Baxi Combi cuts out after 5 seconds

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

Reply to
alex
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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

Reply to
Mungo "two sheds" Toadfoot

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

Reply to
burbeck

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

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

-- Paul Barker

Reply to
Paul Barker

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

Reply to
alex

It;s a very sad situation. I had a multipoint to look at today, i needs a gas valve which costs 185 plus vat. I can get them a ne multipoint for 235 plus vat. There is no way on this earth I will fi them a new gas valve, I point blank refused. I said to them, I get n 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. left it with them.

I won't fit parts that are not economic, since the manufacturer leave me with the need to guarantee that part. They can stuff that, I wal 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 m van for the same fault, 500 down the line it had the same fault, in th end it blew up and I'm having to scrap it because I can't trust th reched mechanics any longer.

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

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

-- Paul Barker

Reply to
Paul Barker

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

Reply to
alexeveritt

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?

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.

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

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.

Reply to
John

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

Reply to
alexeveritt

Did you ever find what the fault was ?

Reply to
Martin

Obvious innit, using a broken website by the name of Homeowners Hub.

Reply to
Harry Bloomfield, Esq.

Yes it is, Unfortunately there are few easy to find resources out there to tell people what newsgroups are and how useful they can be. Brian

Reply to
Brian Gaff (Sofa

Brian Gaff (Sofa) used his keyboard to write :

Judging by the number of posts bounced back to that site, from this group, you would thnk by now something might have dawned on them..

Reply to
Harry Bloomfield, Esq.

Not 5 secs but my Baxi has run for about 30 sces then cuts out from new. Although the water gets piping hot, its done this even in the coldest days. Baxi came along with the installers but its always been the same. Only the 2 of us in the house so its not a problem. I can only see it being a problem if more than 1 bath was needed a night - we share the water. Even when the central heating is on it doesnt run on startup for more than 2 mins.

Reply to
sintv

I'm not sure anyone posting on that site can find the thread again to see the reply or to ask further questions.

Reply to
alan_m

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