My baxi bahama 100 cuts out exactly the same time each time after
trying to fire up. Everything fires up smoothly and then the gas valve
is closed and the fan stops after about 5 seconds.

I have changed the pump along with most of the parts on this boiler.
My last guess is that the flame sensing electrode is gone as I
disconnected it and the boiler behaved exatly the same. Other guesses
include the pressure switch not working properly.

Whenever the water is turned on the pressure drops on the boiler and
then returns when the boiler fails. I have charged the expansion
vessel to 1 bar and it seems to be holding the charge. I have checked
for leaks and bled the rads but still no joy.

I have read 100's of messages now on everything including fans,
pressure switches, pumps and electrodes. I see many similar stories on
a number of different boilers but have yet to read any definate
answers.

alex

alex wrote:
My baxi bahama 100 cuts out exactly the same time each time after
trying to fire up. Everything fires up smoothly and then the gas valve
is closed and the fan stops after about 5 seconds.


I haven't much knowledge of boilers but the first thing I thought of was
that maybe an over-temp. switch has stuck closed? Or would that stop it
firing up at all?

Si

On 14 Feb 2005 08:48:04 -0800, (alex) wrote:

My baxi bahama 100 cuts out exactly the same time each time after
trying to fire up. Everything fires up smoothly and then the gas valve
is closed and the fan stops after about 5 seconds.

I have changed the pump along with most of the parts on this boiler.
My last guess is that the flame sensing electrode is gone as I
disconnected it and the boiler behaved exatly the same. Other guesses
include the pressure switch not working properly.

Whenever the water is turned on the pressure drops on the boiler and
then returns when the boiler fails. I have charged the expansion
vessel to 1 bar and it seems to be holding the charge. I have checked
for leaks and bled the rads but still no joy.

I have read 100's of messages now on everything including fans,
pressure switches, pumps and electrodes. I see many similar stories on
a number of different boilers but have yet to read any definate
answers.

alex

hi alex,
has the live and neutral supply to the boiler been connected
correctly? if the wires are reversed, then this will have the effect
you describe.
the reason for this is that the flame sensor does not work and the
controls shut the boiler down in a few seconds.
double check that Live at the boiler is realy live and not neutral, it
is quite easy for them to get mixed up either on the boiler terminals
or the spur.
i discovered this myself after running a new boiler on an extention
lead as a tempory measure, and you guessed it the extention lead was
reversed L and N internaly. had the extention lead for years too.
hope this helps
regards
bob

Sounds like a fault coming in after the pressure switch is proven, so it's either not enough gas getting through or faulty flame rectification. Before main burner goes out how big is the flame? If it's not very large what is A/ the working pressure and secondly operating pressure. i.e. is enough gas getting through? Is the modureg functioning correctly? Check the dc voltage on it at the time the burner is lit. I'm not sure what the Bahama requires is there a service manual in your hands? Clean the electrode and check the ht lead, maybe replace that anyway. Make sure good contact at each end.

i.e. lots of things to explore before giving up.

In message , alex
writes
My baxi bahama 100 cuts out exactly the same time each time after
trying to fire up. Everything fires up smoothly and then the gas valve
is closed and the fan stops after about 5 seconds.

I have changed the pump along with most of the parts on this boiler.
My last guess is that the flame sensing electrode is gone as I
disconnected it and the boiler behaved exatly the same. Other guesses
include the pressure switch not working properly.

Whenever the water is turned on the pressure drops on the boiler and
then returns when the boiler fails. I have charged the expansion
vessel to 1 bar and it seems to be holding the charge. I have checked
for leaks and bled the rads but still no joy.

I have read 100's of messages now on everything including fans,
pressure switches, pumps and electrodes. I see many similar stories on
a number of different boilers but have yet to read any definate
answers.

Scaling or a blockage causing the heat exchanger to overheat ?

--
geoff

Thanks for all the comments,

The boiler was working for a couple of months after it was serviced by
a baxi engineer so I imagine that most of the cabling is generally in
order (the wiring lumb etc was all upgraded).

I am going to change all 3 electrodes and ht cables because i have
noticed that the earth casing is damaged even though the cable seems
ok when I test it.

I know the electrodes are sparking ok however I do not know how to
check if the earthing electrode is doing its job properly.

The system was failing intermitently previously but then If I turned
it on and off a few times it would start up. As for the gas pressure,
the valve is new the burners look powerful for the time they remain
on.(however I am not corgi and won't mess with anything to do with the
gas)

Finally I wonder if there is air in the system that could be causing
it as there is an immediate jump in pressure when the heating fires up
(before failing)

I know I will probably have to get someone in to look at it however I
have been stung for a lot of money by the BAXI cowboys who did a bit
of hatchett job to get it working again and I am therefore reluctant
to pay much more(I could of purchased a new boiler by now) Since most
of the parts have been changed including the gas valve the only things
left are the fan,pressure switch, electrodes and heat exchanger.

alex

It;s a very sad situation. I had a multipoint to look at today, it needs a gas valve which costs 185 plus vat. I can get them a new multipoint for 235 plus vat. There is no way on this earth I will fit them a new gas valve, I point blank refused. I said to them, I get no guarantee with a gas valve, you get a full guarantee for a new boiler, there is no decisiuon to make, I am not fitting you a new gas valve. I left it with them.

I won't fit parts that are not economic, since the manufacturer leaves me with the need to guarantee that part. They can stuff that, I walk away to pastures more green.

