UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions.

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
Posted to uk.d-i-y
Milleniumaire
 
Posts: n/a
Default Boiler low pressure problems

I have a Saunier Duval Thelia Twin 28E combination boiler which was
installed when the house was built seven years ago. Over the last 3/4
years it has caused us a lot of problems usually due to lack of
pressure but for the last 8 months (since it was last repaired) it has
been okay.

Now it is loosing pressure so quickly that it needs to be topped up
every 3/4 hours. I have placed a bucket underneath and this is
catching water leaking from an overflow pipe under the boiler. There
is also an overflow pipe outside but this is dry. The boiler only
seems to leak when I initially top up the pressure, it then settles
down, but after 3/4 hours has lost so much pressure that it cuts out.

I have found that if I turn down the CH thermostat so that the boiler
is off and ensure no hot water is being used, then I allow water in to
top the pressure up, the pressure still falls slightly over a short
period e.g. 15 minutes even though the boiler isn't being used. During
this period no water is seen to be coming out of the overflow pipe
under the boiler. Initially, this suggested to me that I had a leak in
the CH system and so checked all the radiators and pipes in the house
but couldn't see any evidence of this. The only pipes I can't check
are those under the downstairs floorboards. I would expect to see damp
patches in the ceiling if pipes between the floors were leaking.
Besides, if there was a leak in the CH system then surely this would
result in the highest radiators (in the loft) having "cold patches"
where air had replaced the lost water. This is not the case, in fact,
I have bled all radiators and none had any significant amount of air in
them. Does this suggest that the CH system is NOT leaking and that the
problem is definately with the boiler?

We have already had an engineer replace a part last week (after waiting
for 2 weeks for the replacement part to arrive) but this hasn't made
the slightest bit of difference. Sorry, but I don't know what part he
changed!

Are there any more tests I can perform to try to confirm that this is
definately a boiler problem and not caused by leaking radiators/pipes?
The boiler is covered by an insurance policy, but the radiators and
pipes aren't so I want to make sure that the engineer doesn't try to
blame a leaking system for the fault rather than a faulty boiler on his
next visit.

If it is the boiler, any idea what might be causing it?

Thanks.

  #2   Report Post  
Posted to uk.d-i-y
IAN CAPEL
 
Posts: n/a
Default Boiler low pressure problems

The first thing you need to do is to stop it leaking from the " overflow
pipe " which I guess is the pressure relief pipe. As it is leaking
underneath the boiler that could be the reason for no water from it outside.
The pressure relief valve may need renewing. Also I would look at the
expansion vessel on the boiler. To see if it is faulty you would need to
fill the boiler to about 1.5bar, turn on the heating and see if the pressure
rises to 3bar in about 15 mins or less. That would indicate that the
expansion vessel is knackered taking the pressure too high, opening the
pressure relief valve, losing your water in the system, hence " a leak "

"Milleniumaire" wrote in message
oups.com...
I have a Saunier Duval Thelia Twin 28E combination boiler which was
installed when the house was built seven years ago. Over the last 3/4
years it has caused us a lot of problems usually due to lack of
pressure but for the last 8 months (since it was last repaired) it has
been okay.

Now it is loosing pressure so quickly that it needs to be topped up
every 3/4 hours. I have placed a bucket underneath and this is
catching water leaking from an overflow pipe under the boiler. There
is also an overflow pipe outside but this is dry. The boiler only
seems to leak when I initially top up the pressure, it then settles
down, but after 3/4 hours has lost so much pressure that it cuts out.

I have found that if I turn down the CH thermostat so that the boiler
is off and ensure no hot water is being used, then I allow water in to
top the pressure up, the pressure still falls slightly over a short
period e.g. 15 minutes even though the boiler isn't being used. During
this period no water is seen to be coming out of the overflow pipe
under the boiler. Initially, this suggested to me that I had a leak in
the CH system and so checked all the radiators and pipes in the house
but couldn't see any evidence of this. The only pipes I can't check
are those under the downstairs floorboards. I would expect to see damp
patches in the ceiling if pipes between the floors were leaking.
Besides, if there was a leak in the CH system then surely this would
result in the highest radiators (in the loft) having "cold patches"
where air had replaced the lost water. This is not the case, in fact,
I have bled all radiators and none had any significant amount of air in
them. Does this suggest that the CH system is NOT leaking and that the
problem is definately with the boiler?

We have already had an engineer replace a part last week (after waiting
for 2 weeks for the replacement part to arrive) but this hasn't made
the slightest bit of difference. Sorry, but I don't know what part he
changed!

