Hello,

We've got a gravity fed CH system. I think you call it plan C. I don't
know everything because much of it is hidden under the floor or behind
boxes but it seems as though we have 28mm pipe from the boiler to the
cyclinder. There is only one pump (next to the boiler) and no valves.
The pump is energised by the room thermostat for the CH. There is no
cylinder stat. We can have HW only or HW and CH but not CH only. Does
this sound about right?

A neighbour has just paid thousands to have his system converted so
that HW and CH may be switched separately. Is it worth us doing the
same (the converting, not the paying thousands!)

Is it just a matter of inserting a valve and a bypass to control
whether the hot water goes to the cylinder only or carries on to the
radiators? What else is involved?

Thanks.

On Mon, 17 Sep 2007 16:48:13 +0000, nospam wrote:

Hello,

We've got a gravity fed CH system. I think you call it plan C. I don't
know everything because much of it is hidden under the floor or behind
boxes but it seems as though we have 28mm pipe from the boiler to the
cyclinder. There is only one pump (next to the boiler) and no valves.
The pump is energised by the room thermostat for the CH. There is no
cylinder stat. We can have HW only or HW and CH but not CH only. Does
this sound about right?

A neighbour has just paid thousands to have his system converted so
that HW and CH may be switched separately. Is it worth us doing the
same (the converting, not the paying thousands!)

Is it just a matter of inserting a valve and a bypass to control
whether the hot water goes to the cylinder only or carries on to the
radiators? What else is involved?

This work would normally be done as part of a package of upgrading the
heating system including a new boiler. There is no reason why you couldn't
improve the existing arrangements. We have discussed heating over and over
on this ng.
The FAQs below, The wiki and the subject of C-plan should get you started.


--
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

On Mon, 17 Sep 2007 16:48:13 GMT someone who may be nospam
wrote this:-

We've got a gravity fed CH system. I think you call it plan C. I don't
know everything because much of it is hidden under the floor or behind
boxes but it seems as though we have 28mm pipe from the boiler to the
cyclinder. There is only one pump (next to the boiler) and no valves.
The pump is energised by the room thermostat for the CH. There is no
cylinder stat. We can have HW only or HW and CH but not CH only. Does
this sound about right?

It sounds like the hot water is heated by gravity circulation of
primary water. Fairly standard a long time ago, but increasingly
uncommon.

A neighbour has just paid thousands to have his system converted so
that HW and CH may be switched separately.

It is worth converting to a fully pumped system. It sounds like your
neighbour had a lot more done, or he was diddled.

Is it just a matter of inserting a valve and a bypass to control
whether the hot water goes to the cylinder only or carries on to the
radiators?

No. The pipe that circulates primary water to the hot water cylinder
almost certainly continues to form the expansion pipe. You can
probably see this if you look at the cylinder connections and follow
the pipes.

Installing a valve that will shut this pipe converts the heating
system into one which has inadequate provision to cope with the
expansion of the water as it heats up. The end result tends to be a
loud bang and lots of very hot water being flung around.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

In an earlier contribution to this discussion,
nospam wrote:

Hello,

We've got a gravity fed CH system. I think you call it plan C. I don't
know everything because much of it is hidden under the floor or behind
boxes but it seems as though we have 28mm pipe from the boiler to the
cyclinder. There is only one pump (next to the boiler) and no valves.
The pump is energised by the room thermostat for the CH. There is no
cylinder stat. We can have HW only or HW and CH but not CH only. Does
this sound about right?

A neighbour has just paid thousands to have his system converted so
that HW and CH may be switched separately. Is it worth us doing the
same (the converting, not the paying thousands!)

Is it just a matter of inserting a valve and a bypass to control
whether the hot water goes to the cylinder only or carries on to the
radiators? What else is involved?

Thanks.

Whatever you've got, it ain't a C-Plan - because that would have a valve and
a cylinder stat, and would permit CH without HW if desired.

How many pipes are connected to the boiler? My guess is that there are
four - two for the gravity HW circuit and two more for the pumped CH
circuit.

If that is the case, you can convert it to a C-Plan, which will give you
independent control over the HW and CH - albeit not quite as efficiently as
as a fully-pumped system, but nevertheess a lot better that what you
currently have.

All you need is a 28mm 2-port valve of the right type (see the C-Plan
diagram on the Honeywell site) and a cylinder stat. As others have
indicated, you have to be careful where you insert the valve so that it
never prevents the boiler from having a clear path to the expansion tank. If
the pipe to the expansion tank tees off near the HW cylinder, the valve
needs to be on the *cylinder* side of the tee. You'll probably also find
that your programmer has a link fitted which forces the HW on whenever the
CH is on in order to ensure that the boiler runs for the CH, 'cos the room
stat only controls the pump. But if you re-wire as necessary to comply with
the C-Plan diagram, you should be ok.

If you're doing it youself, it should cost you less than £100 for the bits.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

On Mon, 17 Sep 2007 19:18:41 +0100, "Roger Mills"
wrote:

Whatever you've got, it ain't a C-Plan - because that would have a valve and
a cylinder stat, and would permit CH without HW if desired.

Hello,

You are quite right that it isn't a C-plan. I thought the C-plamn was
the simplest set-up but I re-read the Honeywell site and the C-plan
does have a valve; so my set-up is not C-plan but something even more
basic.

How many pipes are connected to the boiler? My guess is that there are
four

Yes there are.

If that is the case, you can convert it to a C-Plan, which will give you
independent control over the HW and CH

All you need is a 28mm 2-port valve of the right type (see the C-Plan
diagram on the Honeywell site) and a cylinder stat.

The cyclinder is covered in foam insulation. Do I just carefully cut
out a chunk to fasten a cylinder stat to? Then wire the cylinder stat
to the controller.

What is the function of this? Does it switch off the boiler when the
HW is at the right temperature?

I will have another look at the Honeywell site to see where the valve
should go.

[snip]

You'll probably also find
that your programmer has a link fitted which forces the HW on whenever the
CH is on in order to ensure that the boiler runs for the CH

Correct again.

On Mon, 17 Sep 2007 18:15:59 +0100, David Hansen
wrote:

A neighbour has just paid thousands to have his system converted so
that HW and CH may be switched separately.

It is worth converting to a fully pumped system. It sounds like your
neighbour had a lot more done, or he was diddled.

