Hi all, first of all thanks to anyone who takes the time to read about
this problem, and more thanks to anyone who replies

Trying to give advice to a customer regarding an 'inadequate' central
heating design. He has, a Victorian three floor terraced house with
toilet on the ground floor,an ensuite with an electric shower as well
as the main bathroom containing a bath and a large steam cubicle with
shower jets etc. (It's specifications state that it requires 10lpm cold
and 10lpm hot water at 1.5bar) on first floor, and a further en-suite
ont he secon floor containing a bath and an electric shower.

The newly installed Biasi 28 combi, (which states at best 12 lpm
(summertime) but more likely around 8lpm.) is required to supply the
four basins, two baths, kitchen sink and steam cubicle,

There is a 100% certainty that the three bathrooms will be frequently
used simultaneously

My suggestion... the bath and steamroom in the main bathroom should be
supplied from the cylinder, all other points around the house from the
combi. My assumptions, bathrooms will rarely be used at the same time
as the toilet and kitchen on ground floor. The bath and shower in the
main bathroom will rarely be used at the same time.

There is space on the second floor which could accomodate a cylinder
and header tank . The tank would sit about 1.6 to 1.8m above the steam
room shower head, but only 0.3m above the bath/basin in the en-suite on
the same second floor

My questions.
1. Based on the required flow rate for the steamroom shower, what size
cylinder should I recommend?
2. Will the 1.6m head of water create sufficient pressure for the multi
headed monster steamroom shower?
3. Should I take the cold water for the steamroom shower from the
header tank to ensure like pressures between hot and cold - or would a
pressure equalising valve be sufficent to balance cold mains water
pressure, and the cylinder fed hot water, and how efficient are they at
coping with fluctuation on e.g the cold, when someone flushes a toilet
and the runs a basin concurrently?
4. Based on the above, what size header tank should I recommend?

"sparkydude" wrote in message
oups.com...
Hi all, first of all thanks to anyone who takes the time to read about
this problem, and more thanks to anyone who replies

Trying to give advice to a customer regarding an 'inadequate' central
heating design. He has, a Victorian three floor terraced house with
toilet on the ground floor,an ensuite with an electric shower as well
as the main bathroom containing a bath and a large steam cubicle with
shower jets etc. (It's specifications state that it requires 10lpm cold
and 10lpm hot water at 1.5bar) on first floor, and a further en-suite
ont he secon floor containing a bath and an electric shower.

The newly installed Biasi 28 combi, (which states at best 12 lpm
(summertime) but more likely around 8lpm.) is required to supply the
four basins, two baths, kitchen sink and steam cubicle,

There is a 100% certainty that the three bathrooms will be frequently
used simultaneously

My suggestion... the bath and steamroom in the main bathroom should be
supplied from the cylinder, all other points around the house from the
combi. My assumptions, bathrooms will rarely be used at the same time
as the toilet and kitchen on ground floor. The bath and shower in the
main bathroom will rarely be used at the same time.

There is space on the second floor which could accomodate a cylinder
and header tank . The tank would sit about 1.6 to 1.8m above the steam
room shower head, but only 0.3m above the bath/basin in the en-suite on
the same second floor

My questions.
1. Based on the required flow rate for the steamroom shower, what size
cylinder should I recommend?

I reckon a shower is at least 50 litres, and if the HW is at +60C and the
cold ( winter ) at +5C, then a +40C shower needs to be about 2/3 hot
water, i.e. 2/3x50=34litres. Call it 100 litres for two consecutive four
minute showers, minimum.

Your shower specs may call for 10l/min hot water and 10l/min cold water,
but that is more of a desireable characteristic of the supply piping, not
necessarily what it will use in practise. Half and half hot and cold water
will give
you a cool shower, so I don't think you will exceed 15l/min total supply
to the shower head in practise.

2. Will the 1.6m head of water create sufficient pressure for the multi
headed monster steamroom shower?

The specs call for 1.5 bar, and simple maths says that your header tank will
deliver 0.16bar. Doesn't look good.

