I have read the Home made Heat Bank thread (and the faq on DIY Heat
stores plus a few other threads) from start to finish with great
interest.

As it wont let me post a reply to the group on the original thread,
I'll reluctantly have to start a new thread.

I am in a similar situation needing more pressure for showers
particularly, but for the DHW in general. I currently have a bog std
vented primary feeding CH and indirect DHW tank via pump motorised 3
way valve. I'm happy enough with the CH - its the DHW that's the
problem. I dislike the energy useage of a 3bar shower pump c 850watts
for a Stuart Taylor pump I saw, so would like to make use of the
pressure there for free in the water mains. I have a friend with a
very nice but very expensive Pandora Heat Bank - there's absolutely no
way I want to shell out that sort of money!!

On the whole, thanks due to a number of contributors I am reasonably
clear on what is required. I have a specific queries before I take
the plunge next week:


1] So, adding 2 Essex flanges gives 4 connections to the main body of
the tank (coil connections now unconnected and treating the tank as a
direct) Where should the flow and return to the boiler be connected
and where should the flow and return to the PHE be located?

2] And related... is the positioning of the Essex flanges on the tank
critical/is there a good spot ie a certain distance from the top/
bottom to locate them?

Now for the heat exchange circuit...

3] Are there any concrete recommendations for the capacity of the
PHE? eg is 100kW regarded as a minimum for DHW at mains pressure ad
flow? I see gea-ecobraze PHEs are recommended, so will probably go
for one of these. Is there any heat output (kW) stats for the gea-
ecobraze PHEs? ...are they not quoted as this would depend on the
rate of primary flow.... mmmm...??

4] What rating does the pump need to be? I know the water needs to go
round fast for the PHE to get enough throughput. But it's only
shifting a tiny volume of water (if it's all juxtaposed to the tank),
so presumably a "high geared" design is required - if there is such a
thing - big impeller, but not hugely powerful motor?? Is a standard
CH pump not overkill for this job? Basically I want to avoid using
more electricity on the pumping than I have to, so want to get this
"tuned" right.

5] I get a bit nervous (plumbing is fine and electrics yep thats fine
too, but electronics - not especially my forte) with talk of triacs
and making up the electrics for this from components. I understand
why the flow switch cannot directly switch the pump. Are there any
suitable relay circuits available off the shelf to operate a pump off
a flow switch? If so any suggestions of make and model again would be
really useful.

6] On the circuit diagram on http://wiki.diyfaq.org.uk/index.php?title=DIY_Heat_Bank
there is an MOV - what is that please? Also 2 refs to 100R?

7] There is a "TMV" displayed in http://wiki.diyfaq.org.uk/index.php?title=DIY_Heat_Bank
It looks like it's blending hot and cold water is it a thermostatic
valve? If so are these mechanical or electronically controlled. If
electronically controlled, what is required for the controller?
Presumably this is required so the hot water is always the same temp
regardless of flow rate (within reason!) I guess they must have to
react very quickly unlike a radiator TRV for example.

8] Also referred to in http://wiki.diyfaq.org.uk/index.php?title=DIY_Heat_Bank
is an in-line 'Y' strainer. Presumably servicable to stop crud going
into the PHE and clogging it up?

9] Finally on the subject of the CH, I gather to get heat bank temps
for the DHW I'll prob have to turn the boiler up and therefore make
the rads hotter. Apart from the issue of potentially burnt little
fingers (what is the optimum/recomended temp for rads anyway?? Is
there one??) this should just mean that the rooms heat up quicker and
the TRVs shut down the flow sooner. This should mean the boiler works
harder for a shorter period of time before its own thermostat shuts it
off, which is better isn't it? Or perhaps that's not adequately
taking into account the return temp potentially being too high for
effective condensation? Isn't it a bit swings and roundabouts this
one?

Cheers

Mike

Mike Holmes wrote:

6] On the circuit diagram on http://wiki.diyfaq.org.uk/index.php?title=DIY_Heat_Bank
there is an MOV - what is that please? Also 2 refs to 100R?

MOV = Metal Oxide Varistor - basically a spike suppressor. It has a high
resistance at 240V, but the resistance then falls as the applied voltage
rises. Its effect is to short out spikes of high voltage that you may
typically get when switching inductive loads (which can generate big
back voltages (or reverse EMF if you prefer).

