I am having a problem with my combi boiler intermittently shutting down
and showing a red light (flame failure)

It seems to happen when there is a demand for hot water, but I am not
100% sure about this, but not far off.

I think the safety thermostat may be faulty. If I was to remove the
safety thermostat temporarily and connect the two cables together to
see if that removes the dreaded red light syndrome, would the boiler
work ok whilst like this?

It would only be an experiment for a few days to see if it removes the
red light problem.

Is it safe to do this?




Steve

wrote in message
ups.com...
I am having a problem with my combi boiler intermittently shutting down
and showing a red light (flame failure)

It seems to happen when there is a demand for hot water, but I am not
100% sure about this, but not far off.

I think the safety thermostat may be faulty. If I was to remove the
safety thermostat temporarily and connect the two cables together to
see if that removes the dreaded red light syndrome, would the boiler
work ok whilst like this?

It would only be an experiment for a few days to see if it removes the
red light problem.

Is it safe to do this?


NO

If you do this and the problem is not the safety thermostat then whenever
the problem recurs the system is not protected. An explosion takes
milliseconds.

Is there anyway (as a novice) I can test the safety thermostat for a
fault?

Or is it a matter of buying a replacement and perhaps wasting my money?

Any advice gratefully received.



Steve..

James Salisbury wrote:

wrote in message
ups.com...
Is there anyway (as a novice) I can test the safety thermostat for a
fault?

Or is it a matter of buying a replacement and perhaps wasting my money?

Any advice gratefully received.

Err yes. Sorry to sound smug but yes, you can test them but finding out on
such a critical item is not an option. If you had some electrical knowlage
you would'nt be asking here. If it has been a non safety matter elsewhere I
would be more helpfull. I would suggest calling a good plumber.


I don't see any problem in testing them, as long as you know that if you
screw up it can be lethal. (though perhaps not particularly likely to be so
(but you could get lucky))

Turn off power.
Remove stat.
Either drain system, or plug hole.

Immerse sensing end in hot water of various heats, and measure response.
If you need to test at temperatures of over boiling, add lots of salt
to the water.

Do not attempt to modify it, or bypass.

True but for what it costs just buy a new one and eliminate it from the chain, get one with new leeds attached where possible, more than once I've been tricked by the leeds tracking a small current to boiler chassis.

With regard to shorting them out, that depends on how they work, it can't be assumed that they are all simple interuptors anymore with modern electronic sensing methods.
A neighbour asked me to help him as his boiler wouldn't light the other day. The boiler was ancient Can't recall the make but it was basically a multipoint style of heat exchanger with the cooling veins of 15mm pipe running through. A previous fitter had shorted out the oh stat (most likely because parts were unobtainium) and told them to leave the temp control where it is (though the user had forgotten exactly where that "where it is" was. He had taped the whole thing together with closure plate tape.

Man I could have earned money from Gas Installer sending in pictures, but this is a neighbour.

I had to refuse to fix it of course, and said I'd look out for a better boiler for them.

A few days later they said they were going to ask their original gas fitter to find them another boiler because they had always stuck with him.

I suppose if he jumped off a cliff they'd follow.

Probably if I see who it is I should give local corgi inspector a ring anonymously. Lives are put at risk by these guys.

Turn off power.
Remove stat.
Either drain system, or plug hole.

This safety thermostat that I am talking about is like a Very large
flat battery (watch type) which has two connectors on it. It clips to a
pipe coming from the main heat exchanger.

If I remove a cable from it, whilst running bolier as normal, it will
invoke the flame failure red light.

After reading the fault trackingpages in my bolier manual, I suspect
that this thermostat could be on it's way out but at the moment it is
only an intermittant fault.


Baxi Genesis 80



Steve...

On Sun, 06 Feb 2005 06:02:29 -0800, steve wrote:

Turn off power.
Remove stat.
Either drain system, or plug hole.

This safety thermostat that I am talking about is like a Very large
flat battery (watch type) which has two connectors on it. It clips to a
pipe coming from the main heat exchanger.

If I remove a cable from it, whilst running bolier as normal, it will
invoke the flame failure red light.

After reading the fault trackingpages in my bolier manual, I suspect
that this thermostat could be on it's way out but at the moment it is
only an intermittant fault.


Baxi Genesis 80



This type do not usually require that you drain the boiler down.
If you have some heat conducting grease when you install the new one that
is so much the better (to make good contact with its location).
I doubt very much if a replacement unit will exceed £10.

The red light is a lockout indicator which might be due to overheating or
due to flame failure.

There is also the possibility that the boiler is actually over heating!

--
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

It seems to happen when a hot water tap is turned on. It will happen
before the water gets hot.

If the tap is turned on and off several times in a very short space of
time, this will increase the chance of it happening.

If it is down to overheating, what are the likely reasons for this
happening?


Steve......

A bit more info.....

You can actually see the gas igniting, then a switching sound several
times followed by the flame extinguishing and the red light.

It will always fire up normally when pressing the reset button.


Steve..

In article ,
Paul Barker writes:
A neighbour asked me to help him as his boiler wouldn't light the other
day. The boiler was ancient Can't recall the make but it was basically a
multipoint style of heat exchanger with the cooling veins of 15mm pipe
running through. A previous fitter had shorted out the oh stat (most
likely because parts were unobtainium) and told them to leave the temp
control where it is (though the user had forgotten exactly where that
"where it is" was. He had taped the whole thing together with closure
plate tape.

For a description of what happens when one of these
overheats, see "The Self-Uninstalling Gas Water Heater"
http://www.diyfaq.org.uk/humour.html#uninstalling

This was a 1970's model and didn't have the overheat
stat. The 2000 one which replaced it did (and it's a
bog standard electrical component, so easily replacable
if needs be).

--
Andrew Gabriel

On Sun, 06 Feb 2005 14:25:49 -0800, steve wrote:

It seems to happen when a hot water tap is turned on. It will happen
before the water gets hot.

If the tap is turned on and off several times in a very short space of
time, this will increase the chance of it happening.

If it is down to overheating, what are the likely reasons for this
happening?


I strongly suspect (in no particular order) :

a) Some control system failure which means the pump is not running when
doing HW.
b) the secondary heat exchanger is blocked on the primary side thus not
permitting the water to flow.
c) the temperature sensor for HW has become insensitive.
d) the flow sensor for HW gets stuck in the on position which means the
boiler continues on after the tap is closed.
e) Some problem with the diverter valve


--
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

On Sun, 06 Feb 2005 14:29:03 -0800, steve wrote:

A bit more info.....

You can actually see the gas igniting, then a switching sound several
times followed by the flame extinguishing and the red light.

It will always fire up normally when pressing the reset button.

That could just the way the OH stat switches off, especially if it is
dodgy.


--
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