3. Should I take the cold water for the steamroom shower from the
header tank to ensure like pressures between hot and cold - or would a
pressure equalising valve be sufficent to balance cold mains water
pressure, and the cylinder fed hot water, and how efficient are they at
coping with fluctuation on e.g the cold, when someone flushes a toilet
and the runs a basin concurrently?

I'd fight shy of having cold water at mains pressure and hot at 0.16bar.
I'm sure you'll have to do something. However, as I said, will your shower
cope with hot water at 0.16 bar?

4. Based on the above, what size header tank should I recommend?


Sorry I can't suggest a decent solution, someone else out there will know
more.

Andy.

On 31 Oct 2005 05:45:10 -0800, "sparkydude"
wrote:

Hi all, first of all thanks to anyone who takes the time to read about
this problem, and more thanks to anyone who replies

Trying to give advice to a customer regarding an 'inadequate' central
heating design. He has, a Victorian three floor terraced house with
toilet on the ground floor,an ensuite with an electric shower as well
as the main bathroom containing a bath and a large steam cubicle with
shower jets etc. (It's specifications state that it requires 10lpm cold
and 10lpm hot water at 1.5bar) on first floor, and a further en-suite
ont he secon floor containing a bath and an electric shower.

The newly installed Biasi 28 combi, (which states at best 12 lpm
(summertime) but more likely around 8lpm.) is required to supply the
four basins, two baths, kitchen sink and steam cubicle,

There is a 100% certainty that the three bathrooms will be frequently
used simultaneously

My suggestion... the bath and steamroom in the main bathroom should be
supplied from the cylinder, all other points around the house from the
combi. My assumptions, bathrooms will rarely be used at the same time
as the toilet and kitchen on ground floor. The bath and shower in the
main bathroom will rarely be used at the same time.

There is space on the second floor which could accomodate a cylinder
and header tank . The tank would sit about 1.6 to 1.8m above the steam
room shower head, but only 0.3m above the bath/basin in the en-suite on
the same second floor

My questions.
1. Based on the required flow rate for the steamroom shower, what size
cylinder should I recommend?
2. Will the 1.6m head of water create sufficient pressure for the multi
headed monster steamroom shower?
3. Should I take the cold water for the steamroom shower from the
header tank to ensure like pressures between hot and cold - or would a
pressure equalising valve be sufficent to balance cold mains water
pressure, and the cylinder fed hot water, and how efficient are they at
coping with fluctuation on e.g the cold, when someone flushes a toilet
and the runs a basin concurrently?
4. Based on the above, what size header tank should I recommend?

If mains flow rate is high enough and you are going to install a
cylinder anyway then it seems like a thermal store or heatbank would
be appropriate.

Await the large flood of people recommending heatbanks and the odd
person recommending one combi for each bathroom. :-)

Mr F.

There is space on the second floor which could accomodate a cylinder
and header tank . The tank would sit about 1.6 to 1.8m above the steam
room shower head, but only 0.3m above the bath/basin in the en-suite on
the same second floor

My questions.

1. Based on the required flow rate for the steamroom shower, what size
cylinder should I recommend?

For an installation like this, I'd be looking at 180 litre plus.

2. Will the 1.6m head of water create sufficient pressure for the multi
headed monster steamroom shower?

Not a hope in hell. Not even close. You would need at least 15m to meet the
minimum spec and it would appreciate twice this.

3. Should I take the cold water for the steamroom shower from the
header tank to ensure like pressures between hot and cold - or would a
pressure equalising valve be sufficent to balance cold mains water
pressure, and the cylinder fed hot water, and how efficient are they at
coping with fluctuation on e.g the cold, when someone flushes a toilet
and the runs a basin concurrently?
4. Based on the above, what size header tank should I recommend?

Personally, I would measure the flow rate available at the house. If
sufficient, I would install a mains pressure hot water storage based system,
either a heat bank or unvented cylinder (probably the former). The combi hot
can be used solely for the kitchen. You could run one of the showers off it
too, to provide backup if the storage system is down for maintenance.