100R simply means a 100 ohm resistor. 100K would be 100K ohm, 2K2 would
be 2.2K or 2200 ohms. Its all to do with writing values in a way that
means you don't need to use the decimal point which can get lost on spec
sheets. Helps Cut down errors.

7] There is a "TMV" displayed in http://wiki.diyfaq.org.uk/index.php?title=DIY_Heat_Bank
It looks like it's blending hot and cold water is it a thermostatic
valve?

It is: TMV = Thermostatic Mixing Valve. See http://www.bes.ltd.uk part
no: 12163

If so are these mechanical or electronically controlled. If

Mechanical - wax capsule etc

8] Also referred to in http://wiki.diyfaq.org.uk/index.php?title=DIY_Heat_Bank
is an in-line 'Y' strainer. Presumably servicable to stop crud going
into the PHE and clogging it up?

Yup, see http://www.bes.ltd.uk part number 7533

9] Finally on the subject of the CH, I gather to get heat bank temps
for the DHW I'll prob have to turn the boiler up and therefore make
the rads hotter. Apart from the issue of potentially burnt little
fingers (what is the optimum/recomended temp for rads anyway?? Is

Is your boiler a condensing one?

there one??) this should just mean that the rooms heat up quicker and
the TRVs shut down the flow sooner. This should mean the boiler works
harder for a shorter period of time before its own thermostat shuts it
off, which is better isn't it? Or perhaps that's not adequately
taking into account the return temp potentially being too high for
effective condensation? Isn't it a bit swings and roundabouts this
one?

With a condensing boiler, lower return temps give more efficiency. On a
conventional boiler that is not true. (in fact lower return tempts might
help promote condensing which is not a good thing on a conventional
boiler where higher temps will prolong the life of the HE.


--
Cheers,

John.

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

I'm in a similar position to the OP, trying to get my head around the
details of a heatbank design.

Mine will differ slightly in that it will be built from scratch and I
really need a mains pressure CH circuit (difficult pipe routings),
whilst sticking with the unpressurised boiler/tank circuit.

To do this, is it simply a case of duplicating the DHW/PHE circuit?
(With an expansion vessel on the CH side) How should the pipework be
split off for this duplicate circuit?

What would the control system look like? Would the boiler simply be
controlled by a tank thermostat, so it's function in life is simply to
maintain tank temp? Would the CH circuit have TRV's on rads every
location except one main rad, and then a room thermostat to cut the
pump(s) on that circuit?

Finally, this diagram http://wiki.diyfaq.org.uk/index.php?title=DIY_Heat_Bank
doesn't show an expansion vessel on the DHW circuit - does it need
one, or does it rely on the fact that a tap must be open before any
significant mains pressure water is heated?

wrote in message
oups.com...
snip


Finally, this diagram
http://wiki.diyfaq.org.uk/index.php?title=DIY_Heat_Bank
doesn't show an expansion vessel on the DHW circuit - does it need
one, or does it rely on the fact that a tap must be open before any
significant mains pressure water is heated?

Cold water (potable and under pressure) is presented at / into one side of a
heat exchanger -
When a 'hot' tap is opened water flows through the pipe and is observed by a
flow-detector; this detection enables a pump which pumps water into the
'other' side of the heat exchanger (think, a twin-tube car radiator). (Now)
Hot water at the tank's temperature is blended with cold water via a
wax-cartridge thermostatic mixer valve to produce 'Hot' water at your
pre-set temperature. Effectively. there's no 'Hot' water until you open a
tap. The 'hot' water is off the 'cold' mains- only the energy required to
bring incoming mains at (say) ten degrees is extracted from the tank to heat
it up to (say) fifty-five degrees. The 'rest' of the energy remains
available for use in the tank. [There's owt for nowt and you'll need to have
your boiler replace the energy sometime.]

--

Brian

With a condensing boiler, lower return temps give more efficiency. On a
conventional boiler that is not true. (in fact lower return tempts might
help promote condensing which is not a good thing on a conventional
boiler where higher temps will prolong the life of the HE.

Thanks for all the specific info John.

Boiler is a Worcester Greenstar 24Ri, about a year old - so yes it's a
good condensing boiler

Mike

Finally, this diagram http://wiki.diyfaq.org.uk/index.php?title=DIY_Heat_Bank
doesn't show an expansion vessel on the DHW circuit - does it need
one, or does it rely on the fact that a tap must be open before any
significant mains pressure water is heated?

