Worcester 24cdi hot water cutout

[Wirral_guy]

Hi Guys(and girls)

I have the above boiler and it has started to cut out after about 10 secs of running the hot water. Everything seems to work OK but it just cuts out and the water runs cold.

If you leave it 10 seconds or so and try again, it looks like the flow is reduced ( although this may be just me seeing things that aren't there!).

Has anyone seen this fault? If so, can anyone give me a pointer as to what is wrong?

Thanks

Dave

 

[calore]

Seems to me that the DHW heat exchanger is scaled-up.

 

[bengasman]

Seems to me that the DHW heat exchanger is scaled-up.

Which of course the company using this site for free advertising could do.
What a shame for the poster that it probably is no more than a bit of dirt in the inlet filter which would come out with the next service.

Should you trust a company that is dishonest enough to ignore the purpose of the forum ( and the forum condition that you not use it to advertise), and assumes without testing that the fault is the most expensive of the various possibilities?

 

[Wirral_guy]

Sorry Guys, I'm a little confused! Has an errant poster been deleted cos the flow of the conversation seems a little odd!!

From what I understand it could either be the DHW heat exchanger scaled up (can this be done easily or is it a job for a boiler engineer?) or simply the inlet filter gunged up (which would make sense as our water often has brown sediment - a whole other argument).

Thanks

Dave

 

[kevplumb]

check the inlet filter first it's cheaper

which would make sense as our water often has brown sediment

all the more reason to

 

[Wirral_guy]

Thanks Kev, I will give that a try first. The other option sounds expensive!

Dave

 

[Wirral_guy]

Just tried cleaning the inlet filter - no difference. The water flow is also fine (plenty at the taps). Any other ideas?

Thanks

Dave

 

[kevplumb]

flow switch

go through all the cheap options first

 

[BingoBongo]

does the heating work perfectly fine?

 

[Wirral_guy]

Yes, the CH works fine.

For the hot water, it now seems to be, after lots of testing: a low flow doesn't even start the boiler, a fast flow (tap full on) starts the boiler but only lasts for approx 10 secs and then the boiler shuts off (no errors) and the water runs cold.

Is there a flow switch on these? If so, can I test/replace it easily?

Thanks

Dave

 

[kevplumb]

check the microswitch on the diverter page 25 of the m'is

 

[Wirral_guy]

Damn!

I've checked the switch and diverter plunge and, from what I can see, the plunge doesn't come out far enough from the valve to actuate the switch when the water is turned on. The switch works fine. Am I right in thinking this is the diaphragm gone/going?

Looking at where the diverter valve is, it looks like they put the valve on a bench and build the boiler around it!! I take it this is going to be an expensive plumbing repair?

Thanks

Dave

 

[kevplumb]

afore you get the razor blades out get a bucket and check the flowrate

having said that if you have a softener fitted i cant see it being scale

they are a git to change

best bet is get somebody local that knows how

 

[Wirral_guy]

Our water is generally soft with little scale buildup. Watching the diverter valve when the water gets turned on, it doesn't come out far enough to trip the micro-switch hence the boiler doesn't fire up.

Way too big a job for me so I have an engineer coming this morning to resolve. I know the dubious legalities of working on a boiler in the UK but, as an electronics engineer I am happy to diagnose the electrical faults and replace any external type components (micro switches, heat sensors etc) but wouldn't dare work on the actual boiler workings and safety items. Hopefully, everything will be OK soon.

Thanks all for the input, it really helped to talk it through the diagnostic process.

Dave

 

[Wirral_guy]

Final analysis and fix for future searches

It was the diverter valve and the engineer replaced the diaphragm (took about 1.5 hours). Seems to have done the trick. Out of interest, the diaphragm was almost falling to bits so not sure how it has held up so well for so long.

Dave