I've recently had a number of quotes for the installation of a new
condensing combi boiler and new radiators. Currently, we have an old
gravity fed system with 20 year old rads.

Some of the plumbers we've spoken to strongly suggest chemical or power
flushing the system and fitting a filter on the return to the combi.
However, the plumber we are feeling inclined to go with suggests just
letting the boiler run and water flushing. He said that he hadn't heard
of people fitting filters on the return.

Is it necessary to have a filter on the return if the system has been
water flushed and the radiators are new?

In article . com,
"JavaEnquirer" writes:
I've recently had a number of quotes for the installation of a new
condensing combi boiler and new radiators. Currently, we have an old
gravity fed system with 20 year old rads.

Some of the plumbers we've spoken to strongly suggest chemical or power
flushing the system and fitting a filter on the return to the combi.
However, the plumber we are feeling inclined to go with suggests just
letting the boiler run and water flushing. He said that he hadn't heard
of people fitting filters on the return.

Is it necessary to have a filter on the return if the system has been
water flushed and the radiators are new?

I would suggest it in the case of a combi, otherwise the
plate exchanger will act as a filter and unlike hard water
scale on the other side of it, the rust debris doesn't clean
out easily. If the whole system is new, or it's not a combi
boiler (i.e. no plate exchanger to block), then it's probably
not worth it.

--
Andrew Gabriel

You say that the "rust debris doesn't clean out easily". Is this
actually a problem, will it actually cause the boiler to work less
efficiently or break down prematurely, or does it just make servicing a
little more time consuming?

Some of the quotes I've had have mentioned chemical flushing, filters
and inhibitor. However, those quotes are roughly £2000 pounds more
than the one without. I mentioned this to the "cheaper" plumber ( Corgi
registered ), but he didn't seem to think not having a filter was a
problem.

Could this be down to the actual boiler? Do some have in-built filters?
I'm going for a Worcester Combi Junior 28i.

With the boiler comes a benchmark certificate which asks was the system
cleansed in accordance with the manufacturers requirements, what cleanser
was used and what inhibitor was installed. Should the system not be cleansed
and you have a problem with the boiler the manufacturer will not honour the
guarantee. Also the building control certificate that your decent installer
will apply for will require the boiler to be installed to the manufacturers
requirements. So the system needs to be cleansed. I do not see why a
properly cleansed system would need a filter but others may disagree


"JavaEnquirer" wrote in message
ups.com...
You say that the "rust debris doesn't clean out easily". Is this
actually a problem, will it actually cause the boiler to work less
efficiently or break down prematurely, or does it just make servicing a
little more time consuming?

Some of the quotes I've had have mentioned chemical flushing, filters
and inhibitor. However, those quotes are roughly £2000 pounds more
than the one without. I mentioned this to the "cheaper" plumber ( Corgi
registered ), but he didn't seem to think not having a filter was a
problem.

Could this be down to the actual boiler? Do some have in-built filters?
I'm going for a Worcester Combi Junior 28i.

JavaEnquirer wrote:

You say that the "rust debris doesn't clean out easily". Is this
actually a problem, will it actually cause the boiler to work less
efficiently or break down prematurely, or does it just make servicing a
little more time consuming?

The first two... the plate heat exchanger is full of loads of tiny water
pathways. This is how it achieves the large surface area required for
rapid heat transfer between the central heating water and the incoming
fresh water that goes to the taps.

If the primary side fo this gets cloged with rust or other debis then it
is often going to need replacement to restore decent hot water performance.

Some of the quotes I've had have mentioned chemical flushing, filters

All of these are worth doing. The chimical flush is best done a couple
of weeks before you decommision the old boiler. Stick it in the system
so it has a good chance to get to work (and it means you need it in
there while the heating is actually on as well so it gets to all the
rads). The state of the system (level of existing sludge / corrosian
etc) will then dictate what other flushing it requires (ranging from a
good rinse through with fresh water, to powerflushing or individually
taking out each rad and flushing). If lots of pipework changes are
happening a flush with a system cleaner to remove flux residue etc can
be worthwhile. Finally inhibitor is essential for the long term
protection of the system and will hopefully prevent the strainers etc
from having much work to do.

and inhibitor. However, those quotes are roughly £2000 pounds more
than the one without. I mentioned this to the "cheaper" plumber ( Corgi
registered ), but he didn't seem to think not having a filter was a
problem.

Well a simple strainer on the return will go a long way to catch any
rust etc before it gets to the boiler and is only a five quid part.
Nothing stopping you buying one and asking the plumber to fit it (pref
with a couple of full bore valves either side to make servicing easy).

Could this be down to the actual boiler? Do some have in-built filters?

Some may - but an external one is usually simpler to get at and clean.