The easiest way to explain this is that if you had an expansion vessel
(assuming you're just meanign a normal vented F&E tank) your house
would flood horribly :-( The DHW is directly connected to the mains
via the PHE. Open a hot tap or any other point in the circuit and
you'll get mains pressure and flow.

HTH

Mike

Now I think on a bit more, my mind ventures onto controls.

I seem to recall reading something about having 2 tank-stats on the
tank in this kind of setup... is that correct. I'm thinking that
would be ideal - one stat set at 80degC, one stat set at something
much lower eg 45degC, to provide max and min temps for the store. The
theory being that the boiler would fire up when the store got below
45deg and burn on full until 80deg then cut out. I'm assuming this
would be more efficient than even a modern condensing boiler that can
modulate down, as it would remove boiler cycling phenomenon
altogether. The big question for me is, is this possible? And more
to the point is it feasible for me with my modest electronics
skills!

I'm thinking a simpler alternative might be to time how long it takes
for the boiler to heat the tank to 80deg on an average day (ie average
hot water useage and therefore initial tank temperature). Once I have
this info I could just tune the timer clock for the DHW programmer
(which I already have)

Mike

"Mike Holmes" wrote in message
ups.com...
Now I think on a bit more, my mind ventures onto controls.

I seem to recall reading something about having 2 tank-stats on the
tank in this kind of setup... is that correct. I'm thinking that
would be ideal - one stat set at 80degC, one stat set at something
much lower eg 45degC, to provide max and min temps for the store. The
theory being that the boiler would fire up when the store got below
45deg and burn on full until 80deg then cut out. I'm assuming this
would be more efficient than even a modern condensing boiler that can
modulate down, as it would remove boiler cycling phenomenon
altogether. The big question for me is, is this possible? And more
to the point is it feasible for me with my modest electronics
skills!

I'm thinking a simpler alternative might be to time how long it takes
for the boiler to heat the tank to 80deg on an average day (ie average
hot water useage and therefore initial tank temperature). Once I have
this info I could just tune the timer clock for the DHW programmer
(which I already have)

Mike

I can only attempt to answer you by comparison with 'my' Pandora unit.

The heatbank accepts heated 'fluid' from the boiler which flows in at the
top.
The working fluid is pumped back down to the boiler controlled by a
wax-cylinder mixing valve.
This working fluid temperature is selected by the 'thermostat' mixing valve;
the duration of the circulating pump is set by the 'timer'. The thermo
mixing valve accepts a 'Hot' input from the top of the heatbank and a
'Colder' flow from the bottom of the heatbank. In other words, the fluid is
circulated all the time the 'timer' is 'ON' and is maintained at the setting
on the wax-cylinder mixing valve. This fluid is available for circulating
through the CH system -where it will relinquish heat - when the fluid flows
back into the heatbank then back to the boiler to regain heat energy. The
boiler should 'switch off' when the 'demand heat' line is dis-abled .

The controls seem premised on marinating the HeatBanks working fluid at a
constant temperature, and the boiler supplying heat into the working fluid
only when necessary.

In practise, I find that switching the boiler on for thirty odd minutes is
sufficient to provide all day hot water for two/three baths/showers and all
the kitchen sink requirements. Worst case - no heat in the tank - the hot
fluid , for DWW and CH usage, is taken off the top of the heat tank and will
apply the energy from the boiler directly to the taps and radiators. It's
only then that the 'heat' sinks down through the heatbank to the bottom -
they call it stratification.

--

Brian

On Thu, 24 May 2007 16:43:28 -0700, Mike Holmes wrote:

. I dislike the energy useage of a 3bar shower pump c 850watts
for a Stuart Taylor pump I saw

I wouldn't have thought that'd be a significant consideration in the big
picture, since it'd only be running for some tens of minutes a day and the
power that it uses would be dwarfed by the energy used to heat the water
it's pumping. However if you want to go the DIY heat bank route ..

Oh and I think it's Stuart Turner, not Taylor.

1] So, adding 2 Essex flanges gives 4 connections to the main body of
the tank (coil connections now unconnected and treating the tank as a
direct) Where should the flow and return to the boiler be connected
and where should the flow and return to the PHE be located?

2] And related... is the positioning of the Essex flanges on the tank
critical/is there a good spot ie a certain distance from the top/
bottom to locate them?