If the flow rate available from the mains is less than 40lpm or thereabouts,
I would use a gravity cylinder with pumped output, with a 50 gallon header
tank. I would feed the cold either from the header tank, or direct from
mains (if the flow is adequete, say around 30lpm) with pressure balancing
valve. Other alternatives are to replace the water mains, or to fit a very
large accumulator on the mains supply, if the static pressure is good
enough, but the flow inadequete.

Christian.

Thanks to all for replies so far. The method of adding a second combi,
I had discounted as a suggestion because I am not convinced that it
would be a 'definite' solution, there is also a lack of wall space and
a wish to keep his costs down, however this does now seems to be the
cheapest option. The heatstore/unvented cylinder option would require
a degree of knowledge/expertise/confidence that the plumber does not
posess, I believe the cylinder option I had initially been most keen on
still has merit when combined with a twin pump for both hot and cold,
from a 180+litre cylinder and a 50 gallon tank respectively and a
'traditional' plumber. Thanks everyone for your assistance - and if
you feel I'm risking my reputation by suggesting the above. Please feel
free to tell me so.

Thanks to all for replies so far. The method of adding a second combi,
I had discounted as a suggestion because I am not convinced that it
would be a 'definite' solution,

Rightly so. Remember the drencher shower requires 10 lpm HOT water, not 40C
tepid. If it wants it at 60C, that is equivalent to a combi claiming 16
litres per minute. That leaves nothing left for additional showers or hot
taps. So you would need to find a 45kW combi to run it, or find a way of
reliably combining the outputs of two smaller combis.

Quite frankly, if you can't install a heat bank, then you shouldn't claim to
be a plumber. They require you to plumbing in the cold mains input, the hot
mains output and the indirect coil in just the same way as any other
cylinder. Any plumber who couldn't do this would not be allowed past my
door.

Christian.

"Christian McArdle" wrote in message
. net...
There is space on the second floor which could accomodate a cylinder
and header tank . The tank would sit about 1.6 to 1.8m above the steam
room shower head, but only 0.3m above the bath/basin in the en-suite on
the same second floor

My questions.

1. Based on the required flow rate for the steamroom shower, what size
cylinder should I recommend?

For an installation like this, I'd be looking at 180 litre plus.

2. Will the 1.6m head of water create sufficient pressure for the multi
headed monster steamroom shower?

Not a hope in hell. Not even close. You would need at least 15m to meet
the
minimum spec and it would appreciate twice this.

3. Should I take the cold water for the steamroom shower from the
header tank to ensure like pressures between hot and cold - or would a
pressure equalising valve be sufficent to balance cold mains water
pressure, and the cylinder fed hot water, and how efficient are they at
coping with fluctuation on e.g the cold, when someone flushes a toilet
and the runs a basin concurrently?
4. Based on the above, what size header tank should I recommend?

Personally, I would measure the flow rate available at the house. If
sufficient, I would install a mains pressure hot water storage based
system,
either a heat bank or unvented cylinder (probably the former). The combi
hot
can be used solely for the kitchen. You could run one of the showers off
it
too, to provide backup if the storage system is down for maintenance.

If the flow rate available from the mains is less than 40lpm or
thereabouts,
I would use a gravity cylinder with pumped output, with a 50 gallon header
tank. I would feed the cold either from the header tank, or direct from
mains (if the flow is adequete, say around 30lpm) with pressure balancing
valve. Other alternatives are to replace the water mains, or to fit a very
large accumulator on the mains supply, if the static pressure is good
enough, but the flow inadequete.

Best go for a heat bank and have the combi do the kitchen and one shower.
The mains supply should be tested and replaced as suggested. Also take a
22mm cold feed pipe from stopcock to the heat bank. At the stopcock run
another pipe just to the cold outlets. The cold supply for the showers take
off just before the heat bank.

Another suggestion is supplement the combi boiler with a 75kW MAN Micromat
combi boiler which will deliver about 30 litres/min, plus the 10-12
litres/min of the BIASI. The MAN is not cheap though, but v good. You will
need the next size up gas meter fitted for the MAN.