the 10mm ran hot.

Robert

In article
,
RobertL writes
On Feb 18, 5:56*pm, fred wrote:
In article
,
RobertL writes



On Feb 18, 3:57*pm, fred wrote:

*From experience, 10 & 8mm cause a disproportionate restriction on flow,
even at mains pressures, for 40m I'd say 15mm is borderline but worth a
try.

I was wondering about a tirck to get round this.

Ideally, I could just run a 10mm to the basin (fast to heat up, but
low pressure) *and 22mm to the shower (slower to get hot, but high
pressure) , but that would mean taking up the bathroom floor.

So, how about using a thermostatic mixer and running both a a 22mm and
a 10mm hot supply from boiler to bathroom. *The two would split at the
boiler and join again at the bathroom with the 10mm going in to the
'hot' inlet of the thermostatic mixer and the 22mm going in to the
'cold' inlet (even though it will carry hot water).

When you first turn on the tap your get hot through the 10mm only
(thermostat senses outlet too cold so shuts off the 22mm inlet) so it
arrives fast but at reduced pressure. *Then once the hot water arrives
in the 10mm the thermostatic mixer mixes cold from the 22mm.
Eventually the 22mm runs hot as well and you have high pressure hot.

So, you'd get hot water quickly (but at lower pressure) at first and
then hot water at high pressure.

Nice try but the disproportionately higher frictional losses on the
smaller pipe would mean that the 22mm pipe would go hot before the 10mm.

Ah, but there would be no flow in the 22mm becuase the thermostatic
mixer woudl shut it off until the 10mm ran hot.

For a fully open tap, hot water will arrive quicker on a 22mm pipe run
that it will on a 10.
--
fred
BBC3, ITV2/3/4, channels going to the DOGs

On Thu, 18 Feb 2010 23:50:04 -0800 (PST)
NT wrote:

On Feb 19, 1:12Â*am, Andy Dingley wrote:
On 18 Feb, 23:20, "Tim" wrote:

Perhaps you could trigger it with a wireless doorbell type switch? Â*Then you
could stick it in your pocket and trigger it on you way to the kitchen.

In article , TheOldFellow
writes

I think it's worth saying that for us, the biggest issue is wasted
water, not the time taken. We'd like to have a meter, and reduce the
water bills, but not at the expense of the electricity or oil costs.

If it also means that sometimes the delay waiting for washing-up water
can be avoided, then that's a bonus. And it can, because we wash up
after a meal, and there is plenty of time while clearing dishes to the
sink area for the system to 'run to hot' - and that without the
current waste.

This has been an interesting thread, I'm glad I started it. I've
learnt a lot, it's particularly interesting that OSO planed for it in
the design of the cylinder.

I estimate that it would cost at least £250 to install though, and
that's a lot of water to save! Payback is not a quicky. More thought
required. Mind you, if I can find a potable-OK pump for under, say
£60, then it becomes much more do-able.

Moving the cylinder is out of the question I suppose?
--
fred
BBC3, ITV2/3/4, channels going to the DOGs

fred wrote:
In article ,
TheOldFellow writes

I think it's worth saying that for us, the biggest issue is wasted
water, not the time taken. We'd like to have a meter, and reduce the
water bills, but not at the expense of the electricity or oil costs.

If it also means that sometimes the delay waiting for washing-up
water can be avoided, then that's a bonus. And it can, because we
wash up after a meal, and there is plenty of time while clearing
dishes to the sink area for the system to 'run to hot' - and that
without the current waste.

This has been an interesting thread, I'm glad I started it. I've
learnt a lot, it's particularly interesting that OSO planed for it in
the design of the cylinder.

I estimate that it would cost at least £250 to install though, and
that's a lot of water to save! Payback is not a quicky. More
thought required. Mind you, if I can find a potable-OK pump for
under, say £60, then it becomes much more do-able.

Moving the cylinder is out of the question I suppose?

Or perhaps a multipoint gas water heater in the kitchen?