I'd be inclined not to bother with the Essex flanges and just connect the
boiler flow (after the 3-port valve) and return to the top and bottom
connections of the HW cylinder, Teed with the connections to the heat
exchanger and pump.


3] Are there any concrete recommendations for the capacity of the
PHE? eg is 100kW regarded as a minimum for DHW at mains pressure ad
flow? I see gea-ecobraze PHEs are recommended, so will probably go
for one of these. Is there any heat output (kW) stats for the gea-
ecobraze PHEs? ...are they not quoted as this would depend on the
rate of primary flow.... mmmm...??

Mine was 50kW which runs cold at full flow into the bath. I haven't done
calculations or measurements to check but I think this is because the heat
exchanger can't cope at that flow rate, so 100kW would be better. I think
that's what DPS use and they ought to know!


4] What rating does the pump need to be?

I just use a standard Grundfos (clone) 15-50.

5] I get a bit nervous (plumbing is fine and electrics yep thats fine
too, but electronics - not especially my forte) with talk of triacs
and making up the electrics for this from components. I understand
why the flow switch cannot directly switch the pump. Are there any
suitable relay circuits available off the shelf to operate a pump off
a flow switch? If so any suggestions of make and model again would be
really useful.

If you want to avoid all electronics you can get a flow switch capable of
driving the pump directly as a part from DPS. (You can buy a PHE from them
too.)



--
John Stumbles

I'm less competitive than you

"Mike Holmes" wrote in message
oups.com...
I have read the Home made Heat Bank thread (and the faq on DIY Heat
stores plus a few other threads) from start to finish with great
interest.

As it wont let me post a reply to the group on the original thread,
I'll reluctantly have to start a new thread.

I am in a similar situation needing more pressure for showers
particularly, but for the DHW in general. I currently have a bog std
vented primary feeding CH and indirect DHW tank via pump motorised 3
way valve. I'm happy enough with the CH - its the DHW that's the
problem. I dislike the energy useage of a 3bar shower pump c 850watts
for a Stuart Taylor pump I saw, so would like to make use of the
pressure there for free in the water mains. I have a friend with a
very nice but very expensive Pandora Heat Bank - there's absolutely no
way I want to shell out that sort of money!!

On the whole, thanks due to a number of contributors I am reasonably
clear on what is required. I have a specific queries before I take
the plunge next week:


1] So, adding 2 Essex flanges gives 4 connections to the main body of
the tank (coil connections now unconnected and treating the tank as a
direct) Where should the flow and return to the boiler be connected
and where should the flow and return to the PHE be located?

2] And related... is the positioning of the Essex flanges on the tank
critical/is there a good spot ie a certain distance from the top/
bottom to locate them?

Now for the heat exchange circuit...

3] Are there any concrete recommendations for the capacity of the
PHE? eg is 100kW regarded as a minimum for DHW at mains pressure ad
flow? I see gea-ecobraze PHEs are recommended, so will probably go
for one of these. Is there any heat output (kW) stats for the gea-
ecobraze PHEs? ...are they not quoted as this would depend on the
rate of primary flow.... mmmm...??

4] What rating does the pump need to be? I know the water needs to go
round fast for the PHE to get enough throughput. But it's only
shifting a tiny volume of water (if it's all juxtaposed to the tank),
so presumably a "high geared" design is required - if there is such a
thing - big impeller, but not hugely powerful motor?? Is a standard
CH pump not overkill for this job? Basically I want to avoid using
more electricity on the pumping than I have to, so want to get this
"tuned" right.

5] I get a bit nervous (plumbing is fine and electrics yep thats fine
too, but electronics - not especially my forte) with talk of triacs
and making up the electrics for this from components. I understand
why the flow switch cannot directly switch the pump. Are there any
suitable relay circuits available off the shelf to operate a pump off
a flow switch? If so any suggestions of make and model again would be
really useful.

6] On the circuit diagram on
http://wiki.diyfaq.org.uk/index.php?title=DIY_Heat_Bank
there is an MOV - what is that please? Also 2 refs to 100R?

7] There is a "TMV" displayed in
http://wiki.diyfaq.org.uk/index.php?title=DIY_Heat_Bank
It looks like it's blending hot and cold water is it a thermostatic
valve? If so are these mechanical or electronically controlled. If
electronically controlled, what is required for the controller?
Presumably this is required so the hot water is always the same temp
regardless of flow rate (within reason!) I guess they must have to
react very quickly unlike a radiator TRV for example.

