Our current tank is an old 22 gal. (100 litre, ish) one and after fitting
a new bath which is a shade bigger than the old one, is only just enough
to fill it hot, so this years project is to fit a new tank. (One of this
years projects, oh will it ever end!!!)

Current way to heat it is from conventional back boiler (non condnesing
with hopefully a good few years left in it yet) on a standard Y-Plan
system with a 3-way valve feeding the tank and CH loop (5 rads, but I
want to add 1 or 2 more). The tank coil for this heater is a "top-loader"
presumably replacing an old immersion heater. (system fitted by previous
owners) There is also a range cooker (Stanley DWH) with a back boiler
feeding a conventional coil in the tank. The top-loading coil doesn't
seem too efficient to me - the boiler cycles a bit quicker than I'd
like when trying to heat the tank up, and it takes a long time to get
the whole tank really hot...

So rather than just fit a conventional (2 coil) tank, I'm thinking of
moving to a heat bank/thermal store system and after enquiring, realise
I can't really afford a DPS/Pandora system, (was quoted close to £1500)
so wondering about DIYing it...

I'm not a fan of pressurised systems - it's true that I do a lot of SCUBA
diving where I encounter tank pressures of over 250 bar, but I try to
avoid it if I can... So, the idea is to start with a big well-insulated
coil-less tank with loft F&E tank. I'd love to put the tank in the loft,
but the hatch isn't big enough )-:

Bathroom Hot & Cold will be fed from tanks in the loft (via existing
Stuart Turner pump), kitchen will be gravity fed (as it is currently -
HW tank is on same floor as bathroom, loft is one up, kitchen one down)
- mains pressure is high where I am (8 bar!) but flow rate is low and
that won't be fixed unless I dig up a lot of tarmac/concrete to see
where the restriction is)

The tank will be directly heated from the existing conventional back boiler
assisted by the cooker with small back boiler and eventually supplementary
heated from roof-top solar panels.

So Q1: Can I just parallel up the heat sources like this, and just tap
into the top and bottom of the tank round its periphery with 3 inlet &
outlet pipes to the various heat generators? Each one will be pumped
(Although the cooker right now is gravity fed)

(I've heard the words "Dunsley Neutraliser" banded about, to combine
heat sources like this, but as I understand it, a thermal store will
just act like a big DN...?)

Would there be a problem with the cooker, back boiler, central heating
system (and solar) all sharing the same water and F&E tank? (The down
side is having to drain the lot if there's a problem, but with isolation
valves in the right places, I think I can live with that)

Q2 is how to get the heat out - A plate heat exchanger would seem to be
the most efficient - can these be bought independently of a tank and
DIY installed? A pump on the tank side and a flow-switch on the other
side is all I need, presumably.

They seem to have diffusers on the inlet & exit inside the tank (going
to the heat exchanger) - does the tank have to come with these fitted,
or are they just sections of pipe with holes drilled horizontally?

The only other conundrum is how to heat the radiators... Do I tap off
the tank with another pump, (+TRVs, thermostats, timers, etc.) or use
a conventional Y-plan system off the back boiler?

This system will have more pumps that I can shake a vacuum tube at,
and the tank end up looking like a colander!!!

I suspect the major cost is the plate heat exchanger and control
units. (And maybe the tank, and dozen essex flanges I'll need to plumb
into it!) Basically if I can save £500 on the bits, I'd put it towards
the solar panels. (Although fitting them will require scaffolding, to
bridge over a lower glass roof, so it might work out to be even less
attractive, but thats another problem for another day ...

I guess the only issue with a non-pressurised system like this is that
the F&E tank will have to be above the solar panels, but I can worry
about that later...

And any ideas where the best online places I can use to get the basic
parts? Essentially tank and heat exchanger...

Thoughts/comments welcome!

(Eg. how many building regs I'll be breaking!!!)

Thanks,

Gordon

So Q1: Can I just parallel up the heat sources like this, and just tap
into the top and bottom of the tank round its periphery with 3 inlet &
outlet pipes to the various heat generators? Each one will be pumped
(Although the cooker right now is gravity fed)

It won't be expensive. A suitable exchanger costs around 80 quid. The cooker
can (and probably should) stay on gravity circulation if the heat bank is
sufficiently above it with wide enough pipes. Having reliable gravity
circulation is better for the health of your average cooker back boiler,
especially if solid fuel.

The controls for this system are relatively simple. You shouldn't need any
external control boxes. It only gets a little complicated when it needs to
make decisions like "should I run the gas boiler, if I'm already getting
solar heat". Even this can be simplified by having the solar thermostat
lower than the boiler one. Then the boiler only comes on when the tank has
depleted somewhat. Unfortunately, this would lead to needing a larger
cylinder, as you could only rely on there being hot water above the boiler
stat.

If you don't like the colander effect, you might get away with T-ing off
from fewer flanges, although you should pay attention to mixing pumped and
unpumped circuits in this configuration as unpumped circuits are sensitive
to neutral points and might get reverse or parasitic circulation.

And any ideas where the best online places I can use to get the basic
parts?

You could use your existing tank if large enough, but otherwise pretty much
any cylinder will do. I'd buy an indirect one. Even if you don't use the
coil now, you may wish to use one in the future and it will do no harm. You
can get hot water cylinders anywhere, really.

The plate exchangers are available from GEA Ecobraze. A 14 plate 100kW is
fine, although you can go for more if you like.

