Heating Capacity of 15 and 22mm pipe
Eddie Cairns
be carried. I remember something about 15mm taking up to 20,000 Btu's and
22mm up to 50,000 Btu's but there was also pipe length coming into it.
Eddie
Ed Sirett
much heat they can deliver.
I'd guess, mainly from looking at many instalations, that under typical
usage 15mm pipe can deliver about 3 rads worth of heat and 22mm pipe about 8
rads worth. I think it works out to about the BTU/hr values given.
Ed Sirett
Property Maintainer - North London.
Eddie Cairns wrote in message ...
simpso...@my-deja.com
as someone who is about to have a new boiler installed on Saturday,
this posting caught my eye. Especially when I looked at the technical
specs of the boiler that is to be installed and see that the heating
flow and return is 22mm.
Just to check you are talking about the pipes going from the boiler to
the rads and back again, right?
That looks like a stupid question written down, but I just want to
check.
So, if I have a house with 8 rads, then the pipes should be 22 mm. Is
that right?
Great, something to lie awake thinking about tonight (I'm not at home).
Actually, I'm at a friend's house which also has 8 rads and almost all
the heating pipes that I can see (except for one) are 15mm. Is it the
case that you have a 22 mm basic framework of piping and then branch
off this framework to the individual rads with 15mm?
If so, how extensive should this framework be? What I mean is should it
be the case that the piping should be 22 mm to within a few feet of the
rads and only 15 mm for that last bit, or can the framework be quite
minimal and the branches much longer?
thanks,
Alan
Sent via Deja.com http://www.deja.com/
Before you buy.
Andy Wade
> Has anyone a table of the capacity of 15mm and 22 mm pipe re Btu's that
can
> be carried. I remember something about 15mm taking up to 20,000 Btu's
and
> 22mm up to 50,000 Btu's but there was also pipe length coming into it.
Conventional wisdom has it that the speed of water flow in heating pipes
shouldn't exceed about 1m/s - otherwise noise and vibration will result.
Assuming the usual 10degC difference between flow and return gives the
following 'load limits'.
Pipe size Max load
--------- --------
6mm 750W
8mm 1.5kW
10mm 2.5kW
12mm 4.1kW
15mm 6kW
22mm 13.4kW
28mm 22.5kW
35mm 35kW
To convert from kW to BThU/hr multiply by 3,412.
--
Andy
Eddie Cairns
Eddie Cairns
"Andy Wade" <ajw...@dial.pipex.com> wrote in message
news:01bf5c85$a3df7640$LocalHost@dog40...
Eddie Cairns
> Just to check you are talking about the pipes going from the boiler to
> the rads and back again, right?
>
If you do not have too many radiators then the main runs can be in 15mm.
>
> So, if I have a house with 8 rads, then the pipes should be 22 mm. Is
> that right?
>
No don't talk about radiators, talk about heating load on the main runs.
> Actually, I'm at a friend's house which also has 8 rads and almost all
> the heating pipes that I can see (except for one) are 15mm. Is it the
> case that you have a 22 mm basic framework of piping and then branch
> off this framework to the individual rads with 15mm?
>
Yes
> If so, how extensive should this framework be? What I mean is should it
> be the case that the piping should be 22 mm to within a few feet of the
> rads and only 15 mm for that last bit, or can the framework be quite
> minimal and the branches much longer?
If say three radiators had a total load of 15,000 btu then hte main run to
them can be 15mm. Or if upstairs is only 15,000 btu then the upstairs branch
can be 15mm .
Eddir Cairns
Chris French
writes
>
>
>Especially when I looked at the technical
>specs of the boiler that is to be installed and see that the heating
>flow and return is 22mm.
>
>the rads and back again, right?
>
>That looks like a stupid question written down, but I just want to
>check.
>
rubbish.
>So, if I have a house with 8 rads, then the pipes should be 22 mm. Is
>that right?
>
Probably at least some of it.
>Actually, I'm at a friend's house which also has 8 rads and almost all
>the heating pipes that I can see (except for one) are 15mm. Is it the
>case that you have a 22 mm basic framework of piping and then branch
>off this framework to the individual rads with 15mm?
>
That's the normal domestic layout
>If so, how extensive should this framework be? What I mean is should it
>be the case that the piping should be 22 mm to within a few feet of the
>rads and only 15 mm for that last bit, or can the framework be quite
>minimal and the branches much longer?
