I am going to balance my radiators this weekend, I just want to check some
facts that hopefully some of you can help me with.

I need to open up all the control and LSVs and find out what the flow is and
find the index radiator. As I understand it the control valve should be
where the flow is in and the LSV on the outflow. Two of my radiators appear
to the the other way round - is it a simple matter of just swapping over the
knob from the control valve and putting it on the LSV?

Do I leave the index radiator fully open and work back to the boiler or do I
start from the radiator closest to the boiler?

From what I understand I might have to adjust the speed of the pump. I have
no idea how to do that! I have a Potterton Puma 100 boiler and I can't even
see a pump let alone adjust the speed! I understand that some boilers have
automatic pumps - is that right? Does my boiler have one?

Is it correct that the drop needs to be 20 deg F?

TIA

Angela

"AK" wrote in message
...
I am going to balance my radiators this weekend, I just want to check some
facts that hopefully some of you can help me with.

I need to open up all the control and LSVs and find out what the flow is
and
find the index radiator. As I understand it the control valve should be
where the flow is in and the LSV on the outflow. Two of my radiators
appear
to the the other way round - is it a simple matter of just swapping over
the
knob from the control valve and putting it on the LSV?

Do I leave the index radiator fully open and work back to the boiler or do
I
start from the radiator closest to the boiler?

From what I understand I might have to adjust the speed of the pump. I
have
no idea how to do that! I have a Potterton Puma 100 boiler and I can't
even
see a pump let alone adjust the speed! I understand that some boilers
have
automatic pumps - is that right? Does my boiler have one?

Is it correct that the drop needs to be 20 deg F?

TIA

Angela


Have a read of this:

http://www.diyfaq.org.uk/plumbing/rad-balance.html

Ric.

"Ric" wrote in message
...

Have a read of this:

http://www.diyfaq.org.uk/plumbing/rad-balance.html

Ric.

Yes but it doesn't answer all of the questions though, it doesn't say which
order you do the rads in, nor does it say anything about if you can just
swap the control or LSV. I have a 3 story house, so where you start could
make a difference!

In an earlier contribution to this discussion,
AK wrote:

I am going to balance my radiators this weekend, I just want to check
some facts that hopefully some of you can help me with.

I need to open up all the control and LSVs and find out what the flow
is and find the index radiator. As I understand it the control valve
should be where the flow is in and the LSV on the outflow. Two of my
radiators appear to the the other way round - is it a simple matter
of just swapping over the knob from the control valve and putting it
on the LSV?

Yes, provided the two valve bodies are the same, and one of them isn't a
thermostatic valve!


Do I leave the index radiator fully open and work back to the boiler
or do I start from the radiator closest to the boiler?

Neither. Firstly, go round and measure and record the temperature drop
across *every* radiator. You will need a non-contact IR thermometer to be
able to do this is a reasonable time. Then turn down the LSVs on the rads
with the *lowest* drops - regardless of their position relative to the
boiler. This will restrict the flow - and increase the drop - of these, so
starting to even things up. Aim to get all the drops more or less the same -
without worrying too much about the *actual* value at this stage. It is an
iterative process - because decreasing the flow on one rad will increase it
on the others - so you'll have to go round the lot several times - allowing
a bit of time for any adjustments to take effect. The LSV on the rad with
the largest drop should remain fully open at all times.

From what I understand I might have to adjust the speed of the pump.
I have no idea how to do that! I have a Potterton Puma 100 boiler
and I can't even see a pump let alone adjust the speed! I understand
that some boilers have automatic pumps - is that right? Does my
boiler have one?

Is it correct that the drop needs to be 20 deg F?

Once all the drops are the same, you can adjust the pump speed - if
necessary - to achieve the desired value. For a conventional
(non-condensing) boiler, the norm is 11 degC (20 degF). If the drop is
significantly less than this, slow the pump down a bit - and vice versa. A
bit of fine tuning on the rads may be needed after this. [Don't be *too*
much of a perfectionist - it isn't an exact science!]