8] Also referred to in
http://wiki.diyfaq.org.uk/index.php?title=DIY_Heat_Bank
is an in-line 'Y' strainer. Presumably servicable to stop crud going
into the PHE and clogging it up?

9] Finally on the subject of the CH, I gather to get heat bank temps
for the DHW I'll prob have to turn the boiler up and therefore make
the rads hotter. Apart from the issue of potentially burnt little
fingers (what is the optimum/recomended temp for rads anyway?? Is
there one??) this should just mean that the rooms heat up quicker and
the TRVs shut down the flow sooner. This should mean the boiler works
harder for a shorter period of time before its own thermostat shuts it
off, which is better isn't it? Or perhaps that's not adequately
taking into account the return temp potentially being too high for
effective condensation? Isn't it a bit swings and roundabouts this
one?

Use a 100kW plate heat ex. Use a flow switch not electronics as in the
Stumble Wiki sketch. Use the top and bottom ports of the cylinder - maybe
using a Surrey flange. If buying a new cylinder then use a direct cylinder
with a Maganclean filter on the return to the boiler from the rads - this
eliminates sludge build up in the cylinder. For a totally sludge free
system use a direct cylinder using a 100kW plate heat ex to heat the
cylinder - these work out cheaper than a coil and far, far more efficient in
re-heat than a coil and return a low temp for condensing. The new Glow Worm
stored water combis use a plate to heat the cylinder rather than an internal
coil as they re-heat far quicker and give lower return temperatures for
condensing. There will also be a higher cylinder water capacity without the
coil.

"Mike Holmes" wrote in message
ups.com...
Now I think on a bit more, my mind ventures onto controls.

I seem to recall reading something about having 2 tank-stats on the
tank in this kind of setup... is that correct. I'm thinking that
would be ideal - one stat set at 80degC, one stat set at something
much lower eg 45degC, to provide max and min temps for the store. The
theory being that the boiler would fire up when the store got below
45deg and burn on full until 80deg then cut out. I'm assuming this
would be more efficient than even a modern condensing boiler that can
modulate down, as it would remove boiler cycling phenomenon
altogether. The big question for me is, is this possible? And more
to the point is it feasible for me with my modest electronics
skills!

All you need is a cheap £5 relay from Maplin. Only electrical. Look at
DPS's web site they give the wiring diagram. The larger the cylinder the
less storage temperature. You may get away with 70 to 75C. Set the bottom
stat to say 80C and top to say 50 to 60C. The bigger the boiler, the faster
the re-heat, and the lower the storage temperature.

I'm thinking a simpler alternative might be to time how long it takes
for the boiler to heat the tank to 80deg on an average day (ie average
hot water useage and therefore initial tank temperature). Once I have
this info I could just tune the timer clock for the DHW programmer
(which I already have)

You may have to live with it and set to suit. Some have winter and summer
settings - lower storage temps in the summer.

wrote in message
oups.com...
I'm in a similar position to the OP, trying to get my head around the
details of a heatbank design.

Mine will differ slightly in that it will be built from scratch and I
really need a mains pressure CH circuit (difficult pipe routings),
whilst sticking with the unpressurised boiler/tank circuit.

You mean pressurised CH circuit?

To do this, is it simply a case of duplicating the DHW/PHE circuit?
(With an expansion vessel on the CH side) How should the pipework be
split off for this duplicate circuit?

Use a plate Heat Exchanger and pump to heat the low pressure direct
cylinder. That is a DHW plate and a plate to heat the cylinder.

What would the control system look like? Would the boiler simply be
controlled by a tank thermostat, so it's function in life is simply to
maintain tank temp? Would the CH circuit have TRV's on rads every
location except one main rad, and then a room thermostat to cut the
pump(s) on that circuit?

Have the CH off the heat bank, have TRVs on all rads and use a Grunfoss
Alpha pump or the Wilo equiv in S/fix.

The boiler then only maintains the cylinder temperature - a simple task for
the boiler.

Finally, this diagram
http://wiki.diyfaq.org.uk/index.php?title=DIY_Heat_Bank
doesn't show an expansion vessel on the DHW circuit - does it need
one, or does it rely on the fact that a tap must be open before any
significant mains pressure water is heated?