I'm going for a Worcester Combi Junior 28i.

Out of curiosity, why do so many people fit the Jnr model? Is it that
much cheaper? IIUC the Jnr models are very similar to the Si models
however they only run in condensing mode for CH, and not for HW. So you
are throwing away some of your potential energy efficency gains.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Sat, 08 Apr 2006 14:53:31 +0100, John Rumm wrote:

JavaEnquirer wrote:

If the primary side fo this gets cloged with rust or other debis then it
is often going to need replacement to restore decent hot water performance.

Have you heard of this actually happening on a system that's been flushed
(chemically, not power-flushed) and treated with inhibitor in accordance
with the boiler manufacturer's instructions & benchmark requirements?


Well a simple strainer on the return will go a long way to catch any
rust etc before it gets to the boiler and is only a five quid part.
Nothing stopping you buying one and asking the plumber to fit it (pref
with a couple of full bore valves either side to make servicing easy).

The valves are a must. The strainer will block up with a minute amount of
crud and stop effective circulation in the system. (You'll know because
the boiler will short cycle.)

Could this be down to the actual boiler? Do some have in-built filters?

AFAIK only the Alphas, which have a cyclonic trap to encourage sediment to
precipitate out into a chamber (which can presumably be cleaned out
periodically).


I'm going for a Worcester Combi Junior 28i.

Out of curiosity, why do so many people fit the Jnr model? Is it that
much cheaper? IIUC the Jnr models are very similar to the Si models
however they only run in condensing mode for CH, and not for HW. So you
are throwing away some of your potential energy efficency gains.

They're a lot lighter (advertised as being a one-man lift) so they're
attractive to installers working singlehanded. I wasn't aware of
(and I'm a bit surprised about) the difference you quote in DHW mode,
although I don't think that's a major issue: condensing boilers
are still more efficient than non-condensing ones even when they're not
condensing, and the amount of energy used providing DHW is
generally vastly less than for heating.

"John Stumbles" wrote in message
news
On Sat, 08 Apr 2006 14:53:31 +0100, John Rumm wrote:

JavaEnquirer wrote:

If the primary side fo this gets cloged with rust or other debis then it
is often going to need replacement to restore decent hot water
performance.

Have you heard of this actually happening on a system that's been flushed
(chemically, not power-flushed) and treated with inhibitor in accordance
with the boiler manufacturer's instructions & benchmark requirements?


Well a simple strainer on the return will go a long way to catch any
rust etc before it gets to the boiler and is only a five quid part.
Nothing stopping you buying one and asking the plumber to fit it (pref
with a couple of full bore valves either side to make servicing easy).

The valves are a must. The strainer will block up with a minute amount of
crud and stop effective circulation in the system. (You'll know because
the boiler will short cycle.)

Could this be down to the actual boiler? Do some have in-built filters?

AFAIK only the Alphas, which have a cyclonic trap to encourage sediment to
precipitate out into a chamber (which can presumably be cleaned out
periodically).


I'm going for a Worcester Combi Junior 28i.

Out of curiosity, why do so many people fit the Jnr model? Is it that
much cheaper? IIUC the Jnr models are very similar to the Si models
however they only run in condensing mode for CH, and not for HW. So you
are throwing away some of your potential energy efficency gains.

They're a lot lighter (advertised as being a one-man lift) so they're
attractive to installers working singlehanded. I wasn't aware of
(and I'm a bit surprised about) the difference you quote in DHW mode,
although I don't think that's a major issue: condensing boilers
are still more efficient than non-condensing ones even when they're not
condensing, and the amount of energy used providing DHW is
generally vastly less than for heating.

My brother fitted a strainer after I mentioned them to him, and he found
quite a lot of debris in it after he had run the combi for a week and
drained it down to refill with Fernox. Mostly it was solder splats, copper
shards and bits of cloth etc. Of course, he did not flush the pipes out
before turning on, so it was a lazy way of catching the debris.

Andy.

John Stumbles wrote:

If the primary side fo this gets cloged with rust or other debis then it
is often going to need replacement to restore decent hot water performance.


Have you heard of this actually happening on a system that's been flushed
(chemically, not power-flushed) and treated with inhibitor in accordance
with the boiler manufacturer's instructions & benchmark requirements?

The only one that I have direct experiance of (and hence know in detail
what treatment was carried out) is my own... I have certiainly heard of
HW heat exchangers getting filled with crud, but don't know enough of
the back story to know what steps were taken.

Well a simple strainer on the return will go a long way to catch any
rust etc before it gets to the boiler and is only a five quid part.
Nothing stopping you buying one and asking the plumber to fit it (pref
with a couple of full bore valves either side to make servicing easy).


