Complete new CH or just new boiler
 

Background:
We live in a 3 bedroom house-on-a-hill. From the front it looks like a
bungalow. Once inside you go downstairs to the bedrooms. The (non
combi) boiler is in the garage on the front. The hot water tank is
downstairs in the airing cupboard (pumping hot water downstairs against
convection, hmm who thought of that one!). There is a header tank in
the loft. The CH radiators are all on Microbore pipe. In the 6 months
we have lived there the CH top up tank has required about 2-4 litres of
water to top it up.
We had a combi boiler fitted in our last house (non condensing £1000).
Running a bath took long enough to undress our toddler and clean his
teeth and get him ready for bed, just about acceptable, certainly not
quick. Showers were great with a very good flow and pressure, enough to
make you want to stay in there longer.

Situation:
We want to extend into the loft and so need to lose the header tank.
We intend to have a bedroom, nursery and shower room in the loft as well
as a sizable landing (there's plenty of space due to the layout of the
house).

I've been told that microbore pipes and combi boilers don't mix.
Is this true?
I've also been told that if your system leaks a combi boiler will make
it worse because of the pressure. (Remember its needed toping up already!)
I would imagine the plumber who fits the new radiators in the loft may
want to avoid using microbore and so we would have both standard and
microbore radiators. Is this an issue?
I have no idea how much it would cost to replace all the existing CH
pipes (floor boards not sheets, at least in some rooms, no concrete
floors afaict) and radiators (3 bedrooms, kitchen, dining, lounge, hall,
lower floor hall, bathroom and washroom (10 rad in total) and whether
this would be a better solution than using the existing microbore.
There will be a plumber coming in to add new rad.s to the loft anyway.
Existing CH and boiler is original fitted in 1992 when house was built.

Things never seem to be simple though.

ATM my understanding is our DHW comes from the hot water tank in the
airing cupboard downstairs (there's also a pressure vessel in there too,
not sure what for though).

Siting the new boiler in the place of the old bolier in the garage puts
it just the other side of the garage wall to the kitchen sink. The
exiting bathroom is directly below that and the new shower room will be
just above and to the back of the house so the pipe runs to the majority
of the taps from the boiler will be short. (Our main gripe with the
combi boiler in the old house was that it took ages to get any hot water
through and then if you were just rinsing the pots you had to leave the
tap running at a fair lick in order for the water not to go cold which
it would do if you turned the tap off.)
The current hot water pipes from the boiler go to the airing cupboard
and the DHW pipes come back from there. It seems silly to send the
water half way round the house so we are intending drilling through the
garage wall into the space where the washing machine currently is in the
kitchen and connecting the DHW feed from the new boiler to the end of
those pipes. I'm presuming all the DHW taps are on branches off one run
from the exisitng hot water tank so capping of the other end at the hot
water tank (with a drain plug) will mean we still get hot water to the
all the taps.

For the CH we were going to try and locate the existing loop and break
into it as close to the new boiler as possible and close the loop in the
airing cupboard where the hw tank is.

My questions a

Does the above sound feasible? (IE are there any glaringly obvious
mistakes I've made or things I've overlooked.?)

Are there issues with microbore pipes for CH?

Can you mix micro bore and standard piping in one CH system?

Considering the minimum job for the loft will be addition of 4
radiators, new boiler and the plumbing to (re)move the HW tank from
downstairs would replacing our existing 10 radiators on micro bore with
new radiators on standard pipe add significantly to the price (+10%?,
+50%?, double? triple?)???

Where is a good place to start looking on the net for prices for
boilers/rads etc.

We will then have the possibility of using 2 showers at the same time
(one a floor up from the boiler and one a floor down from the boiler if
than makes any difference). I'm presuming some sort of HW storage tank
(as opposed to a combi) will be required to allow both to be used
together. Is this the case (most "Combi yes/no?" threads so far have
only concerned one shower being used. Could a combi and mini tank be
used or would the best idea be to go for a mains pressure storage tank
solution?
As the back half of our garage has been converted to a store room there
is not a space issue with putting a hot water tank in there with the
boiler but I'd prefer it to be compact as possible.

