I am thinking of a loft conversion and wondering if I should upgrade to
an Unvented system. However house heating layout is non standard. We
have goundfloor underfloor heating (Nuheat) and first floor radiator
Happy with both and would prefer adding radiators to loft conversion (2
x bedrooms with ensuite). Currently have recently fitted Baxi 100HE
boiler and standard imersion tank running off gravity fed loft headers.
Underfloor can be converted I know, but what is needed to convert the
rest ?

wrote:
I am thinking of a loft conversion and wondering if I should upgrade to
an Unvented system. However house heating layout is non standard. We
have goundfloor underfloor heating (Nuheat) and first floor radiator
Happy with both and would prefer adding radiators to loft conversion (2
x bedrooms with ensuite). Currently have recently fitted Baxi 100HE
boiler and standard imersion tank running off gravity fed loft headers.
Underfloor can be converted I know, but what is needed to convert the
rest ?

the word you're looking for is 'downgrade', theyre not as reliable.

NT

On Mon, 29 May 2006 08:58:42 -0700, lloydwatkins wrote:

I am thinking of a loft conversion and wondering if I should upgrade to
an Unvented system. However house heating layout is non standard. We
have goundfloor underfloor heating (Nuheat) and first floor radiator
Happy with both and would prefer adding radiators to loft conversion (2
x bedrooms with ensuite). Currently have recently fitted Baxi 100HE
boiler and standard imersion tank running off gravity fed loft headers.
Underfloor can be converted I know, but what is needed to convert the
rest ?

See the Sealed CH FAQ.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

wrote in message
oups.com...
I am thinking of a loft conversion and wondering if I should upgrade to
an Unvented system. However house heating layout is non standard. We
have goundfloor underfloor heating (Nuheat) and first floor radiator
Happy with both and would prefer adding radiators to loft conversion (2
x bedrooms with ensuite). Currently have recently fitted Baxi 100HE
boiler and standard imersion tank running off gravity fed loft headers.
Underfloor can be converted I know, but what is needed to convert the
rest ?

Ignore the unvented cylinder and use a thermal store/heat bank. The thermal
store is ideal to have mains pressure DHW, rads and UFH run off it. See
http://www.heatweb.com This will fill you in. I am not saying use this
company, but they do explain it well.

What an unvented cylinder can do:
http://www.waterheaterblast.com

"Ed Sirett" wrote in message
news
On Mon, 29 May 2006 08:58:42 -0700, lloydwatkins wrote:

I am thinking of a loft conversion and wondering if I should upgrade to
an Unvented system. However house heating layout is non standard. We
have goundfloor underfloor heating (Nuheat) and first floor radiator
Happy with both and would prefer adding radiators to loft conversion (2
x bedrooms with ensuite). Currently have recently fitted Baxi 100HE
boiler and standard imersion tank running off gravity fed loft headers.
Underfloor can be converted I know, but what is needed to convert the
rest ?

See the Sealed CH FAQ.

That is for CH systems not unvented cylinders.

Perhaps DD can answer this. Boiler is on ground floor in attached
garage (loads of space around it). Hot water tank is in airing
cupboard on first floor (space also available). Need to run 3 showers
at same time (teenaged daughters as well as us). 2 showers will be in
converted loft, almost above current airing cupboard, so access no
problem, loft also heated by radiators. Will a heat store serve this
layout well ? Will I need the expansion tank to be in loft ? Heatweb
didn't quite cover this with their otherwise excellent site.

LHW

I am thinking of a loft conversion and wondering if I should upgrade to
an Unvented system.

You've got two issues here.

Firstly, you want sealed pressurised operation of the primary heating
circuit, so that you can have radiators on the top floor. Secondly, you may
want mains pressure operation of the domestic hot water (from the taps) so
you can have an en-suite shower or such like.

In most cases, it is simple to convert a gravity primary circuit to sealed
pressurised operation. The main thing to check is that the boiler is
certified for such operation. If so, a simple and cheap kit of parts and
removal of the header tank is all that is required. Occasionally you will
get leaks on corroded radiator connections or pipework when the pressure
increases. If so, it would soon have expired anyway and at least you've got
a plumber on site to fix the leaks.

If you also need hot water on the loft floor, your choices a

1. Point of use electric heaters. Ideal if you want the minimum of
disruption to your system. They also reduce dead leg problems. However, if a
shower is desired, you do have to put up with electric shower performance
which is low.

