DIYbanter - Worcester Bosch Boiler flowrates vs Kw Output

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Worcester Bosch Boiler flowrates vs Kw Output

1) In the WB literature, the WB Greenstar Hightflow has a max ouput of
29.2 Kw, and a max flowrate of 20 l/min with a increase in temp of 35
deg C. The 40 HE Plus can output 40Kw and only manage 16 l/min but
has an almost identical efficiency.
Q - How is this possible?

The Greenstar Highflow has an internal heatbank to store energy. It is not
an instantaneous combi, like the 40HE Plus. This is why the Highflow is a
large floor mounted appliance.

2) Are manufacturers boiler statistics accurate?

Yes, but for comparisons, always check the Delta-T. It should be 35C to be
meaningful. Better still, just look at the kW for a condensing instantaneous
combi.

3) Does WB performance degrade after 1 month / 1 year?

No, provided you take precautions against scaling if you are in a hard water
area.

4) I have read that it is illegal to place a pump in an unvented
system. Is this true? I wondering if a flow limited pump exists (and
it legal) that I can put after my mains feed for cold water into
kitchen.

No. It is illegal. For good reason. If you pump mains water, you reduce the
pressure of the incoming mains. You may reduce the pressure below the
ambient, which leads to any leaks in the water company's pipes to draw in
contaminated ground water (very bad), rather than leak fresh water out (only
a bit bad).

This would be able to boost the pressure through the maze of pipes in
my house and ensure that the showers can operate at the maximum flow
available. (Shower has 6body jets at uses about 18 l/min )

If the pressure is not good enough from the mains, then a mains pressure
solution might not be appropriate.

5) Is there such a thing as an unvented Cold Water tank with an
expansion vessle inside? I was thinking that this would enable a short
term higher feed rate of the hot and cold water requirements of the
house.

Yes. It is called an accumulator. It can't fix problems with static
pressure, but it can help with flow rates, at least for short periods. The
following link is to a supplier of such systems. Not a recommendation as
such, I've never used them.

http://www.hwch.co.uk/boosting.html

6) Are there any recent high flow combi boilers equivalent to the WB
Greenstar 440 that are Better that it terms of Continuous unlimited
Flowrate. (Note: I am not looking for a multi boiler info, nor info on
one that involves storing hot water when not in use, just continuous HW
supply)

Then the Highflow is not for you, as it is a storage solution. You won't
find many boilers larger than the 40kW WB, although there are some out
there. However, don't be afraid of storage solutions. You may have had
experience of a wanky 1970s storage cylinder that always goes cold for hours
after a bath. A modern storage solution using rapid recovery coils, or
direct circulation heat banks can maintain the same hot water output as a
combi indefinitely (i.e. it will never run out even if you showered 24 hours
a day). The only difference is that they can boost to many times the flow
rate for a period of time, which is ideal for bath taking. You also don't
have to wait for the genuinely instantaneous combi to fire before hot water
is available.

Christian.

Worcester Bosch Boiler flowrates vs Kw Output

(i.e. it will never run out even if you showered 24 hours a day).

Just noticed your comment about a 18lpm shower. This would eventually run
out. However, a bog standard 28kW system boiler and a 180L heat bank, like
mine, would be capable of running this shower for 40 minutes before running
out. In this time, it will have heated 720 litres of water to 40C, which is
about the equivalent of 6 baths. If you actually ran such a shower for such
a period on a regular basis, I'll personally nominate you for a "fat arsed
american" environmental damage award. I'm not actually suggesting that you
intend to, mind, just that such a storage solution would easily meet any
sane needs for a domestic property. i.e. a 5 or 10 minute 18lpm shower won't
trouble it at all. OTOH, even the largest genuinely instantaneous combis
with no storage would struggle with a 18lpm body jet shower. You certainly
couldn't turn on a tap elsewhere without problems.

Christian.

Worcester Bosch Boiler flowrates vs Kw Output

"Christian McArdle" wrote in message
et...
1) In the WB literature, the WB Greenstar Hightflow has a max ouput of
29.2 Kw, and a max flowrate of 20 l/min with a increase in temp of 35
deg C. The 40 HE Plus can output 40Kw and only manage 16 l/min but
has an almost identical efficiency.
Q - How is this possible?

The Greenstar Highflow has an internal heatbank to store energy. It is not
an instantaneous combi, like the 40HE Plus. This is why the Highflow is a
large floor mounted appliance.

2) Are manufacturers boiler statistics accurate?

Yes, but for comparisons, always check the Delta-T. It should be 35C to be
meaningful. Better still, just look at the kW for a condensing
instantaneous
combi.

3) Does WB performance degrade after 1 month / 1 year?

No, provided you take precautions against scaling if you are in a hard
water
area.

4) I have read that it is illegal to place a pump in an unvented
system. Is this true? I wondering if a flow limited pump exists (and
it legal) that I can put after my mains feed for cold water into
kitchen.

No. It is illegal. For good reason. If you pump mains water, you reduce
the
pressure of the incoming mains. You may reduce the pressure below the
ambient, which leads to any leaks in the water company's pipes to draw in
contaminated ground water (very bad), rather than leak fresh water out
(only
a bit bad).

