I live in a 30 year old block of flats; two flats per floor, three
floors.

Each flat has its own, conventional, vented hot water cylinder.

In the roof void of the building there's a set of header tanks, all
interconnected (so effectively one big header tank).

In the service duct through the building is a single 3 inch riser,
supplying mains water to each flat and refilling the header tanks in
the roof.

From the base of the header tanks there's a single 3 inch downcomer,
feeding the base of each of the six hot water cylinders. Another 3
inch downcomer feeds domestic cold to each flat.

There appears to be a separate vent pipe (22mm copper) running from the
top of each cylinder up to a separate 'overflow' tank up in the roof
(access is difficult, so we're not entirely sure about this). This
tank has six copper pipes hooked over the top - and it's empty. There's
no ballcock to fill it, and it just has a discharge/drain pipe to a
visible point outside the building.

Can I, unilaterally, convert my hot water cylinder into a heat bank?
Would Building Regs forbid it?


I've been trying to figure out the risks, in this arrangement, of the
contents of any cylinder commingling with the contents of another
cylinder in another flat. There are no check valves, so reverse flow
into the common downcomer is theoretically possible, but I can't see a
mechanism that would cause it.



--
Roger Morton

In 5TJqjLDdKEWdsY9uxuyStQ@LIVING, Roger Morton wrote:



I live in a 30 year old block of flats; two flats per floor, three
floors.


Anyone?



--
Roger Morton

"Roger Morton" wrote in message
news:ctEYfM$I2Eys3hrMLqI01Q@LIVING...
In 5TJqjLDdKEWdsY9uxuyStQ@LIVING, Roger Morton wrote:



I live in a 30 year old block of flats; two flats per floor, three
floors.


A couple of thoughts - I converted our conventional hot cylinder to a heat
bank system a couple of years ago, as we had no head or sensible flow rate
in a bungalow, and have been very happy with the result.

You will need to fill the heat bank with water and inhibitor to protect the
pump. and keep it reasonably sterile. It would not be a good idea to mix
this water/inhibitor mix with your neighbours hot tank cold feeds, and you
wont want your expensive inhibitor diluted. You will also need some degree
of expansion provision as the heat bank warms and cools.

My suggestion would be to install a small expansion tank (central heating
type) anywhere convenient, so long as it is above the top of your cylinder.
Feed this via a ball valve from your existing cold water feeds, stored or
mains, via a stopcock. This will isolate your system from that of your
neighbours should you use the stored feed.

From the expansion tank feed the bottom of your cylinder WITHOUT any means
of shutoff - no stopcocks etc - this is very important. Add an air vent to
the top, to release air while filling. You do not need an open vent from the
top of the cylinder, as it's at close to atmospheric pressure, and has an
expansion path back to the header tank. I fed mine to the top of the
cylinder, and find it a pig to fill - and will change this next time I
re-arrange the pipework.

Add a loop from top to bottom of the cylinder for your pumped feed to the
heat exchanger as per your existing planning.

If I can provide any other info let me know.

Charles F

That would be my thoughts too, for an entirely self-contained heatbank
- though the simplest (but more expensive) solution would be a thermal
store type cylinder with integrated feed & expansion tank in the top
half.

You do not need an open vent from the
top of the cylinder, as it's at close to atmospheric pressure, and has an
expansion path back to the header tank.

Sorry - but that goes against everything I know - AIUI a second safety
pipe is always required on vented systems, and should loop over the
f&e tank.

I fed mine to the top of the
cylinder, and find it a pig to fill - and will change this next time I
re-arrange the pipework.

Again, AIUI cylinder-filling feeds are always to the bottom, often
teed off from the feed to the boiler, and positioned just before the
pump.

(IANAP - I Am Not A Plumber, so don't take my safety advice as gospel
- get it from someone qualified and/or manufacturers/professional
literature)

wrote in message
...
That would be my thoughts too, for an entirely self-contained heatbank
- though the simplest (but more expensive) solution would be a thermal
store type cylinder with integrated feed & expansion tank in the top
half.

You do not need an open vent from the
top of the cylinder, as it's at close to atmospheric pressure, and has an
expansion path back to the header tank.

Sorry - but that goes against everything I know - AIUI a second safety
pipe is always required on vented systems, and should loop over the
f&e tank.

I fed mine to the top of the
cylinder, and find it a pig to fill - and will change this next time I
re-arrange the pipework.

Again, AIUI cylinder-filling feeds are always to the bottom, often
teed off from the feed to the boiler, and positioned just before the
pump.