>
The precise set up depends on the size of rads supplied, layout etc. 15
mm can often be used to supply more than one rad. In an average house
you proably wouldn't need a run of 22mm pipe just to supply one rad.
In our house the 22mm pipe only runs from the boiler along the length of
the hallway floor. From this 15mm branches supply either single rads, or
in the case of upstairs, a pair of rads for each branch.
--
Chris French, Leeds
Chris French
<ajw...@dial.pipex.com> writes
>Eddie Cairns wrote ...
>
>> Has anyone a table of the capacity of 15mm and 22 mm pipe re Btu's that
>can
>> be carried. I remember something about 15mm taking up to 20,000 Btu's
>and
>> 22mm up to 50,000 Btu's but there was also pipe length coming into it.
>
>Conventional wisdom has it that the speed of water flow in heating pipes
>shouldn't exceed about 1m/s - otherwise noise and vibration will result.
>Assuming the usual 10degC difference between flow and return gives the
>following 'load limits'.
>
>Pipe size Max load
>--------- --------
>22mm 13.4kW
Pretty much what my which plumbing and heating book says.
Re pipe length. This is important because of heat losses from the pipe
obviously increase with length. But unless you are near the limit of the
pipes carrying capacity you don't need to worry about it when designing
the system
--
Chris French, Leeds
Adam
>
> > Has anyone a table of the capacity of 15mm and 22 mm pipe re Btu's that
> can
> > be carried. I remember something about 15mm taking up to 20,000 Btu's
> and
> > 22mm up to 50,000 Btu's but there was also pipe length coming into it.
>
> Conventional wisdom has it that the speed of water flow in heating pipes
> shouldn't exceed about 1m/s - otherwise noise and vibration will result.
> Assuming the usual 10degC difference between flow and return gives the
> following 'load limits'.
>
> Pipe size Max load
> --------- --------
> 8mm 1.5kW
> 10mm 2.5kW
> 12mm 4.1kW
> 15mm 6kW
> 22mm 13.4kW
> 28mm 22.5kW
> 35mm 35kW
>
> To convert from kW to BThU/hr multiply by 3,412.
Running at what water temperature? The hotter the more Kws transfered
through the pipe.
Adam
> shouldn't exceed about 1m/s - otherwise noise and vibration will result.
> Assuming the usual 10degC difference between flow and return gives the
> following 'load limits'.
>
> Pipe size Max load
> --------- --------
> 6mm 750W
> 8mm 1.5kW
> 10mm 2.5kW
> 12mm 4.1kW
> 15mm 6kW
> 22mm 13.4kW
> 28mm 22.5kW
> 35mm 35kW
>
> To convert from kW to BThU/hr multiply by 3,412.
Andy,
You say 1m/s. I assume this is 1metre of water per sec (a cubic metre of
water?). Flow is usually in litres per second.
Roger Chapman
from "Adam" <ad...@NOSPAMmail.com> contains these words:
> You say 1m/s. I assume this is 1metre of water per sec (a cubic metre of
> water?). Flow is usually in litres per second.
OTOH *speed* is usually quote in terms of unit distance/time. :-)
Roger
Tony Bryer
> You say 1m/s. I assume this is 1metre of water per sec (a cubic metre of
> water?). Flow is usually in litres per second.
It's the linear speed at which the water is flowing in the pipe - above
this the householder is likely to complain about noisy pipework.
Tony Bryer
Andy Wade
>Running at what water temperature? The hotter the more Kws transfered
>through the pipe.
Wrong. For a given flow rate the power transferred depends (to engineering
orders of accuracy) only on the temperature difference between flow and
return. In fact for a given water speed (volumetric flow rate) the power
will fall slightly as the temperature rises and the water becomes less dense
and the mass flow rate falls.
Obviously a radiator will transfer more heat to the room if the flow is
hotter, but that isn't what we were talking about.
--
Andy
Adam
Tony Bryer <to...@sda.co.uk> wrote in message
news:VA.000009bb.14287b6e@mesh...
Tony,
Is this linear speed in cubic metres per second?