I'm not sure exactly what he had done nor exactly how much he paid. I
saw a new cylinder being carried in too. Perhaps he went fully pumped?
What are the advantages of this: the HW gets hot quicker?

On Mon, 17 Sep 2007 17:10:37 +0000 (UTC), Ed Sirett
wrote:

We have discussed heating over and over
on this ng.
The FAQs below, The wiki and the subject of C-plan should get you started.


Thanks. I had already found and read the faq which pointed me to the
Honeywell site. The faq is great but I needed to see the pictures at
Honeywell. Where do I find the wiki?

On Wed, 19 Sep 2007 08:32:34 GMT, nospam wrote:

Where do I find the wiki?


Sorry to answer my own question but is it:
http://www.wiki.diyfaq.org.uk ?

On 2007-09-19 09:28:36 +0100, nospam said:

On Mon, 17 Sep 2007 19:18:41 +0100, "Roger Mills"
wrote:

Whatever you've got, it ain't a C-Plan - because that would have a valve and
a cylinder stat, and would permit CH without HW if desired.

Hello,

You are quite right that it isn't a C-plan. I thought the C-plamn was
the simplest set-up but I re-read the Honeywell site and the C-plan
does have a valve; so my set-up is not C-plan but something even more
basic.

How many pipes are connected to the boiler? My guess is that there are
four

Yes there are.

If that is the case, you can convert it to a C-Plan, which will give you
independent control over the HW and CH

All you need is a 28mm 2-port valve of the right type (see the C-Plan
diagram on the Honeywell site) and a cylinder stat.

The cyclinder is covered in foam insulation. Do I just carefully cut
out a chunk to fasten a cylinder stat to? Then wire the cylinder stat
to the controller.

Yes.


What is the function of this? Does it switch off the boiler when the
HW is at the right temperature?

The thermostat closes the valve to stop circulation around the gravity
loop and a switch on the valve switches off the boiler.

This is why you have to be careful where you install the valve - i.e.
not on the path from boiler to vent pipe.



I will have another look at the Honeywell site to see where the valve
should go.

That's a stylised diagram so be careful. Trace the pipes to the roof
tank and be sure that the valve is not between boiler and vent.

All of this set up only has the effect of saving some energy by
preventing the boiler cycling when the water is already hot.

If you want to improve performance, and you are installing a new
controller anyway, it's usually not much more work to convert to fully
pumped using a three way valve.

Then you can have completely separate CH and HW control as well as the
water heating more quickly.








[snip]

You'll probably also find
that your programmer has a link fitted which forces the HW on whenever the
CH is on in order to ensure that the boiler runs for the CH

Correct again.

On Mon, 17 Sep 2007 19:18:41 +0100, "Roger Mills"
wrote:

All you need is a 28mm 2-port valve of the right type (see the C-Plan
diagram on the Honeywell site) and a cylinder stat.

Sorry to post so many questions!

I have had another look at the cylinder. Two 28mm pipes come into the
airing cupboard. These are then reduced to 22mm pipe which connects to
the side of the cylinder. The one pipe has a tee: one side of the tee
connects to the cylinder, the other goes into the loft to vent in the
tank.

So it looks as if I need a 22mm valve which blocks the flow into the
cylinder but leaves the other side of the tee (boiler to vent) open at
all times: is that right?

The two pipes are not marked. Is the one with the tee piece the flow
into the cylinder and the lower one the flow out? Do you always put
the valve on the pipe with the tee?

I have looked at the Honeywell diagram and read the wiki but I am
still confused about one point. The diagram makes it look like a loop:
boiler to cylinder to radiators to boiler. If a valve stops flow at
the cylinder, won't it stop flow around the whole circuit? Doesn't
there need to be a bypass so that when the cylinder is blocked water
is diverted straight to the radiators?

Thanks.

On Sep 17, 5:48 pm, nospam wrote:
Hello,

We've got a gravity fed CH system. I think you call it plan C. I don't
know everything because much of it is hidden under the floor or behind
boxes but it seems as though we have 28mm pipe from the boiler to the
cyclinder. There is only one pump (next to the boiler) and no valves.
The pump is energised by the room thermostat for the CH. There is no
cylinder stat.

So it's not totally gravity fed, the CH is pumnped, only the HW is
gravity fed.

My father's old system was completely gravity fed and the gas boiler
did not use electricity (clockwork clock). It might not have been
very efficient but it worked during power cuts!

Robert

On 2007-09-19 09:57:05 +0100, nospam said:

On Mon, 17 Sep 2007 19:18:41 +0100, "Roger Mills"
wrote:

All you need is a 28mm 2-port valve of the right type (see the C-Plan
diagram on the Honeywell site) and a cylinder stat.

Sorry to post so many questions!

I have had another look at the cylinder. Two 28mm pipes come into the
airing cupboard. These are then reduced to 22mm pipe which connects to
the side of the cylinder. The one pipe has a tee: one side of the tee
connects to the cylinder, the other goes into the loft to vent in the
tank.

So it looks as if I need a 22mm valve which blocks the flow into the
cylinder but leaves the other side of the tee (boiler to vent) open at
all times: is that right?

Yes that's it.


The two pipes are not marked. Is the one with the tee piece the flow
into the cylinder and the lower one the flow out? Do you always put
the valve on the pipe with the tee?

The thing is to avoid it being on the vent path and to make it only on
the cylinder path. Other than that it doesn't really matter.


I have looked at the Honeywell diagram and read the wiki but I am
still confused about one point. The diagram makes it look like a loop:
boiler to cylinder to radiators to boiler. If a valve stops flow at
the cylinder, won't it stop flow around the whole circuit? Doesn't
there need to be a bypass so that when the cylinder is blocked water
is diverted straight to the radiators?

The boiler will be fired up if either the HW or the CH demand heat.
Assuming that this is allowed by the timer, then the room thermostat
indirectly controls the pump running and demand to the boiler. If you
do the Cplan, the thermostat on the cylinder opens the valve and that
fires up the boiler.




Thanks.

On Wed, 19 Sep 2007 11:34:14 +0100, Andy Hall
wrote:

The boiler will be fired up if either the HW or the CH demand heat.
Assuming that this is allowed by the timer, then the room thermostat
indirectly controls the pump running and demand to the boiler. If you
do the Cplan, the thermostat on the cylinder opens the valve and that
fires up the boiler.