If I was to redo the exising pipes and radiators myself what's the best
way of getting the pipes laid when their direction is across the joists?
(I want to minimise pulling up the floor. My intention would be to
use copper pipes from the radiators into the under floor space and
plastic pipes to link these as I've been lead to believe that the
plastic pipes are easier to work with.

Any comments appreciated.

Chris.

PS Apologies for the long post (as the bishop said to the actress)

"ChrisJ" wrote
| I've also been told that if your system leaks a combi boiler
| will make it worse because of the pressure. (Remember its needed
| toping up already!)

If by 'combi boiler' you actually mean sealed pressurised radiator (primary)
loop, then the *advantage* of this is that if there is a leak, the amount of
water in the system is limited. With a header tank (fed by mains from a
ballcock) the amount of water is unlimited.

| ATM my understanding is our DHW comes from the hot water tank in the
| airing cupboard downstairs (there's also a pressure vessel in there
| too, not sure what for though).

But from where does the cold water come from for the hot. From the "header
tank" or is the hot water tank (cylinder) actually a mains pressure hot
water system?

| Does the above sound feasible? (IE are there any glaringly obvious
| mistakes I've made or things I've overlooked.?)

It sounds like you don't want a combi, so you don't need a new boiler. You
need a pressurised primary system and a mains pressure hot water system.

| Are there issues with microbore pipes for CH?
| Can you mix micro bore and standard piping in one CH system?

No and yes.

| We will then have the possibility of using 2 showers at the same time
| (one a floor up from the boiler and one a floor down from the boiler if
| than makes any difference). I'm presuming some sort of HW storage tank
| (as opposed to a combi) will be required to allow both to be used
| together. Is this the case (most "Combi yes/no?" threads so far have
| only concerned one shower being used. Could a combi and mini tank be
| used or would the best idea be to go for a mains pressure storage tank
| solution?

Mains pressure, I think. Remember you do have the option of having some
taps/shower on the 'hot water' part of the combi, and a conventional hot
water cylinder powered by the 'radiator' part of the combi.

| As the back half of our garage has been converted to a store room there
| is not a space issue with putting a hot water tank in there with the
| boiler but I'd prefer it to be compact as possible.

As you will be taking a 2 storey to a 3 storey building you may be subject
to additional fire precautions with your loft conversion. I say "may"
because with a middle-floor ground level you may be able to plead exemption.

You can avoid the hot water taking ages to reach the taps by taking a loop
back from the far end taps to the cylinder and putting in a circulation
pump. With insulated pipes and the pump on a timer for peak use periods
only, there should not be significant energy loss.

Thermostatic blending valves below all the hot taps except the kitchen may
save accidents.

With 3 storeys you might want to put some cabling in for a home intercom
system.

Owain

In an earlier contribution to this discussion,
ChrisJ chris@youmustbekiddingifyouthinkimusingarealaddre ss.com wrote:

Background:
We live in a 3 bedroom house-on-a-hill. From the front it looks like
a bungalow. Once inside you go downstairs to the bedrooms. The (non
combi) boiler is in the garage on the front. The hot water tank is
downstairs in the airing cupboard (pumping hot water downstairs
against convection, hmm who thought of that one!). There is a header
tank in
the loft. The CH radiators are all on Microbore pipe. In the 6
months we have lived there the CH top up tank has required about 2-4
litres of water to top it up.
We had a combi boiler fitted in our last house (non condensing
£1000). Running a bath took long enough to undress our toddler and
clean his teeth and get him ready for bed, just about acceptable,
certainly not quick. Showers were great with a very good flow and
pressure, enough to make you want to stay in there longer.

Situation:
We want to extend into the loft and so need to lose the header tank.
We intend to have a bedroom, nursery and shower room in the loft as
well as a sizable landing (there's plenty of space due to the layout
of the house).

