Hello,

I spoke over the phone to a plumber to arrange a boiler service. The
plumber tried to sell me a new boiler. Apparently this model is about
20 years old and is relatively inefficient compared to new models. He
tried to sell me a replacement with the argument that the oil saved
will pay for a new boiler in no time, and with the price of oil, he
may have a point!

He said that a new boiler may require changes to the pipework to avoid
an open vent system. He said these were bad because a boiler
malfunction would boil the header tank, which would melt and kill
people. I remember a report in the news about that happening.

What is the alternative to open vent systems. Are open vent systems
really discouraged? How much can I DIY regarding either changing the
pipework or the boiler?

Thanks,
Stephen.

In article ,
Stephen wrote:
Hello,

I spoke over the phone to a plumber to arrange a boiler service. The
plumber tried to sell me a new boiler. Apparently this model is about
20 years old and is relatively inefficient compared to new models. He
tried to sell me a replacement with the argument that the oil saved
will pay for a new boiler in no time, and with the price of oil, he
may have a point!

He said that a new boiler may require changes to the pipework to avoid
an open vent system. He said these were bad because a boiler
malfunction would boil the header tank, which would melt and kill
people. I remember a report in the news about that happening.

Which was caused by an immersion heater - not boiler. You'd need a number
of faults before a boiler could produce boiling water. And even then, a
properly designed open system should cope without the above sort of
incident.

What is the alternative to open vent systems. Are open vent systems
really discouraged? How much can I DIY regarding either changing the
pipework or the boiler?

First - are you talking about open vent primary or secondary?

I've just DIY replaced my gas boiler and changed the primary to
pressurized, but kept the secondary (hot water) open vented.

--
*Someday, we'll look back on this, laugh nervously and change the subject

Dave Plowman London SW
To e-mail, change noise into sound.

On Thu, 24 Jul 2008 11:58:37 GMT, Stephen
wrote:

Hello,

I spoke over the phone to a plumber to arrange a boiler service. The
plumber tried to sell me a new boiler. Apparently this model is about
20 years old and is relatively inefficient compared to new models. He
tried to sell me a replacement with the argument that the oil saved
will pay for a new boiler in no time, and with the price of oil, he
may have a point!

He said that a new boiler may require changes to the pipework to avoid
an open vent system. He said these were bad because a boiler
malfunction would boil the header tank, which would melt and kill
people. I remember a report in the news about that happening.

What is the alternative to open vent systems. Are open vent systems
really discouraged? How much can I DIY regarding either changing the
pipework or the boiler?

Thanks,
Stephen.


The plumber was a double glazing salesman in his previous job. He has
used the lowest of scare tactics on you to sell a new system.

On 24 Jul, 12:58, Stephen
wrote:
Hello,

I spoke over the phone to a plumber to arrange a boiler service. The
plumber tried to sell me a new boiler. Apparently this model is about
20 years old and is relatively inefficient compared to new models. He
tried to sell me a replacement with the argument that the oil saved
will pay for a new boiler in no time, and with the price of oil, he
may have a point!

He said that a new boiler may require changes to the pipework to avoid
an open vent system. He said these were bad because a boiler
malfunction would boil the header tank, which would melt and kill
people. I remember a report in the news about that happening.

What is the alternative to open vent systems. Are open vent systems
really discouraged? How much can I DIY regarding either changing the
pipework or the boiler?

Thanks,
Stephen.

He is an opportunist ******* posing as a salesman! The case in
question was an electric immersion heater with a one stage (failed on)
thermostat. The tenants ignored the bubling and banging (were they
deaf or simple?) The header tank was not fully supported but rather
balanced on two joists so it sagged and split pouring boiling water
onto the ceiling which softened and collapsed with a cot beneath it.
If your oil boiler does not have a back-up overheat thermostat it can
easily be sorted. If it has tell him to sod off. It would be sensible
to make sure any plastic header tank has a full supported base.
The relative efficiency is another matter but if you had told us what
model you have it would have enabled us to estimate the likely
benefits.
Oh and one last point -most plumbers have no idea about how an oil
boiler works!