Are there any more tests I can perform to try to confirm that this is
definately a boiler problem and not caused by leaking radiators/pipes?
The boiler is covered by an insurance policy, but the radiators and
pipes aren't so I want to make sure that the engineer doesn't try to
blame a leaking system for the fault rather than a faulty boiler on his
next visit.

If it is the boiler, any idea what might be causing it?

Thanks.



  #3   Report Post  
Posted to uk.d-i-y
Milleniumaire
 
Posts: n/a
Default Boiler low pressure problems

Ian,

I tried what you suggested and that's exactly what happened. Having
set the pressure to 1.5 bar while it was "quiet" I then left it and
returned 15 minutes later to find the pressure over 3 bar and water
pouring out of the pipe at the bottom.

We have boiler insurance through Homeserve GB Ltd (because we have so
many problems with the boiler) and I'm not sure if the engineer who
visited worked directly for them or was on contract. I'm guessing that
they have a policy of attempting to replace the cheaper parts, such as
the pressure relief valve, before changing the biggies like the
expansion vessel.

I get the impression that the expansion vessel is quite an expensive
part and is difficult to change. Is this true do you know?

I'm guessing that the engineer doesn't really know what the problem is
otherwise he would have fixed it during his last visit. He is due
again next Tuesday at which time it will have been 3 weeks since we
first reported this problem to Homeserve. I'm afraid their service
leaves a lot to be desired and I'm tempted to have a chat with him to
try and persuade him to change the expansion vessel.

Thanks.

IAN CAPEL wrote:
The first thing you need to do is to stop it leaking from the " overflow
pipe " which I guess is the pressure relief pipe. As it is leaking
underneath the boiler that could be the reason for no water from it outside.
The pressure relief valve may need renewing. Also I would look at the
expansion vessel on the boiler. To see if it is faulty you would need to
fill the boiler to about 1.5bar, turn on the heating and see if the pressure
rises to 3bar in about 15 mins or less. That would indicate that the
expansion vessel is knackered taking the pressure too high, opening the
pressure relief valve, losing your water in the system, hence " a leak "

"Milleniumaire" wrote in message
oups.com...
I have a Saunier Duval Thelia Twin 28E combination boiler which was
installed when the house was built seven years ago. Over the last 3/4
years it has caused us a lot of problems usually due to lack of
pressure but for the last 8 months (since it was last repaired) it has
been okay.

Now it is loosing pressure so quickly that it needs to be topped up
every 3/4 hours. I have placed a bucket underneath and this is
catching water leaking from an overflow pipe under the boiler. There
is also an overflow pipe outside but this is dry. The boiler only
seems to leak when I initially top up the pressure, it then settles
down, but after 3/4 hours has lost so much pressure that it cuts out.

I have found that if I turn down the CH thermostat so that the boiler
is off and ensure no hot water is being used, then I allow water in to
top the pressure up, the pressure still falls slightly over a short
period e.g. 15 minutes even though the boiler isn't being used. During
this period no water is seen to be coming out of the overflow pipe
under the boiler. Initially, this suggested to me that I had a leak in
the CH system and so checked all the radiators and pipes in the house
but couldn't see any evidence of this. The only pipes I can't check
are those under the downstairs floorboards. I would expect to see damp
patches in the ceiling if pipes between the floors were leaking.
Besides, if there was a leak in the CH system then surely this would
result in the highest radiators (in the loft) having "cold patches"
where air had replaced the lost water. This is not the case, in fact,
I have bled all radiators and none had any significant amount of air in
them. Does this suggest that the CH system is NOT leaking and that the
problem is definately with the boiler?

We have already had an engineer replace a part last week (after waiting
for 2 weeks for the replacement part to arrive) but this hasn't made
the slightest bit of difference. Sorry, but I don't know what part he
changed!

Are there any more tests I can perform to try to confirm that this is
definately a boiler problem and not caused by leaking radiators/pipes?
The boiler is covered by an insurance policy, but the radiators and
pipes aren't so I want to make sure that the engineer doesn't try to
blame a leaking system for the fault rather than a faulty boiler on his
next visit.

If it is the boiler, any idea what might be causing it?

Thanks.


  #4   Report Post  
Posted to uk.d-i-y
Roger Mills
 
Posts: n/a
Default Boiler low pressure problems

In an earlier contribution to this discussion,
Milleniumaire wrote:

Ian,

I tried what you suggested and that's exactly what happened. Having
set the pressure to 1.5 bar while it was "quiet" I then left it and
returned 15 minutes later to find the pressure over 3 bar and water
pouring out of the pipe at the bottom.