I've been told that microbore pipes and combi boilers don't mix.
Is this true?
I've also been told that if your system leaks a combi boiler will make
it worse because of the pressure. (Remember its needed toping up
already!) I would imagine the plumber who fits the new radiators in
the loft may want to avoid using microbore and so we would have both
standard and microbore radiators. Is this an issue?
I have no idea how much it would cost to replace all the existing CH
pipes (floor boards not sheets, at least in some rooms, no concrete
floors afaict) and radiators (3 bedrooms, kitchen, dining, lounge,
hall, lower floor hall, bathroom and washroom (10 rad in total) and
whether this would be a better solution than using the existing
microbore.
There will be a plumber coming in to add new rad.s to the loft anyway.
Existing CH and boiler is original fitted in 1992 when house was
built.

Things never seem to be simple though.

ATM my understanding is our DHW comes from the hot water tank in the
airing cupboard downstairs (there's also a pressure vessel in there
too, not sure what for though).

Siting the new boiler in the place of the old bolier in the garage
puts it just the other side of the garage wall to the kitchen sink.
The exiting bathroom is directly below that and the new shower room
will be just above and to the back of the house so the pipe runs to
the majority of the taps from the boiler will be short. (Our main
gripe with the combi boiler in the old house was that it took ages to
get any hot water through and then if you were just rinsing the pots
you had to leave the tap running at a fair lick in order for the
water not to go cold which
it would do if you turned the tap off.)
The current hot water pipes from the boiler go to the airing cupboard
and the DHW pipes come back from there. It seems silly to send the
water half way round the house so we are intending drilling through
the garage wall into the space where the washing machine currently is
in the kitchen and connecting the DHW feed from the new boiler to the
end of those pipes. I'm presuming all the DHW taps are on branches
off one run from the exisitng hot water tank so capping of the other
end at the hot water tank (with a drain plug) will mean we still get
hot water to the all the taps.

For the CH we were going to try and locate the existing loop and break
into it as close to the new boiler as possible and close the loop in
the airing cupboard where the hw tank is.

My questions a

Does the above sound feasible? (IE are there any glaringly obvious
mistakes I've made or things I've overlooked.?)

Are there issues with microbore pipes for CH?

Can you mix micro bore and standard piping in one CH system?

Considering the minimum job for the loft will be addition of 4
radiators, new boiler and the plumbing to (re)move the HW tank from
downstairs would replacing our existing 10 radiators on micro bore
with new radiators on standard pipe add significantly to the price
(+10%?, +50%?, double? triple?)???

Where is a good place to start looking on the net for prices for
boilers/rads etc.

We will then have the possibility of using 2 showers at the same time
(one a floor up from the boiler and one a floor down from the boiler
if than makes any difference). I'm presuming some sort of HW storage
tank (as opposed to a combi) will be required to allow both to be used
together. Is this the case (most "Combi yes/no?" threads so far have
only concerned one shower being used. Could a combi and mini tank be
used or would the best idea be to go for a mains pressure storage tank
solution?
As the back half of our garage has been converted to a store room
there is not a space issue with putting a hot water tank in there
with the boiler but I'd prefer it to be compact as possible.

If I was to redo the exising pipes and radiators myself what's the
best way of getting the pipes laid when their direction is across the
joists? (I want to minimise pulling up the floor. My intention
would be to
use copper pipes from the radiators into the under floor space and
plastic pipes to link these as I've been lead to believe that the
plastic pipes are easier to work with.

Any comments appreciated.

Chris.

PS Apologies for the long post (as the bishop said to the actress)



I'm struggling a bit to understand your current setup! You mention a header
tank in the attic. I assume that this is a large tank (50 gallons or so)
acting as the header tank for the hot water supply?