[I've no idea about your specific boiler/pump. Some boilers have a pump
inside the casing. Some systems use external pumps - often in the airing
cupboard. Once you find the pump, you should find a speed control lever or
knob on the side somewhere].

One other point worth noting: When you're rushing round measuring one rad
after another, you need the flow temperature to stay as constant as
possible - otherwise you won't be comparing apples with apples. This means
running the system flat out - with the room stat turned up to max. This time
of year, you'll probably need to open a few doors and windows while you do
it in order to dump the heat.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

In an earlier contribution to this discussion,
AK wrote:

"Ric" wrote in message
...

Have a read of this:

http://www.diyfaq.org.uk/plumbing/rad-balance.html

Ric.

Yes but it doesn't answer all of the questions though, it doesn't say
which order you do the rads in, nor does it say anything about if you
can just swap the control or LSV. I have a 3 story house, so where
you start could make a difference!


Then have a read of my post!
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

"AK" wrote in message
...

"Ric" wrote in message
...

Have a read of this:

http://www.diyfaq.org.uk/plumbing/rad-balance.html

Ric.

Yes but it doesn't answer all of the questions though,

I didn't say it did - I was just referring you to a very good article on the
subject which, despite not answering all your questions, I though would be a
worthwhile read if you were undertaking the task.

it doesn't say which
order you do the rads in,

That's because there isn't one - that was an unnecesary compication you
added yourself. As the article explains, you are simply trying to make the
resistance across each radiator the same - you will discover which ones have
the most/least resistance when you take your first readings.

nor does it say anything about if you can just
swap the control or LSV. I have a 3 story house, so where you start could
make a difference!

I would say that it probably wouldn't matter which one you use to restrict
the flow as long as you end up with the desired temperature drop but I'm
sure others will disagree!

On Wed, 22 Sep 2004 14:55:19 +0100, Set Square wrote:

In an earlier contribution to this discussion,
AK wrote:

I am going to balance my radiators this weekend, I just want to check
some facts that hopefully some of you can help me with.

I need to open up all the control and LSVs and find out what the flow
is and find the index radiator. As I understand it the control valve
should be where the flow is in and the LSV on the outflow. Two of my
radiators appear to the the other way round - is it a simple matter
of just swapping over the knob from the control valve and putting it
on the LSV?

Yes, provided the two valve bodies are the same, and one of them isn't a
thermostatic valve!


Do I leave the index radiator fully open and work back to the boiler
or do I start from the radiator closest to the boiler?

Neither. Firstly, go round and measure and record the temperature drop
across *every* radiator. You will need a non-contact IR thermometer to be
able to do this is a reasonable time. Then turn down the LSVs on the rads
with the *lowest* drops - regardless of their position relative to the
boiler. This will restrict the flow - and increase the drop - of these, so
starting to even things up. Aim to get all the drops more or less the same -
without worrying too much about the *actual* value at this stage. It is an
iterative process - because decreasing the flow on one rad will increase it
on the others - so you'll have to go round the lot several times - allowing
a bit of time for any adjustments to take effect. The LSV on the rad with
the largest drop should remain fully open at all times.

From what I understand I might have to adjust the speed of the pump.
I have no idea how to do that! I have a Potterton Puma 100 boiler
and I can't even see a pump let alone adjust the speed! I understand
that some boilers have automatic pumps - is that right? Does my
boiler have one?

Is it correct that the drop needs to be 20 deg F?

Once all the drops are the same, you can adjust the pump speed - if
necessary - to achieve the desired value. For a conventional
(non-condensing) boiler, the norm is 11 degC (20 degF). If the drop is
significantly less than this, slow the pump down a bit - and vice versa. A
bit of fine tuning on the rads may be needed after this. [Don't be *too*
much of a perfectionist - it isn't an exact science!]

[I've no idea about your specific boiler/pump. Some boilers have a pump
inside the casing. Some systems use external pumps - often in the airing
cupboard. Once you find the pump, you should find a speed control lever or
knob on the side somewhere].

One other point worth noting: When you're rushing round measuring one rad
after another, you need the flow temperature to stay as constant as
possible - otherwise you won't be comparing apples with apples. This means
running the system flat out - with the room stat turned up to max. This time
of year, you'll probably need to open a few doors and windows while you do
it in order to dump the heat.

