I have had a loft conversion on a two-storey house, now three storey.
As part of the conversion the hot-water system was changed from non-
pressurised to pressurised. The new cylinder and associated pressure
vessels were re-sited in the loft. The top storey radiators are run
off a separate control system.

Since installation of the new system (last August), I have had
continual problems with the boiler over-heating and cutting out,
usually after around 30 minutes but sometimes even more frequently
than that. The builder has had his heating subbies back many times
and they have done the following (allegedly):

- replaced the mother board on the boiler
- drained and cleaned the radiator system
- installed an additional pump in series

None of it has made any difference.

The boiler is a Baxi Solo 3 PFL 70. On the ground floor there are 5
rads, 7 on the first floor and 3 on the second floor.

Finally a different heating engineer came round and diagnosed the
following:

- boiler too small for the new environment
- flow pipes from boiler to tank should be 28mm, rather than 22mm
(replacing these would involve major work ripping out stud walls in
the newly finished conversion)

When this information was presented to the builder he indicated that
this was rubbish and that only a new boiler was required, as it wasn't
powerful enough. However, surely a weak boiler would just take longer
to heat up the rads?

On the advice of a friend I de-synchronised the hot water and central
heating. This cured the problem for about a week; then the boiler
began cutting out again on the hot water phase, and now is cutting out
again on the heating phase.

I do not want to have to buy a new boiler if its a simple problem -
two suggested faults are a new thermostat and a faulty bypass valve.

Any suggestions as to the likely cause of the problem, or what to do
next???

Many thanks!

wrote in news:fc7746dc-e5ba-4de9-973a-
:

I have had a loft conversion on a two-storey house, now
three storey.
As part of the conversion the hot-water system was changed
from non-
pressurised to pressurised. The new cylinder and associated
pressure
vessels were re-sited in the loft. The top storey radiators
are run
off a separate control system.

Since installation of the new system (last August), I have
had
continual problems with the boiler over-heating and cutting
out,
usually after around 30 minutes but sometimes even more
frequently
than that. The builder has had his heating subbies back
many times
and they have done the following (allegedly):

- replaced the mother board on the boiler
- drained and cleaned the radiator system
- installed an additional pump in series

None of it has made any difference.

The boiler is a Baxi Solo 3 PFL 70. On the ground floor
there are 5
rads, 7 on the first floor and 3 on the second floor.

Finally a different heating engineer came round and
diagnosed the
following:

- boiler too small for the new environment
- flow pipes from boiler to tank should be 28mm, rather than
22mm
(replacing these would involve major work ripping out stud
walls in
the newly finished conversion)

When this information was presented to the builder he
indicated that
this was rubbish and that only a new boiler was required, as
it wasn't
powerful enough. However, surely a weak boiler would just
take longer
to heat up the rads?

On the advice of a friend I de-synchronised the hot water
and central
heating. This cured the problem for about a week; then the
boiler
began cutting out again on the hot water phase, and now is
cutting out
again on the heating phase.

I do not want to have to buy a new boiler if its a simple
problem -
two suggested faults are a new thermostat and a faulty
bypass valve.

Any suggestions as to the likely cause of the problem, or
what to do
next???

Many thanks!


Was the system changed to have all TRV if so was a bypass
circuit fitted.
Does the overheat LED flash or is a constant on
Try turning the boiler thermostat knob to just a quarter on,
i.e. water temp lower then about 63c

On Nov 23, 2:44 pm, John wrote:

Was the system changed to have all TRV if so was a bypass
circuit fitted.
Does the overheat LED flash or is a constant on
Try turning the boiler thermostat knob to just a quarter on,
i.e. water temp lower then about 63c- Hide quoted text -

- Show quoted text -

John - thanks for the reply.

TRV (Thermostatic radiator valves?) - all the new upstairs radiators
have these. The circuit is off at the moment.

On the old bit of the house, 2 of the twelve rads have TRV.

The overheat light is on constantly. Sometimes the bolier on light
(next to it) is also on; and sometimes that light flickers.

I will try the boiler thermostat route.

wrote in news:b647b83d-3da7-4e5e-9c4e-
:

On Nov 23, 2:44 pm, John wrote:

Was the system changed to have all TRV if so was a bypass
circuit fitted.
Does the overheat LED flash or is a constant on
Try turning the boiler thermostat knob to just a quarter
on,
i.e. water temp lower then about 63c- Hide quoted text -

- Show quoted text -

John - thanks for the reply.

TRV (Thermostatic radiator valves?) - all the new upstairs
radiators
have these. The circuit is off at the moment.

On the old bit of the house, 2 of the twelve rads have TRV.

The overheat light is on constantly. Sometimes the bolier
on light
(next to it) is also on; and sometimes that light flickers.

That doesn't sound good ;(


I will try the boiler thermostat route.

Baxis realty dont like running hot
often the firebox gasket is leaking which trips the overheat
stat.
When was the boiler properly serviced?