You also mention a top-up tank for the heating. Is this the *same* tank, or
are there two? If separate, how big is it, and where is it? You also mention
a pressure vessel. I am confused about this, because if the primary circuit
(i.e. the "sealed" circuit taking water from the boiler to the indirect coil
in the hot water cylinder and to the radiators) is non-vented (pressurised),
there won't be a top-up tank - but there will be a filling loop and pressure
gauge instead.

As I see it, you need, in addition to your existing requirements:

* Extra radiators in the attic at a height equal to or greater than your
existing primary circuit header tank (if any!). This means in my view that
the primary circuit will *have* to be pressurised.

* Hot water delivered to the attic for the new shower/washbasin. Whilst your
existing hot water flow is gravity driven from the header tank in the attic,
your new shower/washbasin cannot be gravity fed without raising this header
tank above roof level!

You thus need a mains pressure hot water system for your upstairs
requirements. There are three and a half possible ways of achieving this:
1. Replace the existing conventional boiler with a combi, and use it for all
your hot water requirements. This is a BAD solution - particularly if you
want to use both showers at the same time, or have lots of baths.
2A. Install a mains pressure hot water system, still heated by a (new or
existing) conventional boiler. This is fine as long as you've got adequate
mains pressure/flow - but needs expert installation because you'll have a
*lot* of hot water at high pressure.
2B. Install a heat-bank, heated by a conventional boiler - and obtain
instant mains-pressure hot water via a plate heat exchanger. Almost as good,
and can be DIY'd.
3. Install a combi boiler, but retain your existing stored hot water system.
Let the HW side of the combi provide just *part* of your hot water
requirements - I would suggest the kitchen sink and the new upstairs shower.
"Zone" the CH side of the combi so that it heats both the radiators *and*
the hot water cylinder. Use the hot water from the cylinder for the
downstairs bathroom/shower. You will still need a header tank for the hot
water, of course. You'll have lashings of hot water for baths, and no
problems running 2 showers at once because one will be using the stored hot
water and the other will use instant mains pressure hot water from the
combi.

I think 3 would be my preferred solution - but you'll still have to find
somewhere for the header tank. [Actually, you could go for a combination of
2B and 3 - getting the combi to heat the heat bank. You wouldn't then need a
header tank.]

I haven't attempted to answer the questions about micro-bore and pipe runs -
lets get the basic principles established first!
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

On Tue, 14 Sep 2004 16:42:09 +0100, ChrisJ
chris@youmustbekiddingifyouthinkimusingarealaddre ss.com wrote:

Background:
We live in a 3 bedroom house-on-a-hill. From the front it looks like a
bungalow. Once inside you go downstairs to the bedrooms. The (non
combi) boiler is in the garage on the front. The hot water tank is
downstairs in the airing cupboard (pumping hot water downstairs against
convection, hmm who thought of that one!). There is a header tank in
the loft. The CH radiators are all on Microbore pipe. In the 6 months
we have lived there the CH top up tank has required about 2-4 litres of
water to top it up.
We had a combi boiler fitted in our last house (non condensing £1000).
Running a bath took long enough to undress our toddler and clean his
teeth and get him ready for bed, just about acceptable, certainly not
quick. Showers were great with a very good flow and pressure, enough to
make you want to stay in there longer.

Situation:
We want to extend into the loft and so need to lose the header tank.
We intend to have a bedroom, nursery and shower room in the loft as well
as a sizable landing (there's plenty of space due to the layout of the
house).

I've been told that microbore pipes and combi boilers don't mix.
Is this true?

Old wive's tale. With respect to the heating system, a combi
boiler is not really any different to a system boiler.
Microbore pipe is a form of pipe - there is nothing magic about it
either positively or negatively. What you do have to do, and should
do with any system design is to make sure that the bore of pipe used
is adequate to support the water flow rate required for each radiator.
If you look at the web site of the Copper Development Association,
there is a downloadable paper on how to calculate this.
Where 15mm pipe is used, it is possible to get away with some degree
of murder in that a reasonable length will support flow for about 6kW
of radiators. Similar lengths of microbore will support 1-2.5kW
which is normally one radiator. It is why microbore systems are
often done with manifolds but there is nothing to mandate that.
If an installing firm is giving you stories about microbore, it either
means that they don't know how to calculate for it or can't be
bothered. Either is a flag to consider shopping elsewhere.