I think Set Sqaure has covered most of the points.

It makes no difference which valve you choose as the locksheild (for
balancing) and which you choose as the user valve. However generaly one
valve or other will be the more convinient for a user valve.
Obviously if one of the valves is a TRV then the other is a lockshield.

Not most valves have just about no effect until the last 1/2 a turn to
closed. Beaware that older valves can have a certain amount of backlash in
them so adjust them down to the settings if you need to open one up then
open it up a lot then down to what you what.

Finally setting the closest 1/3 of all the radiators to the boiler (as the
pipes run not as the tape measures) to about 1/2 turn open rather than
fully open [1] might save you one whole cycle of measurements. [2]

[1] All non-quarter turn valves are fully opened if they are open full on
less about 1/4 turn. This is too prevent them jamming in the open
position.

[2] This would be the finish of the subject for the mediocre professionals.

--
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

"Ric" wrote in message
...
That's because there isn't one - that was an unnecesary compication you
added yourself. As the article explains, you are simply trying to make
the
resistance across each radiator the same - you will discover which ones
have
the most/least resistance when you take your first readings.

It's not somthing I made up myself. I have looked at various sites and
there is conflicting advice this site for examples says you should balance
the radiators working back to the boiler
http://www.diyfaq.org.uk/plumbing/pl...html#balancing

On Wed, 22 Sep 2004 14:09:33 +0100, "AK" wrote:

I am going to balance my radiators this weekend, I just want to check some
facts that hopefully some of you can help me with.

I need to open up all the control and LSVs and find out what the flow is and
find the index radiator. As I understand it the control valve should be
where the flow is in and the LSV on the outflow. Two of my radiators appear
to the the other way round - is it a simple matter of just swapping over the
knob from the control valve and putting it on the LSV?

Hello Angela,

Most of your points have been covered by others, but just to clarify one
or two things...

Do I leave the index radiator fully open

The term 'index' is a very old one deriving from a crude rule of thumb
design method. What they mean by 'index' is simply the radiator that has
the most resistance to flow. It is the one that has the longest/thinnest
pipe run and is often (but not always) the furthest from the boiler.
This one should have both its valves wide open during balancing.

and work back to the boiler or do I
start from the radiator closest to the boiler?

Start by opening all of the valves on both sides. Then generally the
Rads closest to the boiler will take more than their fair share of the
flow so you will start by turning them down to get a larger temperature
drop.

From what I understand I might have to adjust the speed of the pump. I have
no idea how to do that! I have a Potterton Puma 100 boiler and I can't even
see a pump let alone adjust the speed! I understand that some boilers have
automatic pumps - is that right? Does my boiler have one?

There is usually a switch or dial on the pump itself, marked 1, 2, 3 (3
being fast) or similar. The pump may even be under the floor, in which
case don't worry unless you really suspect a problem with it.

Is it correct that the drop needs to be 20 deg F?

No. What matters is that all rads have roughly the same drop and have
really hot water reaching them. In other words they are all getting HOT!

TIA

Angela

Phil
The uk.d-i-y FAQ is at http://www.diyfaq.org.uk/
Remove NOSPAM from address to email me

On Wed, 22 Sep 2004 15:54:28 +0100, "Set Square"
wrote:

In an earlier contribution to this discussion,
AK wrote:

"Ric" wrote in message
...

Have a read of this:

http://www.diyfaq.org.uk/plumbing/rad-balance.html

Ric.

Yes but it doesn't answer all of the questions though, it doesn't say
which order you do the rads in, nor does it say anything about if you
can just swap the control or LSV. I have a 3 story house, so where
you start could make a difference!


Then have a read of my post!

Er, which one?

Phil
The uk.d-i-y FAQ is at http://www.diyfaq.org.uk/
Remove NOSPAM from address to email me

On Wed, 22 Sep 2004 16:11:27 +0100, "Ric" wrote:


"AK" wrote in message
...

"Ric" wrote in message
...

Have a read of this:

http://www.diyfaq.org.uk/plumbing/rad-balance.html

Ric.