(IANAP - I Am Not A Plumber, so don't take my safety advice as gospel
- get it from someone qualified and/or manufacturers/professional
literature)

I think that the vertical safety vent, certainly necessary on conventional
systems, is probably not necessary for a heat bank PROVIDED that there is a
permanently open pipe to the expansion tank - which can be 22mm if you
prefer.

If you look at http://www.heatweb.com/techtips/Pandora.html and continue to
the filling pages, there is only one pipe to the expansion tank - in this
case to the top, but I don't see that that matters particularly in safety
terms. Additionally, on my MK1 heatbank I find that I'm losing some heat via
the vertical fill pipe from the top of the tank, even though lagged. A fill
pipe from the base of the cylinder should improve this loss.

I'd be interested to know what your reasoning is to need a fill and vent
pipe in the case of a heat bank?

One thing I forgot - you will need a drain cock for the cylinder, and
isolation valves either side of the pump and heat exchanger save draining
the cylinder if you need to remove either item.

Charles F

If you look athttp://www.heatweb.com/techtips/Pandora.htmland continue to
the filling pages, there is only one pipe to the expansion tank - in this
case to the top, but I don't see that that matters particularly in safety
terms.

That's designed to be unvented, and I would expect there are secondary
safety valves as are usually used on sealed systems - "details omitted
for clarity" as they say.

Additionally, on my MK1 heatbank I find that I'm losing some heat via
the vertical fill pipe from the top of the tank, even though lagged.

Usually there's a couple of near-90 degree bends to make a 300-400mm
offset in the vertically-rising vent pipe to reduce in-pipe
circulation.

I'd be interested to know what your reasoning is to need a fill and vent
pipe in the case of a heat bank?

I've recently installed an Albion mainsflow thermal store, and the
manufacturers instructions say "combined feed and vent pipes should
not be used".

I know combined feed and vent pipes *are* sometimes used, but I don't
know when that's ok.

Speculation here - but I would imagine it's on systems that can never
overheat to the point of producing steam, under any fault conditions.
e.g. a cylinder that's only heated by hot water from another separate
system.

Regarding using the vent pipe as fill pipe (rather than the lowest
point on the cylinder), there is the possibility under fault
conditions of a plastic f&e tank getting so hot that it fails.

Again, IANAP.

In , Charles Fearnley wrote:


You will need to fill the heat bank with water and inhibitor to
protect the
pump. and keep it reasonably sterile. It would not be a good idea to
mix
this water/inhibitor mix with your neighbours hot tank cold feeds,
and you
wont want your expensive inhibitor diluted. You will also need some
degree
of expansion provision as the heat bank warms and cools.

My suggestion would be to install a small expansion tank (central
heating
type) anywhere convenient, so long as it is above the top of your
cylinder.
Feed this via a ball valve from your existing cold water feeds,
stored or
mains, via a stopcock. This will isolate your system from that of
your
neighbours should you use the stored feed.


Not sure I've got the height to do that within the flat - wouldn't this
expansion tank have to be above the highest point in the central
heating circuit, rather than (just) the top of the cylinder? I have
tall radiators, to within a foot of the ceiling....

I can see that isolation from neighbours would be a Good Thing - but is
it a Required Thing?

If the vent pipes from everyone's cylinders are, as we suspect, kept
separate up to the common, empty, overflow tank in the roof, then back
flow around vent pipes must be inconceivable, mustn't it?

It's the shared feed to the cylinder bases (plural) that's the concern.

From the expansion tank feed the bottom of your cylinder WITHOUT any
means
of shutoff - no stopcocks etc - this is very important.

Dumb q - why is it important, if there's also a separate vent pipe? As
long as one of the feed and vent pipes has no means of isolation, isn't
that enough to ensure you can't pull a vacuum on the cylinder? In
fact, with our existing, common cylinder feed, each flat has to have an
isolation valve on its feed branch - otherwise you'd have to drain the
header tanks for the entire block before working on any one flat's
cylinder :-(

Given that, would a check valve in the feed branch help assure no
reverse flow into the common downcomer?

--
Roger Morton

"Roger Morton" wrote in message
news:h5WqIwhV7EKmjINoqR16pw@LIVING...
In , Charles Fearnley wrote:


You will need to fill the heat bank with water and inhibitor to
protect the
pump. and keep it reasonably sterile. It would not be a good idea to
mix
this water/inhibitor mix with your neighbours hot tank cold feeds,
and you
wont want your expensive inhibitor diluted. You will also need some
degree
of expansion provision as the heat bank warms and cools.