We have boiler insurance through Homeserve GB Ltd (because we have so
many problems with the boiler) and I'm not sure if the engineer who
visited worked directly for them or was on contract. I'm guessing
that they have a policy of attempting to replace the cheaper parts,
such as the pressure relief valve, before changing the biggies like
the expansion vessel.

I get the impression that the expansion vessel is quite an expensive
part and is difficult to change. Is this true do you know?

I'm guessing that the engineer doesn't really know what the problem is
otherwise he would have fixed it during his last visit. He is due
again next Tuesday at which time it will have been 3 weeks since we
first reported this problem to Homeserve. I'm afraid their service
leaves a lot to be desired and I'm tempted to have a chat with him to
try and persuade him to change the expansion vessel.

Thanks.

I would say that the expansion vessel was pretty certainly the prime
suspect.

However, it may not actually need replacing - it may just need re-charging
with air. A fairly simple DIY job as long as you've got slightly more than
half a clue.
--
Cheers,
Roger
______
Please reply to newsgroup.
Reply address IS valid, but not regularly monitored.


  #5   Report Post  
Posted to uk.d-i-y
IAN CAPEL
 
Posts: n/a
Default Boiler low pressure problems

They are not that expensive, but first I would try pumping it back up/
repressurising it. The problem with some boilers is that to renew the
expansion vessel you need to remove the boiler
Now you know what the problem is you can amaze the engineer with your
knowledge when he appears and charge him £80 call out and £ 80 per hour plus
vat ( isn't that the norm when it comes to heating engineers )( not me)

Good Luck

"Milleniumaire" wrote in message
ups.com...
Ian,

I tried what you suggested and that's exactly what happened. Having
set the pressure to 1.5 bar while it was "quiet" I then left it and
returned 15 minutes later to find the pressure over 3 bar and water
pouring out of the pipe at the bottom.

We have boiler insurance through Homeserve GB Ltd (because we have so
many problems with the boiler) and I'm not sure if the engineer who
visited worked directly for them or was on contract. I'm guessing that
they have a policy of attempting to replace the cheaper parts, such as
the pressure relief valve, before changing the biggies like the
expansion vessel.

I get the impression that the expansion vessel is quite an expensive
part and is difficult to change. Is this true do you know?

I'm guessing that the engineer doesn't really know what the problem is
otherwise he would have fixed it during his last visit. He is due
again next Tuesday at which time it will have been 3 weeks since we
first reported this problem to Homeserve. I'm afraid their service
leaves a lot to be desired and I'm tempted to have a chat with him to
try and persuade him to change the expansion vessel.

Thanks.

IAN CAPEL wrote:
The first thing you need to do is to stop it leaking from the " overflow
pipe " which I guess is the pressure relief pipe. As it is leaking
underneath the boiler that could be the reason for no water from it
outside.
The pressure relief valve may need renewing. Also I would look at the
expansion vessel on the boiler. To see if it is faulty you would need to
fill the boiler to about 1.5bar, turn on the heating and see if the
pressure
rises to 3bar in about 15 mins or less. That would indicate that the
expansion vessel is knackered taking the pressure too high, opening the
pressure relief valve, losing your water in the system, hence " a leak "

"Milleniumaire" wrote in message
oups.com...
I have a Saunier Duval Thelia Twin 28E combination boiler which was
installed when the house was built seven years ago. Over the last 3/4
years it has caused us a lot of problems usually due to lack of
pressure but for the last 8 months (since it was last repaired) it has
been okay.

Now it is loosing pressure so quickly that it needs to be topped up
every 3/4 hours. I have placed a bucket underneath and this is
catching water leaking from an overflow pipe under the boiler. There
is also an overflow pipe outside but this is dry. The boiler only
seems to leak when I initially top up the pressure, it then settles
down, but after 3/4 hours has lost so much pressure that it cuts out.

I have found that if I turn down the CH thermostat so that the boiler
is off and ensure no hot water is being used, then I allow water in to
top the pressure up, the pressure still falls slightly over a short
period e.g. 15 minutes even though the boiler isn't being used. During
this period no water is seen to be coming out of the overflow pipe
under the boiler. Initially, this suggested to me that I had a leak in
the CH system and so checked all the radiators and pipes in the house
but couldn't see any evidence of this. The only pipes I can't check
are those under the downstairs floorboards. I would expect to see damp
patches in the ceiling if pipes between the floors were leaking.
Besides, if there was a leak in the CH system then surely this would
result in the highest radiators (in the loft) having "cold patches"
where air had replaced the lost water. This is not the case, in fact,
I have bled all radiators and none had any significant amount of air in
them. Does this suggest that the CH system is NOT leaking and that the
problem is definately with the boiler?

