Hot water system
 

I'll leave off combifying the boiler and combining with heatbank output,
though. With 180L I do not envisage running out of water at all, so it is
probably a lot of complexity for little gain.

BTW, did DPS leave the CH tappings on the heat bank?

I didn't specify them, so I assume they're not there. I'll take a look,
though. I decided I didn't want to do it that way. I wasn't convinced that I
would get higher SEDBUK through the heat bank, due to the higher condensing
boiler temperature compared to running the CH directly offsetting the
expected short high power burn savings. It would also be a more complicated
system with yet more pumps required.

I also have no intention of using the immersion as electrical backup central
heating!

Christian.

Hot water system
 

"Christian McArdle" wrote in message
t...
I'll leave off combifying the boiler and combining with heatbank output,
though. With 180L I do not envisage running out of water at all, so it is
probably a lot of complexity for little gain.

Complexity? a plate (no moving parts), 3-way valve and stat? What was the
difference in price from a 140 litre to a 180 litre heat bank? Probably
the cost of the ext plate and 3-way valve. The point is, if you have all
that power available in the boiler use it to good effect.

BTW, did DPS leave the CH tappings on the heat bank?

I didn't specify them, so I assume they're not there. I'll take a look,
though. I decided I didn't want to do it that way. I wasn't convinced that
I
would get higher SEDBUK through the heat bank, due to the higher
condensing
boiler temperature compared to running the CH directly offsetting the
expected short high power burn savings. It would also be a more
complicated
system with yet more pumps required.

With a heat bank you can specify the tappings for each zone. In short, two
zones 4 tappings. The zones can all come off the heat bank. All you need
is a pump and check valve for each zone. A pump is about the price of a
2-port valve. The heat bank is a neutral point so better balancing.

The condensing boiler will work efficiently enough.



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Hot water system
 

With a heat bank you can specify the tappings for each zone. In short, two
zones 4 tappings. The zones can all come off the heat bank.

I'm having 5 zones, which might end up with more pipework than you could
imagine festooned on the cylinder. Most of the 2 port valves will be two
floors away and I don't want multiple runs of piping. So I suspect even if I
had decided to take the central heating off the bank, I would have valved
off a single tapping.

However, I might have required a bigger heat bank if I was to use it for
heating as well. I was also worried about heat stratification performance if
the central heating was forever stirring up the water.

At the end of the day, a decent condensing boiler can get 97% efficiency
without the use of a heat bank. I doubt that the heat bank could improve on
that much. Obviously, it is very useful if there are other heat sources
involved, such as solar or a solid fuel boiler, but there isn't and never
will be.

Christian.

Hot water system
 

On Fri, 3 Oct 2003 10:59:42 +0100, Peter Smithson
wrote:

You take your personal hygene seriously! :-)

Perhaps he needs to? ;)

PoP

Hot water system
 

"Christian McArdle" wrote in message
t...

With a heat bank you can specify the tappings for each zone. In short,
two
zones 4 tappings. The zones can all come off the heat bank.

I'm having 5 zones, which might end up with more pipework than you could
imagine festooned on the cylinder. Most of the 2 port valves will be two
floors away and I don't want multiple runs of piping. So I suspect even if
I
had decided to take the central heating off the bank, I would have valved
off a single tapping.

However, I might have required a bigger heat bank if I was to use it for
heating as well. I was also worried about heat stratification performance
if
the central heating was forever stirring up the water.

At the end of the day, a decent condensing boiler can get 97% efficiency
without the use of a heat bank. I doubt that the heat bank could improve
on
that much. Obviously, it is very useful if there are other heat sources
involved, such as solar or a solid fuel boiler, but there isn't and never
will be.

Christian,

I intend to have a direct heat bank with the following:

- The top 2/3 of the cylinder, DHW section, will be heated to approx 75C

- A blending valve will be on the return to the boiler on the DHW side, set
to 53C promoting condensing efficiency, boiler efficiency in that it
operates at designed delta T, and rapid heat up of the stored water, with a
one boiler pass of all the stored water.

- The bottom 1/3 (or 1/4), CH section, will be heated to whatever a weather
compensator dictates. There will be an outside temp sensor and a sensor on
the cylinder. Another sensor will be in the living space dropping the
cylinder temp accordingly to room influences. If, for e.g., the outside
temp is 10C it may require a cylinder temp of 48C or less.

- From the boiler the flow will have a 3-way diverter valve that diverts
flow from the top cylinder section to the bottom and vice versa. The two
sections will operate on two temperatures. The DHW section set and the CH
section variable via a weather compensator.

- The top section takes priority, in that if the DHW cylinder stat calls for
heat the diverter valve takes all the boilers heat to then top section for
rapid heat up.

- The bottom CH section will have two zones run off this. One for upstairs
and one for down. This is easy for system balance. Each will have a
non-return valve and a Grundfos Alpha auto variable speed pump, variable on
pressure sensing to compensate when rad valves start to close.

So, when on CH the bottom section may only be 25-30C forcing the condensing
boiler into very low temps promoting high efficiency. In total 3 pumps and
one 3-way valve and an outside weather compensator.



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