Andy Wade
>Re pipe length. This is important because of heat losses from the pipe
>obviously increase with length. But unless you are near the limit of the
>pipes carrying capacity you don't need to worry about it when designing
>the system
Except that you do need to check the pressure drop (aka 'head loss') to
ensure that pumping requirements can be met. The normal procedure is to
identify the circuit with the highest head loss (with the initial proposed
pipe sizing). This is called the index circuit. A pump must be selected
which can deliver the required total system flow rate against the head loss
of the index cct. If this takes you outside the capability of a standard
size pump, it is usually better to increase the pipe size on (part of) the
index cct. to reduce the head loss. Of course another circuit may then
become the index circuit, so the design procedure is somewhat iterative.
--
Andy
Dave Liquorice
>> Pipe size Max load
>> --------- --------
>> 6mm 750W
>> 8mm 1.5kW
>> 10mm 2.5kW
>> 12mm 4.1kW
>> 15mm 6kW
>> 22mm 13.4kW
>> 28mm 22.5kW
>> 35mm 35kW
Useful table, thanks. Just as well our 38.2kW boiler has 2 28mm circuuits on
it. B-)
> Running at what water temperature? The hotter the more Kws transfered
> through the pipe.
Actual water temperature isn't particulary relevant. The big one is the
difference between flow and return temperatures.
Water flow at 50C return at 40C transfers the same amount as heat as water
flow at 80C return at 70C. Of course getting the 10C drop is easier with the
higher temp flow as the temperature gradients ar higher.
--
Cheers new...@nexus.demon.co.uk
Dave. Remove "spam" for valid email.
Chris French
<ad...@NOSPAMmail.com> writes
pipework at. (unrelated to the amount of water)
--
Chris French, Leeds
Chris French
<ajw...@dial.pipex.com> writes
>Chris French wrote ...
>
>>Re pipe length. This is important because of heat losses from the pipe
>>obviously increase with length. But unless you are near the limit of the
>>pipes carrying capacity you don't need to worry about it when designing
>>the system
>
>
>Except that you do need to check the pressure drop (aka 'head loss') to
>ensure that pumping requirements can be met
Yes of course, I was just really talking about the heat loss from the
pipes as an issue to be concerned about.
--
Chris French, Leeds
Adam
Chris French <news...@spennithorne.demon.co.uk> wrote in message
news:05aLlJAG...@spennithorne.demon.co.uk...
Chris,
There agian is that cubic metres/sec? If so, this must relate to
litres/sec. I find litres per second easier to grasp and it's more precise.
Jon Rouse
>
>Is this linear speed in cubic metres per second?
Not unless you drive your car in cubic miles per hour.
Oh, sorry, humour, you don;t understand that do you?
--
The views expressed are my own, and may not necessarily reflect those of my
employer.
Jon Rouse
>Yes of course, I was just really talking about the heat loss from the
>pipes as an issue to be concerned about.
Thinking of heat loss from pipes, I've got a row of bookcases against a
dampish wall and, as a temporary fix until we sort out the house, I was
thinking of laying a length of pipe along the foot of the wall behind the
bookcases and connecting it to a spare spur I happen to have on the heating.
How does Hep20 compare with copper for heat output, as it would be a heck of
a lot easier to install.
Ledswinger
Jon Rouse <rou...@nospam.postoffice.co.uk> wrote in message
news:94776731...@igateway.postoffice.co.uk...
> dampish wall and, as a temporary fix until we sort out the house, I was
> thinking of laying a length of pipe along the foot of the wall behind the
> bookcases and connecting it to a spare spur I happen to have on the
heating.
> How does Hep20 compare with copper for heat output, as it would be a heck
of
> a lot easier to install.
Intuitively I thought that plastic pipe would be shit as an impromptu
radiator since plastic is a far better insulator than copper, but thought
I'd better check my facts, and lo! It is apparently suggested by the makers
for some heating uses (you can find the references on any search engine).
However I did find references to Hep2o having "lower thermal diffusivity"
and to "water remaining warm in pipes for longer", so I'd suggest the
following option:
Since your wall is (presumably) straight, why not use a mix of Hep2o to
connect to the heating, and a straight length of copper pipe along the wall?
Led
Adam
> >the more Kws transfered
> >through the pipe.
>
engineering
> orders of accuracy) only on the temperature difference between flow and
> return. In fact for a given water speed (volumetric flow rate) the power
> will fall slightly as the temperature rises and the water becomes less
dense
> and the mass flow rate falls.