We have already had an engineer replace a part last week (after waiting
for 2 weeks for the replacement part to arrive) but this hasn't made
the slightest bit of difference. Sorry, but I don't know what part he
changed!

Are there any more tests I can perform to try to confirm that this is
definately a boiler problem and not caused by leaking radiators/pipes?
The boiler is covered by an insurance policy, but the radiators and
pipes aren't so I want to make sure that the engineer doesn't try to
blame a leaking system for the fault rather than a faulty boiler on his
next visit.

If it is the boiler, any idea what might be causing it?

Thanks.






  #6   Report Post  
Posted to uk.d-i-y
Ed Sirett
 
Posts: n/a
Default Boiler low pressure problems

On Thu, 30 Mar 2006 04:28:29 -0800, Milleniumaire wrote:

I have a Saunier Duval Thelia Twin 28E combination boiler which was
installed when the house was built seven years ago. Over the last 3/4
years it has caused us a lot of problems usually due to lack of
pressure but for the last 8 months (since it was last repaired) it has
been okay.

Now it is loosing pressure so quickly that it needs to be topped up
every 3/4 hours. I have placed a bucket underneath and this is
catching water leaking from an overflow pipe under the boiler. There
is also an overflow pipe outside but this is dry. The boiler only
seems to leak when I initially top up the pressure, it then settles
down, but after 3/4 hours has lost so much pressure that it cuts out.

I have found that if I turn down the CH thermostat so that the boiler
is off and ensure no hot water is being used, then I allow water in to
top the pressure up, the pressure still falls slightly over a short
period e.g. 15 minutes even though the boiler isn't being used. During
this period no water is seen to be coming out of the overflow pipe
under the boiler. Initially, this suggested to me that I had a leak in
the CH system and so checked all the radiators and pipes in the house
but couldn't see any evidence of this. The only pipes I can't check
are those under the downstairs floorboards. I would expect to see damp
patches in the ceiling if pipes between the floors were leaking.
Besides, if there was a leak in the CH system then surely this would
result in the highest radiators (in the loft) having "cold patches"
where air had replaced the lost water. This is not the case, in fact,
I have bled all radiators and none had any significant amount of air in
them. Does this suggest that the CH system is NOT leaking and that the
problem is definately with the boiler?

We have already had an engineer replace a part last week (after waiting
for 2 weeks for the replacement part to arrive) but this hasn't made
the slightest bit of difference. Sorry, but I don't know what part he
changed!

Are there any more tests I can perform to try to confirm that this is
definately a boiler problem and not caused by leaking radiators/pipes?
The boiler is covered by an insurance policy, but the radiators and
pipes aren't so I want to make sure that the engineer doesn't try to
blame a leaking system for the fault rather than a faulty boiler on his
next visit.

If it is the boiler, any idea what might be causing it?

Thanks.


Try the SealedCH FAQ. It's the expansion vessel for sure.



--
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


  #7   Report Post  
Posted to uk.d-i-y
Milleniumaire
 
Posts: n/a
Default Boiler low pressure problems

I checked the pressure on the expansion vessel with the boiler "quiet"
and this showed 2.25 bar. According to the technical data in the
manual:

Expansion vessel charge pressu 3 bar
Expansion valve setting: 6 bar

On the expansion vessel itself (this is a large silver container at the
front of the boiler) it shows that the vessel should be set at 1 bar.

I'm therefore a little confused at these different figures, so I tried
a couple of different settings!

When set at 3 bar the pressure gauge on the boiler went up quickly
within about 5 minutes and it started venting water. I then released
some pressure, down to 1.5 bar and this reduced the pressure shown in
the gauge to just below 2 where it hovered for a short time before
jumping up to over 3 bar again and started leaking.

So, setting the expansion vessel pressure to 1.5 or 3 bar doesn't seem
to solve the problem and appears to just affect how quickly the boiler
starts loosing water.

I did determine that no water is leaking out of the expansion vessel
valve so I guess this means that it isn't punctured.

Any comments on my findings?

Paul.
Ed Sirett wrote:
On Thu, 30 Mar 2006 04:28:29 -0800, Milleniumaire wrote:

I have a Saunier Duval Thelia Twin 28E combination boiler which was
installed when the house was built seven years ago. Over the last 3/4
years it has caused us a lot of problems usually due to lack of
pressure but for the last 8 months (since it was last repaired) it has
been okay.

Now it is loosing pressure so quickly that it needs to be topped up
every 3/4 hours. I have placed a bucket underneath and this is
catching water leaking from an overflow pipe under the boiler. There
is also an overflow pipe outside but this is dry. The boiler only
seems to leak when I initially top up the pressure, it then settles
down, but after 3/4 hours has lost so much pressure that it cuts out.

