Hi All,

Somebody mentioned that maybe I should invest in
a thermal store rather than a megaflow boiler.
What are you experiences with them and any particular
manufacturers that are favourite?

I hadnt come across thermal stores before so Ill
do some info searching, I did think that megaflow and
thermal stores were the same system...

Our house has lousy pressure from the gravity system
upstairs and the two bathroom showers and baths are crap.
Originally I was going to fit a pump however they break
and are noisy. Id prefer to fix it the professional way!

Thanks,
Matthew

Matthew wrote:

Somebody mentioned that maybe I should invest in
a thermal store rather than a megaflow boiler.
What are you experiences with them and any particular
manufacturers that are favourite?

I hadnt come across thermal stores before so Ill
do some info searching, I did think that megaflow and
thermal stores were the same system...

Our house has lousy pressure from the gravity system
upstairs and the two bathroom showers and baths are crap.
Originally I was going to fit a pump however they break
and are noisy. Id prefer to fix it the professional way!


I fitted a Range thermal store about 4 years ago (all plumbed in plastic
:-), and we're very pleased with it. It's particularly well suited to
our place, because we have an oil boiler. The large thermal capacity
totally eliminates boiler cycling - the boiler does long, clean burns.
This makes for very efficient operation


--
Grunff

Somebody mentioned that maybe I should invest in
a thermal store rather than a megaflow boiler.
What are you experiences with them and any particular
manufacturers that are favourite?

I have a DPS Pandora heat bank. Here's a non-exhaustive comparison of the
various systems:

Way they work:

Unvented cylinder:
Basically the mains pressure water (regulated by a pressure reducing valve)
goes into the bottom of the cylinder. It is heated by immersion or indirect
coil. Hot pressurised water is taken from the top to the taps. A pressure
vessel or integral air bubble handles expansion of the water as it is
heated.

Thermal sto
A vented cylinder is filled with chemically corrosion inhibited water. This
water is heated by immersion, indirect coil, or is heated by directly
pumping it through a boiler. The mains pressure cold water enters through a
high surface area coil and is hot when it leaves on the way to the tap.
Temperature is regulated either by primary water temperature, or using a
thermostatic mixing valve on the output.

Heat bank:
Identical to a thermal store, except in the way that hot water is generated.
Instead of an indirect coil, the mains pressure cold water enters a plate
heat exchanger and a flow switch on the way to the tap. The flow switch
turns on a pump, which pumps hot inhibited water from the top of the
cylinder, through the plate exchange and back into the bottom. Temperature
is regulated using a thermostatic mixing valve on output, or by regulating
the pump speed to ensure output temperature. The latter is more efficient,
whilst the former usually provides better regulation.

Advantages/disadvantages of systems:

Unvented cylinder:
1. Very high potential flow rate.
2. Requires yearly servicing and special training for installers.
3. Possibly safety risk, if not maintained or installed properly.
4. Can't use very high recovery rates.
5. More complicated plumbing, with pressure/temperature relief required.
6. Must have pressure reducing valve.
7. Excellent stratification (water goes cold quickly when run out, showing
efficient energy storage).

Thermal sto
1. Stores water at atmospheric pressure. (Safety and
installation/maintenance benefit).
2. Medium flow rates at full temperature. Better than instantaneous combi.
3. Can run rads off it.
4. Can add multiple heat sources (solid fuel/solar)
5. Cylinder water is corrosion inhibited.
6. Stratification less good.

Heat bank:
1. Stores water at atmospheric pressure. (Safety and
installation/maintenance benefit).
2. Much better flow rates than a thermal store (but potentially less than an
unvented cylinder, although this depends on circumstances).
3. Can run rads off it.
4. Can add multiple heat sources (solid fuel/solar)
5. Cylinder water is corrosion inhibited.
6. More complicated than thermal store.
7. Stratification less good (particularly when using low flow rates), unless
pump modulation (rather than TMV) used.

Christian.

Thanks thats brilliant info!

On Thu, 13 Oct 2005 14:29:55 +0100, Grunff wrote:

The large thermal capacity totally eliminates boiler cycling - the
boiler does long, clean burns. This makes for very efficient
operation

Hum, I like that idea or beast of a boiler (38kW) cycles liike crazy
and overheats unless we wind it's stat well down when it only has the
HW to heat or just a little bit of CH. Solar would be nice to add
along with a woodburner so a thermal store or a heatbank sound like a
very good idea if it can soak up 38kW from the boiler as well...

The boiler size is probably overkill but not by much when you consider
it may have to heat 2 3 bed semis with external temps down to -10C and
a gale blowing...

--
Cheers
Dave. pam is missing e-mail

Dave Liquorice wrote:

Hum, I like that idea or beast of a boiler (38kW) cycles liike crazy
and overheats unless we wind it's stat well down when it only has the
HW to heat or just a little bit of CH. Solar would be nice to add
along with a woodburner so a thermal store or a heatbank sound like a
very good idea if it can soak up 38kW from the boiler as well...

The boiler size is probably overkill but not by much when you consider
it may have to heat 2 3 bed semis with external temps down to -10C and
a gale blowing...


I would definitely recommend it - it's a pretty simple arrangement, and
works very well with oil boilers. As long as the boiler to cylinder pipe
run is adequate, you should be able to dump your 38kW into the cylinder
without any problems. Probably go for 28mm, with as few bends as possible.


--
Grunff

Solar would be nice to add along with a woodburner so a thermal store
or a heatbank sound like a very good idea if it can soak up 38kW from
the boiler as well...

