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Christian McArdle
 
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Default DPS Pandora heat bank

Just to let anyone who is interested know, I have just installed my DPS
Pandora heat bank. Possibly anyone considering a new hot water system might
be want to read on.

It is a 180 litre model with the standard plate exchanger and indirected
heated by coil. Except it isn't, because the new boiler hasn't been
installed yet and the old one is using a feed/expansion tank below the level
of the tappings so can't be plumbed into it. It is currently electrically
heated by 3kW immersion. The immersion thermostat is set to be identical to
the indirect coil thermostat, so performance should be similar.

It does work exactly as expected. It easily fills an entire bath up. Flow
rates are higher than my old gravity system into the bath (but not really a
patch on my parent's Megaflo or the pumped gravity system in my previous
house). However, at the top end of flow rate, the temperature does start to
drop a little. I still need to mix cold in though, even at full pelt.
However, you need to turn it down to half near the end to bring the
temperature up to the TMV's set point. (If you are anything like me, you'll
fill the bath with warm water, get accustomed to it and then pour in very
hot only to raise it up to just sub-scalding).

The performance on a shower is absolutely superb and totally comparable to
an unvented cylinder, as you would expect. Despite the much longer run to
the kitchen in the new layout, I also get hot water quicker due to the extra
pressure helping with the long 15mm run to that tap and the high pressure
only design (I bought the tap in anticipation of the mains pressure).

So all in all, for the same purchase cost as an unvented cylinder, you do
get a system that isn't much lower in performance in practice. Obviously,
there are benefits to it, such as the main vessel containing static
inhibited water that will eliminate scaling, the inherently greater safety
of using zero head pressure in a large heated vessel, and the fact that the
DHW itself is not stored and can be poured straight into the kettle or cup
(assuming no phosphate dosers or ion-exchange softeners).

Christian.


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IMM
 
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Default DPS Pandora heat bank


"Christian McArdle" wrote in message
t...
Just to let anyone who is interested know, I have just installed my DPS
Pandora heat bank. Possibly anyone considering a new hot water system

might
be want to read on.

It is a 180 litre model with the standard plate exchanger and indirected
heated by coil. Except it isn't, because the new boiler hasn't been
installed yet and the old one is using a feed/expansion tank below the

level
of the tappings so can't be plumbed into it. It is currently electrically
heated by 3kW immersion. The immersion thermostat is set to be identical

to
the indirect coil thermostat, so performance should be similar.

It does work exactly as expected. It easily fills an entire bath up. Flow
rates are higher than my old gravity system into the bath (but not really

a
patch on my parent's Megaflo or the pumped gravity system in my previous
house). However, at the top end of flow rate, the temperature does start

to
drop a little. I still need to mix cold in though, even at full pelt.
However, you need to turn it down to half near the end to bring the
temperature up to the TMV's set point. (If you are anything like me,

you'll
fill the bath with warm water, get accustomed to it and then pour in very
hot only to raise it up to just sub-scalding).

The performance on a shower is absolutely superb and totally comparable to
an unvented cylinder, as you would expect. Despite the much longer run to
the kitchen in the new layout, I also get hot water quicker due to the

extra
pressure helping with the long 15mm run to that tap and the high pressure
only design (I bought the tap in anticipation of the mains pressure).

So all in all, for the same purchase cost as an unvented cylinder, you do
get a system that isn't much lower in performance in practice. Obviously,
there are benefits to it, such as the main vessel containing static
inhibited water that will eliminate scaling, the inherently greater safety
of using zero head pressure in a large heated vessel, and the fact that

the
DHW itself is not stored and can be poured straight into the kettle or cup
(assuming no phosphate dosers or ion-exchange softeners).


And no pressure reducing valves and no large overflow and no yearly service,
and descaling the cylinder is a DIY job, whereas descaling an unvented
cylinder is major task. And expanding the system is childs play by
installing other plate heat exchanger in parallel - see if you can that with
an unvented cylinder.

Christian,

Sounds good. You will be installing a 25kWish boiler, so best to use the
power available instead of trickle charging (re-heating) the cylinder. We
still have this ingrained notion of only using the stored water and waiting
for the water to be re-heated, from the old coal fire back boiler days.
And depending on the heat bank system you can have 10 bar pressure, not 3.5
as on unvented cylinders.

