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Home made heatbank system |
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| message from Rob Graham on 18 May 2004 |
I'm trying to solve a low hot water pressure problem - long feeds, low
head, etc. I've looked at pumps; I've looked at a 'geyser'
arrangement, and I've now come across the heatbank system.
Searching through the archive found IMM's suggestion of a year ago
(6/5/2003) of using an ordinary DHW tank, etc.
The questions are :-
1 Has anyone tried this ?
2 There is a 3 way diverter valve talked about in the 2nd
arrangement - what is this for ?
3 Again on the 2nd arrangement, 2 ports are required at the base of
the tank - why?
4 If someone has built this - or IMM himself - I wouldn't mind a
drawing of the pipework and electrics as what I've taken from the
written description doesn't look as if it would work.
5 Where does one get the plate exchanger from?
Rob
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| Lurch replied to Rob Graham on 18 May 2004 |
<fx> Alarm bells, v. loud
Just a word of advice, if IMM suggested it, it's probably a madcap
idea, and if it involves plastic pipe it'll leak, and if he built one
himself it probably blew up while he was trying to shower his
overly-ample frame. I've no doubt the concept might work but listen to
other peoples advice on construction methods.
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| IMM replied to Lurch on 19 May 2004 |
Please. the man is requesting serious information. He doesn't need a clown
interjecting.
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| Andy Hall replied to IMM on 19 May 2004 |
So why have you?
.andy
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| IMM replied to Andy Hall on 19 May 2004 |
What wisdom have you imparted? Err, err...... none at all.
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| Andy Hall replied to IMM on 19 May 2004 |
Actually I did comment on the efficacy of GEA heat exchangers - having
actually used one.....
.andy
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| IMM replied to Andy Hall on 19 May 2004 |
< snip tripe by Andy >
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| The Natural Philosopher replied to IMM on 19 May 2004 |
Precisely his point.
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| IMM replied to The Natural Philosopher on 19 May 2004 |
< snip drivel by a snot >
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| G&M replied to Rob Graham on 18 May 2004 |
Wasn't around here then, but if the intention was to get heat out of a
standard hot water tank via the coil usually used to heat the water, forget
it. On most tanks the transfer rate is poor so peak hot water flow rate is
low and as the coil doesn't go anywhere near the hottest water at the top
of the tank so you need to keep the tank at a very high temperature just to
get the water warm.
Conversely if the suggestion wasn't this, my apologies to IMM.
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| nick smith replied to G&M on 18 May 2004 |
No - you use an external heat exchanger and circulating pump between the hot outlet at the
top and the cold inlet at the bottom.
The other side of the heat exchanger is rising main straight to hot taps or shower mixer
valve and transfer rates can be several tens of kilowatts, so a good shower !! - going to
do the same myself !
Nick
"G&M" <m1111b@yahoo.com> wrote in message news:c8e27q$b1a$1@news6.svr.pol.co.uk...
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| John Stumbles replied to nick smith on 19 May 2004 |
news:c8e27q$b1a$1@news6.svr.pol.co.uk...
hot outlet at the
shower !! - going to
I think there are some pictures on the DPS web site (google ...)
Basically you'll need a flow sensor switch which turns on a pump (like CH
pump, but should be non-corrodible rotor) when water flows in the DHW
pipework (i.e. someone turns a hot tap on) and pumps water from the hw
cylinder through the plate heat exchanger.
Another homebrew way to do it (which I haven't tried either) would be to
have a tank of primary hot water (i.e. heated directly by the boiler) with a
coil of perhaps 20m of 10mm dia tube immersed in it which carries mains
water to the taps, getting heated directly as it goes (i.e. that's your heat
exchanger). You'd have to have the tank at the top of your system, at the
same level as your f&e tank (implying an open-vented system).
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| IMM replied to John Stumbles on 19 May 2004 |
Many quick recovery cylinders are suitable.
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| Andy Hall replied to John Stumbles on 19 May 2004 |
DPS also sell the complete thing as an assembled entity.
You can buy the stainless steel heat exchanger separately as well.
I bought one from them made by a Swedish company, GEA Ecobraze for an
application where I wanted to have a second heating circuit totally
isolated from the first.
These heat exchangers are extremely good and have a massive surface
area between the primary and secondary sides. The result is that
they can easily transfer 100-200kW in a unit about the size of a
brick. Cost is about £80.
.andy
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| IMM replied to Andy Hall on 20 May 2004 |
The expansion vessels are mainly to prevent a clunk when turning off a tap
quickly. Check valves are not mandatory. Expansion can be via the cold
mains pipe; expanding backwards.
Very true.
http://www.alfalaval.com/scripts/WebObjects.dll/ecore.woa/wa/showNode?siteN
odeID=5532&contentID=27043&languageID=1>
DPS were selling a 14 plate one for around £30-40, last time I dealt with
them. It may have changed since then.