Yes but it doesn't answer all of the questions though,

I didn't say it did - I was just referring you to a very good article on the
subject which, despite not answering all your questions, I though would be a
worthwhile read if you were undertaking the task.

it doesn't say which
order you do the rads in,

That's because there isn't one - that was an unnecesary compication you
added yourself. As the article explains, you are simply trying to make the
resistance across each radiator the same - you will discover which ones have
the most/least resistance when you take your first readings.

nor does it say anything about if you can just
swap the control or LSV. I have a 3 story house, so where you start could
make a difference!

I would say that it probably wouldn't matter which one you use to restrict
the flow as long as you end up with the desired temperature drop but I'm
sure others will disagree!

That's true so far as literal balancing goes. The whole point of a LSV
is that the lock (as in Lock Shield Valve) prevents anyone from messing
with the setting after you have balanced it.

However, it is quite in order to swap the caps around, or - if you are
up to it - even completely remove the valves from the rad and reverse
them. As others said, it does not matter which end they are on. As an
aside, that is not always the case with TRVs (Thermostatic radiator
Valves) - some models have an arrow determining whether they must go on
the flow or return.

Phil
The uk.d-i-y FAQ is at http://www.diyfaq.org.uk/
Remove NOSPAM from address to email me

On Thu, 23 Sep 2004 09:18:45 +0100, "AK" wrote:


"Ric" wrote in message
...
That's because there isn't one - that was an unnecesary compication you
added yourself. As the article explains, you are simply trying to make
the
resistance across each radiator the same - you will discover which ones
have
the most/least resistance when you take your first readings.

It's not somthing I made up myself. I have looked at various sites and
there is conflicting advice this site for examples says you should balance
the radiators working back to the boiler
http://www.diyfaq.org.uk/plumbing/pl...html#balancing

Good point!! I left that older article in the FAQ because one or two
folk thought it was a better description than mine. I guess it's time to
give it the boot. Sorry Rick (the other one).

Phil
The uk.d-i-y FAQ is at http://www.diyfaq.org.uk/
Remove NOSPAM from address to email me

On Wed, 22 Sep 2004 14:55:19 +0100, "Set Square"
wrote:

In an earlier contribution to this discussion,
AK wrote:

I am going to balance my radiators this weekend, I just want to check
some facts that hopefully some of you can help me with.

Neither. Firstly, go round and measure and record the temperature drop
across *every* radiator.

You will need a non-contact IR thermometer to be
able to do this is a reasonable time.

Angela, If you haven't got one you can get tolerable results simply by
following the procedure, but simply turning each LSV until the flow is
*very* hot to the touch and the return feels almost as hot. In fact that
is probably the best way to get an initial balance, before fine tuning
with a thermometer.

Phil
The uk.d-i-y FAQ is at http://www.diyfaq.org.uk/
Remove NOSPAM from address to email me

"Phil Addison" wrote in message
...
The term 'index' is a very old one deriving from a crude rule of thumb
design method. What they mean by 'index' is simply the radiator that has
the most resistance to flow. It is the one that has the longest/thinnest
pipe run and is often (but not always) the furthest from the boiler.
This one should have both its valves wide open during balancing.

and work back to the boiler or do I
start from the radiator closest to the boiler?

Start by opening all of the valves on both sides. Then generally the
Rads closest to the boiler will take more than their fair share of the
flow so you will start by turning them down to get a larger temperature
drop.

From what I understand I might have to adjust the speed of the pump. I
have
no idea how to do that! I have a Potterton Puma 100 boiler and I can't
even
see a pump let alone adjust the speed! I understand that some boilers
have
automatic pumps - is that right? Does my boiler have one?

There is usually a switch or dial on the pump itself, marked 1, 2, 3 (3
being fast) or similar. The pump may even be under the floor, in which
case don't worry unless you really suspect a problem with it.

Is it correct that the drop needs to be 20 deg F?

No. What matters is that all rads have roughly the same drop and have
really hot water reaching them. In other words they are all getting HOT!