Tim

On Fri, 19 Feb 2010 13:07:09 +0000
fred wrote:
snip

For a fully open tap, hot water will arrive quicker on a 22mm pipe run
that it will on a 10.

In my kitchen, the tap, a mixer has 10mm ss-flexy tails, and so that is
the limiting factor. Even if the pipework to it was 28mm, it's still
got to get through the 10mm flexy. I don't like the tap much, but
SWMBO loves it :-(

If I do the re-circulator, then the limiting factor will be the smallest
bore in the circuit. ATM that's the 15mm from the bathroom.

The rising main is also 15mm, but that's at full pressure. The feed to
the pressurised tank is limited to 2.1 bar - it's permitted
to take that to 5 bar if I fit an external expansion vessel (potable,
sized to system, charged to 5bar). We are getting into diminishing
returns here.

R.

In an earlier contribution to this discussion, TheOldFellow
wrote:

This has been an interesting thread, I'm glad I started it. I've
learnt a lot, it's particularly interesting that OSO planed for it in
the design of the cylinder.

I estimate that it would cost at least £250 to install though, and
that's a lot of water to save! Payback is not a quicky. More thought
required. Mind you, if I can find a potable-OK pump for under, say
£60, then it becomes much more do-able.

R.

Does it *need* to be potable-ok? We never drink anything that comes out of
the hot tap because the water has previously been in an unsealed tank in the
attic.
--
Cheers,
Roger
_______
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

In article , TheOldFellow
writes
On Fri, 19 Feb 2010 13:07:09 +0000
fred wrote:
snip

For a fully open tap, hot water will arrive quicker on a 22mm pipe run
that it will on a 10.

In my kitchen, the tap, a mixer has 10mm ss-flexy tails, and so that is
the limiting factor. Even if the pipework to it was 28mm, it's still
got to get through the 10mm flexy. I don't like the tap much, but
SWMBO loves it :-(

If I do the re-circulator, then the limiting factor will be the smallest
bore in the circuit. ATM that's the 15mm from the bathroom.

The rising main is also 15mm, but that's at full pressure. The feed to
the pressurised tank is limited to 2.1 bar - it's permitted
to take that to 5 bar if I fit an external expansion vessel (potable,
sized to system, charged to 5bar). We are getting into diminishing
returns here.

Bear in mind that the length of each restriction is important too, a 40m
run of 22mm followed by a 30cm length of 10mm tail will flow a lot more
than a 40m run of 10mm (you'd get barely a trickle from a full length of
10).

If you have an electrical or electronic bent then thin and thick cables
(or large and small resistors) in series are a good analogy.
--
fred
BBC3, ITV2/3/4, channels going to the DOGs

On Feb 19, 1:16*pm, TheOldFellow wrote:
On Thu, 18 Feb 2010 23:50:04 -0800 (PST)

NT wrote:
On Feb 19, 1:12*am, Andy Dingley wrote:
On 18 Feb, 23:20, "Tim" wrote:

Perhaps you could trigger it with a wireless doorbell type switch? *Then you
could stick it in your pocket and trigger it on you way to the kitchen.

PIR occupancy sensor over the sink

exactly. One in bathroom, one in kitchen, so the pump only runs when
someone comes into the room. But is it worth it?

NT

I think it's worth saying that for us, the biggest issue is wasted
water, not the time taken. *We'd like to have a meter, and reduce the
water bills, but not at the expense of the electricity or oil costs.

If it also means that sometimes the delay waiting for washing-up water
can be avoided, then that's a bonus. *And it can, because we wash up
after a meal, and there is plenty of time while clearing dishes to the
sink area for the system to 'run to hot' - and that without the
current waste.

This has been an interesting thread, I'm glad I started it. *I've
learnt a lot, it's particularly interesting that OSO planed for it in
the design of the cylinder.

I estimate that it would cost at least £250 to install though, and
that's a lot of water to save! *Payback is not a quicky. *More thought
required. *Mind you, if I can find a potable-OK pump for under, say
£60, then it becomes much more do-able.