My suggestion would be to install a small expansion tank (central
heating
type) anywhere convenient, so long as it is above the top of your
cylinder.
Feed this via a ball valve from your existing cold water feeds,
stored or
mains, via a stopcock. This will isolate your system from that of
your
neighbours should you use the stored feed.


Not sure I've got the height to do that within the flat - wouldn't this
expansion tank have to be above the highest point in the central
heating circuit, rather than (just) the top of the cylinder? I have
tall radiators, to within a foot of the ceiling....

This depends wether the water in the heat bank is directly connected to the
central heating water - assuming that your cylinder is an indirect type with
a heating coil then it is separate, and an expansion tank need only be
higher than the heatbank cylinder.

I can see that isolation from neighbours would be a Good Thing - but is
it a Required Thing?

Your neighbours wont like having inhibiter in their baths, and you will not
like the gradual dilution in your heatbank - so yes, you do need to isolate.

If the vent pipes from everyone's cylinders are, as we suspect, kept
separate up to the common, empty, overflow tank in the roof, then back
flow around vent pipes must be inconceivable, mustn't it?

cross connection via existing vent pipes is not going to happen -

It's the shared feed to the cylinder bases (plural) that's the concern.

Yes


From the expansion tank feed the bottom of your cylinder WITHOUT any
means
of shutoff - no stopcocks etc - this is very important.

Dumb q - why is it important, if there's also a separate vent pipe? As
long as one of the feed and vent pipes has no means of isolation, isn't
that enough to ensure you can't pull a vacuum on the cylinder? In
fact, with our existing, common cylinder feed, each flat has to have an
isolation valve on its feed branch - otherwise you'd have to drain the
header tanks for the entire block before working on any one flat's
cylinder :-(

If you are using a separate expansion vent then the feed can indeed be
isolated. However, in this case you need more expansion than your exsisting
dry vent can provide, otherwise you run the risk of having air at the top of
the cylinder, which your exchanger pump won't like.

Given that, would a check valve in the feed branch help assure no
reverse flow into the common downcomer?

--
Roger Morton


I think there may be some misunderstandings over how a heat bank works - the
water in the bank is there long term, needs to have inhibiter, and has to
have some means of expansion to maintain levels in the heatbank cylinder.
Have a look at DPS's info, and also look at Gledhill's info on their Torrent
heatbanks. They both use vented expansion tanks (one with a diagraph), and
both mention inhibitor.

Charles F

In , Charles Fearnley wrote:



"Roger Morton" wrote in message
news:h5WqIwhV7EKmjINoqR16pw@LIVING...

Not sure I've got the height to do that within the flat - wouldn't
this
expansion tank have to be above the highest point in the central
heating circuit, rather than (just) the top of the cylinder? I have
tall radiators, to within a foot of the ceiling....

This depends wether the water in the heat bank is directly connected
to the
central heating water - assuming that your cylinder is an indirect
type with
a heating coil then it is separate, and an expansion tank need only
be
higher than the heatbank cylinder.

I'd been assuming a direct heat bank, like the Xcel 2009, with no
heating coil. But I'd forgotten the indirect boiler option they've
got, with a second plate exchanger. That should let me keep the boiler
and the ch radiators as a sealed system, as they are at the moment.

If you are using a separate expansion vent then the feed can indeed
be
isolated. However, in this case you need more expansion than your
exsisting
dry vent can provide, otherwise you run the risk of having air at the
top of
the cylinder, which your exchanger pump won't like.


In fact the DPS literature shows a gate valve in the feed :-)


I think there may be some misunderstandings over how a heat bank
works - the
water in the bank is there long term, needs to have inhibiter, and
has to
have some means of expansion to maintain levels in the heatbank
cylinder.

I think I understood all that - the flow into (and/or back out of) the
base of a heat bank fed from the common downcomer would be tiny, except
on initial fill and heat. Probably never enough back flow to get a
check valve to close, but small amounts of inhibited water will get
back eventually.

I'll pursue the fully isolated (from the neighbours) option with an
indirect boiler - looks the best best for this situation.

Ta for the help

--
Roger Morton

On 2 Feb, 09:45, (Roger Morton) wrote:

Can I, unilaterally, convert my hot water cylinder into a heat bank? *
Would Building Regs forbid it?

Why would you want to?