Stephen wrote:
Hello,

I spoke over the phone to a plumber to arrange a boiler service. The
plumber tried to sell me a new boiler. Apparently this model is about
20 years old and is relatively inefficient compared to new models. He
tried to sell me a replacement with the argument that the oil saved
will pay for a new boiler in no time, and with the price of oil, he
may have a point!


He may also have an ulterior motive

He said that a new boiler may require changes to the pipework to avoid
an open vent system. He said these were bad because a boiler
malfunction would boil the header tank, which would melt and kill
people. I remember a report in the news about that happening.


Everybody does, which is why, having already sold you the boiler with his
opening sentence, he's now in the process of bumping the price up with scare
tactics.

What is the alternative to open vent systems. Are open vent systems
really discouraged? How much can I DIY regarding either changing the
pipework or the boiler?

Thanks,
Stephen.

If the boiler does what it's supposed to, IE give you HW and CH, then leave
it as it is

On Thu, 24 Jul 2008 11:58:37 +0000, Stephen wrote:

Hello,

I spoke over the phone to a plumber to arrange a boiler service. The
plumber tried to sell me a new boiler. Apparently this model is about 20
years old and is relatively inefficient compared to new models. He tried
to sell me a replacement with the argument that the oil saved will pay
for a new boiler in no time, and with the price of oil, he may have a
point!

Pay back is likely to be a number of years, but less than the life the new
system.




He said that a new boiler may require changes to the pipework to avoid
an open vent system. He said these were bad because a boiler malfunction
would boil the header tank, which would melt and kill people. I remember
a report in the news about that happening.

Read the SealedCH FAQ.

If the installer has to resort to scaring you it does not bode well.

--
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 Thu, 24 Jul 2008 15:09:52 +0100, "Dave Plowman (News)"
wrote:


He said that a new boiler may require changes to the pipework to avoid
an open vent system. He said these were bad because a boiler
malfunction would boil the header tank, which would melt and kill
people. I remember a report in the news about that happening.

Which was caused by an immersion heater - not boiler. You'd need a number
of faults before a boiler could produce boiling water. And even then, a
properly designed open system should cope without the above sort of
incident.

Thanks. I had heard of the story but didn't know the full details.

What is the alternative to open vent systems. Are open vent systems
really discouraged? How much can I DIY regarding either changing the
pipework or the boiler?

First - are you talking about open vent primary or secondary?

I've just DIY replaced my gas boiler and changed the primary to
pressurized, but kept the secondary (hot water) open vented.

Well I'm not sure what open vent means! I think both halves of my
system are open vent because both have header tanks. There's no
pressurisation like there is on say a combi boiler. What was the
advantage of pressurising your CH?

On Thu, 24 Jul 2008 07:12:28 -0700 (PDT), cynic
wrote:

He is an opportunist ******* posing as a salesman! The case in
question was an electric immersion heater with a one stage (failed on)
thermostat. The tenants ignored the bubling and banging (were they
deaf or simple?)

As it happens I occasionally hear the odd bubble first thing in the
morning when we use Economy seven to heat the water. The immersion
heater is set to 60C. Is an odd bubble ok or does it mean the
thermostat is a bit iffy?

The header tank was not fully supported but rather
balanced on two joists so it sagged and split pouring boiling water
onto the ceiling which softened and collapsed with a cot beneath it.

I would have thought a plastic tank would melt at high temperature no
matter how it was supported but I can see that in that scenario, the
lack of support may have speeded things up. I am reassured that our
tank sits on a sheet of plywood over a number of joists.

The relative efficiency is another matter but if you had told us what
model you have it would have enabled us to estimate the likely
benefits.