I have same problem with van mechanics you have had with your boiler. I've lost count of the number of experts that have titivated with my van for the same fault, 500 down the line it had the same fault, in the end it blew up and I'm having to scrap it because I can't trust the reched mechanics any longer.

Maybe you should buy a boiler with a five year guarantee and let bye gon's be bye gon's (however that is spelt, I'm a gas fitter not an English teacher for goodness sake..).

No it's tough mate, we do our best for you, but there's no escaping the fact this stuff costs a lot of money and a new boiler is cheaper than the sum of it's parts by a very large margine.

I have done a bit more investigative work on my baxi bahama 100 boiler
and found that there are a number of subtle things that occur

-Some times the pump runs but the fan does not start (about 1 in 15
times)

-If the above happens or if the boiler starts and cuts out it must be
reset before you can try again.

-After changing all electrodes and cables the boiler ran for about 1
minute before cutting out and then went back cutting out again.

-Some times when the boiler fires up there is a soft clicking noise
after about 5 seconds, if this occurs then the boiler remains alight
for longer(about 8 seconds in total).

-The fan was making a bad noise and the baxi engineer from heatteam
(arghh!!!) snapped of the impeller (among other things) saying he
didn't think it was important. I have changed the fan ( It is quiter
but still cuts out)

Almost everyhing on the boiler has been changed so it is pretty much a
new boiler. (fan, pump, flow switches, diverter valve,wiring lumb,gas
valve,ignition unit, electrodes and leads) In all fairness the boiler
is 6 years old and those parts would need replacing.

Everything now indicates the gas valve or cvi unit however they were
replaced only a couple of months ago, also I wonder if the fact that
the pump runs sometimes and the boiler does not start could be related
to it cutting out when it does start. Plus after changing the
electrodes the boiler ran for a minute or 2 so therefore that rules out
flame sensor.

Pressure was a bit up and down at first but I drained the system and
bled everyhing and now that seems ok.

Alex

p.s.
Initially the problem with the boiler was that it would not start
everytime. sometimes as mentioned above the pump would run but nothing
else. The system would lock out and need to be switched off and on a
couple of times to reset it. This happened in the mornings quite often
however once it started it was usually ok

wrote in message
oups.com...
I have done a bit more investigative work on my baxi bahama 100 boiler
and found that there are a number of subtle things that occur

-Some times the pump runs but the fan does not start (about 1 in 15
times)

-If the above happens or if the boiler starts and cuts out it must be
reset before you can try again.

-After changing all electrodes and cables the boiler ran for about 1
minute before cutting out and then went back cutting out again.

-Some times when the boiler fires up there is a soft clicking noise
after about 5 seconds, if this occurs then the boiler remains alight
for longer(about 8 seconds in total).

-The fan was making a bad noise and the baxi engineer from heatteam
(arghh!!!) snapped of the impeller (among other things) saying he
didn't think it was important. I have changed the fan ( It is quiter
but still cuts out)

I assume you mean the small additional cooling vanes since its near
impossible to snap off the actual fan inside the casing. Loss of the plastic
blades would have no bearing at all on the operation of the main fan. I am
also a bit concerned about the remark "quieter" - is it a new or fully recon
fan or secondhand from somewhere?


Almost everyhing on the boiler has been changed so it is pretty much a
new boiler. (fan, pump, flow switches, diverter valve,wiring lumb,gas
valve,ignition unit, electrodes and leads) In all fairness the boiler
is 6 years old and those parts would need replacing.

I don't see any reference in this list to the differential air pressure
switch or the printed circuit board. You seem to have adopted a scattergun
approach in conjunction with wild guessing and god only knows how much money
you have thrown at it.
Erratic starting such as you describe is frequently down to a failing air
switch but considering Baxis developing reputation IMHO the PCB is also a
really serious candidate for the cause. I come across dry joints regularly
and no doubt CET can confirm this.
Sorry if you have mentioned these items in an earlier post but if you did I
haven't seen them.


Everything now indicates the gas valve or cvi unit however they were
replaced only a couple of months ago, also I wonder if the fact that
the pump runs sometimes and the boiler does not start could be related
to it cutting out when it does start. Plus after changing the
electrodes the boiler ran for a minute or 2 so therefore that rules out
flame sensor.

A simple check with a multimeter would have ruled out the flame sensor and
its lead


Pressure was a bit up and down at first but I drained the system and
bled everyhing and now that seems ok.

Alex

p.s.
Initially the problem with the boiler was that it would not start
everytime. sometimes as mentioned above the pump would run but nothing
else. The system would lock out and need to be switched off and on a
couple of times to reset it. This happened in the mornings quite often
however once it started it was usually ok


So go back and check the air switch. It must be at rest (C-NC made) when not
running and operated when the fan is running (C-NO made). The switch should
give a "clean" on / off i.e. nil or very low resitance / infinity or very
high resistance. Also check the pressure sensing tubes are clear and the
connections into the flue are clean everywhere without any dead insects or
corrosion products in them. Simply switching off and on could have given a
slight movement allowing the pressure switch to reset properly hence the
boiler started after reset.

Baxi have made many of the changes not me. The changes I made were
because there were genuine problems. i.e. the fan sounded like an
aircraft taking off and the pump made a bad noise (they were very old)

The electrodes was a guess but in total for all electrodes and cables i
spent =A320.
Baxi Installed an upgrade kit which includes gas
valve,cvi,thermister,pcb,wiring lumb.

They (Baxi) said the pressure switch needed changing but then changed
their mind and didn't bother.

I have cleaned out the pipes on pressure switch and I can also here it
working and switching off after the fan stops.

alex