Thanks for your reply but I am confused about this: if the cylinder
stat says that the water is hot but the room thermostat says the room
is cold, won't this switch on the pump and close the valve? If so,
doesn't the water that goes through the radiators also circulate
through the cylinder to warm it? If the valve is closed, won't this
water be unable to move, damaging the pump and leaving the radiators
cold?

On 2007-09-19 13:13:32 +0100, nospam said:

On Wed, 19 Sep 2007 11:34:14 +0100, Andy Hall
wrote:

The boiler will be fired up if either the HW or the CH demand heat.
Assuming that this is allowed by the timer, then the room thermostat
indirectly controls the pump running and demand to the boiler. If you
do the Cplan, the thermostat on the cylinder opens the valve and that
fires up the boiler.

Thanks for your reply but I am confused about this: if the cylinder
stat says that the water is hot but the room thermostat says the room
is cold, won't this switch on the pump and close the valve?

yes.

If so,
doesn't the water that goes through the radiators also circulate
through the cylinder to warm it?

No. It should go through radiators only.

If the valve is closed, won't this
water be unable to move, damaging the pump and leaving the radiators
cold?

If you are doing Cplan, the branch to the radiators needs to be before
the cylinder and valve.

In effect this means that the CH circulation is based on whether or not
the pump is running and the HW on whether or not the valve is open.

The valve and branch to the pump need to be positioned appropriately
and the vent allowed either way.

That's why I said that it might be almost as easy to do a three way
valve and pump all of it.

On Wed, 19 Sep 2007 16:00:26 +0100, Andy Hall
wrote:

If you are doing Cplan, the branch to the radiators needs to be before
the cylinder and valve.

In effect this means that the CH circulation is based on whether or not
the pump is running and the HW on whether or not the valve is open.

Thanks for your continued help. Is there a diagram of the C-plan other
than on the Honeywell site because I think if I saw another schematic
I would understand. It's just that the Honeywell diagram gives the
impression that its one big loop, so I can't see how the rads can work
when the HW valve is closed.

The valve and branch to the pump need to be positioned appropriately
and the vent allowed either way.

That's why I said that it might be almost as easy to do a three way
valve and pump all of it.

If I did this, what plan would this become? What advantages would
there be: I think I read HW heats faster is this right? What more work
would have to be done: just adding a pump to the HW pipes?

Thanks.

In an earlier contribution to this discussion,
nospam wrote:

On Mon, 17 Sep 2007 19:18:41 +0100, "Roger Mills"
wrote:

Whatever you've got, it ain't a C-Plan - because that would have a
valve and a cylinder stat, and would permit CH without HW if desired.

Hello,

You are quite right that it isn't a C-plan. I thought the C-plamn was
the simplest set-up but I re-read the Honeywell site and the C-plan
does have a valve; so my set-up is not C-plan but something even more
basic.

Yes, you've got uncontrolled gravity hot water, and pumped CH. The HW heats
whenever the boiler is on, and will eventually get up to a scalding
temperature if you run the radiators hot.

How many pipes are connected to the boiler? My guess is that there
are
four

Yes there are.


Thought so!

If that is the case, you can convert it to a C-Plan, which will give
you independent control over the HW and CH

All you need is a 28mm 2-port valve of the right type (see the C-Plan
diagram on the Honeywell site) and a cylinder stat.

The cyclinder is covered in foam insulation. Do I just carefully cut
out a chunk to fasten a cylinder stat to? Then wire the cylinder stat
to the controller.

Yes. It's probably held in place with a piece of stretchy curtain wire round
the cylinder, which can go outside the foam - but the stat itself must make
metal to metal contact with the cylinder.

What is the function of this? Does it switch off the boiler when the
HW is at the right temperature?


In effect, though not directly. The cylinder stat opens the valve when the
HW needs to be heated, and allows it to close (by its spring return) when
the HW demand is satisfied. The actuator of the valve has a changeover
switch - which is electrically isolated from the motor circuit - which
changes position when the valve is fully open. This switch causes the boiler
to run via the room stat and pump when the valve is closed (CH only) and
causes just the boiler to run when the valve is open (HW only). If there is
a simultaneous demand for HW and CH, the switch on the valve controls the
boiler, and the room stat controls the pump. All very cunning - but it
*must* be wired exactly as per the Honeywell diagram if it is to work.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

On Wed, 19 Sep 2007 16:30:25 GMT, nospam wrote:

. Is there a diagram of the C-plan other
than on the Honeywell site because I think if I saw another schematic
I would understand.

Sorry to answer myself but I have found this:

http://www.diyfixit.co.uk/diy/centra...s/systems.html

Does this diagram look right? If so, I finally understand it.
According to this diagram the cylinder and the radiators are piped in
parallel rather than in series. If this is the case I can understand
how the cylinder can be closed off and the radiators can be heated at
the same time.

But I am surprised because if the HW is on, what is to stop the heat
"leaking" into the radiators? Is it just that it follows the path of
least resistance (i.e. to the cylinder). Also how does the water get
heated when the CH is on? I would have thought that all the hot water
would get "sucked" away by the pump and very little would find its way
to the cylinder.

Looking at these various diagrams they all seem to show the hot water
from the pump going into the upper side connection of the cylinder and
out of th elower side connection. I thought it would have been the
other way around considering that heat rises, or is this to prevent
shock?

Thanks.

In an earlier contribution to this discussion,
nospam wrote:

On Wed, 19 Sep 2007 11:34:14 +0100, Andy Hall
wrote:

The boiler will be fired up if either the HW or the CH demand heat.
Assuming that this is allowed by the timer, then the room thermostat
indirectly controls the pump running and demand to the boiler. If
you do the Cplan, the thermostat on the cylinder opens the valve and
that fires up the boiler.

Thanks for your reply but I am confused about this: if the cylinder
stat says that the water is hot but the room thermostat says the room
is cold, won't this switch on the pump and close the valve? If so,
doesn't the water that goes through the radiators also circulate
through the cylinder to warm it? If the valve is closed, won't this
water be unable to move, damaging the pump and leaving the radiators
cold?

No! You've got two separate circuits. One goes from the boiler to the
cylinder by gravity circulation, and back to the boiler. The other goes from
the boiler and is pumped round the radiators and back to the boiler. Closing
the valve stops the gravity circulation to the cylinder, but still allows
the pumped CH circuit to operate.