It is a Mistral M1A. The manufacturer cannot find the serial number in
records for the last fifteen years, so they think it is 18-20 years
old. The manufacturer told me that the boiler would have been 65-70%
efficient when new but loses 1% per year so is now about 45-50%
efficient.

Of course, like the plumber, they have a commercial interest to sell
me a new one. Does the above ring true or does it sound a little
fishy?

When I bought oil last time (Jan 08) it was £400 for 1000L. I heard
someone bought 1000L recently for £800. The manufacturer (Mistral)
said that a new boiler would be 95% efficient and mine is 50%. Will my
old boiler will use twice as much oil (95/50=about 2) or is it not as
simple as comparing efficiencies?

If so, I was thinking that in three years the cost of a new boiler
(£1200) would equal the cost of the saved oil. Or are my maths wrong?

Oh and one last point -most plumbers have no idea about how an oil
boiler works!

I searched through the Yellow Pages to try and find an OFTEC one, so I
had hoped this chap knew more than most.

On Thu, 24 Jul 2008 17:01:17 +0000 (UTC), Ed Sirett
wrote:

Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

Thanks. I shall have a look at these.

In article ,
Stephen wrote:
I would have thought a plastic tank would melt at high temperature

Aren't many kettles plastic?

--
*I yell because I care

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Stephen wrote:
On Thu, 24 Jul 2008 15:09:52 +0100, "Dave Plowman (News)"
wrote:


He said that a new boiler may require changes to the pipework to avoid
an open vent system. He said these were bad because a boiler
malfunction would boil the header tank, which would melt and kill
people. I remember a report in the news about that happening.

Which was caused by an immersion heater - not boiler. You'd need a
number of faults before a boiler could produce boiling water. And even
then, a properly designed open system should cope without the above
sort of incident.

Thanks. I had heard of the story but didn't know the full details.

They're elsewhere in the thread. Of course the meja made a sensation out
of it and blamed the wrong things.

What is the alternative to open vent systems. Are open vent systems
really discouraged? How much can I DIY regarding either changing the
pipework or the boiler?

First - are you talking about open vent primary or secondary?

I've just DIY replaced my gas boiler and changed the primary to
pressurized, but kept the secondary (hot water) open vented.

Well I'm not sure what open vent means! I think both halves of my
system are open vent because both have header tanks.

Correct.

There's no pressurisation like there is on say a combi boiler.

Think you're getting confused - a combi boiler simply heats the hot water
directly. Pressurization doesn't come into it - although most will be.

What was the advantage of pressurising your CH?

Basically I bought a system boiler which has the pressure vessel built in.
Advantages are (in no particular order) easy filling with no airlocks. Any
leaks restricted to the content of the system - with a header tank it
could continue being topped up. The ability to have rads higher than where
a tank could go. Easier and cheaper installation costs - and possibly
space saving.

--
*Hard work has a future payoff. Laziness pays off NOW.

Dave Plowman London SW
To e-mail, change noise into sound.

On Jul 24, 12:58*pm, Stephen
wrote:
Hello,

I spoke over the phone to a plumber to arrange a boiler service. The
plumber tried to sell me a new boiler. Apparently this model is about
20 years old and is relatively inefficient compared to new models. He
tried to sell me a replacement with the argument that the oil saved
will pay for a new boiler in no time, and with the price of oil, he
may have a point!

A case of the truth but not the whole truth. The price of the new
boiler isnt what you really pay. You'll pay:
purchase price
installation cost
asstd mods to installation to get it to meet newer regs
repeat repair costs as you find the new boiler unreliable
boiler replacement after a surprisingly short life


He said that a new boiler may require changes to the pipework to avoid
an open vent system.

Vented header tank installs are preferable in most cases, since theyre
more reliable. Pressurised systems are better in flats, where space
for even a little header tank is a problem.

He said these were bad because a boiler
malfunction would boil the header tank, which would melt and kill
people. I remember a report in the news about that happening.