Cheers Phil, that's very helpful advice. The pump is inside the boiler
casing according to the installation booklet, and I can't see anyway of
adjusting it so it will just have to stay as it is!!

I have managed to borrow an infrared thermometer..........I can't stop
playing with it - Although I can't think of a single use for one apart from
balancing radiators!!!

Angela

On Thu, 23 Sep 2004 15:43:40 +0100, "AK" wrote:


"Phil Addison" wrote in message
...

There is usually a switch or dial on the pump itself, marked 1, 2, 3 (3
being fast) or similar. The pump may even be under the floor, in which
case don't worry unless you really suspect a problem with it.

Cheers Phil, that's very helpful advice. The pump is inside the boiler
casing according to the installation booklet, and I can't see anyway of
adjusting it so it will just have to stay as it is!!

According to http://www.partsarena.com/baxi/ you have a 'system boiler'
(ie with all/most of the peripherals like the pump contained in the
case). The pump illustration looks as though there is no speed control,
and the pump is a Myson C61 'special'. I imagine the 'special' means it
has the speed switch omitted. It is possible that the pump is controlled
by the boiler electronics instead.

As you say, leave it as is. You only need to look into it if it is too
fast; = noisy and very low temp rise across boiler, or too slow; = not
enough heat in radiators, boiler short cycles, large temp rise (well
over 11C).

I have managed to borrow an infrared thermometer..........I can't stop
playing with it - Although I can't think of a single use for one apart from
balancing radiators!!!

You can get a rough measure of your body temp by pointing it into your
ear, but clinical IR thermometers have a narrower probe to facilitate
that, and have a 3 digit display to measure to 0.1degree.

Other than that - hot food, though you really want to know the
temperature inside it. Freezer, fridge, oven (not through the glass
though).

Phil
The uk.d-i-y FAQ is at http://www.diyfaq.org.uk/
Remove NOSPAM from address to email me

"Phil Addison" wrote in message
...
On Thu, 23 Sep 2004 15:43:40 +0100, "AK" wrote:


"Phil Addison" wrote in message
...

There is usually a switch or dial on the pump itself, marked 1, 2, 3 (3
being fast) or similar. The pump may even be under the floor, in which
case don't worry unless you really suspect a problem with it.

Cheers Phil, that's very helpful advice. The pump is inside the boiler
casing according to the installation booklet, and I can't see anyway of
adjusting it so it will just have to stay as it is!!

According to http://www.partsarena.com/baxi/ you have a 'system boiler'
(ie with all/most of the peripherals like the pump contained in the
case). The pump illustration looks as though there is no speed control,
and the pump is a Myson C61 'special'. I imagine the 'special' means it
has the speed switch omitted. It is possible that the pump is controlled
by the boiler electronics instead.

As you say, leave it as is. You only need to look into it if it is too
fast; = noisy and very low temp rise across boiler, or too slow; = not
enough heat in radiators, boiler short cycles, large temp rise (well
over 11C).

I have managed to borrow an infrared thermometer..........I can't stop
playing with it - Although I can't think of a single use for one apart
from
balancing radiators!!!

You can get a rough measure of your body temp by pointing it into your
ear, but clinical IR thermometers have a narrower probe to facilitate
that, and have a 3 digit display to measure to 0.1degree.

Other than that - hot food, though you really want to know the
temperature inside it. Freezer, fridge, oven (not through the glass
though).

I think they use them in supermarkets and the likes when doing trading
standards checks on fridges and freezers.

Phil
The uk.d-i-y FAQ is at http://www.diyfaq.org.uk/
Remove NOSPAM from address to email me

In article , AK
writes

I have managed to borrow an infrared thermometer..........I can't stop
playing with it - Although I can't think of a single use for one apart from
balancing radiators!!!
You're kidding, point, shoot, you're hot, sorry you're not ;-)
--
fred

On Thu, 23 Sep 2004 15:43:40 +0100, "AK" wrote:

I have managed to borrow an infrared thermometer..........I can't stop
playing with it - Although I can't think of a single use for one apart from
balancing radiators!!!