In general, you'll want your HW at about 60 degrees and the flow to your
radiators at 80 degrees. So the boiler has to operate at 80 degrees. As soon
as the water in the cylinder reaches 60 degrees (or wahatever the cylinder
stat is set to) the valve closes. The boiler can continue to heat the
radiators, but the HW doesn't get any hotter - which is exactly what you
want.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

On Wed, 19 Sep 2007 18:13:29 +0100, "Roger Mills"
wrote:

No! You've got two separate circuits. One goes from the boiler to the
cylinder by gravity circulation, and back to the boiler. The other goes from
the boiler and is pumped round the radiators and back to the boiler. Closing
the valve stops the gravity circulation to the cylinder, but still allows
the pumped CH circuit to operate.


Thank you. The Honeywell diagram confused me because it is abit vague
about what happens at the boiler.

You say I've got two circuits but I presume they must be connected
because they both fill from the CH header tank don't they?

I know there are four pipes going to the boiler 2* 28mm and 2 * 22mm
(HW and CH respectively) but I can't see what they do behind the
boiler to work it out myself.

One suggestion was to put a pump on the HW too, but I just looked at
this:

http://www.screwfix.com/app/sfd/cat/...1616&id=67174#

and they have the pump positioned before the cylinder-radiator tee so
that it pumps both. Is there are reason why two pumps are preferable
to doing this?

Thanks again for your help (and patience)

On Wed, 19 Sep 2007 17:20:14 GMT, nospam wrote:

I know there are four pipes going to the boiler 2* 28mm and 2 * 22mm
(HW and CH respectively) but I can't see what they do behind the
boiler to work it out myself.


I've done what i should have done before I posted: had a good look at
the boiler: on one side there are two 28mm pipes and on the other two
22mm pipes. Just curious but are these heated separately by the
boiler? If not, I'm wondering why there isn't just one inlet and one
outlet to the boiler.

Thanks.

On 2007-09-19 17:30:25 +0100, nospam said:

On Wed, 19 Sep 2007 16:00:26 +0100, Andy Hall
wrote:

If you are doing Cplan, the branch to the radiators needs to be before
the cylinder and valve.

In effect this means that the CH circulation is based on whether or not
the pump is running and the HW on whether or not the valve is open.

Thanks for your continued help. Is there a diagram of the C-plan other
than on the Honeywell site because I think if I saw another schematic
I would understand. It's just that the Honeywell diagram gives the
impression that its one big loop, so I can't see how the rads can work
when the HW valve is closed.

The valve and branch to the pump need to be positioned appropriately
and the vent allowed either way.

That's why I said that it might be almost as easy to do a three way
valve and pump all of it.

If I did this, what plan would this become? What advantages would
there be: I think I read HW heats faster is this right? What more work
would have to be done: just adding a pump to the HW pipes?

That would be W or Y plan.

You don't normally add a pump but rather put a valve after it. Then
when there is HW demand the pump circulates the water through the
cylinder coil. When the CH demands it goes through the radiators.

You *can* implement with two pumps but it's a bit unusual.

On 2007-09-19 18:05:57 +0100, nospam said:

But I am surprised because if the HW is on, what is to stop the heat
"leaking" into the radiators?

Well spotted. Normally the radiator circuit is 22mm and the pump
tends to spoil any flow. However, you can have a valve operated by a
light spring or a flap in the CH circuit. This stops natural
"gravity" circulation unless the pump is running.


Is it just that it follows the path of
least resistance (i.e. to the cylinder). Also how does the water get
heated when the CH is on?

Generally when the pump runs there is still some cylinder circulation -
just not as much as before.




I would have thought that all the hot water
would get "sucked" away by the pump and very little would find its way
to the cylinder.

That can happen.





Looking at these various diagrams they all seem to show the hot water
from the pump going into the upper side connection of the cylinder and
out of th elower side connection. I thought it would have been the
other way around considering that heat rises, or is this to prevent
shock?


With a gravity system the water is usually on a separate circuit to the
pumped one but is fed to the upper connection. This promotes the
natural circulation by convection in the gravity circuit,. "Gravity"
is a misnomer. What is really happening is convection of the water
between boiler and cylinder. Hot water from boiler rises to cylinder.
Cool wate from cylinder falls to boiler.

This is why having a fully pumped system is better. You have complete
control of both circuits.

On 2007-09-19 18:20:14 +0100, nospam said:

On Wed, 19 Sep 2007 18:13:29 +0100, "Roger Mills"
wrote:

No! You've got two separate circuits. One goes from the boiler to the
cylinder by gravity circulation, and back to the boiler. The other goes from
the boiler and is pumped round the radiators and back to the boiler. Closing
the valve stops the gravity circulation to the cylinder, but still allows
the pumped CH circuit to operate.


Thank you. The Honeywell diagram confused me because it is abit vague
about what happens at the boiler.

You say I've got two circuits but I presume they must be connected
because they both fill from the CH header tank don't they?

They are connected in the sense that it's the same water.

They are separate in the sense that they start and end separately near
the boiler




I know there are four pipes going to the boiler 2* 28mm and 2 * 22mm
(HW and CH respectively) but I can't see what they do behind the
boiler to work it out myself.

This is common in a gravity configuration. Boiler heat exchanger
has one lot of water inside. There are four taps. Two are used to
form the circuit with the cylinder and are in 28mm. The other two are
22mm and with a pump make the heating circuit.

Equally you could have one set of taps and a tee on those going to each circuit



One suggestion was to put a pump on the HW too, but I just looked at
this:

http://www.screwfix.com/app/sfd/cat/...1616&id=67174#

and they have the pump positioned before the cylinder-radiator tee so
that it pumps both. Is there are reason why two pumps are preferable
to doing this?



If you do a system Y or W then you have a pump on that circuit and a
valve after it.

You could also have two pumps - one on each circuit - although this is
relatively unusual.

Honeywell's plans are based around their standard controls and valves
and they also sell packs with all the bits needed. Their diagrams
don't show the plumbing too well. There is nothing to say that you
*have" to follow their methodology but then you do need to understand
clearly what the components are going to do.

The plans are for the convenience of installers and maintainers.

On Wed, 19 Sep 2007 19:27:17 +0100, Andy Hall
wrote:


This is common in a gravity configuration. Boiler heat exchanger
has one lot of water inside. There are four taps. Two are used to
form the circuit with the cylinder and are in 28mm. The other two are
22mm and with a pump make the heating circuit.