>
> Obviously a radiator will transfer more heat to the room if the flow is
> hotter, but that isn't what we were talking about.
Andy,
A practical question. Some quick recovery coils in cylinders can take all
the output from say a 36Kw boiler. How would I size the pipes to guarantee
that I am extracting all the heat from the boiler and putting it into the
cylinder via the quick recovery coil?
It is clear that the temperature drop across the flow and return is a
measure of the heat extracted from the flow pipe. If a cylinder maker says
their coil can take 36Kw how do I size the pipes? I don't want to put in
28mm or 35mm pipes when 15mm or 22mm at 82C instead of 70C and a fast pump
speed would do.
I notice you table was over a 10C flow and return temperature difference.
If there a table available that give the Kw extracted with other flow and
return temperature differences?
Dave Plowman
Adam <ad...@NOSPAMmail.com> wrote:
> It is clear that the temperature drop across the flow and return is a
> measure of the heat extracted from the flow pipe. If a cylinder maker
> says their coil can take 36Kw how do I size the pipes? I don't want to
> put in 28mm or 35mm pipes when 15mm or 22mm at 82C instead of 70C and a
> fast pump speed would do.
First, the speed of the pump has little to do with the transfer of the
heat from the boiler to either the cylinder or radiators. All it needs to
do is circulate the water to the most 'difficult' point. Speeding it up
beyond this is likely to cause pumping over in an open system and more
noise.
Most 3-way valves will accomodate 28mm pipe, so it makes sense, on an
average installation, to do the run to and from the boiler to the valve in
this size, and site the valve close to the tank. The overall extra cost of
using 28mm over 22mm is likely to be insignificant on a new installation.
--
* If at first you don't succeed, destroy all evidence that you tried *
Dave Plowman dave....@argonet.co.uk London SW 12
RIP Acorn
Jon Rouse
>
>Since your wall is (presumably) straight, why not use a mix of Hep2o to
>connect to the heating, and a straight length of copper pipe along the
wall?
That was my original thought, but as it would involve converting from copper
to plastics four times I began to wonder if the plastics pipe might give out
enough heat to do the job.
Ledswinger
> Ledswinger wrote in message <85kiju$hmm$1...@barcode.tesco.net>...
> >
> >Since your wall is (presumably) straight, why not use a mix of Hep2o to
> >connect to the heating, and a straight length of copper pipe along the
> wall?
>
>
> That was my original thought, but as it would involve converting from
copper
> to plastics four times I began to wonder if the plastics pipe might give
out
> enough heat to do the job.
Apparently its recommended for under floor heating applications, but you
presumably want a fair amount of heat at the bottom of the wall/bookcase,
rather than the sort of slow diffuse heat required for underfloor?
All I can think of if you don't want copper, is to suggest a larger diameter
Hep2o section, but with the wall thickness in the first place you might find
that you have a fairly large pipe?
Led
Andy Wade
>A practical question. Some quick recovery coils in cylinders can take all
>the output from say a 36Kw boiler. How would I size the pipes to guarantee
>that I am extracting all the heat from the boiler and putting it into the
>cylinder via the quick recovery coil?
36kW will fully reheat a 117 litre cylinder (900 x 450mm, the most common
domestic size) in about 10 minutes flat. Do you really need that sort of
performance, or do you have an unusually large cylinder - non-domestic
perhaps? That said, fast recovery does make efficient use of the boiler,
provided that you shut it down once the cylinder is up to temperature.
From the pipe load capacity table I posted you will see that for 36kW you
need 35mm pipework to keep within 1m/s and 10degC temperature drop. In
practice though a larger temperature drop won't affect the heat exchanger
performance too much, so 28mm would probably be perfectly OK. I certainly
wouldn't go any smaller though, at that power level. The main thing is to
be sure that you have enough pump capacity to get the required flow rate.
One litre/sec at 1degC drop will transfer about 4.2kW, so you're going to
need just under 0.6litre/sec and about 15degC drop to shift 36kW. At that
flow rate the linear speed in 28mm pipe works out at about 1.1m/s, which
should just about be OK. A higher flow rate would improve performance, but
runs the risk of noisy pipes, whereas a flow rate much lower will fairly
seriously erode the heat transfer performance.
>I notice you table was over a 10C flow and return temperature difference.
>If there a table available that give the Kw extracted with other flow and
>return temperature differences?