R.


Electric heating tape along the hot pipe may be a lot cheaper to
install, plus good pipe insulation.


NT

"NT" wrote in message
...
On Feb 19, 1:16 pm, TheOldFellow wrote:
On Thu, 18 Feb 2010 23:50:04 -0800 (PST)

NT wrote:
On Feb 19, 1:12 am, Andy Dingley wrote:
On 18 Feb, 23:20, "Tim"
wrote:

Perhaps you could trigger it with a wireless doorbell type
switch? Then you
could stick it in your pocket and trigger it on you way to the
kitchen.

PIR occupancy sensor over the sink

exactly. One in bathroom, one in kitchen, so the pump only runs
when
someone comes into the room. But is it worth it?

NT

I think it's worth saying that for us, the biggest issue is wasted
water, not the time taken. We'd like to have a meter, and reduce the
water bills, but not at the expense of the electricity or oil costs.

If it also means that sometimes the delay waiting for washing-up
water
can be avoided, then that's a bonus. And it can, because we wash up
after a meal, and there is plenty of time while clearing dishes to
the
sink area for the system to 'run to hot' - and that without the
current waste.

This has been an interesting thread, I'm glad I started it. I've
learnt a lot, it's particularly interesting that OSO planed for it
in
the design of the cylinder.

I estimate that it would cost at least £250 to install though, and
that's a lot of water to save! Payback is not a quicky. More thought
required. Mind you, if I can find a potable-OK pump for under, say
£60, then it becomes much more do-able.

R.


Electric heating tape along the hot pipe may be a lot cheaper to
install, plus good pipe insulation.


NT


At my last house I installed a circulating hot water system to avoid
the cold leg, and it worked fine by gravity for the 23 years I was
there. I had 22mm feed from the top of the cylinder to all the
services and a 15mm return pipe back to about 18" down the cylinder,
with a gate valve to shut it off if needed. It worked fine - I'd
expected to have to install a pump but never did. Needless to say the
loop was very well lagged. This was in a 7 bedroomed four storey
Edwardian pile so there was a goodly chance of gravity working in my
favour!

AWEM

On Sat, 20 Feb 2010 08:23:43 -0000
"Andrew Mawson" wrote:

At my last house I installed a circulating hot water system to avoid
the cold leg, and it worked fine by gravity for the 23 years I was
there. I had 22mm feed from the top of the cylinder to all the
services and a 15mm return pipe back to about 18" down the cylinder,
with a gate valve to shut it off if needed. It worked fine - I'd
expected to have to install a pump but never did. Needless to say the
loop was very well lagged. This was in a 7 bedroomed four storey
Edwardian pile so there was a goodly chance of gravity working in my
favour!

AWEM


Hmm? Yes, well I live in a Bungalow, the maximum I can get is about 2
metres from return boss on the cylinder to the run of pipe on the flat
in the loft. So with 80 metres of pipe to manage (flow and return) do
you think a thermal-only system would work? Is it worth trying?

R.

In article , TheOldFellow wrote:
I'm guessing a well insulated pipe run with a bronze pump in the return
switched by a pipe thermostat at the highest/furthest point is the
idea, but connected how to the cylinder? Feed from the top and return
to the bottom with cold feed tee-ed in somehow. Check valve in the
circuit and another on the cold feed?

Does anyone have any experience of actually doing one? Advice?

I haven't done one, but my house has one. Whoever fitted it failed totally
on the "well-insulated" part, so the potential saving in not having to
run the hot tap is more than balanced by having to run the cold tap to
get rid of the water which has warmed up being alongside the hot pipe
(along with wasting heat in summer)...

It uses a combined pump and time switch, and tees back into the cold feed
to the heat exchanger on the tank (it's a thermal store system, with mains
pressure hot water). For the reasons above, the time switch is generally
just left to "off" (I did turn it on while there was no heating upstairs).