Now what you need to do to bring the system up to top spec is:

in the hot water draw-off before the baths and showers draw-offs and after
the rest, install a flow switch, which will fire the boiler immediately as
there is a large demand, instead of firing when 2/3 of the thermal stores
energy is exhausted. No sense in switching in the boiler if the kitchen
sink tap is constantly turned on and off, which will switch in the boiler
with each tap turn; this will eliminate this sort of boiler cycling.

This will combine the energy of the thermal store and the power of the
boiler, in effect making the cylinder larger. You have all that boiler
power laying there - USE IT. Very simple to do and just amending the
heating/hot water control setup. This can be done with any cylinder heated
by a boiler.



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Christian McArdle
 
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Default DPS Pandora heat bank

And depending on the heat bank system you can have 10 bar pressure, not 3.5
as on unvented cylinders.


Well, it is limited to 6 bar. If your mains even approaches this pressure,
you need a PRV in case of natural variations. I haven't measured mine, but
I'm sure it isn't that high. I'm on a hill and the flow rate is about
average. No banging from the taps, either when turned off.

This will combine the energy of the thermal store and the power of the
boiler, in effect making the cylinder larger.


No need. The cylinder is well overspecced, getting on for two baths with no
recovery. I can wait for the cylinder stat to kick in, which it will fairly
quickly, as it is right at the bottom. It is an indirect system, so I can't
directly combine the boiler output without a rats nest of expensive zone
valves, flow switches and additional heat exchangers. It is indirect as I
need to run a pressurised primary system.

Christian.


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IMM
 
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Default DPS Pandora heat bank


"Christian McArdle" wrote in message
t...
And depending on the heat bank system you can have 10 bar pressure, not

3.5
as on unvented cylinders.


Well, it is limited to 6 bar. If your mains even
approaches this pressure,


Mine actually does. Which is still far higher than the 3.5 of an unvented
cylinder.

you need a PRV in case of natural variations.


Nice to have one as it acts as a regulator when the pressure is above the
setpoint.

I haven't measured mine, but
I'm sure it isn't that high. I'm on a hill
and the flow rate is about
average. No banging from the taps,
either when turned off.

This will combine the energy of the thermal
store and the power of the
boiler, in effect making the cylinder larger.


No need. The cylinder is well overspecced,


Not the right thing to do. It should be sized correctly with the combined
output of the boiler taken into account.

getting on for two baths with no
recovery. I can wait for the cylinder stat
to kick in, which it will fairly quickly, as it
is right at the bottom.


What make of stat and what temp is is set at?

It is an indirect system, so I can't
directly combine the boiler output
without a rats nest of expensive zone
valves, flow switches and additional heat exchangers.
It is indirect as I need to run a pressurised
primary system.


The boiler can still pump 25kW into the cylinder when draw-off large water
volumes, although not directly combining its full output with the thermal
stores.



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IMM
 
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Default DPS Pandora heat bank


"Christian McArdle" wrote in message
t...

This will combine the energy of the
thermal store and the power of the
boiler, in effect making the cylinder larger.


No need. The cylinder is well overspecced,
getting on for two baths with no recovery.


Then you can lower the temp of the heat bank by ensuring the boiler licks in
when any shower or bath draws off hot water. The boiler can be a lower temp
and store a lower temp, all promoting condensing efficiency.


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Andy Hall
 
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Default DPS Pandora heat bank

On Tue, 28 Oct 2003 20:06:01 -0000, "IMM" wrote:



This will combine the energy of the thermal
store and the power of the
boiler, in effect making the cylinder larger.


No need. The cylinder is well overspecced,


Not the right thing to do. It should be sized correctly with the combined
output of the boiler taken into account.



It's an entirely valid thing to do.


The boiler can still pump 25kW into the cylinder when draw-off large water
volumes, although not directly combining its full output with the thermal
stores.



---


..andy

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IMM
 
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Default DPS Pandora heat bank


"Andy Hall" wrote in message
...
On Tue, 28 Oct 2003 20:06:01 -0000, "IMM" wrote:



This will combine the energy of the thermal
store and the power of the
boiler, in effect making the cylinder larger.