Fairly obviously, for any given flow rate, the power transferred is directly
proportional to the temperature difference.
HTH
--
Andy
Roger Chapman
from "Andy Wade" <ajw...@dial.pipex.com> contains these words:
>One litre/sec at 1degC drop will transfer about 4.2kW, so you're going to
>need just under 0.6litre/sec and about 15degC drop to shift 36kW.
I many be missing a very vital point but does the temperature drop
necessarily follow. It seems to me that the temperature drop at any
given flowrate is governed by the dimensions of the internal coil of
the cylinder and the temperature difference between DHW and coil and
it may well be that the coil is too small and a flow rate of 0.6 l/s
will not lead to such a large temperature drop.
Raising the flow rate would increase the heat transfer but not
perhaps by very much as the temperature difference between inlet and
outlet will be reduced, the increase in heat transfer being governed
entirely by the marginal increase in temperature gradient towards the
cooler end of the coil.
Raising the boiler temperature would provide a bigger temperature
difference between the coil and DHW and thus a potentially larger
temperature drop across the coil but at maximum boiler temperature
and desired HW temperature the internal coil might still not be big
enough to transfer enough heat to give the desired temperature drop
across the coil.
On the subject of noise does the 1 metre/sec rule apply to the
cylinder coil? Because if it does there seems little advantage in
using a supply pipe of larger bore than the coil.
My apologies if this all seems rather convoluted but I cannot find a
form of words to express myself more clearly.
Roger
Adam
> Adam wrote ...
>
> >A practical question. Some quick recovery coils in cylinders
> >can take all the output from say a 36Kw boiler. How would
> >I size the pipes to guarantee that I am extracting all the heat
> >from the boiler and putting it into the cylinder via the quick
> >recovery coil?
>
> 36kW will fully reheat a 117 litre cylinder (900 x 450mm, the
> most common domestic size) in about 10 minutes flat.
Andy,
Is that a British Standard, or quick recovery cylinder?
> That said, fast recovery does make efficient use of
> the boiler, provided that you shut it down once the
> cylinder is up to temperature.
The Haynes Plumbing books emphasises that quick recovery cylinders can be
downsized by about half. A 50 litre cylinder will do a normal domestic
house. I believe that you can save about 1/3 of you DHW bills by using quick
recovery? Travis Perkins are also selling them cheap.
> From the pipe load capacity table I posted you
> will see that for 36kW you need 35mm pipework
> to keep within 1m/s and 10degC temperature drop.
Is that a cubic meter of water a second? No one I ask seems to know.
> In practice though a larger temperature drop won't
> affect the heat exchanger performance too much,
> so 28mm would probably be perfectly OK. I certainly
> wouldn't go any smaller though, at that power level.
I don't want to fit 28mm pipe as it is obtrusive. If I can get away with
15mm I would be delighted as the cylinder is some way from the boiler. :-)
I want to divert all the output of a boiler to the cylinder to give a quick
warm up, have a smaller cylinder, and save about 1/3 of DHW bills per year.
The boiler will be minimum of 24kW, maybe more. I want to calculate it
rather than go rule of thumb, which is how most CH systems are sized and
installed.
John Armstrong
wrote:
>
>Chris French <news...@spennithorne.demon.co.uk> wrote in message
>news:05aLlJAG...@spennithorne.demon.co.uk...
>> In article <85ih35$1qr$1...@newsg3.svr.pol.co.uk>, Adam
>> <ad...@NOSPAMmail.com> writes
>> >
>> >Tony Bryer <to...@sda.co.uk> wrote in message
>> >news:VA.000009bb.14287b6e@mesh...
>> >> In article <85hurr$o5h$1...@newsg3.svr.pol.co.uk>, Adam wrote:
>> >> > You say 1m/s. I assume this is 1metre of water per sec (a cubic metre
>of
>> >> > water?). Flow is usually in litres per second.
>> >>
>> >> It's the linear speed at which the water is flowing in the pipe - above
>> >> this the householder is likely to complain about noisy pipework.
>> >
>> >Tony,
>> >
>> >Is this linear speed in cubic metres per second?
>> >
>> No speed in plain old metres/sec that the water travels through the
>> pipework at. (unrelated to the amount of water)
>
>Chris,
>
>There agian is that cubic metres/sec? If so, this must relate to
>litres/sec. I find litres per second easier to grasp and it's more precise.