2. Negative head pump. Simplest to install, as it doesn't affect the
existing system. However, they can be noisy and inconvenient (some designs
require you to pull a cord after turning on the tap).

3. Unvented cylinder. Provides mains pressure water. Efficient to use, as
you can run the boiler at a lower temperature. However, they require annual
safety inspections due to the large quantity of pressurised hot water.

4. Heat bank. Also provides mains pressure water. Less efficient, as you
need to turn your boiler temp right up. However, has much higher fundamental
safety, as the hot water storage itself is vented.

5. Combi boiler. If you are replacing the boiler anyway, you could install a
combi boiler that provides instantaneous mains pressure hot water. If you
also have additional bathrooms or you prefer soaking in the bath, an
instantaneous combi may be too small, so an alternative is to keep your
existing hot water cylinder for the main bathroom and use the combi to
supply the new loft extension, where it will be ideal for showers.

Christian.

On Tue, 30 May 2006 12:39:19 +0100, wrote
(in article .com):

Boiler is on ground floor in attached
garage (loads of space around it). Hot water tank is in airing
cupboard on first floor (space also available). Need to run 3 showers
at same time (teenaged daughters as well as us). 2 showers will be in
converted loft, almost above current airing cupboard, so access no
problem, loft also heated by radiators. Will a heat store serve this
layout well ? Will I need the expansion tank to be in loft ? Heatweb
didn't quite cover this with their otherwise excellent site.

LHW


You can get a heatbank (e.g. DPS Pandora) with an expansion vessel in the
top. Other types have a small header tank.

In effect, you have three lots of water.

- The primary, which circulates though boiler, radiators and a coil in the
heatbank can be sealed or open vented.

- Secondary, which is the bulk water in the heatbank. This is heated via
the coil. It is pumped through a plate heat exchanger when hot water is
used.

- Mains water through plate heat exchanger is heated by the secondary water
and delivered to showers and taps.


A heatbank of this design can be positioned at any height and there is no
need for any kind of roof tank.

Direct heatbanks where the bulk water of the cylinder becomes part of the
heating circuit obviously have more restrictions on positioning because they
are open vented.

The main things to watch is adequacy of the cold mains supply and the
capacity of the store.

A decent shower requires 15 litres per minute of warm water at 40 degrees.
Three showers will require 45 litres/min and the mains has to deliver it all.
This may be a struggle and may require an upgrade to the service pipe
from the road. Do check before committing yourself.

Ask the females how long they want the shower to run. Many like to wash
their hair and take 15-20 mins to do so. Calculate back how much hot
water that will be in the winter when the mains is at 5 degrees. I suspect
that you would need at least a 250 - 300 litre store.

Andy Hall wrote:

Ask the females how long they want the shower to run. Many like to wash
their hair and take 15-20 mins to do so. Calculate back how much hot
water that will be in the winter when the mains is at 5 degrees. I suspect
that you would need at least a 250 - 300 litre store.



There are only two of us and a 750 liter sealed pressurised tank. We run
out of how water quite regularly. It just takes one person to leave a
hot tap dribbling, and the other to take a bath up to the overflow
(regular occurrences) and there is bugger all left to wash the dogs paws in.

IMHO there is no such thing as too large a hot water tank, especially if
it can bi sited inside the insulation of the house, where any heatloss
is a net gain to the house..

"The Natural Philosopher" wrote in message
...
Andy Hall wrote:

Ask the females how long they want the shower to run. Many like to wash
their hair and take 15-20 mins to do so. Calculate back how much hot
water that will be in the winter when the mains is at 5 degrees. I
suspect that you would need at least a 250 - 300 litre store.



There are only two of us and a 750 liter sealed pressurised tank. We run
out of how water quite regularly. It just takes one person to leave a hot
tap dribbling, and the other to take a bath up to the overflow (regular
occurrences) and there is bugger all left to wash the dogs paws in.

IMHO there is no such thing as too large a hot water tank, especially if
it can bi sited inside the insulation of the house, where any heatloss is
a net gain to the house..

A decent sized boiler with a priority system (all the boilers output goes to
the cylinder) will virtually eliminate this. With a heat bank using a
blending valve ob the Flow and Return only 75C water goes into the top of
the cylinder and this is used directly to heat DHW.