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| IMM replied to Rob Graham on 19 May 2004 |
Yes. I have. Work a treat.
Draw this out.
Take a normal cylinder:
- Fit a Surrey flange on the draw-off tapping (at the top)
- Fit a Surrey flange on the cold feed tapping (at the bottom)
- Take the boiler flow to the port on the Surrey flange that is not
protruding immersed in the water.
- Take the boiler return to the port on the Surrey flange that is protruding
in the water.
- From the remaining port on the draw-off take a pipe to the plate heat
exchanger.
- Insert an auto air vent into this pipe above the cylinder.
- Insert an anti vacuum valve also into this pipe above the cylinder, as
near to the cylinder as possible.
- From the remaining port on the cold feed take a pipe to the other side of
the plate heat exchanger.
- Take the cold mains into the plate heat excahnger and out of it to the
taps. Try and keep it 22mm.
- in the cold main (on the cold side) fit a flow switch.
- After the plate heat exchanger fit a blending valve on the hot draw-off.
The now new heat bank will be filled via the heating system. No zone valves
are needed. Ensure that the cylinder can vent and has no zone valve in the
pipe.
If you already have tappings on the side of the cylinder use these for the
boiler flow and return instead of the Surrey flanges.
Fit two cylinder thermostats on the side of the cylinder to eliminate boiler
cycling.
The flow and return to the cylinder can be the existing flow and return
pipes feeding the internal indirect coil.
Make sure you put in enough inhibitor.
http://www.heatweb.com
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| Andy Hall replied to IMM on 19 May 2004 |
This is not a complete solution. There are numerous missing pieces to
the description and a general lack of clarity.
While the idea may be interesting in principle, you have spoiled it by
not describing it in enough detail to make it usable.
.andy
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| IMM replied to Andy Hall on 19 May 2004 |
< snip tripe by Andy >
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| Andy Hall replied to IMM on 19 May 2004 |
Given that you are unable to document the proposed solution adequately
enough to make it useful, the only conclusion that one can come to is
to
<< snip tripe by IMM>>
.andy
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| IMM replied to Andy Hall on 19 May 2004 |
< snip tripe by Andy >
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| Andy Hall replied to IMM on 19 May 2004 |
Which Surrey flange? You should clarify.
Which flange?
Isn't there a pump missing? How do you circulate the primary water
from the cylinder through the heat exchanger?
Where does the vent connect? Presumably to the top of the cylinder,
but now venting into the heating F/E tank? Provided that the
existing vent is in place and there is a vent valve on top of the
cylinder, an extra vent pipe shouldn't be needed..
If there are no zone valves or a diverter valve, how is the heatbank
prevented from overheating and kept separate from the heating?
Connected how?
Are you suggesting an indirect cylinder i.e. heating water, heatbank
water separate?
If so, the cylinder needs supply and vent arrangement from another
small FE tank or equivalent. Otherwise the indirect coil is
redundant.
.andy
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| IMM replied to Andy Hall on 19 May 2004 |
< snip tripe by Andy >
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| Lurch replied to IMM on 19 May 2004 |
< snip tripe by IMM >
<un-snip Andys unanswered questions as to why half the solution is
missing>
Which Surrey flange? You should clarify.
Which flange?
Isn't there a pump missing? How do you circulate the primary water
from the cylinder through the heat exchanger?
Where does the vent connect? Presumably to the top of the cylinder,
but now venting into the heating F/E tank? Provided that the
existing vent is in place and there is a vent valve on top of the
cylinder, an extra vent pipe shouldn't be needed..
If there are no zone valves or a diverter valve, how is the heatbank
prevented from overheating and kept separate from the heating?
Connected how?
Are you suggesting an indirect cylinder i.e. heating water, heatbank
water separate?
If so, the cylinder needs supply and vent arrangement from another
small FE tank or equivalent. Otherwise the indirect coil is
redundant.
.andy
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| IMM replied to Lurch on 19 May 2004 |
< snip tripe by Mr Pole >
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| Christian McArdle replied to Rob Graham on 19 May 2004 |
Basically, if you understand the principles, it is simple.
Keep it heated exactly the same way (i.e. via the indirect coil and
immersion). No need to fiddle there, really, if the cylinder is already
adequetly warmed by the existing boiler. You do need to ensure you have a
cylinder thermostat and you need to bump up the temperature a bit (i.e. 75C)
and ensure boiler flow temperature is higher still (i.e. 82C).
Then you can use the hot water outlet at the top, pass it through the heat
exchanger, then the pump and back into the old cold feed at the bottom. No
need for extra flanges, etc.
The mains cold water goes through a flow switch and then through the other
channel of the heat exchanger. The flow switch controls the pump directly.
