johnmb

As always , they go wrong just as the winter starts , Boiler only 4 years old , BAXI overheat swith keeps cutting in . and switching off , Read the fault manuall and to me it seems likel;y the fan is not running . Looks an easy job take off cover unplug wires and replace fan , got part number and can buy of internet . Question is do i do it myself , can not get an engineer call out for 10 to 14 days . What do you think .

ag.morley

10 /14 days is ridiculus ........Tell 'em you can smell gas coming out of the boiler "They should be round before the explosion"

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WW_VRS

If you have kids or you can do a little babysitting at your house you will be able to get it sorted within a day I'd have said.

On mine (stone-aged boiler) I don't have a fan or anything, it's a low-efficiency jobber, not really comparable, the motorised valve that switches between heating the hot water and the radiators, tends to cease if you don't use it.

I try to remember to switch on the heating once a week on a bit of a blast, then turn it off again, before airing the house (mainly as it gets too hot funny that ) and that keeps the little motor thing working for the winter

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johnmb

Its the hung on wall type , and am certain its the Fan , as has been noisey over thelast week , water and radiators work ok , had a new 3 way valve fitted some 6 months ago . The fault finding sheet shows that if fan light is on and its overheated ( red light up ) its either replace fan or check power to fan . As the fan is easy to get to thougt i could unplug power to it , a few bolts and replace with a new one . Can not be any harder than replacing the radiator fan on a car , and done one of those . What do you think any Gas fitters out there . Thanks

tfboy

Just a thought:

could it be that you have air in the system and the whole system / radiators need bleeding?

I ask because my man had a very similar problem - boiler said it was shutting down due to overheating and in fact, there was air in the system which caused it to overheat.

His would run for a few minutes, then shutdown. After bleeding the radiators, resetting the boiler, letting the water pump move the water around, he eventually got the the point where no more air was in the system and the boiler wasn't reporting "overheating" any more.

Just a thought

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Xavier

johnmb

Will bleed radiators , but dont think thats the problem , as it shuts down when just set for the hot water ,even if programme for central heating is off. .

AndyC

Our boiler did something like this. Turned out to be the pump. It wasn't working very well, so that the water literally boiled in the boiler and caused it to shut down. The pump itself also got very hot because the bearings had gone.

AndyC

ncarring

If it doesn't involve meddling with the gas supply I'd think you'd be OK to look at the fan. I'm no gas installer though so please don't take my advice as informed.

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North Wiltshire RoADAR

heresmo

I think you should get a CORGI registered proper guy to come and look at it. First, I'm not sure if the boiler would work at all with a faulty fan, since there are cut-outs; second, if it's a closed system, then bleeding the radiators will reduce (or raise?) the pressure in the system and it will need adjusting, if you know how (said in bold print!).

You really are playing with fire, and a blinking big one if it goes up. There must surely be a proper engineer who can come out to you sooner than 10-14 days. Personally, I'd recommend that either you find one or leave the whole lot switched off and start boiling kettles. Aside from anything else, it might need a proper service to remove all the fluffy gunk that accumulates, so making it work doesn't mean it's safe.

Just my opinion, but when you see houses blown out completely, it's a different diy proposition from putting a shelf up.

Mo

Johnnyc

Easy job. But do a visual check on the fan first in case you are hearing a faulty pump. Isolate boiler. Remove 2 screws behind hinged panel, lift up and pull off casing. Remove the cover of the the heat exchanger (big box above expansion vessel-6 or 8 screws) with ignitors at the base. You'll see the fan near the top of the boiler. Turn on boiler and watch to see if fan is functioning when the boiler fires (or tries to fire). Isolate boiler again. Allow heat exchanger to cool and then replace fan if necessary.

As previously said as long as you don't work on or disburb the gas connections you are not breaking any laws. My Baxi Bahama has had a fault which means it does not fire occassionally. A plastic joint on the boiler failed a couple of years ago and water ****ed everywhere including the ignitor module electronics. I dried it out with a hairdryer and it worked ok but I think oxidisation has probably got the better of it now.

Baxi main pcb failures seem to be common. They are a couple of hundred quid each. The relay contacts burning out is the main issue i've seen. An engineer would replace the whole board, charge you for it and may even forget to make the required adjustments on the new PCB. Personally speaking i'll be changing the relay myself.

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Johnny

"Americans have different ways of saying things. They say "elevator", we say "lift" ... they say "President", we say "stupid psychopathic git."

Johnnyc

Easy job. But do a visual check on the fan first in case you are hearing a faulty pump. Isolate boiler. Remove 2 screws behind hinged panel, lift up and pull off casing. Remove the cover of the the heat exchanger (big box above expansion vessel-6 or 8 screws) with ignitors at the base. You'll see the fan near the top of the boiler. Turn on boiler and watch to see if fan is functioning when the boiler fires (or tries to fire). Isolate boiler again. Allow heat exchanger to cool and then replace fan if necessary.

As previously said as long as you don't work on or disburb the gas connections you are not breaking any laws. My Baxi Bahama has had a fault which means it does not fire occassionally. A plastic joint on the boiler failed a couple of years ago and water ****ed everywhere including the ignitor module electronics. I dried it out with a hairdryer and it worked ok but I think oxidisation has probably got the better of it now.

Baxi main pcb failures seem to be common. They are a couple of hundred quid each. The relay contacts burning out is the main issue i've seen. An engineer would replace the whole board, charge you for it and may even forget to make the required adjustments on the new PCB. Personally speaking i'll be changing the relay myself.