The valves are a must. The strainer will block up with a minute amount of
crud and stop effective circulation in the system. (You'll know because
the boiler will short cycle.)

I found on my one (chemical flush for 14 days, and then flushed via
continous mains feed before filling and dosing), that the filter has
only so far (in two years) collected one solitary grain of "something
solid". Having said that, the system prior to that had been treated with
inhibitor by me, and also its previous owner.

I'm going for a Worcester Combi Junior 28i.

Out of curiosity, why do so many people fit the Jnr model? Is it that
much cheaper? IIUC the Jnr models are very similar to the Si models
however they only run in condensing mode for CH, and not for HW. So you
are throwing away some of your potential energy efficency gains.


They're a lot lighter (advertised as being a one-man lift) so they're
attractive to installers working singlehanded. I wasn't aware of

Yup, I can see that may make a differance...

(then again my boiler was in theory a one man lift, and it still took
two of us to get it on the wall!)

(and I'm a bit surprised about) the difference you quote in DHW mode,

In fact looking at (see page 14):

http://www.worcester-bosch.co.uk/ind...File&id=139624

It suggests that it is the CDi and not the Si that condenses in both
modes. I must admit I am supprised that they claim this to be "one of
the few" boilers that does this however.

although I don't think that's a major issue: condensing boilers
are still more efficient than non-condensing ones even when they're not
condensing, and the amount of energy used providing DHW is
generally vastly less than for heating.

Oh sure... It will vary a bit depending on household as well no doubt so
may be more of an issue for some than others.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In message , IAN CAPEL
writes
With the boiler comes a benchmark certificate which asks was the system
cleansed in accordance with the manufacturers requirements, what cleanser
was used and what inhibitor was installed. Should the system not be cleansed
and you have a problem with the boiler the manufacturer will not honour the
guarantee. Also the building control certificate that your decent installer
will apply for will require the boiler to be installed to the manufacturers
requirements. So the system needs to be cleansed. I do not see why a
properly cleansed system would need a filter but others may disagree


"JavaEnquirer" wrote in message
oups.com...
You say that the "rust debris doesn't clean out easily". Is this
actually a problem, will it actually cause the boiler to work less
efficiently or break down prematurely, or does it just make servicing a
little more time consuming?

Some of the quotes I've had have mentioned chemical flushing, filters
and inhibitor. However, those quotes are roughly £2000 pounds more
than the one without. I mentioned this to the "cheaper" plumber ( Corgi
registered ), but he didn't seem to think not having a filter was a
problem.

Could this be down to the actual boiler? Do some have in-built filters?
I'm going for a Worcester Combi Junior 28i.

I installed one last year ... it's still going

--
geoff

On Sat, 08 Apr 2006 14:33:14 GMT John Stumbles wrote :
AFAIK only the Alphas, which have a cyclonic trap to encourage sediment
to precipitate out into a chamber (which can presumably be cleaned out
periodically).

A Magnaclean does the same thing: not cheap bull well thought out.
http://www.magnaclean.co.uk/

I put one on my mother's system after I got feed up with a Y strainer for
ever clogging on next to nothing.

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
Free SEDBUK boiler database browser http://www.sda.co.uk/qsedbuk.htm
[Latest version QSEDBUK 1.12 released 8 Dec 2005]

On Sat, 08 Apr 2006 20:16:22 +0000, raden wrote:

I'm going for a Worcester Combi Junior 28i.

I installed one last year ... it's still going

I've just pointed out in a reply further up the thread this is likely
to be the same as the one "JavaEnquirer" is planning to fit only in name
and manufacturer :-)

On Sat, 08 Apr 2006 21:43:40 +0100, Tony Bryer wrote:

A Magnaclean does the same thing: not cheap bull well thought out.
http://www.magnaclean.co.uk/

I put one on my mother's system after I got feed up with a Y strainer for
ever clogging on next to nothing.

Ooh! a recommendation based on personal experience: how novel! (At least,
compared to A Certain Other contributor who's been lauding them recently :-)

Thanks Tony - think I might give one a whirl.

On Sun, 09 Apr 2006 15:18:59 GMT, John Stumbles
wrote:

On Sat, 08 Apr 2006 21:43:40 +0100, Tony Bryer wrote:

A Magnaclean does the same thing: not cheap bull well thought out.
http://www.magnaclean.co.uk/

I put one on my mother's system after I got feed up with a Y strainer for
ever clogging on next to nothing.

Ooh! a recommendation based on personal experience: how novel! (At least,
compared to A Certain Other contributor who's been lauding them recently :-)

If we all get one, there should be enough reward for him for that one
way Eyebyeza trip....... :-)



Thanks Tony - think I might give one a whirl.

That does appear to be how they work......

--

..andy