Equally you could have one set of taps and a tee on those going to each circuit


Thank you for your patience, I think I finally understand.

I know that I need to fit a valve to the cylinder and a cylinder stat.
So far so good. This will involve running new wires: do I use 1.5mm^2
T&E? This will need to go to the controller, which is above the
boiler. Now the direct route to the boiler is along the pipework! Is
it ok to run the wire near the pipes, i.e. inside the same boxing?
Obviously I would not tape it onto the pipes or anything daft, but I
imagine these enclosed spaces still get hot. What temperature is
standard T&E rated for?

I'm just a bit unsure about the pump. People have recommended I make
it a pumped system. If the boiler had one outlet, it would be simple
to put the pump before the tee, but as my boiler has two separate
outlets, with a pump fitted on the 22mm CH side, how do I get the
cylinder side pumped?

And of course, I'll need to drain down the system to fit the valve. Is
it possible to fit a gate valve to the header tank outlet to make this
easier in the future?

Thanks.

On 2007-09-19 20:27:27 +0100, nospam said:

On Wed, 19 Sep 2007 19:27:17 +0100, Andy Hall
wrote:


This is common in a gravity configuration. Boiler heat exchanger
has one lot of water inside. There are four taps. Two are used to
form the circuit with the cylinder and are in 28mm. The other two are
22mm and with a pump make the heating circuit.

Equally you could have one set of taps and a tee on those going to each circuit


Thank you for your patience, I think I finally understand.

I know that I need to fit a valve to the cylinder and a cylinder stat.
So far so good. This will involve running new wires: do I use 1.5mm^2
T&E?

This is OK, but you could run a cable with more ways if needed.


This will need to go to the controller, which is above the
boiler. Now the direct route to the boiler is along the pipework! Is
it ok to run the wire near the pipes, i.e. inside the same boxing?
Obviously I would not tape it onto the pipes or anything daft, but I
imagine these enclosed spaces still get hot. What temperature is
standard T&E rated for?

It's best to run them separately so not inside the same compartment
unless you put in a barrier.



I'm just a bit unsure about the pump. People have recommended I make
it a pumped system. If the boiler had one outlet, it would be simple
to put the pump before the tee, but as my boiler has two separate
outlets, with a pump fitted on the 22mm CH side, how do I get the
cylinder side pumped?

There are diiferent ways. One is to keep the existing 28mm pipework to
provide the vent and fill arrangements. Then on the output side of the
pump, assuming that it is in the flow path, fit a three way valve and
run that to the cylinder.



And of course, I'll need to drain down the system to fit the valve. Is
it possible to fit a gate valve to the header tank outlet to make this
easier in the future?

Thanks.

Gate valves are a bad idea in general. full bore lever valves are the
thing to use.

In an earlier contribution to this discussion,
nospam wrote:


If I did this, what plan would this become? What advantages would
there be: I think I read HW heats faster is this right? What more work
would have to be done: just adding a pump to the HW pipes?

Thanks.

As Andy has said, you'd have either a W-Plan or a Y-Plan. W-Plan uses a
3-port diverter valve - which gives you either HW or CH but not both at the
same time - usually with HW priority. With this system, you get no CH while
the HW is being heated. Its ok if you've got a fast recovery cylinder with a
big heat exchanger inside which can absorb all of the boiler output and heat
the water quickly - otherwise not so good. Far more common these days is
Y-Plan which uses a 3-port mid-position valve. At one end of its travel it
gives you just HW, and at the other end it gives just CH. In the mid
position it gives both at the same time.

You would have to make some plumbing changes to convert to a W or Y Plan -
reducing the boiler connections from 4 to 3. You can leave the two returns
as they are, but you need to blank off one of the flow connections so that
the other one feeds first the pump and then the inlet of the 3-port valve.
The CH and HW flow pipes then connect to the appropriate outputs of the
3-port valve. *But* you'll have to be extremely careful to make sure you
always have an unrestricted path to the vent pipe - which may be very
difficult - if not impossible - with your setup. [It's more usual - with
Y-Plan - to have the pump and valve next to the HW cylinder rather than near
the boiler, and for the fill and vent pipes to connect into the flow pipe
just before the pump - but you can't do that because your CH circuit starts
and ends at the boiler rather than in the airing cupboard.]

You *could* fit an additional pump in the HW circuit and, in your case, it
may well be the easiest way of converting to a fully pumped solution. Again
you'll need to put the pump somewhere where it won't restrict the path to
the vent - maybe in the return rather than the flow pipe. You'll also need
some logic - maybe involving one or two relays[1] - to ensure that the right
combination of boiler and pump(s) are running, depending on the demand.

[1] I have a feeling that I worked out how to do a 2-pump solution without
needing relays a year or two ago. If you're interested in pursuing this
route, I'll try to find it.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

In an earlier contribution to this discussion,
nospam wrote:


But I am surprised because if the HW is on, what is to stop the heat
"leaking" into the radiators? Is it just that it follows the path of
least resistance (i.e. to the cylinder). Also how does the water get
heated when the CH is on? I would have thought that all the hot water
would get "sucked" away by the pump and very little would find its way
to the cylinder.

You're unlikely to get gravity circulation through the CH circuit because it
has a much higher flow resistance than the HW circuit - but it *may* happen.
If so, you can get a valve with a weighted flap which shuts off the circuit
unless the pump is running to provide a bit more 'urge'.


Looking at these various diagrams they all seem to show the hot water
from the pump going into the upper side connection of the cylinder and
out of th elower side connection. I thought it would have been the
other way around considering that heat rises, or is this to prevent
shock?

No - that's the right way round. It rises by convection to the highest
point - the top of the cylinder - and heats the cylinder, cooling as it does
so, on its way back down.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

In an earlier contribution to this discussion,
nospam wrote:


You say I've got two circuits but I presume they must be connected
because they both fill from the CH header tank don't they?

Yes they both use the same water. When you first fill the system, the water
will flow down into the boiler from the F&E tank and then out the other side
to the radiators. But once it is full, you have two loops which can flow
more or less independent of each other. Think of it a bit like connecting
two electrical circuits to the same battery. The same electrons flow round
both, but you can switch them on and off independently.