There are only two of us and a 750 liter sealed pressurised tank. We run
out of how water quite regularly. It just takes one person to leave a
hot tap dribbling, and the other to take a bath up to the overflow
(regular occurrences) and there is bugger all left to wash the dogs paws
in.

Something is going wrong here. My 180 litre heatbank will do two baths even
with the boiler turned off. The boiler could easily keep up with a running
tap, too. 750 litres should do 5 baths even with no boiler.

Christian.

Christian McArdle wrote:
There are only two of us and a 750 liter sealed pressurised tank. We run
out of how water quite regularly. It just takes one person to leave a
hot tap dribbling, and the other to take a bath up to the overflow
(regular occurrences) and there is bugger all left to wash the dogs paws
in.

Something is going wrong here. My 180 litre heatbank will do two baths even
with the boiler turned off. The boiler could easily keep up with a running
tap, too. 750 litres should do 5 baths even with no boiler.


That's not a BATH. That's a PUDDLE. I reckon on 500 liters for a good
soak ;-)


And we don't have the boiler running permanently - its on a timer..so
dribbling taps will cause the tank to empty..

Christian.

Something is going wrong here. My 180 litre heatbank will do two baths
even
with the boiler turned off. The boiler could easily keep up with a
running
tap, too. 750 litres should do 5 baths even with no boiler.

That's not a BATH. That's a PUDDLE. I reckon on 500 liters for a good
soak ;-)

It's stored at 75C+, so will realistically provide 40C water for about 300
litres.

Nice to see you're doing your bit in the drought, anyway. ;-)

Christian.

"Christian McArdle" wrote in message
...
There are only two of us and a 750 liter sealed pressurised tank. We run
out of how water quite regularly. It just takes one person to leave a
hot tap dribbling, and the other to take a bath up to the overflow
(regular occurrences) and there is bugger all left to wash the dogs paws
in.

Something is going wrong here. My 180 litre heatbank will do two baths
even
with the boiler turned off. The boiler could easily keep up with a running
tap, too. 750 litres should do 5 baths even with no boiler.

Christian.

Say, price up a 300 litre thermal store. It gives x baths/showers. It may
be borderline or just too small, so 450 litres is required. Maybe too big
for the cupboard/heavy for floor and more expensive too.

By arranging the pipework so that the hot bathtaps and shower lines are on a
flow switch, the boiler can come in immediately on a priority setup (the
boiler heats only the hot water). The flow switch will override the normal
cylinder stat(s). For about a £30 flow switch a lot can be saved in thermal
store/heat bank costs and most likely you will not run out of hot water too.
This combines the energy of the boiler and the cylinder.

For normal operation on the other taps, the heat bank works off the normal
cylinder stat(s)

By arranging the pipework so that the hot bathtaps and shower lines are on
a
flow switch, the boiler can come in immediately on a priority setup (the
boiler heats only the hot water). The flow switch will override the
normal
cylinder stat(s). For about a £30 flow switch a lot can be saved in
thermal
store/heat bank costs and most likely you will not run out of hot water
too.

In actuality, I find the standard thermostat comes on within seconds of a
substantial draw anyway, so I'm doubtful of the benefit of logic to fire up
the boiler immediately.

Also, even if you decided to implement it, a relay would be a cheaper way,
as a flow switch is already in system. Wiring it up would introduce the
potential for accidentally overheating the store, too.

Christian.

"Christian McArdle" wrote in message
...
By arranging the pipework so that the hot bathtaps and shower lines are
on
a
flow switch, the boiler can come in
immediately on a priority setup (the
boiler heats only the hot water).
The flow switch will override the
normal cylinder stat(s). For about
a £30 flow switch a lot can be saved in
thermal store/heat bank costs and most
likely you will not run out of hot water
too.

In actuality, I find the standard thermostat
comes on within seconds of a substantial
draw anyway, so I'm doubtful of the benefit
of logic to fire up the boiler immediately.

15 to 20% of the hot waer may have gone by then. Also when having two stats
to prevent boiler anti-cycling the flow switch on the bathtaps/showers is
necessary.

Also, even if you decided to implement it,
a relay would be a cheaper way,
as a flow switch is already in system.

That will bring in the boiler if there is any flow, as would a combi. Having
a flow switch on the bathtap/shower lines only, ensures that the boiler
fires up when with large DHW draw-offs.

Wiring it up would introduce the
potential for accidentally overheating the store, too.