Do you want to heat the CH from the heat bank cylinder too? Best to and use
a Magnaclean filter on the CH rads return to the cylinder.

Sorry to be thick, but I don't follow your answer.

Yes, I wan't pressurised CH. So boiler and cylinder are directly
connected to each other (and nothing else) and run at low pressure,
but CH is seperated from the cylinder by a heat exchanger and is
pressurised by a filling-loop?

Is the basic setup as follows?:

Direct connection between boiler and cylinder (unpressurised) with
circulation pump.
Cylinder to heat-exchanger number 1 and heat-exchanger to CH
(pressurised on CH side) (pumps on both sides of PHE).
Cylinder to heat-exchanger number 2 and heat-exchanger to DHW (pump on
cylinder side of PHE)

Or did you mean a heat exchanger between boiler and cylinder?

As far as the control system goes, I follow the explaination of high
and low tank thermostats.

Does the rest of the system go as follows?:

The time clock controls the boiler and pump between boiler and
cylinder.
(Does this pump run continuously when timer says "on", or only when
boiler is firing plus a bit of overun?).
The switch on the time clock for heating&ho****er/ho****er only
controls whether pump(s) in CH circuit are also active.
(Do these run continuously when timer says "on"?)
TRV's on every rad, no room thermostat, and presumably a bypass on the
circuit somewhere?
No motorised valves anywhere.

Apologies if my questions ask again, what has already been explained.

wrote in message
ups.com...
Sorry to be thick, but I don't follow your answer.

Yes, I wan't pressurised CH. So boiler and cylinder are directly
connected to each other (and nothing else) and run at low pressure,

Bzzz. No. They cannot be "directly" connect as one high and one low
pressure. CH at 1 bar, cylidner at 0 1 bar.

but CH is seperated from the cylinder by a heat exchanger and is
pressurised by a filling-loop?

By a heat exchnager? So not "directly" connected. Use a plate heat
exchanger as the exchanger and pump to heat the cylinder.

Is the basic setup as follows?:

Direct connection between boiler and cylinder (unpressurised) with
circulation pump.
Cylinder to heat-exchanger number 1 and heat-exchanger to CH
(pressurised on CH side) (pumps on both sides of PHE).
Cylinder to heat-exchanger number 2 and heat-exchanger to DHW (pump on
cylinder side of PHE)

I'll explain below.

Or did you mean a heat exchanger between boiler and cylinder?

Yep.

As far as the control system goes,
I follow the explaination of high
and low tank thermostats.

Does the rest of the system go as follows?:

The time clock controls the boiler and pump between boiler and
cylinder.
(Does this pump run continuously when timer says "on", or only when
boiler is firing plus a bit of overun?).
The switch on the time clock for heating&ho****er/ho****er only
controls whether pump(s) in CH circuit are also active.
(Do these run continuously when timer says "on"?)
TRV's on every rad, no room thermostat, and presumably a bypass on the
circuit somewhere?
No motorised valves anywhere.

Apologies if my questions ask again, what has already been explained.

1. A pressurised CH system using a 3-way "diverter" valve, not a
"mid-position" valve.
2. Use a direct cylinder, with an F&E tank top up.
3. To heat the cylinder have a plate heat exchanger (pref 100kW) and a
normal CH pump, pumping water from the cylinder into the plate. When
calling for DHW the normal boiler pump is on, as is the plate pump. The
heat transfer is exceptionally high (the best you can get without being
direct), giving low return temps for condensing.
4. Have a 100kW plate for the DHW and normal CH pump too, as per normal heat
banks with a non-return valve after the pump and activated by a flow switch.
5. Have two cylinder stats to prevent boiler cycling.

Then a low pressure cylinder and a high pressure CH circuit with low return
temps. This is heating the rads directly from the boiler. You can have the
CH off the cylinder too. Best to do this but a larger cylinder is needed.
Best a direct one again and heat via a plate. Got it?

"Doctor Drivel" wrote in message
reenews.net...
wrote in message
ups.com...
Sorry to be thick, but I don't follow your answer.

Yes, I wan't pressurised CH. So boiler and cylinder are directly
connected to each other (and nothing else) and run at low pressure,

Bzzz. No. They cannot be "directly" connect as one high and one low
pressure. CH at 1 bar, cylidner at 0 1 bar.

but CH is seperated from the cylinder by a heat exchanger and is
pressurised by a filling-loop?