>
linear metres/sec. Imagine an air bubble in the water and in 1 second
it will travel 1m if the water is flowing at 1m/s. Doing a quick
calculation, if a pipe was 15mm internal diameter, the cross sectional
area would be 0.000177m2, so a 1m length of pipe holds 0.000177m3 of
water, so 1m3 of water would need 5659m of pipe to hold it, so if
water was flowing at 1m3/s through a 15mm pipe, the water and any air
bubbles in it would be flowing at 5658m/s or quite a lot of times
around the average house every second. It is also 16 times the speed
of sound, so the sonic booms will make the pipework a bit on the noisy
side.
--
John
Chris French
<ad...@NOSPAMmail.com> writes
>Andy Wade <ajw...@dial.pipex.com> wrote in message
>news:85l6vi$bik$1...@lure.pipex.net...
>> Adam wrote ...
>>
>> >A practical question. Some quick recovery coils in cylinders
>> >can take all the output from say a 36Kw boiler.
>> From the pipe load capacity table I posted you
>> will see that for 36kW you need 35mm pipework
>> to keep within 1m/s and 10degC temperature drop.
>
>Is that a cubic meter of water a second? No one I ask seems to know.
>
We do and we've answered but you haven't quite understood it seems.. :-)
1m/s refers to the *speed* of the water in the pipe. It is not a flow-
rate which is what a cubic metre/sec would be.
For a speed of 1m/sec the flowrate will vary depending on the size of
the pipe (bigger pipe = bigger flowrate obviously)
--
Chris French, Leeds
Andy Wade
> > 36kW will fully reheat a 117 litre cylinder (900 x 450mm, the
> > most common domestic size) in about 10 minutes flat.
> Is that a British Standard, or quick recovery cylinder?
Well, an ordinary BS cylinder wouldn't be able to absorb that sort of
power, so it's a hypothetical fast-recovery cylinder which could. At my
previous house I installed a 117 litre Range 'Supercal' cyl which, IIRC,
had 0.61m^2 heat exchange surface. That would absorb the total boiler o/p
of about 15kW quite happily for about two-thirds of the recovery cycle,
after which the modulating burner in the boiler started to throttle back.
The 900x450 BS cyl. has about 0.48m^2 heat exchange surface area, IIRC.
> The Haynes Plumbing books emphasises that quick recovery cylinders can
be
> downsized by about half. A 50 litre cylinder will do a normal domestic
> house. I believe that you can save about 1/3 of you DHW bills by using
quick
> recovery? Travis Perkins are also selling them cheap.
These don't seem to have caught on, and I would certainly be sceptical.
The saving comes from the reduced standing losses, and more efficient
boiler utilisation, but:
(1) in a hard water area will the heat exchange surfaces scale up and
drastically reduce the performance?
(2) in the summer the boiler must remain 'available' all the time HW is
required, and you'd need really tight thermostatic control to shut it down
at the end of each recovery cycle;
(3) at the end of every cycle the heat stored in those 28mm primary
circulating pipes will go to waste;
(4) in the winter the boiler o/p will be shared with the heating circuits
and the recovery time will increase;
(5) do they have an immersion heater boss? It's always useful to have a
standby heat source available.
> > to keep within 1m/s and 10degC temperature drop.
> Is that a cubic meter of water a second? No one I ask seems to know.
Several people have already explained that this is linear water speed in
the pipe. Multiply by cross-sectional area of pipe to convert to
volumetric flow.
> I don't want to fit 28mm pipe as it is obtrusive. If I can get away with
> 15mm [...]
You are of course joking. Stick to a conventional size cylinder, with the
largest heat exchange area you can get, and well insulated. Use
conventional Y- or S-plan controls and 22mm primaries and you won't go too
far wrong.
--
Andy
Andy Wade
> I many be missing a very vital point but does the temperature drop
> necessarily follow. It seems to me that the temperature drop at any
> given flowrate is governed by the dimensions of the internal coil of
> the cylinder and the temperature difference between DHW and coil and
> it may well be that the coil is too small and a flow rate of 0.6 l/s
> will not lead to such a large temperature drop.
No, you are absolutely correct in what you say. We came to this through a
discussion about pipe sizing and I was just assuming that the 'load' was
_capable_ of absorbing the stated power.