This would be able to boost the pressure through the maze of pipes in
my house and ensure that the showers can operate at the maximum flow
available. (Shower has 6body jets at uses about 18 l/min )

If the pressure is not good enough from the mains, then a mains pressure
solution might not be appropriate.

5) Is there such a thing as an unvented Cold Water tank with an
expansion vessle inside? I was thinking that this would enable a short
term higher feed rate of the hot and cold water requirements of the
house.

Yes. It is called an accumulator. It can't fix problems with static
pressure, but it can help with flow rates, at least for short periods. The
following link is to a supplier of such systems. Not a recommendation as
such, I've never used them.

http://www.hwch.co.uk/boosting.html

6) Are there any recent high flow combi boilers equivalent to the WB
Greenstar 440 that are Better that it terms of Continuous unlimited
Flowrate. (Note: I am not looking for a multi boiler info, nor info on
one that involves storing hot water when not in use, just continuous HW
supply)

Then the Highflow is not for you,
as it is a storage solution.

It is a one-box solution though.

The ACV Heatmaster 35TC is a one box and has high flowrates - excellent
product.
http://www.acv-uk.com/heatmaster.htm

The Gledhill Gulfstream also have high flow (35 litres/min) one-box
solutions. They have 3 sizes.
http://www.gledhill.net/water-storag...ulfstream2.htm

Worcester Bosch Boiler flowrates vs Kw Output

"Christian McArdle" wrote in message
et...
(i.e. it will never run out even if you showered 24 hours a day).

Just noticed your comment about a 18lpm shower. This would eventually run
out. However, a bog standard 28kW system boiler and a 180L heat bank, like
mine, would be capable of running this shower for 40 minutes before
running
out. In this time, it will have heated 720 litres of water to 40C, which
is
about the equivalent of 6 baths. If you actually ran such a shower for
such
a period on a regular basis, I'll personally nominate you for a "fat arsed
american" environmental damage award. I'm not actually suggesting that you
intend to, mind, just that such a storage solution would easily meet any
sane needs for a domestic property. i.e. a 5 or 10 minute 18lpm shower
won't
trouble it at all. OTOH, even the largest genuinely instantaneous combis
with no storage would struggle with a 18lpm body jet shower. You certainly
couldn't turn on a tap elsewhere without problems.

That is 18 litres/min "mixed" hot and cold. Some can cope OK and even have
the odd tap turned on and not affect the performance.

Worcester Bosch Boiler flowrates vs Kw Output

On Thu, 27 Oct 2005 02:44:56 +0100, aj_newman
wrote:
6) Are there any recent high flow combi boilers equivalent to the WB
Greenstar 440 that are Better that it terms of Continuous unlimited
Flowrate. (Note: I am not looking for a multi boiler info, nor info on
one that involves storing hot water when not in use, just continuous HW
supply)

There is the MAN Micromat 76kw combi boiler from MHG-Heiztechnik based
in Hamburg, Germany. (Formerly part of the volkwagen group).
http://www.mhg.de/en/products/gas_un...cromat_ec.html

I am not sure what the current situation is but if you look back
through the archives of this group, they used to be rebadged by
Eco-hometec and MHS Boilers in the UK.

Officially you would need to upgrade your gas supply as all(?)
domestic meters are U6/E6 by default which means they can supply 6
cubic metres/hour. The 76 kw model uses up to 7.6 cubic metres per
hour according to the installation manual (which I could find only in
German
http://www.mhg.de/de/download/produk...dt_2003-10.pdf
)

Doctor Evil has previously asserted that you can run your gas meter at
double capacity though not many people agreed with him! :-)

Mr F.

Worcester Bosch Boiler flowrates vs Kw Output

"Mr Fizzion" wrote in message
...
On Thu, 27 Oct 2005 02:44:56 +0100, aj_newman
wrote:
6) Are there any recent high flow combi boilers equivalent to the WB
Greenstar 440 that are Better that it terms of Continuous unlimited
Flowrate. (Note: I am not looking for a multi boiler info, nor info on
one that involves storing hot water when not in use, just continuous HW
supply)

There is the MAN Micromat 76kw combi boiler from MHG-Heiztechnik based
in Hamburg, Germany. (Formerly part of the volkwagen group).
http://www.mhg.de/en/products/gas_un...cromat_ec.html

I am not sure what the current situation is but if you look back
through the archives of this group, they used to be rebadged by
Eco-hometec and MHS Boilers in the UK.

Officially you would need to upgrade your gas supply as all(?)
domestic meters are U6/E6 by default which means they can supply 6
cubic metres/hour. The 76 kw model uses up to 7.6 cubic metres per
hour according to the installation manual (which I could find only in
German

http://www.mhg.de/de/download/produk...W_EC-62-76_dt_
2003-10.pdf
)

Doctor Evil has previously asserted that you can run your gas meter at
double capacity though not many people agreed with him! :-)

I don't care if they agree with me or nopt, I have done it and they haven't.
I used to design gas system and the U6 had a 100% overload. We would go up
to around 300 to 350 cu foot per hour for 212 cu foot rated meter. Transco
now probaly would not allow this as they want you to go the next size up and
charge more.