I've also been told that if your system leaks a combi boiler will make
it worse because of the pressure. (Remember its needed toping up already!)

Not exactly. it's more a function of the primary radiator circuit
being sealed and pressurised. Mainly combis are used on sealed
systems, but this is a separate issue.

If the system has old radiator valves, it is worth changing them for
good new ones like Pegler, anyway. Then with competent plumbing, you
won't have leaks.

In any case if you do, the situation is better than with open vented
systems because the volume of water is limited.


I would imagine the plumber who fits the new radiators in the loft may
want to avoid using microbore and so we would have both standard and
microbore radiators. Is this an issue?

No it isn't, but there is no reason not to use microbore. If the
space needs a lot of heat (i.e. 2.5kW or so) then it mivht imply two
radiators, but that's probably a good idea for heat distribution
anyway.

If you add radiators using 15mm and the rest of the system is
microbore, then in order to balance it, you will need to turn down the
lockshield valve on the new radiator(s) so that the flow becomes
comparable to microbore anyway - somewhat defeats the object.


I have no idea how much it would cost to replace all the existing CH
pipes (floor boards not sheets, at least in some rooms, no concrete
floors afaict) and radiators (3 bedrooms, kitchen, dining, lounge, hall,
lower floor hall, bathroom and washroom (10 rad in total) and whether
this would be a better solution than using the existing microbore.

If the radiators are in good condition, there is absolutely no need to
replace them or the pipework. If the plumber is leading you on this
path, you are being taken for a ride.

It certainly does make sense to give the system a good clean by either
emptying and taking the radiators outside for a good flush, or by
using a powerflush machine. Don't get suckered into paying multiple
hundreds for this service - you can rent the machine and DIY it quite
cheaply.



There will be a plumber coming in to add new rad.s to the loft anyway.
Existing CH and boiler is original fitted in 1992 when house was built.

Things never seem to be simple though.

ATM my understanding is our DHW comes from the hot water tank in the
airing cupboard downstairs (there's also a pressure vessel in there too,
not sure what for though).

Is there a large and a small tank in the loft? If just a small one,
then it means that your HW system is pressurised.
Unless you go for a very large combi with production rate of at least
15litres per minute, you are going to get inferior results to it.
In that scenario, with young kids, I would try to keep the cylinder.
You could go for a combi to supply the kitchen requirements perhaps
and keep the cylinder to rapidly fill the bath and give good showers.


Otherwise, if you have a large tank, then the implication is that the
primary circuit is sealed already.


Siting the new boiler in the place of the old bolier in the garage puts
it just the other side of the garage wall to the kitchen sink. The
exiting bathroom is directly below that and the new shower room will be
just above and to the back of the house so the pipe runs to the majority
of the taps from the boiler will be short. (Our main gripe with the
combi boiler in the old house was that it took ages to get any hot water
through and then if you were just rinsing the pots you had to leave the
tap running at a fair lick in order for the water not to go cold which
it would do if you turned the tap off.)
The current hot water pipes from the boiler go to the airing cupboard
and the DHW pipes come back from there. It seems silly to send the
water half way round the house so we are intending drilling through the
garage wall into the space where the washing machine currently is in the
kitchen and connecting the DHW feed from the new boiler to the end of
those pipes. I'm presuming all the DHW taps are on branches off one run
from the exisitng hot water tank so capping of the other end at the hot
water tank (with a drain plug) will mean we still get hot water to the
all the taps.

This is reasonable as long as you make sure you insulate the pipes in
the garage.



For the CH we were going to try and locate the existing loop and break
into it as close to the new boiler as possible and close the loop in the
airing cupboard where the hw tank is.

