"Andy Hall" wrote in message
...
On Wed, 22 Sep 2004 13:20:13 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .
On Wed, 22 Sep 2004 11:21:37 +0100, "IMM" wrote:




If you are going for a heat bank. Preferable is an "integrated",
"direct"
one. Direct is that there is no coil between boiler and cylinder and
integrated means the CH is run from the cylinder too.

Range do the Flowmax and DPS do the GVX (?), which I believe is
cheaper
than
the Pandora. The Flowmax is well priced.

http://www.range-cylinders.co.uk


These are a bad idea with a
condensing boiler for CH use because the
boiler does not modulate down to its more efficient low burn and low
temperature ranges.

If you look at the behaviour of a condensing
boiler with a CH system in spring and autumn
it comes on at low level and works at low and
very efficient temperatures

Depends on the boiler. Most condensing boiler "modulate" on marinating a
setpoint flow temp.

I didn't know that you could prepare food on them as well

Only the up market boilers modulate on load
compensation.

I was really talking about load determination from temperature drop
and firing rate.


The Gledhill Systemate heat bank has two pumps and has the boiler heating
the rads direct. This would be good with a load compensating condensing
boiler.

If you put a heat bank in the middle to run radiators it has the
effect of causing the boiler to burn at high output periodically to
replenish the heatbank. It will never run at low output and
therefore not in its most efficient range.

If the CH is on it would be lowering the water temp at the bottom of the
store. This returns to the boiler at a low efficient temperature. Many
stores have the cycl stat low on the cylinder and set low, as they
calulate
that stratification would keep the top at approx 75-80C and the bottom
very
much lower.

An indirect heatbank just for the DHW makes a lot of sense, because it
is recharged at high boiler output for a short time.

A DHW only heat bank is best as one layer of heat interchange is removed.

Exactly.

A "direct" one.

The return temp from the store would be low in usage promoting condensing
efficiency.


.andy

To email, substitute .nospam with .gl