One suggestion was to put a pump on the HW too, but I just looked at
this:

http://www.screwfix.com/app/sfd/cat/...1616&id=67174#

and they have the pump positioned before the cylinder-radiator tee so
that it pumps both. Is there are reason why two pumps are preferable
to doing this?

Thanks again for your help (and patience)

See my other post re 2 pumps vs a 3-port valve system. A lot depends on
where you're starting from!
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

In an earlier contribution to this discussion,
nospam wrote:

On Wed, 19 Sep 2007 17:20:14 GMT, nospam wrote:

I know there are four pipes going to the boiler 2* 28mm and 2 * 22mm
(HW and CH respectively) but I can't see what they do behind the
boiler to work it out myself.


I've done what i should have done before I posted: had a good look at
the boiler: on one side there are two 28mm pipes and on the other two
22mm pipes. Just curious but are these heated separately by the
boiler? If not, I'm wondering why there isn't just one inlet and one
outlet to the boiler.

Thanks.

I think I've answered that in another recent post.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

In an earlier contribution to this discussion,
nospam wrote:

On Wed, 19 Sep 2007 19:27:17 +0100, Andy Hall
wrote:


This is common in a gravity configuration. Boiler heat exchanger
has one lot of water inside. There are four taps. Two are used to
form the circuit with the cylinder and are in 28mm. The other two
are 22mm and with a pump make the heating circuit.

Equally you could have one set of taps and a tee on those going to
each circuit


Thank you for your patience, I think I finally understand.

I know that I need to fit a valve to the cylinder and a cylinder stat.
So far so good. This will involve running new wires: do I use 1.5mm^2
T&E? This will need to go to the controller, which is above the
boiler. Now the direct route to the boiler is along the pipework! Is
it ok to run the wire near the pipes, i.e. inside the same boxing?
Obviously I would not tape it onto the pipes or anything daft, but I
imagine these enclosed spaces still get hot. What temperature is
standard T&E rated for?

1.5mm^2 cable will be fine as long as it's not *too* close to the pipes. You
have to down-rate its current capacity when it's in a hot environment - but
it's only going to be carrying about 3 amps, and has plenty in hand.

I'm just a bit unsure about the pump. People have recommended I make
it a pumped system. If the boiler had one outlet, it would be simple
to put the pump before the tee, but as my boiler has two separate
outlets, with a pump fitted on the 22mm CH side, how do I get the
cylinder side pumped?

As I said in another post, you'd have to alter the pipework.

And of course, I'll need to drain down the system to fit the valve. Is
it possible to fit a gate valve to the header tank outlet to make this
easier in the future?

You could do - don't forget to open it again when you've finished! Or you
could just stuff a cork in the F&E tank outlet from inside the tank to
reduce the amount to be drained off.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

On Wed, 19 Sep 2007 21:20:33 +0100, "Roger Mills"
wrote:

As Andy has said, you'd have either a W-Plan or a Y-Plan. W-Plan uses a
3-port diverter valve - which gives you either HW or CH but not both at the
same time - usually with HW priority.


Thank you both, for your replies. I don't like the sound of W-plan as
it's either-or approach doesn't seem very useful; I don't know why
anyone would want that.

You would have to make some plumbing changes to convert to a W or Y Plan -
reducing the boiler connections from 4 to 3.

I know you typed this but I'm going to type it back, just to make sure
I have got it right:

At the moment I have four connections to the boiler CH in and out and
HW in and out. If I have understood, I would need to keep one of the
HW connections as this fills the boiler and also functions as the
vent. presumably I keep the top connecion as the bottom connection
would not work as a vent?

Then on the CH output I fit a pump (or rather leave the existing one
there) and after the pump fit a three way valve to divert to CH, HW,
or both.

*But* you'll have to be extremely careful to make sure you
always have an unrestricted path to the vent pipe - which may be very
difficult - if not impossible - with your setup. [It's more usual - with
Y-Plan - to have the pump and valve next to the HW cylinder rather than near
the boiler, and for the fill and vent pipes to connect into the flow pipe
just before the pump - but you can't do that because your CH circuit starts
and ends at the boiler rather than in the airing cupboard.]

That's not strictly true. At th boiler the CH pipes go down into the
floor for the ground floor radiators but they also run up alongside
the 28mm pipe, to feed the upstairs radiators. Could I not move the
pump next to the cylinder and pump into the 22mm pipes upstairs?

I think it's worth adding a cylinder stat and valve when I get round
to it, but I am still unsure about the benefirs of pumped HW. Does it
just mean the cylinder heats quicker?

I don't know if I should have said this before but it's an oil boiler
so we use economy seven to heat the water most of the time; that's why
I think it would be useful to be able to have CH without HW.

Thanks.

nospam wrote:
On Wed, 19 Sep 2007 21:20:33 +0100, "Roger Mills"
wrote:

As Andy has said, you'd have either a W-Plan or a Y-Plan. W-Plan uses a
3-port diverter valve - which gives you either HW or CH but not both at the
same time - usually with HW priority.


Thank you both, for your replies. I don't like the sound of W-plan as
it's either-or approach doesn't seem very useful; I don't know why
anyone would want that.


Limited output Combi. No hot water storage. Divert full power to water
when needed.

You would have to make some plumbing changes to convert to a W or Y Plan -
reducing the boiler connections from 4 to 3.

I know you typed this but I'm going to type it back, just to make sure
I have got it right:

At the moment I have four connections to the boiler CH in and out and
HW in and out. If I have understood, I would need to keep one of the
HW connections as this fills the boiler and also functions as the
vent. presumably I keep the top connecion as the bottom connection
would not work as a vent?

Then on the CH output I fit a pump (or rather leave the existing one
there) and after the pump fit a three way valve to divert to CH, HW,
or both.


Or two valves. One for CH and one for hot.

*But* you'll have to be extremely careful to make sure you
always have an unrestricted path to the vent pipe - which may be very
difficult - if not impossible - with your setup. [It's more usual - with
Y-Plan - to have the pump and valve next to the HW cylinder rather than near
the boiler, and for the fill and vent pipes to connect into the flow pipe
just before the pump - but you can't do that because your CH circuit starts
and ends at the boiler rather than in the airing cupboard.]

That's not strictly true. At th boiler the CH pipes go down into the
floor for the ground floor radiators but they also run up alongside
the 28mm pipe, to feed the upstairs radiators. Could I not move the
pump next to the cylinder and pump into the 22mm pipes upstairs?