I guess the only issue with a non-pressurised system like this is that
the F&E tank will have to be above the solar panels, but I can worry
about that later...

This can also be solved with an additional heat exchanger and pump (are you
counting the pumps yet?!) or by using the indirect coil if you haven't used
it for the boiler.

(Eg. how many building regs I'll be breaking!!!)

None, provided the cylinder is prefoamed and any gas, oil or electric
heating appliances are thermostatically controlled. Also, if radiators are
driven directly from the heat bank, then their pump needs to be
thermostatically controlled to prevent primary circuit wastage which would
result in the boiler firing when neither central heating or DHW demand it.

Christian.

In article ,
Christian McArdle wrote:
So Q1: Can I just parallel up the heat sources like this, and just tap
into the top and bottom of the tank round its periphery with 3 inlet &
outlet pipes to the various heat generators? Each one will be pumped
(Although the cooker right now is gravity fed)

It won't be expensive. A suitable exchanger costs around 80 quid. The cooker
can (and probably should) stay on gravity circulation if the heat bank is
sufficiently above it with wide enough pipes. Having reliable gravity
circulation is better for the health of your average cooker back boiler,
especially if solid fuel.

The cooker is gas, and they recomend a pump - right now without the
internal additional baffles, it cuts out on long runs at high temperatures
(eg. roasting), and thats with a separate heat-sink radiator in paralel
with the tank coil! However, there are quite a few bends in the 28mm
pipework, so ...

The controls for this system are relatively simple. You shouldn't need any
external control boxes. It only gets a little complicated when it needs to
make decisions like "should I run the gas boiler, if I'm already getting
solar heat". Even this can be simplified by having the solar thermostat
lower than the boiler one. Then the boiler only comes on when the tank has
depleted somewhat. Unfortunately, this would lead to needing a larger
cylinder, as you could only rely on there being hot water above the boiler
stat.

I'm not overly woried about the controller - if it needs it, and I can't
find anything suitable, it's not outside my abilities to put together
something with a PIC and a handfull of temperature sensors and switches
to control the various pumps, etc.

If you don't like the colander effect, you might get away with T-ing off
from fewer flanges, although you should pay attention to mixing pumped and
unpumped circuits in this configuration as unpumped circuits are sensitive
to neutral points and might get reverse or parasitic circulation.

And any ideas where the best online places I can use to get the basic
parts?

You could use your existing tank if large enough, but otherwise pretty much
any cylinder will do. I'd buy an indirect one. Even if you don't use the
coil now, you may wish to use one in the future and it will do no harm. You
can get hot water cylinders anywhere, really.

Actually, you've given me a good idea - my current tank is 100l capacity,
small, and has no foam insulation - it's got 2 standard jackets wrapped
round it in a desperate attempt to try to minimise heat loss.. A good
reason to replace it, if nothing else.

However, a tank with a coil will then let me connect the solar into it
at a later date and minimise the colander effect.

The plate exchangers are available from GEA Ecobraze. A 14 plate 100kW is
fine, although you can go for more if you like.

Thanks.

I guess the only issue with a non-pressurised system like this is that
the F&E tank will have to be above the solar panels, but I can worry
about that later...

This can also be solved with an additional heat exchanger and pump (are you
counting the pumps yet?!) or by using the indirect coil if you haven't used
it for the boiler.

If I use the indirect coil, I'll then need to either pressurise the
loop and include an expansion vessel, or have a seaprate F&E tank for
the Solar. I had a look at a friends "professionally" installed solar
system recently and there seemed to be 2 expansion tanks in the loop
which I really couldn't work out... It was also running at 2.5 bar which
I though excessive, however...

Pump count: Boiler, (cooker), Solar, Heat exchanger, CH = 5... (Plus the
existing Shower pump! I'll end up spending more on electrickery driving
the pumps than I'll save in gas...)

(Eg. how many building regs I'll be breaking!!!)

None, provided the cylinder is prefoamed and any gas, oil or electric
heating appliances are thermostatically controlled. Also, if radiators are
driven directly from the heat bank, then their pump needs to be
thermostatically controlled to prevent primary circuit wastage which would
result in the boiler firing when neither central heating or DHW demand it.

I'm presuming you are menaing room thermostats here... Hm. with some
inginuity, I could zone off each room (or at least upstairs/dwnstairs)
if I wanted to, using thermostats in each zone and solenoid valves - the
bathroom towel radiator being un-valved, but I'd also need a thermostat
in there too. Probably no bad thing.

Thanks. Looking at tanks now, they are not that expensive, with foam
insulation, etc.

Tank: £100, heat exchanger £80... plus bits & pieces, pumps, etc. still,
a lot of change from the £1500 I was looking at!!!

Cheers,

Gordon

"Christian McArdle" wrote in message
. net...
(Eg. how many building regs I'll be breaking!!!)

None, provided the cylinder is prefoamed and any gas, oil or electric
heating appliances are thermostatically controlled.

Doesn't the cooker connection require a heat dump radiator ?

In article , Mike wrote:

"Christian McArdle" wrote in message
.net...
(Eg. how many building regs I'll be breaking!!!)

None, provided the cylinder is prefoamed and any gas, oil or electric
heating appliances are thermostatically controlled.

Doesn't the cooker connection require a heat dump radiator ?

Yes - It's already got one.

Thanks,

Gordon