This is really a problem with electric rather than gas heating. For a
gas boiler to do that multiple faults would be needed, and afaik it
never has happened. Electric heating is a different fish of kettle,
and just one common fault has the potential to cause such an accident
on some systems.


What is the alternative to open vent systems. Are open vent systems
really discouraged? How much can I DIY regarding either changing the
pipework or the boiler?

Why make life harder


NT

In article
,
wrote:
Vented header tank installs are preferable in most cases, since theyre
more reliable.

Since a pressure vessel isn't exactly rocket science, is this the case?
Header tanks - or rather the ball valves - do give trouble too.

--
*Many hamsters only blink one eye at a time *

Dave Plowman London SW
To e-mail, change noise into sound.

On Jul 26, 2:48*pm, "Dave Plowman (News)"
wrote:
In article
,
* wrote:

Vented header tank installs are preferable in most cases, since theyre
more reliable.

Since a pressure vessel isn't exactly rocket science, is this the case?
Header tanks *- or rather the ball valves - do give trouble too.

Pipework is pressurised, so more prone to leaks.

Open headers can be turned down to a slow dribble, yes they can
overflow, but it doesnt stop the system working and an exterior
dribble is not too urgent to fix. And chems are easy to add... I'll
stay with headers anyway.


NT

In article
,
wrote:
Since a pressure vessel isn't exactly rocket science, is this the case?
Header tanks - or rather the ball valves - do give trouble too.

Pipework is pressurised, so more prone to leaks.

So your cold water main leaks? Oh - a header tank system is pressurized
too by the head of the tank.

Open headers can be turned down to a slow dribble, yes they can
overflow, but it doesnt stop the system working and an exterior
dribble is not too urgent to fix.

The point was if you have a leak the open system will continue to supply
water for that leak - the pressurized one can't. It will also prompt you
to look for a leak whereas with an open vented type might well go
unnoticed.

And chems are easy to add... I'll stay with headers anyway.

You might find that when new boiler time comes around you have no choice
anyway.

--
*Horn broken. - Watch for finger.

Dave Plowman London SW
To e-mail, change noise into sound.

"Stephen" wrote in message
...
Hello,

I spoke over the phone to a plumber to arrange a boiler service. The
plumber tried to sell me a new boiler. Apparently this model is about
20 years old and is relatively inefficient compared to new models. He
tried to sell me a replacement with the argument that the oil saved
will pay for a new boiler in no time, and with the price of oil, he
may have a point!

He said that a new boiler may require changes to the pipework to avoid
an open vent system. He said these were bad because a boiler
malfunction would boil the header tank, which would melt and kill
people. I remember a report in the news about that happening.

What is the alternative to open vent systems. Are open vent systems
really discouraged? How much can I DIY regarding either changing the
pipework or the boiler?

Thanks,
Stephen.


I replaced my oil fired boiler 2 years ago. All DIY. My new boiler does
use less oil.

I kept my plastic header tank. If the boiler generated boiling water I think
that it would be very obvious that something was wrong!
For this to happen both the normal and the emergency cut thermostats on the
boiler would have had to fail, and probably either the H/W or the room
thermostat. I do recall a story in the press but IIRC the problem was
caused by a immersion heater staying on, and the occupants of the house did
ignore some warning signs.

One reason for not having a sealed system is that they are pressurized, and
the wisdom of preasurizing old radiators is debatable.

The main change to the plumbing was a conversion to a fully pumped system.
For this the supply pipe from the header tank now connects to the boiler
return pipe next to the boiler, rather than the loop to the hot water tank
coil.


--
Michael Chare

In article ,
Michael Chare wrote:
One reason for not having a sealed system is that they are pressurized,
and the wisdom of preasurizing old radiators is debatable.

The amount of pressure is small. If it caused the rads to leak they soon
would anyway. What it might do is find weeping seals on valves, etc.

--
*'ome is where you 'ang your @ *

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote in message
...
In article ,
Stephen wrote:
I would have thought a plastic tank would melt at high temperature

Aren't many kettles plastic?