You'll need to run the boiler circuit direct vented for 38kW. The indirect
coil would have trouble sinking that, especially near the end of the burn.

Christian.

"Grunff" wrote in message
...
Dave Liquorice wrote:

Hum, I like that idea or beast of a boiler (38kW) cycles liike crazy
and overheats unless we wind it's stat well down when it only has the
HW to heat or just a little bit of CH. Solar would be nice to add
along with a woodburner so a thermal store or a heatbank sound like a
very good idea if it can soak up 38kW from the boiler as well...

The boiler size is probably overkill but not by much when you consider
it may have to heat 2 3 bed semis with external temps down to -10C and
a gale blowing...


I would definitely recommend it - it's a pretty simple arrangement, and
works very well with oil boilers. As long as the boiler to cylinder pipe
run is adequate, you should be able to dump your 38kW into the cylinder
without any problems. Probably go for 28mm, with as few bends as possible.

As long as the coil can take 38kW, or if heating the store direct that is
not an issue. The beauty of thermal store/heat bank is that when connected
direct the boiler size can be as big as you like. I know of one man who
picked up a 75kW oil boiler for a few hundred pounds (the contractor messed
up and had it spare) . He only needed 16kW for the CH. I advised a thermal
store with 32mm connections and CH run off the store too. The store was
heated in no time and his 3 bathrooms could be run simultaneously and never
run out of hot water when filling them all. 75kW in combi terms gives
approx 30 litres/min of instant hot water, so when re-heating the store it
poured in the heat.

With gas you are limited to around 55kW (spare for a hob) because of the U6
meter.

"Dave Liquorice" wrote in message
ll.com...
On Thu, 13 Oct 2005 14:29:55 +0100, Grunff wrote:

The large thermal capacity totally eliminates boiler cycling - the
boiler does long, clean burns. This makes for very efficient
operation

Hum, I like that idea or beast of a boiler (38kW) cycles liike crazy
and overheats unless we wind it's stat well down when it only has the
HW to heat or just a little bit of CH. Solar would be nice to add
along with a woodburner so a thermal store or a heatbank sound like a
very good idea if it can soak up 38kW from the boiler as well...

The boiler size is probably overkill but not by much when you consider
it may have to heat 2 3 bed semis with external temps down to -10C and
a gale blowing...

Take the CH off the store using a Grundfoss Alpha pump. Heat the store
"directly" with 28mm piping. Put a TMV on the boiler flow and return to
maximise efficiency.

The store can take solar and stove input by adding coils to the bottom of
the cylinder.

The store can take solar and stove input by adding coils to the bottom of
the cylinder.

Or can be run direct without coils. Stove mustn't normally be pumped, unless
the instructions tell you otherwise, which they probably won't. They need a
reliable gravity circulation with no valves. The heater must be well below
the heat bank.

Christian.

"Christian McArdle" wrote in message
. net...
The store can take solar and stove input by adding coils to the bottom
of
the cylinder.

Or can be run direct without coils. Stove mustn't normally be pumped,
unless
the instructions tell you otherwise, which they probably won't. They need
a
reliable gravity circulation with no valves. The heater must be well below
the heat bank.

For this application the thermal store is the perfect choice.

For this application the thermal store is the perfect choice.

Absolutely, well a heat bank, anyway. I prefer the high flow rates to the
requirement for electricity to get hot water out.

Christian.

"Christian McArdle" wrote in message
. net...
For this application the thermal store is the perfect choice.

Absolutely, well a heat bank, anyway. I prefer the high flow rates to the
requirement for electricity to get hot water out.

On my Gledhill even when running the bath, the plate only ever gets just
over half of it hot, with the other half very cold. It will deliver about
100kW, so it is delivering about 60kW which is about 25 litre/min in combi
terms at 60C delivery. That fills the bath very fast. Although on mine a
have a bath mixer with TMV reducing the bath temp to 46C. So a tot can't
jump in a bath full of 60C water giving 2nd to 3rd degree burns. This slows
down the flow a bit but still fill fast.

100kW in combi terms is about 45 litres/min.

"Christian McArdle" wrote in message
. net...
The store can take solar and stove input by adding coils to the bottom
of
the cylinder.

Or can be run direct without coils. Stove mustn't normally be pumped,
unless
the instructions tell you otherwise, which they probably won't. They need
a
reliable gravity circulation with no valves. The heater must be well below
the heat bank.

On a heat bank/T store, I would always install a Magnaclean on the CH return
to the store (I would put one on all types of system really). Sludge can
build up in an "integrated" store because the iron oxide particles collect
there as the store is the part the water moves slowest through. The filter
will grab the a particles before they enter the store. The boiler should
present no problems as the rads are the problem.

On Fri, 14 Oct 2005 13:12:50 +0100, "Doctor Drivel"
wrote:

Although on mine a
have a bath mixer with TMV reducing the bath temp to 46C. So a tot can't
jump in a bath full of 60C water giving 2nd to 3rd degree burns.

Best thing really. I thought you kept coal in your bath though.



--

..andy

To email, substitute .nospam with .gl

"Andy Hall" wrote in message
...
On Fri, 14 Oct 2005 13:12:50 +0100, "Doctor Drivel"
wrote:

Although on mine a
have a bath mixer with TMV reducing the bath temp to 46C. So a tot can't
jump in a bath full of 60C water giving 2nd to 3rd degree burns.

Best thing really. I thought you kept coal in your bath though.

What for?