I have found that if I turn down the CH thermostat so that the boiler
is off and ensure no hot water is being used, then I allow water in to
top the pressure up, the pressure still falls slightly over a short
period e.g. 15 minutes even though the boiler isn't being used. During
this period no water is seen to be coming out of the overflow pipe
under the boiler. Initially, this suggested to me that I had a leak in
the CH system and so checked all the radiators and pipes in the house
but couldn't see any evidence of this. The only pipes I can't check
are those under the downstairs floorboards. I would expect to see damp
patches in the ceiling if pipes between the floors were leaking.
Besides, if there was a leak in the CH system then surely this would
result in the highest radiators (in the loft) having "cold patches"
where air had replaced the lost water. This is not the case, in fact,
I have bled all radiators and none had any significant amount of air in
them. Does this suggest that the CH system is NOT leaking and that the
problem is definately with the boiler?

We have already had an engineer replace a part last week (after waiting
for 2 weeks for the replacement part to arrive) but this hasn't made
the slightest bit of difference. Sorry, but I don't know what part he
changed!

Are there any more tests I can perform to try to confirm that this is
definately a boiler problem and not caused by leaking radiators/pipes?
The boiler is covered by an insurance policy, but the radiators and
pipes aren't so I want to make sure that the engineer doesn't try to
blame a leaking system for the fault rather than a faulty boiler on his
next visit.

If it is the boiler, any idea what might be causing it?

Thanks.


Try the SealedCH FAQ. It's the expansion vessel for sure.



--
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


  #8   Report Post  
Posted to uk.d-i-y
Roger Mills
 
Posts: n/a
Default Boiler low pressure problems

In an earlier contribution to this discussion,
Milleniumaire wrote:

I checked the pressure on the expansion vessel with the boiler "quiet"
and this showed 2.25 bar. According to the technical data in the
manual:

Expansion vessel charge pressu 3 bar
Expansion valve setting: 6 bar

On the expansion vessel itself (this is a large silver container at
the front of the boiler) it shows that the vessel should be set at 1
bar.

I'm not sure where most of those figures came from - they sound like garbage
to me!

Please explain what you mean by "I checked the pressure on the expansion
vessel".

I suspect that you are talking about water pressure which is *not* what is
required.

The expansion vessel has a synthetic rubber diaphragm inside with air on one
side and water on the other. The air pressure has to be set with zero
pressure on the water side. It is checked using a car-type tyre pressure
guage on the built-in schrader valve. The air pressure typically needs to be
between 0.7 and 1.0 bar - which is probably where the 1 bar message on the
vessel itself comes from. It it's too low, you pump air in with a car tyre
pump.

Once you've got the air charge pressure correct, you can *then* pressurise
the water system - introducing water via the filling loop. The water
pressure when the system is cold should be very slightly higher than the air
charge pressure - so that it just starts to compress the air in the
expansion vessel. When the system gets hot, the water expands - compressing
the air in the expansion vessel further. The vessel provides resilience to
allow the water volume to increase without the pressure rising to too high a
level. A water pressure of 2 bar when the system is hot is about typical. If
the pressure rises above 3 bar - which it can easily do if the expansion
vessel is faulty or not correctly charged with air - the safety valve
operates and lets water out. Then when the system cools, the pressure falls
to zero - which *ain't* what you want!

I've no idea where your information came from stating a charge pressure of 3
bar and blow-off pressure of 6 bar - unless you've got a highly atypical
system. I don't think I'd want those pressures in a domestic situation!
--
Cheers,
Roger
______
Please reply to newsgroup.
Reply address IS valid, but not regularly monitored.


  #9   Report Post  
Posted to uk.d-i-y
Milleniumaire
 
Posts: n/a
Default Boiler low pressure problems

Hi roger,

I'm not sure where most of those figures came from - they sound like garbage
to me!


I got the figures from the boiler manual, but I have no idea what they
mean!

Please explain what you mean by "I checked the pressure on the expansion
vessel".


I checked the pressure using a standard car pump with a pressure gauge
attached to the valve on the expansion vessel. This showed 2.25 bar
which seems high so I reduce it to 1 bar but this doesn't resolve the
problem.

I have an engineer coming tomorrow and will find out what he thinks the
problem is and how he plans to fix it.

Paul.

  #10   Report Post  
Posted to uk.d-i-y
Roger Mills
 
Posts: n/a
Default Boiler low pressure problems

In an earlier contribution to this discussion,
Milleniumaire wrote:

Hi roger,

I'm not sure where most of those figures came from - they sound like
garbage to me!