Heat banks were a method of providing mains/high pressure hot water
before unvented hot water storage cylinders were permitted in the UK.
You have to kep them at around 80 degC and they don't work well with
condensing boilers, which work better with a low temperature return.

Get an unvented cylinder (lease terms & conditions allowing) or a
combi.

In ,
Onetap wrote:


On 2 Feb, 09:45, (Roger Morton) wrote:
Can I, unilaterally, convert my hot water cylinder into a heat
bank? *
Would Building Regs forbid it?
Why would you want to?
Heat banks were a method of providing mains/high pressure hot water
before unvented hot water storage cylinders were permitted in the UK.
You have to kep them at around 80 degC and they don't work well with
condensing boilers, which work better with a low temperature return.
Get an unvented cylinder (lease terms & conditions allowing) or a
combi.

Mains pressure hot water with minimum complexity and maintenance cost -
or maximum reliability and ease of maintenance, perhaps the same thing
:-)

I don't like the control systems an unvented cylinder would need - and
getting landlord consent could be a real issue. An atmospheric
pressure heat bank, particularly if I can isolate it from the common
services properly, would be a much easier sell.

And I want to hang on to my simple, non-condensing boiler for as long
as it carries on working. It's a fine example of the dreaded Suprima
(6 years old, non-condensing), and I've not seen anything on the market
these days that will fit into the same space - not even the condensing
version of it. Replacing it could well involve ripping up a beautifully
fitted kitchen and starting again.



--
Roger Morton

On 5 Feb, 14:56, (Roger Morton) wrote:

Mains pressure hot water with minimum complexity and maintenance cost -
or maximum reliability and ease of maintenance, perhaps the same thing
:-) *

I don't like the control systems an unvented cylinder would need - and
getting landlord consent could be a real issue. *An atmospheric
pressure heat bank, particularly if I can isolate it from the common
services properly, would be a much easier sell. *

The complexity and the explosion risks are exaggerated by the UK's
resident herds of Plumbosaurus Rex and the likes of Drivel who don't
understand them and can't install them, I have an unvented ticket,
they're good gear.The main difficulty is in fitting a metal drain pipe
to a suitable discharge point. Even the Merikins use them without
blowing themselves up (well, not often).

And I want to hang on to my simple, non-condensing boiler for as long
as it carries on working. *It's a fine example of the dreaded Suprima
(6 years old, non-condensing), and I've not seen anything on the market
these days that will fit into the same space - not even the condensing
version of it. Replacing it could well involve ripping up a beautifully
fitted kitchen and starting again. *

I'm sure you could find a boiler that would fit. The logic of fitting
an antiquated device to preserve an antiquated boiler escapes me.

"Onetap" wrote in message
...
On 5 Feb, 14:56, (Roger Morton) wrote:

Mains pressure hot water with minimum complexity and maintenance cost -
or maximum reliability and ease of maintenance, perhaps the same thing
:-)

I don't like the control systems an unvented cylinder would need - and
getting landlord consent could be a real issue. An atmospheric
pressure heat bank, particularly if I can isolate it from the common
services properly, would be a much easier sell.

The complexity and the explosion risks are exaggerated by the UK's
resident herds of Plumbosaurus Rex and the likes of Drivel who don't
understand them and can't install them, I have an unvented ticket,
they're good gear.The main difficulty is in fitting a metal drain pipe
to a suitable discharge point. Even the Merikins use them without
blowing themselves up (well, not often).

I'm sure you could find a boiler that would fit. The logic of fitting
an antiquated device to preserve an antiquated boiler escapes me.

Part of the attraction of heatbank systems, in a DIY group, is that they are
easy to produce and maintain, and can be much less costly. You can also DIY
them, unlike unvented systems (to stay legal anyway)

If you are to buy an off the shelf heatbank system from Gledhill or DPS,
there is probably little to choose in cost compared to an unvented system.
However, there are alternatives....

My system uses the existing cylinder, so additional costs were a plate heat
exchanger from DPS (less than £200), a standard central heating pump, some
basic electronics, and some rearrangement of plumbing - total cost a little
over £300. In the next ten years I may need a new heat exchanger if it furs
up enough, and I'd like to put in a bigger cylinder - £400 ish? I understand
the system, and can easily maintain it if needed. Total cost in the next ten
years - less than £1000, even with improvements.

An unvented cylinder is probably around £1000, and I can't install it
myself - another £250? It also should have an annual service at £100-150 pa.
Total cost over ten years - £2250 to £2750, assuming nothing fails over the
period.