On Nov 23, 4:01 pm, John wrote:
wrote in news:b647b83d-3da7-4e5e-9c4e-
:







On Nov 23, 2:44 pm, John wrote:

Was the system changed to have all TRV if so was a bypass
circuit fitted.
Does the overheat LED flash or is a constant on
Try turning the boiler thermostat knob to just a quarter
on,
i.e. water temp lower then about 63c- Hide quoted text -

- Show quoted text -

John - thanks for the reply.

TRV (Thermostatic radiator valves?) - all the new upstairs
radiators
have these. The circuit is off at the moment.

On the old bit of the house, 2 of the twelve rads have TRV.

The overheat light is on constantly. Sometimes the bolier
on light
(next to it) is also on; and sometimes that light flickers.

That doesn't sound good ;(



I will try the boiler thermostat route.

Baxis realty dont like running hot
often the firebox gasket is leaking which trips the overheat
stat.
When was the boiler properly serviced?- Hide quoted text -

- Show quoted text -

Recently - we have an annual service plan with British Gas.

I've rung Baxi and they've offered a service visit - £250 including
parts and labour. Should I take it up?

wrote in news:a3056267-8088-4adb-afbd-
:


Baxis realty dont like running hot
often the firebox gasket is leaking which trips the
overheat
stat.
When was the boiler properly serviced?- Hide quoted text -

- Show quoted text -

Recently - we have an annual service plan with British Gas.


Oh dear I did say, When was the boiler properly serviced?

I've rung Baxi and they've offered a service visit - £250
including
parts and labour. Should I take it up?


Wait and see if it will run reliably on a low heat first.

On Fri, 23 Nov 2007 04:57:19 -0800, stephen.travis wrote:

I have had a loft conversion on a two-storey house, now three storey. As
part of the conversion the hot-water system was changed from non-
pressurised to pressurised. The new cylinder and associated pressure
vessels were re-sited in the loft. The top storey radiators are run off
a separate control system.

Since installation of the new system (last August), I have had continual
problems with the boiler over-heating and cutting out, usually after
around 30 minutes but sometimes even more frequently than that. The
builder has had his heating subbies back many times and they have done
the following (allegedly):

- replaced the mother board on the boiler - drained and cleaned the
radiator system - installed an additional pump in series

None of it has made any difference.

The boiler is a Baxi Solo 3 PFL 70. On the ground floor there are 5
rads, 7 on the first floor and 3 on the second floor.

Finally a different heating engineer came round and diagnosed the
following:

- boiler too small for the new environment - flow pipes from boiler to
tank should be 28mm, rather than 22mm (replacing these would involve
major work ripping out stud walls in the newly finished conversion)

When this information was presented to the builder he indicated that
this was rubbish and that only a new boiler was required, as it wasn't
powerful enough. However, surely a weak boiler would just take longer
to heat up the rads?

On the advice of a friend I de-synchronised the hot water and central
heating. This cured the problem for about a week; then the boiler began
cutting out again on the hot water phase, and now is cutting out again
on the heating phase.

I do not want to have to buy a new boiler if its a simple problem - two
suggested faults are a new thermostat and a faulty bypass valve.

Any suggestions as to the likely cause of the problem, or what to do
next???

Many thanks!

Almost certainly the CAUSE of the over heating is a lack of primary flow.
This is not likely to be the boiler, pump(s) or mother board. The buggers
should have cleaned the system out when they worked on it, anyway we can
assume that has been done.

My guess is that the control system is wrong. You sound like you need
something like a 3 zone extended S-plan controls.

If you are electrically competent make a complete wiring diagram of the
heating control system. You might also have a pipework routing fault but
seeing as the system does work some of the time perhaps not.



--
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 Fri, 23 Nov 2007 08:12:16 -0800, stephen.travis wrote:

On Nov 23, 4:01 pm, John wrote:
wrote in news:b647b83d-3da7-4e5e-9c4e-
:







On Nov 23, 2:44 pm, John wrote:

Was the system changed to have all TRV if so was a bypass circuit
fitted.
Does the overheat LED flash or is a constant on Try turning the
boiler thermostat knob to just a quarter
on,
i.e. water temp lower then about 63c- Hide quoted text -

- Show quoted text -

John - thanks for the reply.

TRV (Thermostatic radiator valves?) - all the new upstairs
radiators
have these. The circuit is off at the moment.

On the old bit of the house, 2 of the twelve rads have TRV.

The overheat light is on constantly. Sometimes the bolier
on light
(next to it) is also on; and sometimes that light flickers.

That doesn't sound good ;(



I will try the boiler thermostat route.

Baxis realty dont like running hot
often the firebox gasket is leaking which trips the overheat
stat.
When was the boiler properly serviced?- Hide quoted text -

- Show quoted text -

Recently - we have an annual service plan with British Gas.

I've rung Baxi and they've offered a service visit - £250 including
parts and labour. Should I take it up?

Not yet. Till all the more correctable problems have been addressed.


--
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