After this, the hot water (and cold mains feed) go through a thermostatic
mixing valve to get fixed temperature water (i.e. 55-60C), which then goes
into the old hot water pipework.
You can make the filling tank much smaller and bring it just above the
cylinder and out of the loft, if you prefer. I'd recommend making it manual
fill rather than a ball valve as this reduces the ability of the system to
flood the house during a leak. You could still use a ballvalve, but put a
manual lever valve just before to cut off the automatic operation when full.
Don't forget to take advantage of the fact that the cylinder can now contain
corrosion inhibitor.
Don't bother to connect the boiler circuit directly to the cylinder rather
than through the coil. There are distinct disadvantages, such as increased
complexity of the conversion, not being allowed sealed pressurised operation
(required for many modern boilers), and increased leakage/drainage/inhibitor
requirements that aren't usually outweighed by the advantages (which are
basically down to being able to install multiple heat sources, such as solar
or multiple boilers/ranges).
Parts:
1. 22mm TMV3 thermostatic mixing valve.
2. Pump.
3. Flow switch.
4. Plate exchanger (100kW min).
5. Sundry joints, pipework and electrical connections.
Christian.
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| IMM replied to Christian McArdle on 20 May 2004 |
I would not do this as the existing coil is most certainly not big enough to
take all the boilers output.
This is madness. Have the same F&E tanks fill the cylinder and the CH and
have an intermediate coil to heat the cylinder?
What complexity?
If you are havinbg an F&E tank, you may as well get a boioer that can
operate as an open system. Many state-of-the-art boilers can do both sealed
and open.
What are you on about?
An open system can have multiple heat sources.
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| Christian McArdle replied to IMM on 20 May 2004 |
How can you tell? Even DPS's indirect products are based on standard
indirect cylinders. How would you know if the existing system is rapid
recovery or not? Even if not, then all it would mean is a longer recovery
time, just as before. The recovery performance will be no worse.
I said nothing about merging the boiler primary circuit and the heat bank
water. Indeed, I propose the opposite, having separate systems with no
connection other than thermally through the indirect exchanger coil.
Radiator circuits do work much better pressurised even if the boiler allows
open vented. They are easier to fill, with fewer airlocks, no pumping over
and are typically manual fill to avoid house wrecking incidents.
Well, the additional tappings required in the cylinder, basically. The
method I have proposed requires no modification to the cylinder itself. No
requirement for additional Essex flanges or replacement Surrey types. This
makes the entire conversion much simpler.
As stated before, besides limiting boiler choice, open vented radiator
primary circuits are a PITA.
With shared water, you might have 200L+ in your primary circuit, instead of
30L, depending on the size of your cylinder/radiators. This has
repercussions when it comes to refilling, or if the system leaks. Obviously,
you might fit isolation valves to mitigate the effect of a draindown by
keeping the cylinder full. This doesn't solve all the problems, though, such
as system leakage consequences and keeping compatible inhibitors.
You misunderstand. I listed multiple heat sources as the main advantage of
combining the primary circuit and heat bank water. A bit like a 150L Dunsley
Neutraliser. You can always mix and match by having a modern condensing
boiler on an indirect coil, whilst pumping genuine heat bank water round a
range or solar panels.
Christian.
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| IMM replied to Christian McArdle on 20 May 2004 |
It is highly unlikely his cylinder will not even comply with Part L.
Best have it connected directly. It is simple. Many cylinder have a 3/4"
shower takeoff on te side. This can be used for the flow and a Surrey flange
for the cold feed. It is simple to do, by only extending pipe a few feet to
top and bottom of the cylinder.
All you do is fit two Surrey flanges which are simple to do, and extend pipe
a few foot up and down to them. Simple!!!!
You could clean out the now unused coil and use this as a pre-heat and used
only when low flows are draw-off, like a basin. The pump and plate heat
exchanger only come in when high flows are required. This is known a
thermal store hybrid, prevent excessive pump operation.
You know little of heating to come out with that.
You answered your own reservations. Use isolation valves to drain down the
parts of the system that require draining.
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| Aidan replied to Christian McArdle on 19 May 2004 |
Have a look on the Potterton website at the manuals for the Powermax
HE boiler. This is the most efficient domestic boiler in the SEDBUK
list. The non-condensing version is marketed under the Range name,
probably not for much longer though.
The Powermax boiler has an integral heat-store/water cylinder which
contains primary heating water. The combi version has a flat-plate
heat exchanger, and a second pump, instead of the more usual and less
reliable diaphragm diverter valve. The mains water passes through a
BPHE and is heated by primary water pumped from the heat-store by the
second pump. The first (heating) pump stops whilst the second pump is
running. A similar strategy should be feasible for your system.
You'd need a mini-expansion vessel on the DHWS and you'd need a much
bigger expansion vessel to accomodate the expansion of the additional
HTG primary water in the heat store.