By a heat exchnager? So not "directly" connected. Use a plate heat
exchanger as the exchanger and pump to heat the cylinder.

Is the basic setup as follows?:

Direct connection between boiler and cylinder (unpressurised) with
circulation pump.
Cylinder to heat-exchanger number 1 and heat-exchanger to CH
(pressurised on CH side) (pumps on both sides of PHE).
Cylinder to heat-exchanger number 2 and heat-exchanger to DHW (pump on
cylinder side of PHE)

I'll explain below.

Or did you mean a heat exchanger between boiler and cylinder?

Yep.

As far as the control system goes,
I follow the explaination of high
and low tank thermostats.

Does the rest of the system go as follows?:

The time clock controls the boiler and pump between boiler and
cylinder.
(Does this pump run continuously when timer says "on", or only when
boiler is firing plus a bit of overun?).
The switch on the time clock for heating&ho****er/ho****er only
controls whether pump(s) in CH circuit are also active.
(Do these run continuously when timer says "on"?)
TRV's on every rad, no room thermostat, and presumably a bypass on the
circuit somewhere?
No motorised valves anywhere.

Apologies if my questions ask again, what has already been explained.

1. A pressurised CH system using a 3-way "diverter" valve, not a
"mid-position" valve.
2. Use a direct cylinder, with an F&E tank top up.
3. To heat the cylinder have a plate heat exchanger (pref 100kW) and a
normal CH pump, pumping water from the cylinder into the plate. When
calling for DHW the normal boiler pump is on, as is the plate pump. The
heat transfer is exceptionally high (the best you can get without being
direct), giving low return temps for condensing.
4. Have a 100kW plate for the DHW and normal CH pump too, as per normal
heat banks with a non-return valve after the pump and activated by a flow
switch.
5. Have two cylinder stats to prevent boiler cycling.

Then a low pressure cylinder and a high pressure CH circuit with low
return temps. This is heating the rads directly from the boiler. You can
have the CH off the cylinder too. Best to do this but a larger cylinder
is needed. Best a direct one again and heat via a plate. Got it?

Farnell will supply the flow switch http://www.farnell.co.uk Farnell number:
1006771 22mm compression joints.


Flow Switch, makers site: The FS06
http://www.gentechsensors.com/productTemplate.asp?ProdId=113

I wouldn't have thought that'd be a significant consideration in the big
picture, since it'd only be running for some tens of minutes a day and the
power that it uses would be dwarfed by the energy used toheatthe water
it's pumping. However if you want to go the DIYheatbankroute ..

Well there's a bit more to it. I'll be running 2 showers, so will
need a multi-installation pump and I also have a 1800x800 bath which
takes years to fill on the std DHW and I even get bored waiting for
the kitchen sink to fill sometimes - seems there would be many
benefits to having a higher pressure DHW system. I can't afford a
Pandora or similar BUT I can build a DIY Heat Bank system for prob
about the same money as a pump, which will only benefit the showers in
the house.

Oh and I think it's Stuart Turner, not Taylor.

Yep, you're right. I shall have to fire my secretary!! ;-)

I'd be inclined not to bother with the Essex flanges and just connect the
boiler flow (after the 3-port valve) and return to the top and bottom
connections of the HW cylinder, Teed with the connections to theheat
exchanger and pump.


I read in another thread somewhere that if you set it up like this
you'd have one of 2 situations depending how it was set up exactly.
1] If the boiler primary inlet onto the tank was effectively the PHE
circuit outlet, then if boiler was heating the bank and there was
demand for DHW at the same time (hot tap on), then the tank itself
would be effectively out of the loop, the boiler primary flow
effectively preferentially going through the PHE/pump arm of the
circuit, fllow being restored through the tank once the DHW demand
(tap off) had passed. 2] If the inlets and outlets to the tank for
the boiler primary and the PHE circuits were tee'd together, then
they'd be in opposition and cause turbulence at the tee both trying
to force water against the other at the common inlet and water being
forced into the tank.

Which is the best scenario?? Neither seems ideal. What of the
dynamics inside the tank in the latter?


4] What rating does the pump need to be?

I just use a standard Grundfos (clone) 15-50.

How much power does this pump use? Isn't it overkill to have a CH
pump driving such a small circuit?

If you want to avoid all electronics you can get a flow switch capable of
driving the pump directly as a part from DPS. (You can buy a PHE from them
too.)

Thanks