I got the figures from the boiler manual, but I have no idea what they
mean!


Is the manual available on-line? If so, please supply a URL where we can
look at it.


Please explain what you mean by "I checked the pressure on the
expansion vessel".


I checked the pressure using a standard car pump with a pressure gauge
attached to the valve on the expansion vessel. This showed 2.25 bar
which seems high so I reduce it to 1 bar but this doesn't resolve the
problem.


But did you check it without any pressure in the water system? If not, you
must! If there's pressure in the water system, it will compress the air in
the expansion vessel - so that will read pretty much the same as the water
pressure gauge.
--
Cheers,
Roger
______
Please reply to newsgroup.
Reply address IS valid, but not regularly monitored.




  #11   Report Post  
Posted to uk.d-i-y
Ed Sirett
 
Posts: n/a
Default Boiler low pressure problems

On Sat, 01 Apr 2006 08:51:32 -0800, Milleniumaire wrote:

I checked the pressure on the expansion vessel with the boiler "quiet"
and this showed 2.25 bar. According to the technical data in the
manual:

Expansion vessel charge pressu 3 bar
Expansion valve setting: 6 bar

On the expansion vessel itself (this is a large silver container at the
front of the boiler) it shows that the vessel should be set at 1 bar.

I'm therefore a little confused at these different figures, so I tried
a couple of different settings!

When set at 3 bar the pressure gauge on the boiler went up quickly
within about 5 minutes and it started venting water. I then released
some pressure, down to 1.5 bar and this reduced the pressure shown in
the gauge to just below 2 where it hovered for a short time before
jumping up to over 3 bar again and started leaking.

So, setting the expansion vessel pressure to 1.5 or 3 bar doesn't seem
to solve the problem and appears to just affect how quickly the boiler
starts loosing water.

I did determine that no water is leaking out of the expansion vessel
valve so I guess this means that it isn't punctured.

Any comments on my findings?

Paul.
Ed Sirett wrote:
On Thu, 30 Mar 2006 04:28:29 -0800, Milleniumaire wrote:

I have a Saunier Duval Thelia Twin 28E combination boiler which was
installed when the house was built seven years ago. Over the last 3/4
years it has caused us a lot of problems usually due to lack of
pressure but for the last 8 months (since it was last repaired) it has
been okay.

Now it is loosing pressure so quickly that it needs to be topped up
every 3/4 hours. I have placed a bucket underneath and this is
catching water leaking from an overflow pipe under the boiler. There
is also an overflow pipe outside but this is dry. The boiler only
seems to leak when I initially top up the pressure, it then settles
down, but after 3/4 hours has lost so much pressure that it cuts out.

I have found that if I turn down the CH thermostat so that the boiler
is off and ensure no hot water is being used, then I allow water in to
top the pressure up, the pressure still falls slightly over a short
period e.g. 15 minutes even though the boiler isn't being used. During
this period no water is seen to be coming out of the overflow pipe
under the boiler. Initially, this suggested to me that I had a leak in
the CH system and so checked all the radiators and pipes in the house
but couldn't see any evidence of this. The only pipes I can't check
are those under the downstairs floorboards. I would expect to see damp
patches in the ceiling if pipes between the floors were leaking.
Besides, if there was a leak in the CH system then surely this would
result in the highest radiators (in the loft) having "cold patches"
where air had replaced the lost water. This is not the case, in fact,
I have bled all radiators and none had any significant amount of air in
them. Does this suggest that the CH system is NOT leaking and that the
problem is definately with the boiler?

We have already had an engineer replace a part last week (after waiting
for 2 weeks for the replacement part to arrive) but this hasn't made
the slightest bit of difference. Sorry, but I don't know what part he
changed!

Are there any more tests I can perform to try to confirm that this is
definately a boiler problem and not caused by leaking radiators/pipes?
The boiler is covered by an insurance policy, but the radiators and
pipes aren't so I want to make sure that the engineer doesn't try to
blame a leaking system for the fault rather than a faulty boiler on his
next visit.

If it is the boiler, any idea what might be causing it?

Thanks.


Try the SealedCH FAQ. It's the expansion vessel for sure.

This sounds like it might be a boiler with a built in unvented store.
The principles outline in the FAQ will be the same but the numbers will be
bigger. I'm not familiar with this model and would have to look through
the manual.

Not every tradesman who comes to your is automatically dishonest.
In fact IMHO most are honest but the dishonest ones have a
disproportionate presence.

--
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


  #12   Report Post  
Posted to uk.d-i-y
Milleniumaire
 
Posts: n/a
Default Boiler low pressure problems

The engineer appeared yesterday and I got to ask him a few questions.
It was a different guy to the last one and so he had to start from
scratch in determining the problem.