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Johnny

"Americans have different ways of saying things. They say "elevator", we say "lift" ... they say "President", we say "stupid psychopathic git."

johnmb

Thanks for that , pretty certain its the Fan , as Pumb is upstairs near water tank , and for the last week had a rattle in the boiler area which was defo a fan . Will have alook tomorrow , do not intend disturbing any gas connections , look at fan and see if something is obvious , can then decide next action .

gallego1968

I too think it`s the fan. The thing about fitting it yourself, is that if something goes wrong and it goes bang and you tell the insurance that you worked on it, they will not pay out.

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Kentish

Strange thing though, its not illegal to play with gas if its your own stuff, even if its a bit silly. You cant play with gas and charge for it without being Corgi.

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Andy

Owner of a sense of humour.

peterc10

Not sure what you mean by a closed system. Certainly you can bleed a normal CH systems' radiators quite safely and easily - it just removes air from the radiator or pipes, which is topped up by water from the header tank.

Johnnyc

Closed means 'pressurised'. ie no header tank but an expansion vessel is required.

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Johnny

"Americans have different ways of saying things. They say "elevator", we say "lift" ... they say "President", we say "stupid psychopathic git."

heresmo

I know nothing about these things. The last time I bled a radiator cos it was stone cold (seemingly with good reason considering the air which came out), the red needle on the pressure bar at "1" shot up to more than 3 (which I was told previously was not good).

I was severely told off by the boiler engineer for bleeding the radiator since it was a closed system. All he did, though, was adjust something. I don't know what, since he looked at both the water input pressure lever under the sink and "something to do with the boiler". (Oh, and a £90 call out / repair charge.)

Mo

ScoobyChris

I had a problem with the GCH in my last house after I bled the radiators. Boiler kept firing up and then shutting down and we traced the fault back to the cold water feed to the header tank - turned out it had got gunged up so that the header tank wasn't being filled!

Chris

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peterc10

Do you mean a "combi" system - if so you do indeed need to be careful with these - I think you need a special bleed kit in order to get air from system - but not sure since never had one.

Johnnyc

That's right. A cold pressurised heating system has a pressure of about 1 bar. If you bleed a radiator you have to repressurise the sytem as you do it. I personally bleed a little and open the pressurisation valve (which introduces mains water to the system at pressure) a little at a time to ensure the pressure stays at 1 bar. Alternatively I get someone else to open and close the valve a necessary while I bleed the rads.
If you don't do this you effectively end up with even more air in the system. The pressurisation unit is there to ensure that the pressure in the system doesn't exceed a couple of bar when the water heats and expands. It's like a baloon in a metal enclosure and is sized according to the water content of your heating system. At a cold pressure of about 1 bar on an air free system the pressurisation unit will keep the system pressure within safe limits as the water heats up. However, if you have introduced air to the system, it expands more than water and you end up hitting 3 bar or more. The boiler pressure relief valve will activate about 3 bar avoiding an explosion however if your heating system is old or has any weak joints, they may not be able to withstand this level of pressure. I once ran my combi dry like this and it sounded like a steam engine ready to explode. Luckily my pipework held out which is a good thing as most of it is below a concrete floor. Had to replace the built-in pressurusation unit with an external one though.

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Johnny

"Americans have different ways of saying things. They say "elevator", we say "lift" ... they say "President", we say "stupid psychopathic git."

Johnnyc

A pressurised system boiler or combi boiler has a pressurisation unit built in. No special bleed kit required but as in my last post you must repressurise as you bleed the rads. The pressurisation unit is a metal cylinder with a rubber membrane across the middle. One side is connected to the heating system and the other is pressurised with air on installation according to the anticipated expansion of the water in your heating system when it heats up.

There is a special tool for 'pumping up' the pressurisation unit but IMO a foot pump will do. The thing to remember is that the air pressure in the pressurisation unit does fall off slightly over time just like a bicycle tyre. Below 1 bar in a pressurised heating system, the boiler will not operate. The mistake people make when the system pressure drops and the boiler stops working is that they open the mains water pressurisation valve to increase the system pressure again. Eventually there is no air left in the pressurisation unit as the extra water pressure forces the air out more quickly and cosequently there is no space left for expansion of the water in the system. This causes the pressure to shoot up and if you don't rectify the situation quickly the rubber membrane seal may fail too thus rendering the pressurisation vessel useless and in need of replacement.

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Johnny

"Americans have different ways of saying things. They say "elevator", we say "lift" ... they say "President", we say "stupid psychopathic git."

johnmb

Thanks for all the input , gas fitter visited today , good job i did not purchase fan and replace myself , as Problem was a duff Thermistor , which i was not charged for . Service system and replaced part all in cost £48 , which i think is a very fair price ,( No call out charge ) would recomend them as they have done me 2 services now and always found inexpensive and helpfull ( TARA Maintenance Folkstone , ) cover Kent area . They did advise that Fan can go at some point , but will fix when that happens with a quick visit when needed , that is one honest service engineer .

Johnnyc

Glad you got the problem sorted. The gas fitter I use is really honest too and very good if you can actually get hold of him.

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Johnny

"Americans have different ways of saying things. They say "elevator", we say "lift" ... they say "President", we say "stupid psychopathic git."

heresmo

FAO Johnnyc - Thanks for all that info - I think I'm beginning to understand a bit better now about closed systems, FWIW

I.e. I certainly don't have a header tank and the boiler is less than a year old. I read somewhere subsequently on the internet that because air expands at ... psi and water at a different psi, it was essential to keep the balance in alignment within the system.

As you describe, it needs to be co-ordinated properly, methinks, since the time I let the air out (i.e. bled the radiator, at radiator rather than boiler), it blew a "cap" off (about 1.5 inch dia) (safety valve presumably) in the boiler which had to be replaced.

IOW I learnt my lesson then, but now understand why it was to wrong to let the air out.

FAO johnmb

Mo