No need. The cylinder is well overspecced,


Not the right thing to do. It should be sized correctly with the

combined
output of the boiler taken into account.


It's an entirely valid thing to do.


In Fred Dibnahs day, yes.

The boiler can still pump 25kW into the cylinder when draw-off large

water
volumes, although not directly combining its full output with the thermal
stores.




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Christian McArdle
 
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Default DPS Pandora heat bank

It's an entirely valid thing to do.

In Fred Dibnahs day, yes.


It is overspecced for five main reasons.

a) I intend to install an additional shower room at some point.

b) By not taking into account boiler output, it is useful when run from the
immersion, as it is at present.

c) If the calculations had been wrong (perhaps over optimistic from
manufacturer) it would cost a bomb to sort out.

d) It makes any destratification of the temperature profile less important.

e) It does not significantly impact on the space used or the purchase price.

Christian.


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IMM
 
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Default DPS Pandora heat bank


"Christian McArdle" wrote in message
t...
It's an entirely valid thing to do.


In Fred Dibnahs day, yes.


It is overspecced for five main reasons.

a) I intend to install an additional shower room at some point.

b) By not taking into account boiler output, it is useful when run from

the
immersion, as it is at present.

c) If the calculations had been wrong (perhaps over optimistic from
manufacturer) it would cost a bomb to sort out.

d) It makes any destratification of the temperature profile less

important.

e) It does not significantly impact on the space used or the purchase

price.

Christian,

Now you can use the boiler with a flow switch on the bath and shower pipe
(the outlets with most flow), reduce the stores setpoint temp and also
reduce the boilers temp when heating the store. This promotes condensing
efficiency - the engineering to keep temps down. By default you may have
improved efficiency.



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Andy Dingley
 
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Default DPS Pandora heat bank

On Wed, 29 Oct 2003 18:02:25 -0000, "IMM" wrote:

"Andy Hall" wrote in message


It's an entirely valid thing to do.


In Fred Dibnahs day, yes.


It's an odd thing, but you're probably the only person where I'd take
Fred Dibnah's advice on pressurised plumbing over yours....

--
Die Gotterspammerung - Junkmail of the Gods


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IMM
 
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Default DPS Pandora heat bank


"Andy Dingley" wrote in message
...
On Wed, 29 Oct 2003 18:02:25 -0000, "IMM" wrote:

"Andy Hall" wrote in message


It's an entirely valid thing to do.


In Fred Dibnahs day, yes.


It's an odd thing, but you're probably the only person where I'd take
Fred Dibnah's advice on pressurised plumbing over yours....


That is very foolish as I know far more about pressurised plumbing than
Fred. Also this point was not at all about pressurised plumbing, it was
about sizing.


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Andy Hall
 
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Default DPS Pandora heat bank

On Sat, 1 Nov 2003 23:29:18 -0000, "IMM" wrote:


"Andy Dingley" wrote in message
.. .
On Wed, 29 Oct 2003 18:02:25 -0000, "IMM" wrote:

"Andy Hall" wrote in message


It's an entirely valid thing to do.

In Fred Dibnahs day, yes.


It's an odd thing, but you're probably the only person where I'd take
Fred Dibnah's advice on pressurised plumbing over yours....


That is very foolish as I know far more about pressurised plumbing than
Fred. Also this point was not at all about pressurised plumbing, it was
about sizing.

Do you do after-dinner speeches about it, at all?


..andy

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  #13   Report Post  
IMM
 
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Default DPS Pandora heat bank


"Andy Hall" wrote in message
...
On Sat, 1 Nov 2003 23:29:18 -0000, "IMM" wrote:


"Andy Dingley" wrote in message
.. .
On Wed, 29 Oct 2003 18:02:25 -0000, "IMM" wrote:

"Andy Hall" wrote in message

It's an entirely valid thing to do.

In Fred Dibnahs day, yes.

It's an odd thing, but you're probably the only person where I'd take
Fred Dibnah's advice on pressurised plumbing over yours....


That is very foolish as I know far more about pressurised plumbing than
Fred. Also this point was not at all about pressurised plumbing, it was
about sizing.

Do you do after-dinner speeches about it, at all?


My mailbox is inundated with them.


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