He was able to tell me that the last guy had replaced the Pressure
Relief Value but obviously this didn't resolve the problem.

The new guy thought the problem was with the Expansion Vessel (no
surprise there) and set about re-pressurising it. He obviously did a
better job than me at the weekend as this seems to have fixed it
although I will monitor it over the next couple of days.

Your right Roger, I didn't ensure that there wasn't any pressure in the
system before I attempted to pressurise it (not sure how to do this,
but I guess switching it off for a while and letting the water cool
down would do the trick). The other problem I had was each time I
pumped some air in and then attempted to remove the pump, some air
would leak out. Not a huge problem, but when trying to get it to 1
bar, I wanted to be accurate.

Thanks for your help and, for now at least, it looks okay - I haven't
had to fill it for over a day!

I'm seriously considering replacing this boiler in the Summer. Any
recommendations of brands? I have 3 showers on 2 floors (upstairs and
loft), 2 baths and 16 radiators in a 5 bedroomed house.

Paul.
Ed Sirett wrote:
On Sat, 01 Apr 2006 08:51:32 -0800, Milleniumaire wrote:

I checked the pressure on the expansion vessel with the boiler "quiet"
and this showed 2.25 bar. According to the technical data in the
manual:

Expansion vessel charge pressu 3 bar
Expansion valve setting: 6 bar

On the expansion vessel itself (this is a large silver container at the
front of the boiler) it shows that the vessel should be set at 1 bar.

I'm therefore a little confused at these different figures, so I tried
a couple of different settings!

When set at 3 bar the pressure gauge on the boiler went up quickly
within about 5 minutes and it started venting water. I then released
some pressure, down to 1.5 bar and this reduced the pressure shown in
the gauge to just below 2 where it hovered for a short time before
jumping up to over 3 bar again and started leaking.

So, setting the expansion vessel pressure to 1.5 or 3 bar doesn't seem
to solve the problem and appears to just affect how quickly the boiler
starts loosing water.

I did determine that no water is leaking out of the expansion vessel
valve so I guess this means that it isn't punctured.

Any comments on my findings?

Paul.
Ed Sirett wrote:
On Thu, 30 Mar 2006 04:28:29 -0800, Milleniumaire wrote:

I have a Saunier Duval Thelia Twin 28E combination boiler which was
installed when the house was built seven years ago. Over the last 3/4
years it has caused us a lot of problems usually due to lack of
pressure but for the last 8 months (since it was last repaired) it has
been okay.

Now it is loosing pressure so quickly that it needs to be topped up
every 3/4 hours. I have placed a bucket underneath and this is
catching water leaking from an overflow pipe under the boiler. There
is also an overflow pipe outside but this is dry. The boiler only
seems to leak when I initially top up the pressure, it then settles
down, but after 3/4 hours has lost so much pressure that it cuts out.

I have found that if I turn down the CH thermostat so that the boiler
is off and ensure no hot water is being used, then I allow water in to
top the pressure up, the pressure still falls slightly over a short
period e.g. 15 minutes even though the boiler isn't being used. During
this period no water is seen to be coming out of the overflow pipe
under the boiler. Initially, this suggested to me that I had a leak in
the CH system and so checked all the radiators and pipes in the house
but couldn't see any evidence of this. The only pipes I can't check
are those under the downstairs floorboards. I would expect to see damp
patches in the ceiling if pipes between the floors were leaking.
Besides, if there was a leak in the CH system then surely this would
result in the highest radiators (in the loft) having "cold patches"
where air had replaced the lost water. This is not the case, in fact,
I have bled all radiators and none had any significant amount of air in
them. Does this suggest that the CH system is NOT leaking and that the
problem is definately with the boiler?

We have already had an engineer replace a part last week (after waiting
for 2 weeks for the replacement part to arrive) but this hasn't made
the slightest bit of difference. Sorry, but I don't know what part he
changed!

Are there any more tests I can perform to try to confirm that this is
definately a boiler problem and not caused by leaking radiators/pipes?
The boiler is covered by an insurance policy, but the radiators and
pipes aren't so I want to make sure that the engineer doesn't try to
blame a leaking system for the fault rather than a faulty boiler on his
next visit.

If it is the boiler, any idea what might be causing it?

Thanks.

Try the SealedCH FAQ. It's the expansion vessel for sure.

This sounds like it might be a boiler with a built in unvented store.
The principles outline in the FAQ will be the same but the numbers will be
bigger. I'm not familiar with this model and would have to look through
the manual.

