Worcester 28cdi rsf igniting problem

[handful]

Hi guys, newby here to this forum I'm afraid!

I have a Worcester 28cdi rsf boiler and it has worked well until recently when I had a radiator swapped. I don't know whether the fault occurred because of this or whether it's a coincidence.

When the job had been done the plumber had trouble bleeding all of the air out of the system and I eventually agreed to a powerflush as the rads seemed very dirty and also had an auto release valve fitted to help with bleeding in the future.

This seemed to cure my problem but a day or so later the boiler seemed to intermittently fail to ignite, on both CH and DHW. It has now got to the stage that it takes on average 4 or 5 re-sets before it fires. I can hear it kick into life and hear the pilot light clicking away but it fails to ignite and I get a flashing red light come up on the boiler.

I got my local Bosch engineer to look at it and as always, it worked perfectly for him.

Has anyone got any idea what this could be?

I am thinking about replacing it rather than face a hefty repair bill as it is not really man enough for our house as it has been extended quite a bit since it was fitted, 2 bathrooms and 12 rads but if I can keep it going cheaply I would obviously do so.

Any advice very much appreciated, sorry for the long first post

 

[thefloosyonthebeach]

Dont change it. A decent RGI will have it repaired.

 

[barryauid]

Love changing diverter valves on the cdi NOT

 

[handful]

Thanks guys. So is the problem likely to be a divertor valve? Sorry if that is a bit of a numpty question but I have no knowledge of boilers and plumbing at all

 

[barryauid]

No sorry my post was a little misleading i just dont think the cdi range is the easiest boiler to work on

 

[tdesnos]

So know it works? CH works and HW? You just have to reset it a few times? Just need a little more info of any symptoms.

 

[handful]

So know it works? CH works and HW? You just have to reset it a few times? Just need a little more info of any symptoms.

By resetting a few times CH will eventually fire up and once lit it appears to work perfectly and doesn't cut out. On DHW it is hit or miss as to whether it works or not so we are tending to fire up the CH before we need to have a shower purely for convenience....nothing more frustrating than having to trek across the house naked to reset a boiler

Does this give any clues?? Thanks for any responses.

 

[ollski]

Which lights flash and how fast? (1 or3 times a sec ish). Worn air pressure switch is a favourite fault on these.

 

[handful]

Hi ollski

The left hand light flashes at even intervals about once a second. This is after approx 10 seconds of 'clicking' or attempted firing. Would this indicate air pressure switch? Are they expensive? Is it a job that I could do or is it a specialist only type job?

 

[tdesnos]

Hi ollski

The left hand light flashes at even intervals about once a second. This is after approx 10 seconds of 'clicking' or attempted firing. Would this indicate air pressure switch? Are they expensive? Is it a job that I could do or is it a specialist only type job?

If the air pressure switch is faulty then the boiler wouldn't be attempting to light, so we can rule that out. So you turn the CH on to provide you with hot water? However if you turn the HW on alone it will run for a bit and trip out? If this is what is happening then it sounds like the hot water thermistor - this tells the boiler what temperature the HW is coming out at, if it's gone the boiler thinks the water is too hot and shut off prematurely. Off course this is if i've understood you correctly.

 

[handful]

I'm sorry, I'm not very good at describing my problem!

Most of the time the boiler fails to light on CH and DHW. It usually takes 4 or 5 attempts at turning on the CH or turning on a tap before it finally springs into life. When it fails to light it sounds like it's all working fine until the point that the ignition starts to click away but it continues to click away for approx 10 seconds before giving up and at this point the left hand red light starts to flash at intervals of approx 1 flash per second.

When it does eventually 'catch' it's usually after about 6 or 7 seconds of clicking and once lit, it works absolutely perfectly. When the CH is on the DHW will work every time, hence the reason why we tend to make sure the CH is ok before a shower for the reason stated above in an earlier post!

I think this makes more sense now, if anyone could throw any light on my problem I would be eternally grateful.

 

[ollski]

Yes it's liekly to either need a service, a new set of electrodes or a gas valve although this isn't an exhaustive list of possibilities just the likliest.

 

[tdesnos]

wow, ok, my brain is hurting on this one. the only thing i can think of that might be causing discrepancy between the CH and the HW is the frequency of the 'cycling' that is, the burner turning on or off as it reaches temperature and falls below it. the CH might simply be causing the burner to stay on for longer periods in your case long enough for a shower. with this logic i'd be examining that spark electrode which ignites the burner, if it's not making an adequate spark then that gas won't be able to ignite - obv. causes of this are dirt on the electrode, or even sometimes just moving the electrode pin closer to whatever piece of metal it's near to create the spark, sometimes the thing cable can have a break in it so wiggling it around may cause to the break to make a new contact again - for what's involved it's certainly worth inspecting.

 

[handful]

Thanks guys. I was wondering if it was just the 'lighter' that was the problem as this would explain why it works fine once lit. Is this something I could check or change with limited knowledge or is a job for a specialist?

 

[nkw]

Hi, I've got a similar problem with a Worcester 28cdi rsf and fail point H.

After being off overnight, CH starts in morning, runs for about 5 seconds, stops for a second, runs for another 5 seconds then locks out. After reset usually runs OK for the rest of the day.

Also put CH on before running DHW for shower, otherwise water temperature fluctuates.

Yesterday, I decided to check the gas meter (on a whim), could smell gas around meter, called Transco, fixed problem, then the engineer said that the gas pressure was too high at about 26mb, so he lowered it to about 21mb. Since then the DHW has been running at a reasonably stable hot temperature, though CH ignition lockout still occured this morning.

I can only assume that the cold weather affected the gas meter as that was when the problems started.