SWEP make BPHEs, fairly cheap I recall, but I don't know if they do
one to suit. Otherwise salvage some from the local combi
graveyard/dump. Descale and find suitable fittings.
It's very irritating how every other previous post is pasted at the
top of every new post on the group. Why don't people delete all
previous stuff? Sorry if anyone else has mentioned any of the above, I
can't be bothered to plough through all the previous posts.
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| Lurch replied to Aidan on 20 May 2004 |
It's also irritating how people don't put their replies in the right
place, and cut all previous text from the reply. I haven't a clue
whether you are meant to be replying to Christian or Rob, and which
bit of which post you're meant to be replying to.
In future, if you just snip the unrequired text from the post and
reply in the correct place I'm sure we'll get along fine.
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| IMM replied to Aidan on 20 May 2004 |
DPS, sell plate heat exchangers cheap enough. http://www.heatweb.com
The Potterton Powermax incorporates an unvented cylinder full of fresh
water. The older Range (IMI) Powermax incorporates a thermal store. Two
very different approaches.
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| Andy Hall replied to Aidan on 20 May 2004 |
That is the Usenet convention. You are describing what would amount
to top posting, and this is not how Usenet is
New material should be posted below so that the context can be read in
order.
However, it is good practice to snip previous content back to the
point that only the necessary amount remains in order to support the
current point.
Most news readers will indent and/or colour previous posts in a thread
so it is not hard to attribute appropriately.
.andy
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| G&M replied to Andy Hall on 20 May 2004 |
Actually it is the agreed convention of this group. I post to other groups
as well and keep having to remember which group prefers which style. Top
posting is actually prefered in some places.
Agreed
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| MBQ replied to G&M on 21 May 2004 |
When was it agreed? Where is it written down? Certainly not in the
groups posting guidelines.
MBQ
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| Christian McArdle replied to MBQ on 21 May 2004 |
Posting guidelines for the uk.* hierarchy are
http://www.usenet.org.uk/ukpost.html#s3
However, I'm a naughty boy and rarely include attributation as suggested
there. I find it always cocks up a couple of replies further on and everyone
gets attributed to the wrong message...
Christian.
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| Tony Bryer replied to Aidan on 20 May 2004 |
Not by my reading of it - 90.5/90.6%. The most efficient gas boiler at
91.3% is the Baxi Potterton Promax 15 HE which is a wall-hung balanced flue
condensing boiler
http://www.potterton.co.uk/products/gas/highEfficiency/powermaxHE.html
http://www.potterton.co.uk/products/gas/highEfficiency/promaxSystemHE.html
Note the disclaimer from the SEDBUK website:
"Boiler efficiency tests are subject to a degree of measurement
uncertainty. Consequently small differences in the efficiency values
calculated from them are not significant and should not be relied on when
comparing boilers. Statistical analysis suggests that if two boilers have
SEDBUK values 3 percentage points apart then there is 95% confidence that
the boiler with the higher value is more efficient."
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| Aidan replied to Tony Bryer on 20 May 2004 |
Not by my reading of it - 90.5/90.6%.
Yes, I stand corrected. The Promax is now top, the Powermax is
relegated to No. 46. I think the Powermax used to be top when I last
looked at the SEDBUK site, or did I misread Promax as Powermax? We may
never care.
Still, it's a very efficient boiler and there are some relevant
lessons to be learned from it's design; there's no point in
re-inventing an arrangement that some smart person has already figured
out.
I had been replying to the person who wanted to construct a heat-bank
system. If I had bothered to plough through all the posts, the
re-posted posts, the re-posted re-posted posts and the "click here to
read the rest of this message (246 lines)", then I would have posted
my comments in the most appropriate place. Sadly, I didn't.
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| larry replied to Rob Graham on 19 May 2004 |
I did a "cylinder conversion" a couple of months ago. I got heat
exchanger, pump, flow and mixing valve and a few other parts from
www.heatweb.com. for around 300 gbp cant remember exactly so say +-50%
- as spare parts - and very good service. I didn't want to take out my
hotwater cylinder and replace it with their "pandora" heatbank - so I
just replumbed the cylinder so that the original hotwater output goes
to the heat exchanger - thats the only change needed as the CH,
diverter valves and boiler side is left untouched. (I could post a
photo of the outcome)
It works a treat - although some of the original british made tabs in
the house had to be replaced with continental tabs that can handle the
pressure - also the ballcocks in the cisterns needs upgrading.
It was great to chop off the multitude of pipes going into the loft as
well as chuck out the noise shower pump - and bin the water tank on
the loft making room for the loft conversion. Taking a tranquil shower
in the morning is worth all the plumbing.
I was told though that we needed a 22 mm mains feed and I only have 15
mm - but being with thames water a high pressure on their water mains
removes that problem
go for it - good luck
cheers
lars
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