I think it's worth adding a cylinder stat and valve when I get round
to it, but I am still unsure about the benefirs of pumped HW. Does it
just mean the cylinder heats quicker?

Basically that, and independence of tank siting, and smaller bore
pipework with less heatlosses.

I don't know if I should have said this before but it's an oil boiler
so we use economy seven to heat the water most of the time; that's why
I think it would be useful to be able to have CH without HW.


Its still marginally cheaper to use oil to heat.

Thanks.

In an earlier contribution to this discussion,
nospam wrote:

On Wed, 19 Sep 2007 21:20:33 +0100, "Roger Mills"
wrote:

As Andy has said, you'd have either a W-Plan or a Y-Plan. W-Plan
uses a 3-port diverter valve - which gives you either HW or CH but
not both at the same time - usually with HW priority.


Thank you both, for your replies. I don't like the sound of W-plan as
it's either-or approach doesn't seem very useful; I don't know why
anyone would want that.

It's probably that diverter valves were invented before mid-position valves,
but have largely been superceded by the latter.

You would have to make some plumbing changes to convert to a W or Y
Plan - reducing the boiler connections from 4 to 3.

I know you typed this but I'm going to type it back, just to make sure
I have got it right:

At the moment I have four connections to the boiler CH in and out and
HW in and out. If I have understood, I would need to keep one of the
HW connections as this fills the boiler and also functions as the
vent. presumably I keep the top connecion as the bottom connection
would not work as a vent?

Then on the CH output I fit a pump (or rather leave the existing one
there) and after the pump fit a three way valve to divert to CH, HW,
or both.

*But* you'll have to be extremely careful to make sure you
always have an unrestricted path to the vent pipe - which may be very
difficult - if not impossible - with your setup. [It's more usual -
with Y-Plan - to have the pump and valve next to the HW cylinder
rather than near the boiler, and for the fill and vent pipes to
connect into the flow pipe just before the pump - but you can't do
that because your CH circuit starts and ends at the boiler rather
than in the airing cupboard.]

That's not strictly true. At th boiler the CH pipes go down into the
floor for the ground floor radiators but they also run up alongside
the 28mm pipe, to feed the upstairs radiators. Could I not move the
pump next to the cylinder and pump into the 22mm pipes upstairs?


Yes you could indeed, and this would be the best way to go if you're
converting to a fully pumped system with a single pump. Not all systems have
the CH pipes conveniently close to the HW pipes like that! So you could do
this:
* Blank off the CH flow connection on the boiler and remove the pipe which
feeds the up/down distribution pipe, and blank off the end
* Leave the CH return pipe connected to the boiler
[If the pump is currently in the return pipe, remove it and replace it with
a bit of pipe. If it's currently in the flow pipe, it will have been removed
in the first action above, anyway]
* You may need to change where the vent and fill pipes are connected in the
airing cupboard, in order to get everything in. They need to be close to
each other and *before* the pump, on the 28mm flow pipe
* Fit the mid position valve above the pump, with the HW output connecting
to the top of the cylinder coil, and the CH output connecting into the top
of your CH up/down distribution pipe

I think it's worth adding a cylinder stat and valve when I get round
to it, but I am still unsure about the benefirs of pumped HW. Does it
just mean the cylinder heats quicker?

It also means that the boiler doesn't need to keep itself hot for so long
when you're just heating the HW, so it saves a bit of fuel.

I don't know if I should have said this before but it's an oil boiler
so we use economy seven to heat the water most of the time; that's why
I think it would be useful to be able to have CH without HW.

If you don't use the boiler much for HW, and mainly want to be able to have
just the CH on without the HW getting too hot, the C-Plan solution is fine
and is by far the simplest to implement.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

On Thu, 20 Sep 2007 10:21:04 +0100, The Natural Philosopher
wrote:

I think it's worth adding a cylinder stat and valve when I get round
to it, but I am still unsure about the benefirs of pumped HW. Does it
just mean the cylinder heats quicker?

Basically that, and independence of tank siting, and smaller bore
pipework with less heatlosses.

Sorry, you've lost me there. I see that 15mm pipe has a smaller
surface area than the same length of 28mm pipe but isn't heat loss
related to the ratio of surface area to volume? I would have thought
larger pipes would have less ehat loss? Isn't that why 15mm pipes are
more likely to freeze than 22mm ones?

What about the tank siting? Surely that feeds by gravity anyway?

I don't know if I should have said this before but it's an oil boiler
so we use economy seven to heat the water most of the time; that's why
I think it would be useful to be able to have CH without HW.

Its still marginally cheaper to use oil to heat.

I didn't know that: I thought they were about the same. But you never
run out of electricity and never have to phone around for the cheapest
quote and spend a morning waiting to let an electricity delivery man
in.

On Thu, 20 Sep 2007 10:37:53 +0100, "Roger Mills"
wrote:

* Blank off the CH flow connection on the boiler and remove the pipe which
feeds the up/down distribution pipe, and blank off the end
* Leave the CH return pipe connected to the boiler
[If the pump is currently in the return pipe, remove it and replace it with
a bit of pipe. If it's currently in the flow pipe, it will have been removed
in the first action above, anyway]

Sorry if this is a silly question: which CH pipe do I blank? I know
the hot water relies on the hot water rising, so I assume cold water
goes in at the bottom of the boiler and hot out at the top. So I blank
the hot CH out pipe and take my CH and HW from the HW pipe? It's the
28mm HW pipe which vents so this should not be a problem.

Why can't I also blank the CH return and use the 28mm return for both
CH and HW? I think it would be best to leave the old pipes in situ
rather than remove them otherwise it means ripping up a lot of
floorboards.

If you don't use the boiler much for HW, and mainly want to be able to have
just the CH on without the HW getting too hot, the C-Plan solution is fine
and is by far the simplest to implement.

By the time I have drained down to fit the valve, i may as well move
the pump at the same time.

Thanks again.

nospam wrote:
On Thu, 20 Sep 2007 10:21:04 +0100, The Natural Philosopher
wrote:

I think it's worth adding a cylinder stat and valve when I get round
to it, but I am still unsure about the benefirs of pumped HW. Does it
just mean the cylinder heats quicker?

Basically that, and independence of tank siting, and smaller bore
pipework with less heatlosses.