> On the subject of noise does the 1 metre/sec rule apply to the
> cylinder coil? Because if it does there seems little advantage in
> using a supply pipe of larger bore than the coil.
That's probably true as well, but again I was, in effect, assuming that
the heat exchanger had already been competently designed to handle x
kilowatts and that our job was to design the primary circulating pipework
to get that power to it.
It gets even worse with old-fashioned gravity primaries where the
circulating pressure also depends on the temperature drop in the
(vertical component of) the pipework.
--
Andy
Adam
> In article <85lcgg$tqf$1...@newsg4.svr.pol.co.uk>, Adam
> <ad...@NOSPAMmail.com> writes
> >Andy Wade <ajw...@dial.pipex.com> wrote in message
> >news:85l6vi$bik$1...@lure.pipex.net...
> >> Adam wrote ...
> >>
> >> >A practical question. Some quick recovery coils in cylinders
> >> >can take all the output from say a 36Kw boiler.
>
> >> From the pipe load capacity table I posted you
> >> will see that for 36kW you need 35mm pipework
> >
> >Is that a cubic meter of water a second? No one I ask seems to know.
> >
>
>
> 1m/s refers to the *speed* of the water in the pipe. It is not a flow-
> rate which is what a cubic metre/sec would be.
>
> For a speed of 1m/sec the flowrate will vary depending on the size of
> the pipe (bigger pipe = bigger flowrate obviously)
>
Thanks. Clearer now. No one said it that way.
Andrew
<jo...@ggrove.swinternet.co.uk> writes
>On Thu, 13 Jan 2000 12:37:58 -0000, "Adam" <ad...@NOSPAMmail.com>
>wrote:
>
>>
Assume you have a stream at the end of your garden and you chuck in
a pooh stick. The stick travels (relative to the bank) at 1 metre
per second. It makes no difference if it is a stream or the amazon,
if the stick is travelling at the same speed as the water it is
travelling at 1 metre per second. If you wanted to slow the stick
in the stream down to 0.5 metres per second you would dredge the stream
so that its width and depth allowed twice as much *volume* of
water to flow per second. The water (and hopefully) stick would now
travel at half its original speed. To reinstate its speed to 1 metre per
second you would have to double the volume of water attempting to flow
down the stream. Apologies to anyone who considers themselves an expert
in this area, and feels obliged to launch into heavy mathematics mode,
but I am trying to state the obvious <g>
--
Andrew
Adam
> > >
> > >Since your wall is (presumably) straight, why not use a mix of Hep2o to
> > >connect to the heating, and a straight length of copper pipe along the
> > wall?
> >
> >
> > That was my original thought, but as it would involve converting from
> copper
> > to plastics four times I began to wonder if the plastics pipe might give
> out
> > enough heat to do the job.
>
> Apparently its recommended for under floor heating applications, but you
> presumably want a fair amount of heat at the bottom of the wall/bookcase,
> rather than the sort of slow diffuse heat required for underfloor?
>
> All I can think of if you don't want copper, is to suggest a larger
diameter
> Hep2o section, but with the wall thickness in the first place you might
find
> that you have a fairly large pipe?
Led,
Just a point. Underfloor heating does not use Polybuyelene pipe, as Hep2o
is. It uses santoprene and PEX.
Hepworth Plumbing
Just to clarify, Polybutylene is very widely used for underfloor
heating applications, and for comfort cooling (chilled beams).
The inherent flexibility makes it the material of choice for many
installers, both in the UK and in continental Europe. Hep2O has been
and is widely used in these applications.
Hepworth Plumbing
--
Tel: +44 (0)1709 856 300 |Hepworth Plumbing Products
Fax: +44 (0)1709 856 301 |Edlington Lane, Edlington
Email: in...@hepworthplumbing.co.uk|Doncaster, UK
http://www.hepworthplumbing.co.uk |DN12 1BY
Sent via Deja.com http://www.deja.com/
Before you buy.
Adam
Hepworth Plumbing <hepworth...@my-deja.com> wrote in message
news:86i4cl$ovg$1...@nnrp1.deja.com...
Hepworth Plumbing,
What company uses Polybutylene pipe for under floor heating? Most advertise
santoprene and PEX. Can normal Hep2O pipe be used buried in a screed as
long no compression joints are used? Interesting.