Indeed. There are also many different types of plastic. If the OP is
concerned he could have a galvanised steel header tank - if you can buy one
nowadays.

If you keep putting heat into a presssurized system, the pressure will
increase and the water will quite probably just boil at a higher
temperature. The conseqencies of any subsequent failures will likely be that
much worse. Hence the regulations regarding the boilers used in steam
engines!


--
Michael Chare

In article ,
writes:
On Jul 26, 2:48*pm, "Dave Plowman (News)"
wrote:
In article
,
* wrote:

Vented header tank installs are preferable in most cases, since theyre
more reliable.

Since a pressure vessel isn't exactly rocket science, is this the case?
Header tanks *- or rather the ball valves - do give trouble too.
Pipework is pressurised, so more prone to leaks.
Open headers can be turned down to a slow dribble, yes they can
overflow, but it doesnt stop the system working and an exterior
dribble is not too urgent to fix.

Modern tank valves often won't switch off if you do that.

And chems are easy to add... I'll

Well, you have to do it so much more often because the tank
exposed to the air wastes all the inhibitor within a year
(or much faster if it's pumping over, which is something
else you have to be careful to avoid).

stay with headers anyway.

Using the filling loop, I can flush a sealed system using
full mains water pressure/flow. The irony is that a vented
system is much more likely to need flushing in the first
place;-)

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Jul 26, 7:39*pm, "Dave Plowman (News)"
wrote:
In article
,
* wrote:

Since a pressure vessel isn't exactly rocket science, is this the case?
Header tanks *- or rather the ball valves - do give trouble too.
Pipework is pressurised, so more prone to leaks.

So your cold water main leaks? *Oh - a header tank system is pressurized
too by the head of the tank.

Open headers can be turned down to a slow dribble, yes they can
overflow, but it doesnt stop the system working and an exterior
dribble is not too urgent to fix.

The point was if you have a leak the open system will continue to supply
water for that leak - the pressurized one can't.

You said that in the last post. And I then said...

On Sat, 26 Jul 2008 22:31:57 +0100, me9 wrote:

On 26 Jul,
wrote:

Vented header tank installs are preferable in most cases, since theyre
more reliable.

More reliable?? The ball valve regularly seizes resulting in no water in
upstairs radiators. Small leaks aren't detected leading to loss of
inhibitor and corroding radiators. Small undetected leaks can lead to
permanentlky soaked carpets and flooring resulting in extensive damage.
I could go on.....

Pressurised systems are better in flats, where space for even a little
header tank is a problem.

Pressurised systems do have some downsides, but IMHO are *always*
better.

My take is that vented systems have a large number of failure modes, some
of which are quite serious, many of which are due to mis-installation but
go undetected for years.

Pressurized systems have really only one common fault which is failure of
the expansion vessel. This, if the user then resorts to continuous
refilling is quite a serious.

The advantages of pressurised systems outweigh those of vented ones, IME,
IMHO.



--
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 26 Jul, 09:35, Stephen
wrote:
On Thu, 24 Jul 2008 07:12:28 -0700 (PDT), cynic

wrote:
He is an opportunist ******* posing as a salesman! The case in
question was an electric immersion heater with a one stage (failed on)
thermostat. The tenants ignored the bubling and banging (were they
deaf or simple?)

As it happens I occasionally hear the odd bubble first thing in the
morning when we use Economy seven to heat the water. The immersion
heater is set to 60C. Is an odd bubble ok or does it mean the
thermostat is a bit iffy?

An odd bubble means very little A boiling system will thunder and
crash continuously until it runs out of water or someone hears it who
has sufficient brain to switch off.


The header tank was not fully supported but rather
balanced on two joists so it sagged and split pouring boiling water
onto the ceiling which softened and collapsed with a cot beneath it.