Sorry, you've lost me there. I see that 15mm pipe has a smaller
surface area than the same length of 28mm pipe but isn't heat loss
related to the ratio of surface area to volume? I would have thought
larger pipes would have less ehat loss? Isn't that why 15mm pipes are
more likely to freeze than 22mm ones?

What about the tank siting? Surely that feeds by gravity anyway?

I don't know if I should have said this before but it's an oil boiler
so we use economy seven to heat the water most of the time; that's why
I think it would be useful to be able to have CH without HW.

Its still marginally cheaper to use oil to heat.

I didn't know that: I thought they were about the same. But you never
run out of electricity and never have to phone around for the cheapest
quote and spend a morning waiting to let an electricity delivery man
in.

I think here water heating is less than 5% of the total heating.

So it impacts little on the oil fill thing: we need that twice a year
anyway.

In a modern flat of sound insulation with loads of people being anal
about washing, it could of curse be far higher.

On Thu, 20 Sep 2007 11:29:35 +0100, The Natural Philosopher
wrote:

I think here water heating is less than 5% of the total heating.

So it impacts little on the oil fill thing: we need that twice a year
anyway.

In a modern flat of sound insulation


I'm afraid there is precious little insulation here. We have insulated
the loft but all the CH and HW pipes are run in notches cut in the
joists just below floorboard level (22mm and 28mm below!) so there is
no room for lagging. Any suggestions on how to insulate these hot
pipes?

By the way, there is no cross bonding on all these pipes. The only
earth wire I have found is one on the oil pipe. I assume the CH and HW
pipes ought to be bonded at the boiler? I'll add that on to the list!

"nospam" wrote


I'm not sure exactly what he had done nor exactly how much he paid. I
saw a new cylinder being carried in too. Perhaps he went fully pumped?
What are the advantages of this: the HW gets hot quicker?

Absolutely!
I had to re-program my parent's time clock recently and noticed that the hot
water was timed to come on with the heating in the morning (for 3-4 hours).
Thinking this was a mistake, I reduced this to 1/2 hour like my pumped
system.
The next day they rang to complain of no hot water!
Had to increase the time back upto 3 hours IIRC as they have gravity
circulation from back boiler.

Phil

In an earlier contribution to this discussion,
nospam wrote:

On Thu, 20 Sep 2007 10:37:53 +0100, "Roger Mills"
wrote:

* Blank off the CH flow connection on the boiler and remove the pipe
which feeds the up/down distribution pipe, and blank off the end
* Leave the CH return pipe connected to the boiler
[If the pump is currently in the return pipe, remove it and replace
it with a bit of pipe. If it's currently in the flow pipe, it will
have been removed in the first action above, anyway]

Sorry if this is a silly question: which CH pipe do I blank? I know
the hot water relies on the hot water rising, so I assume cold water
goes in at the bottom of the boiler and hot out at the top. So I blank
the hot CH out pipe and take my CH and HW from the HW pipe? It's the
28mm HW pipe which vents so this should not be a problem.

The 3-port valve needs to be on the flow side (rather than the return) of
both circuits - so it's the CH flow pipe which you need to disconnect from
the boiler, and connect (further along it!) to the CH output from the 3-port
valve instead. I would expect it to be the higher pipe on the CH side of the
boiler, but you can easily tell by feeling the pipes when the heating has
been on for a few minutes - the flow pipe will be a lot hotter than the
return.

Why can't I also blank the CH return and use the 28mm return for both
CH and HW? I think it would be best to leave the old pipes in situ
rather than remove them otherwise it means ripping up a lot of
floorboards.

I never suggested ripping out lots of pipe - just removing a short piece
immediately by the boiler. The pipes which go under the floor for the
downstairs rads and up near the 28mm pipes for the upstairs rads need to
remain intact. If you want to blank off both CH connections on the boiler,
and connect the CH return into the 28mm return pipe in the airing cupboard,
that's ok. My rationale for not doing that was to minimise the distance
which the water has to flow.

If you think about it, on the flow side, all the flow for HW and for both
upstairs and downstairs CH will go up to 28mm flow pipe to the airing
cupboard. After the 3-port valve, the CH flow will split into 2 - with the
feeds to the upstairs rads going under the upstairs floorboards, and with
the feed for the downstairs rads coming down the 22mm pipe which it
currently goes up. No problem with that, and no way of avoiding it if the
pump and valve are upstairs.

On the return side, the return from the downstairs rads currently comes back
to the vicinity of the boiler, where it meets the return coming down from
upstairs, and connects into the boiler. If you blank off this connection,
and connect the return upstairs instead, it means that the return water from
the downstairs rads has to go back upstairs in order to come down the 28mm
pipe rather than going straight into the boiler at downstairs level. I don't
see the point of that!
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

On Thu, 20 Sep 2007 13:57:59 +0100, "Roger Mills"
wrote:

If you think about it, on the flow side, all the flow for HW and for both
upstairs and downstairs CH will go up to 28mm flow pipe to the airing
cupboard. After the 3-port valve, the CH flow will split into 2 - with the
feeds to the upstairs rads going under the upstairs floorboards, and with
the feed for the downstairs rads coming down the 22mm pipe which it
currently goes up. No problem with that, and no way of avoiding it if the
pump and valve are upstairs.

On the return side, the return from the downstairs rads currently comes back
to the vicinity of the boiler, where it meets the return coming down from
upstairs, and connects into the boiler. If you blank off this connection,
and connect the return upstairs instead, it means that the return water from
the downstairs rads has to go back upstairs in order to come down the 28mm
pipe rather than going straight into the boiler at downstairs level. I don't
see the point of that!

Thank you for your explanation. I quite agree it would be silly for
the water from the downstairs rads to go up and then down again. I'm
not sure that's what I was thinking of when I posted; I think I meant
using the 28mm pipe downstairs but now I think about it again, it
seems silly putting a tee piece in this and connecting the CH pipe to
the tee, when I get the same effect leaving it connected to the other
side of the boiler without doing any work!

What I will do is on the 28mm from the boiler, fit a tee piece in the
airing cupboard. The one end of this will run into the loft as the
vent. The other connection will go to the pump and then there will be
either one three port valve to CH and HW or two 2 port valves, one
each for CH and HW. (Not forgetting cyclinder stat etc).

Thanks for your help over the last couple of days.