Worcester 280 combi faults...

[Dirntknow]

Hi folks, just having a look around for advice and info regards a couple of faults with the above mentioned boiler.
The hot water runs hot(ish) and cold alternating. The hot water supply is slower and generally not as hot as it should be. It trips out occasionally (reset with a small button on top of the control panel) and now struggles to light up for hot water or central heating if its stands overnight. I'm thinking the heat exchanger is scaled up and the gas valve is u/s. I've had a local corgi man out and he says its probably the gas valve and will change it for £300, he also says the combi sounds scaled up and suggested full replacement at around £1500. I'm neither flush with money nor stupid so looking for some more opinions. I'm pretty mechanically minded and wondering if I could descale or replace the heat exchanger myself and also whether £300 for a gas valve replacement is excessive?

 

[Agile]

I dont see how the gas valve is likely to be faulty. They are pricy and I think the last one we replaced was about £240 inclusive.

It sounds as if the secondary heat exchanger is sludged up. We would clean that chemically in situ.

The o/h trip is probable as a result of the above.

Not starting is not so obvious if it has not tripped out.

They are very simple boilers and any competent engineer should be able to renovate one for about £300 or less.

Tony

 

[Dirntknow]

A local corgi 'engineer' took a quick look and said it was probably the gas valve. It's making a rapid succession of clicks (sounds like a chattering relay to a non gas engineer!) for a few minutes and the flame ignites and goes out as it does this. After a few minutes the clicking stops and we have CH and hottish water for the rest of the day. I think it's more than the HE but they guy wanted £300 just to replace the valve....

edit: Apologies, I left out the clicking symptom from my original post!!

 

[Agile]

A local corgi 'engineer' took a quick look and said it was probably the gas valve.

That sounds to me like he was not paid to diagnose the fault. Anyone who comes free should NOT in my view give a free diagnosis. We always charge to diagnose faults, at least £84.

Its unlikely that he spent enough time to diagnose the fault if he was not going to get paid and then would have put a high price on the job because he did not know what was wrong.

In my view you should pay to have the fault diagnosed and then that the engineer will guarantee his diagnosis and not then proceed to change parts at YOUR cost until he finds by trial and error whats wrong.

Very occasionally its not possible to be 100% sure whats wrong as some parts are interacting in their operation like boilers with two PCBs. In that case you should still only have to pay for one part even if the engineer changes another first.

Tony

 

[lifesagasman]

OP if you are saying that when the boiler is stone cold it won't ignite then the initial problem is not water related.

strangely i might go with the gas valve theory. if it has developed a leak it could well be empty of gas after standing all night. the clicking sound would be the ignition firing as it waits for the gas valve to purge itself. once lit it would run all day and then repeat the event at night.
theoretical but plausible.
any advances?

 

[Agile]

strangely i might go with the gas valve theory. if it has developed a leak it could well be empty of gas after standing all night.

the clicking sound would be the ignition firing

Surely any gas leak would be refilled by the mains supply unless he turns off the gas overnight at the EC.

The clicking MIGHT be the boiler trying to light but thats likely to be as a result of a lack of service rather than any fault in the gas valve.

It could also be a faulty PCB only powering the valve intermittently atr furst as a result of dirty relay contacts.

Tony

 

[jacobball]

Contacts on the gas valve do you mean?

It could be the igntion of rectification lead have been pinched/shorted somewhere and sparking is now only intermittent due to this? Or the elctrode/flame rectification probe tips may be dirty, a dirty burner especially near the flame rectification probe?

 

[lifesagasman]

well, i've never stripped one of WBs valves to study it's construction, but when the solenoid is inop no gas is passing so if it were leaking at some point there would be no gas to replenish the void. as i said it's a theory, but it may be more than just coincidence that it won't relight after standing all night, and then it's fine all day.
i don't mind if my theory is wrong, my boiler works fine

 

[Agile]

The "void" in the gas valve is full of gas from hte supply just waiting for the solenoids to open to allow it to flow to the burners.

Tony

 

[lifesagasman]

i can go with that.

 

[lifesagasman]

It's making a rapid succession of clicks (sounds like a chattering relay to a non gas engineer!) for a few minutes and the flame ignites and goes out as it does this. After a few minutes the clicking stops and we have CH and hottish water for the rest of the day.

edit: Apologies, I left out the clicking symptom from my original post!![/quote]

i missed that bit! 'flame ignites and goes out'. is that the burner flame starts then stops then starts again later?

 

[jackecole]

if the flame ignites then goes out, it could be a fault with the flame supervision device, or a dirty burner port near it?

 

[lifesagasman]

starts to look that way, doesn't it?

after 125 posts you should have a 'thanks'

it's a dirty job, but somebody's got to do it

 

[Dirntknow]

Hi folks, sorry for the delayed response! I've checked a few electrical connections and the burner seems to ignite fine now so £300 on a new gas valve would have been a bit of a rip off I think! I've had a search on here and a bit of a google and I think i'm going to have a look at the secondary heat exchanger. Apparently WB changed the design to a plate exchanger so the new HE needs a 'repair' kit to provide extra metalwork needed. WB tech supports seems spot on so i'm going to have a go at it myself next week!