My questions a

Does the above sound feasible? (IE are there any glaringly obvious
mistakes I've made or things I've overlooked.?)

Yes, although I would check into what you have as a cylinder. If it's
pressurised and you have the space, I would keep it.


Are there issues with microbore pipes for CH?

None apart from those mentioned.


Can you mix micro bore and standard piping in one CH system?


Yes, although bear in mind the balancing issue.


Considering the minimum job for the loft will be addition of 4
radiators, new boiler and the plumbing to (re)move the HW tank from
downstairs would replacing our existing 10 radiators on micro bore with
new radiators on standard pipe add significantly to the price (+10%?,
+50%?, double? triple?)???

I would check the radiators. Don't replace them for the sake of it.
If the system has had inhibitor in it, then they should be fine.

If pipework is changed, it would add a lot to the cost and is not
really necessary. There is no reason to change it to 15mm, even if
the radiators have had it. I would just take one off and have a
look. and see if there is much sludge. Careful because it stains.



Where is a good place to start looking on the net for prices for
boilers/rads etc.

Discounted Heating.


We will then have the possibility of using 2 showers at the same time
(one a floor up from the boiler and one a floor down from the boiler if
than makes any difference). I'm presuming some sort of HW storage tank
(as opposed to a combi) will be required to allow both to be used
together. Is this the case (most "Combi yes/no?" threads so far have
only concerned one shower being used. Could a combi and mini tank be
used or would the best idea be to go for a mains pressure storage tank
solution?

If you have a high end combi at 22 litres per minute, it would imply
11 litres per shower at shower temperature in the winter.
I think that that is marginal.

Some form of storage of the hot water, or a heatbank would be a much
better choice if you think that you are going to use two showers
simultaneously and decently.


As the back half of our garage has been converted to a store room there
is not a space issue with putting a hot water tank in there with the
boiler but I'd prefer it to be compact as possible.

You could look at a CPSU. This is a floor standing unit with some
water storage inside. Whether that is enough to last for the
duration of a shower where women are involved is another thing.



If I was to redo the exising pipes and radiators myself what's the best
way of getting the pipes laid when their direction is across the joists?
(I want to minimise pulling up the floor. My intention would be to
use copper pipes from the radiators into the under floor space and
plastic pipes to link these as I've been lead to believe that the
plastic pipes are easier to work with.

If you are using microbore it is soft and you can thread it through
holes in the joists. With 15mm, you would have to line up the holes
perfectly and joint together short sections - not a good idea.

You can thread plastic through joist holes as well.

15mm copper is normally put in by notching the joists. If you can
avoid that then it's a Good Thing.





Any comments appreciated.

Chris.

PS Apologies for the long post (as the bishop said to the actress)


..andy

To email, substitute .nospam with .gl

On Tue, 14 Sep 2004 16:42:09 +0100, ChrisJ wrote:

Background:
We live in a 3 bedroom house-on-a-hill. From the front it looks like a
bungalow. Once inside you go downstairs to the bedrooms. The (non
combi) boiler is in the garage on the front. The hot water tank is
downstairs in the airing cupboard (pumping hot water downstairs against
convection, hmm who thought of that one!). There is a header tank in
the loft. The CH radiators are all on Microbore pipe. In the 6 months
we have lived there the CH top up tank has required about 2-4 litres of
water to top it up.
We had a combi boiler fitted in our last house (non condensing £1000).
Running a bath took long enough to undress our toddler and clean his
teeth and get him ready for bed, just about acceptable, certainly not
quick. Showers were great with a very good flow and pressure, enough to
make you want to stay in there longer.

Situation:
We want to extend into the loft and so need to lose the header tank.
We intend to have a bedroom, nursery and shower room in the loft as well
as a sizable landing (there's plenty of space due to the layout of the
house).

I've been told that microbore pipes and combi boilers don't mix.
Is this true?

No. It might mean that the installer has little experience of
fitting anything except combis and/or does not have any microbore fittings
in the van.