Not every tradesman who comes to your is automatically dishonest.
In fact IMHO most are honest but the dishonest ones have a
disproportionate presence.

--
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


  #13   Report Post  
Posted to uk.d-i-y
Roger Mills
 
Posts: n/a
Default Boiler low pressure problems

In an earlier contribution to this discussion,
Milleniumaire wrote:


Your right Roger, I didn't ensure that there wasn't any pressure in
the system before I attempted to pressurise it (not sure how to do
this, but I guess switching it off for a while and letting the water
cool down would do the trick).


No - that would only take it down to the static cold setting, which would
still be about 1 bar if it were operating correctly. To take it down to
zero, you'd have to physically let some water out - either by operating the
release valve manually (not recommended) or by bleeding a litre or two out
of a radiator. Or you could let some out at the filling point, without the
filling hose connected.
--
Cheers,
Roger
______
Please reply to newsgroup.
Reply address IS valid, but not regularly monitored.


  #14   Report Post  
Posted to uk.d-i-y
Ed Sirett
 
Posts: n/a
Default Boiler low pressure problems

On Mon, 03 Apr 2006 23:56:10 -0700, Milleniumaire wrote:

The engineer appeared yesterday and I got to ask him a few questions.
It was a different guy to the last one and so he had to start from
scratch in determining the problem.

He was able to tell me that the last guy had replaced the Pressure
Relief Value but obviously this didn't resolve the problem.

The new guy thought the problem was with the Expansion Vessel (no
surprise there) and set about re-pressurising it. He obviously did a
better job than me at the weekend as this seems to have fixed it
although I will monitor it over the next couple of days.

Your right Roger, I didn't ensure that there wasn't any pressure in the
system before I attempted to pressurise it (not sure how to do this,
but I guess switching it off for a while and letting the water cool
down would do the trick). The other problem I had was each time I
pumped some air in and then attempted to remove the pump, some air
would leak out. Not a huge problem, but when trying to get it to 1
bar, I wanted to be accurate.

Thanks for your help and, for now at least, it looks okay - I haven't
had to fill it for over a day!

I'm seriously considering replacing this boiler in the Summer. Any
recommendations of brands? I have 3 showers on 2 floors (upstairs and
loft), 2 baths and 16 radiators in a 5 bedroomed house.

I strongly suggest something other than a combi-boiler but the house
really does warrant something with a reasonable store of HW.


----
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


  #15   Report Post  
Posted to uk.d-i-y
Milleniumaire
 
Posts: n/a
Default Boiler low pressure problems

Ed,

I know what you're saying, when we first bought the house I was
sceptical about having only a combi boiler as all our previous houses
had traditional gravity fed systems with hot water cylinders. In fact,
in one of the three similar houses that were being built the elderly
couple that were buying it paid extra to have a standard heating system
fitted (hot water cylinder + header tanks in loft).

I guess the advantage of the combi / sealed system is that we don't
need to worry about header tanks (which would be difficult now that the
loft has been converted into a bedroom & bathroom) and we don't loose
space for housing a large cylinder.

The down side, as I have found too ofter, it that when the boiler packs
in that means no central heating and no hot water until it is repaired.
Unfortunately, I think the builder (or the plumber) cut costs by
installing a Saunier Duval boiler and I certainly wouldn't choose one
again given the problems we've had with it.

Having said that, when it is working we have never had a cold house or
run out of hot water except when filling a large bath - we have to wait
5 minutes half way through. I guess this is due to the small hot water
cylinder in the boiler being replenished. Most of the time we have
showers and the pressure from all three is good, even the shower in the
loft is acceptable. I'm not sure we would get the same pressure from a
gravity fed system.

So, I'm quite happy to stick with a good quality combi boiler and would
prefer something more powerful (and more efficient) than the Saunier
Duval boiler as I always get the impression it is being over stretched.
It's also a little noisy which is unfortunate as it is located in the
garage below our bedroom so it tends to wake us, especially when it's
not well!

Paul.

Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Setting steam boiler pressure cutoff JKevorkian Home Repair 6 December 19th 05 04:21 PM
Problems with boiler pressure nazn UK diy 13 October 14th 05 02:41 PM
Baxi 'System' Boiler - pressure question kmillar UK diy 6 February 4th 05 05:35 PM
Water Pump / Pressure Tank Problem !!!!!! James Nipper Home Repair 9 June 28th 04 03:13 AM
Near death boiler + replacing a boiler David Hearn UK diy 9 January 26th 04 01:44 PM


All times are GMT +1. The time now is 04:33 PM.

Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 DIYbanter.
The comments are property of their posters.
 

About Us

"It's about DIY & home improvement"