You could always have a high limit stat set to 90-95C. In reality if there
is a draw-off of DHW it will not overheat as enough cold water is being
introduced. A 30kW boiler will give one good shower, so in reality the DHW
temp will stay the same, at worst just above the cylinder temp setpoint.

"The Natural Philosopher" wrote in message
...
Christian McArdle wrote:
There are only two of us and a 750 liter sealed pressurised tank. We run
out of how water quite regularly. It just takes one person to leave a
hot tap dribbling, and the other to take a bath up to the overflow
(regular occurrences) and there is bugger all left to wash the dogs paws
in.

Something is going wrong here. My 180 litre heatbank will do two baths
even
with the boiler turned off. The boiler could easily keep up with a
running
tap, too. 750 litres should do 5 baths even with no boiler.


That's not a BATH. That's a PUDDLE. I reckon on 500 liters for a good soak
;-)

500 liters(sic)? That's half a tonne of water at 40degC (minimum) for a
'good soak'.

What are the dimensions of your 'good soak' device?
500 litres would be 'water' - not extranl bath dimensions- of two metres
(long) by one metre (wide)by half-a-metre (deep). That's some bath! Can you
cite the make and model number? Are you one metre wide?

"Standard" baths appear to be 1.7m x .7m x.5m.

And we don't have the boiler running permanently - its on a timer..so
dribbling taps will cause the tank to empty..


One presumes you're not using a water meter - which company provides water
to your establishment (where you aren't concerned about a dripping tap
wasting three quarters of a tonne of water into the drains overnight -
(dribbling taps will cause the tank to empty)?

--

Brian

wrote in message
oups.com...
I am thinking of a loft conversion and wondering if I should upgrade to
an Unvented system. However house heating layout is non standard. We
have goundfloor underfloor heating (Nuheat) and first floor radiator
Happy with both and would prefer adding radiators to loft conversion (2
x bedrooms with ensuite). Currently have recently fitted Baxi 100HE
boiler and standard imersion tank running off gravity fed loft headers.
Underfloor can be converted I know, but what is needed to convert the
rest ?
Why not just extended and move the tanks into area not used by conversion?
my brother did for his loft conversion. Move CH header tank into space above
loft stair well to be above the radiators and HW feed tank elsewhere. Fitted
a negative head shower pump for the ensuite shower in the loft and all works
fine without having to change any plumbing in the house.

Why not just extended and move the tanks into area not used by conversion?
my brother did for his loft conversion. Move CH header tank into space
above
loft stair well to be above the radiators and HW feed tank elsewhere.
Fitted
a negative head shower pump for the ensuite shower in the loft and all
works
fine without having to change any plumbing in the house.

However, it can be good use of space to use the overstairs area for the
heatbank. This is what I have done. The airing cupboard downstairs was
seriously biting into the space for the 3rd bedroom, so the loft was the
best place for it. The 3rd bedroom is now quite usable.

The cold tanks were in the rear loft, which is my only remaining storage
area, so needed the tanks removed.

Christian.

wrote in message ...
On 30 May,
"Christian McArdle" wrote:

There are only two of us and a 750 liter sealed pressurised tank. We
run
out of how water quite regularly. It just takes one person to leave a
hot tap dribbling, and the other to take a bath up to the overflow
(regular occurrences) and there is bugger all left to wash the dogs
paws
in.

Something is going wrong here. My 180 litre heatbank will do two baths
even
with the boiler turned off. The boiler could easily keep up with a
running
tap, too. 750 litres should do 5 baths even with no boiler.

We only have a compact cylinder
(Albion CF45) and with only a 12KW boiler it
will give baths every 20 minutes, so with
normal time spent in bath, continuous bathing
is possible. I can't imagine needing 750L unless it's the
football team's communal bath.

I think the CF45 is a quick recovery cylinder. I don't know how your system
is setup, but if you have a priority system, so that the boiler sends all
its heat to the cylinder, and install a blending valve on the DHW draw-off,
and the up the storage temp to 70-80C, you will find that the little
cylinder will perform no problem at all and give bath after bath. It will
also give a nice long shower too. If you had a 25kW and above boiler, it
will perform even better, as the larger boiler pumps in heat as you are
extracting it. Combines the energy of the cylinder and the boiler. Using a
probe cylidner stat is better as the stat reacts faster and brings in the
boiler quicker.