Alpha CB28X - Not firing up problem

[julesg007]

Hello again,

Would like a little help with my boiler again.

The boiler seems to have developed 2 problems in the last 24hrs although I suspect that they are linked. It is not firing up to produce HW and although in constant mode for CH it only fires up when it wants to and then shuts off only after a very short period of time, usually less than 1 minute.

With the HW tap open I removed the flow switch and nothing happened.

Could it be that the FS is u/s? For around £21 inc it seems a cheap enough thing to change before having to get my heating engineer out to see me.

I changed the diaphragm in the divertor valve in June '08 and from then until now the boiler has worked without fault.

Any other thoughts and comments would be greatly appreciated.

Thanks again for the help.

Jules

 

[julesg007]

Hi,

Just wanted to add the following;

The boiler seems to be having a mental session and is crazily trying to fire up (as still in constant CH mode).

However the FS seems to be clicking on and off.

Don't know if that helps but thought I'd mention it.

Jules

 

[julesg007]

Hi All,

Would be really grateful for some help on this problem.

Would also like to add the following,

The problem seems to be intermittant. Whilst the boiler is firing up it will cut out for no reason on both HW and CH modes.

It seems to be more succesful when demanding DH, i.e. it fires up but it can and does cut out and then re-fire. There is no set time between the two - sometimes it fires up straightaway other times I just have to wait until it wants to work.

With the CH, this is not so reliable. If I switch the CH to constant, it doesn't always fire up immediately (thermostates are set so it will run) and then for no reason it fires and can run for a fair while but it will cut out again. Again there is no set timing between the two or regular interval.

If you need any further info please ask and I'll be happy to provide some more.

Would really appreciate some help on this one. I am aware I may have to get my guy out to give it the once over but when monies tight if I can get a DIY fix it would keep the bank manager and wife very happy.

Thanks again all for the help

 

[gas4you]

It's one of those impossible faults to try to give a decent answer to from afar.

Something erratic as this could be many things, but as a starting point I would measure the resistance of the primary ntc.

Failing this get your chap in, as it needs someone in front of it when its mis-behaving, otherwise the most common thing you will get is 'it's the pcb', which strangely are usually pretty reliable on Alphas.

 

[julesg007]

Evening Dave,

Thank you for the advice.

I most certainly would concur about distance diagnosis.

If you are able to give me some help or guidance in checking the resistance of the ntc (but must admit not sure what this is) I would be grateful as I do have a mutli meter handy. However, if you feel this is something I should let my guy look into I entirely understand.

I would however, like to add the following but I am not sure if it has any relavence.

When the boiler is up and running and I have hot water running, I get a pulse of air bubbles in the water but as soon as it cuts out they stop.

Thanks again for the help.

Jules

 

[Paul Barker]

last bit not relevant.

won't be diaphragm again.

If you are having problems with flow switch anyway you have to change that and then see what other problems you have if any.

There is only one thermister on this model by the way.

pcb's never gave me any trouble so don't jump to that conclusion without checking all alternatives.

Fix one thing at a time and work on through.

 

[julesg007]

Hi Paul,

Thanks for the advice.

I concur about the diaphragm, the CH pipes are not warming up with the boiler running but only HW being demanded. Also having changed it about 8/9 months ago I didn't think that would be the problem.

I have suspected the FS, so I will get one and change it, is's a relatively cheap item anyway and will report back on what happens or doesn't as the case may be!!!

Thanks again for your help

Regards

Jules

 

[gas4you]

pcb's never gave me any trouble so don't jump to that conclusion without checking all alternatives.

Exactly my point Paul.

Saying that though, I had a C23 about 3 months ago that would intermittently not fire up . Never failed in front of me until the last visit.

PCB had gone, not supplying voltage to fan. Well surprised me

 

[julesg007]

Paul and Dave,

Thanks gents for trying to help me out.

I would like to pass on the following info to you.

At present the boiler has been switched over to HW only - via the selector and reset switch and not just turning the timer off. There is no HW being demanded anywhere and the bolier is trying to fire up and the FS is clicking away like a man posessed!!! Thet boiler is not firing up or of course running.

Don't know if this is relavent but thought I'd mention it.

Thanks again

Jules

 

[Paul Barker]

Isolate cold feed to boiler, and behaviour stops? You have a water leak or very heavily dripping tap.

 

[julesg007]

I've been sitting in front of the boiler for a fair while now and the probelm hasn't seem to re-occured. Definately no leaks or dripping taps.

Got a new FS on order so I'll fit and see what happens and report.

 

[julesg007]

Hi,

Just wanted to update the situation as the new FS has been fitted.

No joy in sorting out the problem, the boiler is has problems.

I am sitting in front of the boiler and it is trying to fire up and with the CH switched off (set to 0 on the timer and HW only selected) and no HW taps open. Again the issues with firing up when HW demanded or CH on or both still present.

There are no leaks or dripping taps in the house.

Any ideas as what to do next or any suggestions would be appreciated, howver, I am aware that I may just have to get my HE out to investigate the problem.

Thanks for the help.

Jules

 

[gas4you]

Assuming the control knob has not broken (snapped, so it is stuck in the on position, I would now be suspecting the primary pressure switch may have stuck in the on position.

If this is ok then it is looking possibly as the pcb

 

[julesg007]

Good evening Dave,

Thank you very much for the further advice.

I don't think any part has snapped or broken off, but if you could direct me to the "control knob" I will double check.

With regards to the PPS, I will follow the instructions I have to remove it and check every thing is working OK, if not I will order a replacement.

Thanks again for the help

Jules

 

[gas4you]

The control knob is the knob you turn to select off, hw, or ch & hw.

Being plastic they can sometimes have the shaft snap.