I've also been told that if your system leaks a combi boiler will make
it worse because of the pressure. (Remember its needed toping up
already!)

See my Sealed CH FAQ. below.

I would imagine the plumber who fits the new radiators in the loft may
want to avoid using microbore and so we would have both standard and
microbore radiators. Is this an issue?

Yes; but it's only a matter of balancing the flow between
the new and old radatiors.


I have no idea how much it would cost to replace all the existing CH
pipes (floor boards not sheets, at least in some rooms, no concrete
floors afaict) and radiators (3 bedrooms, kitchen, dining, lounge, hall,
lower floor hall, bathroom and washroom (10 rad in total) and whether
this would be a better solution than using the existing microbore.
There will be a plumber coming in to add new rad.s to the loft anyway.
Existing CH and boiler is original fitted in 1992 when house was built.

Things never seem to be simple though.

ATM my understanding is our DHW comes from the hot water tank in the
airing cupboard downstairs (there's also a pressure vessel in there too,
not sure what for though).

Since the existing heating is open and the HW cylinder is vented I can't
think what it does. What is it connected to?!


Siting the new boiler in the place of the old bolier in the garage puts
it just the other side of the garage wall to the kitchen sink. The
exiting bathroom is directly below that and the new shower room will be
just above and to the back of the house so the pipe runs to the majority
of the taps from the boiler will be short. (Our main gripe with the
combi boiler in the old house was that it took ages to get any hot water
through and then if you were just rinsing the pots you had to leave the
tap running at a fair lick in order for the water not to go cold which
it would do if you turned the tap off.)
The current hot water pipes from the boiler go to the airing cupboard
and the DHW pipes come back from there. It seems silly to send the
water half way round the house so we are intending drilling through the
garage wall into the space where the washing machine currently is in the
kitchen and connecting the DHW feed from the new boiler to the end of
those pipes. I'm presuming all the DHW taps are on branches off one run
from the exisitng hot water tank so capping of the other end at the hot
water tank (with a drain plug) will mean we still get hot water to the
all the taps.

For the CH we were going to try and locate the existing loop and break
into it as close to the new boiler as possible and close the loop in the
airing cupboard where the hw tank is.

My questions a

Does the above sound feasible? (IE are there any glaringly obvious
mistakes I've made or things I've overlooked.?)

Are there issues with microbore pipes for CH?

Can you mix micro bore and standard piping in one CH system?

Considering the minimum job for the loft will be addition of 4
radiators, new boiler and the plumbing to (re)move the HW tank from
downstairs would replacing our existing 10 radiators on micro bore with
new radiators on standard pipe add significantly to the price (+10%?,
+50%?, double? triple?)???

Where is a good place to start looking on the net for prices for
boilers/rads etc.

We will then have the possibility of using 2 showers at the same time
(one a floor up from the boiler and one a floor down from the boiler if
than makes any difference). I'm presuming some sort of HW storage tank
(as opposed to a combi) will be required to allow both to be used
together. Is this the case (most "Combi yes/no?" threads so far have
only concerned one shower being used. Could a combi and mini tank be
used or would the best idea be to go for a mains pressure storage tank
solution?
As the back half of our garage has been converted to a store room there
is not a space issue with putting a hot water tank in there with the
boiler but I'd prefer it to be compact as possible.

If I was to redo the exising pipes and radiators myself what's the best
way of getting the pipes laid when their direction is across the joists?
(I want to minimise pulling up the floor. My intention would be to
use copper pipes from the radiators into the under floor space and
plastic pipes to link these as I've been lead to believe that the
plastic pipes are easier to work with.

Any comments appreciated.

Chris.

PS Apologies for the long post (as the bishop said to the actress)




A hybrid system with a combi heating nearby small DHW and the airing
cupboard tank, might well serve you best.

If there is no HW needed in the loft conversion then simply pressurizing
the existing primary (if the existing boiler is good for this) is a
simple option.





--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at 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