I meant to add that I find that it helps to get consistent readings with
the IR thermometer if I stick a small square of black PVC tape on all
the flow and return pipes, just below the valves, as a target for the IR
reading. Without that, the reading depends somewhat on the state of the
pipe surface and whether it is painted or not, and varies according to
which bit of pipe you point the meter at. I'm not sure that black is any
better than any other colour in practice, although in theory black is
the ideal colour. The main thing is to get a consistent emissivity
surface to take readings from.

Phil
The uk.d-i-y FAQ is at http://www.diyfaq.org.uk/
Remove NOSPAM from address to email me

In an earlier contribution to this discussion,
Phil Addison wrote:


I meant to add that I find that it helps to get consistent readings
with the IR thermometer if I stick a small square of black PVC tape
on all the flow and return pipes, just below the valves, as a target
for the IR reading. Without that, the reading depends somewhat on the
state of the pipe surface and whether it is painted or not, and
varies according to which bit of pipe you point the meter at. I'm not
sure that black is any better than any other colour in practice,
although in theory black is the ideal colour. The main thing is to
get a consistent emissivity surface to take readings from.


Do you mean ordinary black insulating tape? Doesn't it go all goo-ey with
the heat? Do you leave it on, or remove it immediately after balancing?
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

"AK" wrote in message
...

"Ric" wrote in message
...

Have a read of this:

http://www.diyfaq.org.uk/plumbing/rad-balance.html

Ric.

Yes but it doesn't answer all of the questions though, it doesn't say
which
order you do the rads in, nor does it say anything about if you can just
swap the control or LSV. I have a 3 story house, so where you start could
make a difference!


I wrote an article on balancing rads which was part of the FAQ for a number
of years, it has now been dropped off it ... however if you want a copy of
the article send me a mail .. happily send it to you.

Rick

"Phil Addison" wrote in message
...

Good point!! I left that older article in the FAQ because one or two
folk thought it was a better description than mine. I guess it's time to
give it the boot. Sorry Rick (the other one).

No problem .. .things evolve, I wrote it about 10 years ago.

On Fri, 24 Sep 2004 18:48:53 +0100, "Set Square"
wrote:

In an earlier contribution to this discussion,
Phil Addison wrote:

I meant to add that I find that it helps to get consistent readings
with the IR thermometer if I stick a small square of black PVC tape
on all the flow and return pipes, just below the valves, as a target
for the IR reading. Without that, the reading depends somewhat on the
state of the pipe surface and whether it is painted or not, and
varies according to which bit of pipe you point the meter at. I'm not
sure that black is any better than any other colour in practice,
although in theory black is the ideal colour. The main thing is to
get a consistent emissivity surface to take readings from.

Do you mean ordinary black insulating tape?

Yes

Doesn't it go all goo-ey with the heat?

Dunno... probably. White spirit should clean up any goo.

Do you leave it on, or remove
it immediately after balancing?

It's still on, waiting for that final tweak when I get the round tuits.

Phil
The uk.d-i-y FAQ is at http://www.diyfaq.org.uk/
Remove NOSPAM from address to email me

On Fri, 24 Sep 2004 18:29:33 +0000 (UTC), "Rick Hughes"
wrote:


"Phil Addison" wrote in message
...

Good point!! I left that older article in the FAQ because one or two
folk thought it was a better description than mine. I guess it's time to
give it the boot. Sorry Rick (the other one).

No problem .. .things evolve, I wrote it about 10 years ago.

Hi Rick, glad to see your still keeping an eye on us :-).
The current piece is in need of an overhaul too, in the light of current
queries. Any comments/suggestions welcome, and in any case I will
re-read yours to check if there is anything to be added.

Phil
The uk.d-i-y FAQ is at http://www.diyfaq.org.uk/
Remove NOSPAM from address to email me

On Thu, 23 Sep 2004 13:45:07 GMT, Phil Addison
wrote:

On Wed, 22 Sep 2004 14:09:33 +0100, "AK" wrote:

I am going to balance my radiators this weekend, I just want to check some
facts that hopefully some of you can help me with.