So I have a system that can run two showers at the same time, with water as
hot as is sensible to stand under, which replaced a stored water system with
such poor head that one of the basins never did get any hot water. It will
cost me about £1500 less than an unvented system over the next ten years.

I realise that this is not to everyone's taste, but this is a DIY group, and
heatbanks make good sense for many of us.

Charles F

"Onetap" wrote in message
...
On 5 Feb, 14:56, (Roger Morton) wrote:

Mains pressure hot water with minimum complexity and maintenance cost -
or maximum reliability and ease of maintenance, perhaps the same thing
:-)

I don't like the control systems an unvented cylinder would need - and
getting landlord consent could be a real issue. An atmospheric
pressure heat bank, particularly if I can isolate it from the common
services properly, would be a much easier sell.

The complexity and the explosion risks are exaggerated by the UK's
resident herds of Plumbosaurus Rex and the likes of Drivel who don't
understand them and can't install them, I have an unvented ticket,
they're good gear.The main difficulty is in fitting a metal drain pipe
to a suitable discharge point. Even the Merikins use them without
blowing themselves up (well, not often).

I'm sure you could find a boiler that would fit. The logic of fitting
an antiquated device to preserve an antiquated boiler escapes me.

Part of the attraction of heatbank systems, in a DIY group, is that they are
easy to produce and maintain, and can be much less costly. You can also DIY
them, unlike unvented systems (to stay legal anyway)

If you are to buy an off the shelf heatbank system from Gledhill or DPS,
there is probably little to choose in cost compared to an unvented system.
However, there are alternatives....

My system uses the existing cylinder, so additional costs were a plate heat
exchanger from DPS (less than £200), a standard central heating pump, some
basic electronics, and some rearrangement of plumbing - total cost a little
over £300. In the next ten years I may need a new heat exchanger if it furs
up enough, and I'd like to put in a bigger cylinder - £400 ish? I understand
the system, and can easily maintain it if needed. Total cost in the next ten
years - less than £1000, even with improvements.

An unvented cylinder is probably around £1000, and I can't install it
myself - another £250? It also should have an annual service at £100-150 pa.
Total cost over ten years - £2250 to £2750, assuming nothing fails over the
period.

So I have a system that can run two showers at the same time, with water as
hot as is sensible to stand under, which replaced a stored water system with
such poor head that one of the basins never did get any hot water. It will
cost me about £1500 less than an unvented system over the next ten years.

I realise that this is not to everyone's taste, but this is a DIY group, and
heatbanks make good sense for many of us.

Charles F

In ,
Onetap wrote:


The complexity and the explosion risks are exaggerated by the UK's
resident herds of Plumbosaurus Rex and the likes of Drivel who don't
understand them and can't install them, I have an unvented ticket,
they're good gear.The main difficulty is in fitting a metal drain pipe
to a suitable discharge point.

That's for hot escapes from PRVs? Could be tricky in a utility
cupboard right in the middle of the flat - no exterior walls for many
many feet.... There's a bathroom waste passing through it, but it
would have to be cooled somehow?

I'm sure you could find a boiler that would fit.

The old Suprima body is 490mm high - it's inside a kitchen cupboard
that's 700mm high; with 25mm clearance above the top of the flue bend
(inside the cupboard) at the top and about 40mm at the bottom. I've
spent a lot of time looking :-)

The logic of fitting
an antiquated device to preserve an antiquated boiler escapes me.

You may very well be right - I'm still very much at the pipe-dreaming
stage :-)



--
Roger Morton

In , Charles Fearnley wrote:


My system uses the existing cylinder, so additional costs were a
plate heat
exchanger from DPS (less than £200), a standard central heating pump,
some
basic electronics, and some rearrangement of plumbing - total cost a
little
over £300.

Could you expand on that? How did you connect the boiler and/or what
did you do with the old coil? One of the problems I have with my
existing cylinder is the slow recovery rate.

--
Roger Morton

"Roger Morton" wrote in message
news:0WXwY.eqaUiWAf6C7I7Bvw@LIVING...
In , Charles Fearnley wrote:


My system uses the existing cylinder, so additional costs were a
plate heat
exchanger from DPS (less than £200), a standard central heating pump,
some
basic electronics, and some rearrangement of plumbing - total cost a
little
over £300.

Could you expand on that? How did you connect the boiler and/or what
did you do with the old coil? One of the problems I have with my
existing cylinder is the slow recovery rate.

--
Roger Morton


Roger, I'll get back to you tomorrow - long day at work today....

Charles F