I would have thought a plastic tank would melt at high temperature no
matter how it was supported but I can see that in that scenario, the
lack of support may have speeded things up. I am reassured that our
tank sits on a sheet of plywood over a number of joists.

The relative efficiency is another matter but if you had told us what
model you have it would have enabled us to estimate the likely
benefits.

It is a Mistral M1A. The manufacturer cannot find the serial number in
records for the last fifteen years, so they think it is 18-20 years
old. The manufacturer told me that the boiler would have been 65-70%
efficient when new but loses 1% per year so is now about 45-50%
efficient.

Of course, like the plumber, they have a commercial interest to sell
me a new one. Does the above ring true or does it sound a little
fishy?

Could be within expected limits. the 1% per year sounds unlikely as I
would expect an initial drop then a fairly stable lifetime. Your
service engineer should take combustion readings and your report sheet
ought to show the nominal efficiency based on the temperature
differential of inlet air to flue outlet related to the CO2 content of
the flue gas. Its a close approximation!


When I bought oil last time (Jan 08) *it was £400 for 1000L. I heard
someone bought 1000L recently for £800. The manufacturer (Mistral)
said that a new boiler would be 95% efficient and mine is 50%. Will my
old boiler will use twice as much oil (95/50=about 2) or is it not as
simple as comparing efficiencies?

I seriously doubt your Mistral (I think its a pressure jet burner) is
down to 50%, nearer to 70% if it has been kept in a reasonably well
maintained condition.


If so, I was thinking that in three years the cost of a new boiler
(£1200) would equal the cost of the saved oil. Or are my maths wrong?


Oh and one last point -most plumbers have no idea about how an oil
boiler works!

I searched through the Yellow Pages to try and find an OFTEC one, so I
had hoped this chap knew more than most.

If he is OFTEC registered he ought to know the basics but has he any
good references from other customers?
OFTEC are somewhat similar to CORGI in that they offer registration
for different categories of work. Make sure your guy is ok for boiler
installation and commissioning from his ticket. Or you could ask OFTEC
for confirmation.

On Wed, 30 Jul 2008 11:41:27 -0700 (PDT), cynic wrote:

As it happens I occasionally hear the odd bubble first thing in the
morning when we use Economy seven to heat the water. The immersion
heater is set to 60C. Is an odd bubble ok or does it mean the
thermostat is a bit iffy?

When you heat cold water the dissolved air comes out. Look at the bottom
of a pan of cold water being heated on the cooker, it'll be covered in
bubbles very soon after the heat is applied. I suspect that this releaed
air is collecting somewhere and you are hearing it glug away up the vent
pipe when you first draw of water. The vent pipe should rise straight from
the top of cylinder with the hot water feed T'd from it and angled very
slightly down.

Could be within expected limits. the 1% per year sounds unlikely as I
would expect an initial drop then a fairly stable lifetime. Your
service engineer should take combustion readings and your report sheet
ought to show the nominal efficiency based on the temperature
differential of inlet air to flue outlet related to the CO2 content of
the flue gas. Its a close approximation!

Our service engineer does and our boiler comes out at 70% or so and is
about 15 years old.

When I bought oil last time (Jan 08) *it was £400 for 1000L. I heard
someone bought 1000L recently for £800.

40p/l in Jan is about right, 80p/l appears to be about 20p+ over the
current price of around 55p/l (looks to have dropped a little recently).

The manufacturer (Mistral) said that a new boiler would be 95%
efficient and mine is 50%.

Well I'd take a pinch of salt with both of those figures. I suspect the
makers figure is when running optimally in full condesing mode, in the
real world it won't be doing that all the time. So push the makers one
down 10% and yours up by maybe 20%, giving 85% and 70%. Some fuel saving
but not the best part of half...

I seriously doubt your Mistral (I think its a pressure jet burner) is
down to 50%, nearer to 70% if it has been kept in a reasonably well
maintained condition.

Agreed see above, our boiler is also a Mistral.

--
Cheers
Dave.