I need to open up all the control and LSVs and find out what the flow is and
find the index radiator. As I understand it the control valve should be
where the flow is in and the LSV on the outflow. Two of my radiators appear
to the the other way round - is it a simple matter of just swapping over the
knob from the control valve and putting it on the LSV?

Hello Angela,

Most of your points have been covered by others, but just to clarify one
or two things...

Do I leave the index radiator fully open

The term 'index' is a very old one deriving from a crude rule of thumb
design method. What they mean by 'index' is simply the radiator that has
the most resistance to flow. It is the one that has the longest/thinnest
pipe run and is often (but not always) the furthest from the boiler.
This one should have both its valves wide open during balancing.

and work back to the boiler or do I
start from the radiator closest to the boiler?

Start by opening all of the valves on both sides. Then generally the
Rads closest to the boiler will take more than their fair share of the
flow so you will start by turning them down to get a larger temperature
drop.

From what I understand I might have to adjust the speed of the pump. I have
no idea how to do that! I have a Potterton Puma 100 boiler and I can't even
see a pump let alone adjust the speed! I understand that some boilers have
automatic pumps - is that right? Does my boiler have one?

There is usually a switch or dial on the pump itself, marked 1, 2, 3 (3
being fast) or similar. The pump may even be under the floor, in which
case don't worry unless you really suspect a problem with it.

Is it correct that the drop needs to be 20 deg F?

No. What matters is that all rads have roughly the same drop and have
really hot water reaching them. In other words they are all getting HOT!


I'm being dim, but I can't see the point of balancing radiators that
are fitted with TRVs?

Sure, you can run the whole system flat out with the TRVs open, but
surely as soon as they cut in the system will go out of balance and
undo all ones hard work?

Peter

In an earlier contribution to this discussion,
Peter wrote:


I'm being dim, but I can't see the point of balancing radiators that
are fitted with TRVs?

Sure, you can run the whole system flat out with the TRVs open, but
surely as soon as they cut in the system will go out of balance and
undo all ones hard work?


If you *don't* balance such a system, the rads with the highest flow rate
will heat up first - and only when their TRVs close will the other rads see
any heat. Is this what you want?
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

On Sat, 25 Sep 2004 06:41:12 GMT, Peter wrote:

On Thu, 23 Sep 2004 13:45:07 GMT, Phil Addison
wrote:

I'm being dim, but I can't see the point of balancing radiators that
are fitted with TRVs?

Sure, you can run the whole system flat out with the TRVs open, but
surely as soon as they cut in the system will go out of balance and
undo all ones hard work?

Balance is the word causing trouble here and it may not be the best
choice, but we are stuck with it.

The objective of balancing is to restrict flow in the radiator pipework
such that no radiator takes an excessive flow. If that was not done, the
radiators on more restricted flows would be starved and not get properly
hot.

If the system is correctly designed the pump will be just powerful
enough for the most restricted radiator (usually the one on the longest
run) to get sufficient water to fully heat it when its valves are fully
open. However, if a radiator closer to the boiler has its valves fully
open, it will allow loads of water through itself, bypassing the more
restricted distant one. The effect of this extra flow is to reduce the
pump pressure that is available to push the water to the furthest
radiator, which will then fail to heat properly.

The solution is to restrict the nearer one, and also the intermediate
ones, so that they only takes the water needed. That way a high pump
pressure is maintained and each radiator gets only its proper share, and
the system is said to be balanced.

You ask what happens if a TRV now starts to close down? The answer is
that the TRV radiator just takes less water. Because the pump pressure
is nearly equally applied to all radiators, the others are unaffected.
Actually the pump pressure will rise slightly due to the reduced total
flow, and this will push a very small extra amount equally through the
remaining radiators.

Another way of looking at this is to consider what happens when one
radiator TRV closes down. Once it is closed completely the system just
becomes a system with one less radiator, the remaining ones still being
in balance with each other.

As you extend this process to all the TRVs closing down we find that the
water flow through the radiator circuits is much (or completely)
reduced. This will cause the pump pressure to rise to its maximum value,
and it is this higher pressure that can open an automatic bypass valve
(if fitted) to maintain a minimal flow through the boiler.

Phil
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