Worcester Bosch 24i RSF hot water problems

[mcl07]

I have the Worcester Bosch 24i boiler. I currently have an intermittent problem whereby the hot water is not firing up (particularly upstairs, shower and basin) unless I put the heating on. This has been ongoing for a few weeks now, and an engineer has been out on 3 separate occasions but it is still not sorted.

The water pressure is fine, and so far I have had the water flow switch (?) changed, and also the circuit board (as the heating has not always been triggering), however neither of these changes seem to have made a difference to the intermittent hot water problem.

I have looked on some of the other posts and a Diverter Valve has been mentioned. Could this be the cause in my case?

I have the same engineer coming around this week. Although he has so far not determined the problem he has agreed that I will not have to pay any more money due to the money already spent (£200). Obviously I am getting a little frustrated so I thought I would try and find the info out myself. Any assistance would be very much appreciated.

Regards,

Mark

 

[Agile]

Your boiler does not have a diverter!

Unfortunately your engineer does not seem very competent at diagnosing faults. You would have been better off with a fixed price repair!

There is also a possibility that you had two faults. I have seen your model with intermittent CH operation and that can be a PCB fault but other causes as well. I suspect there is a single fault that has affected CH and DHW.

Diagnosing faults involves testing components using a multimeter and pressure measuring device.

I suppose if he goes on until he has changed all the parts he might eventually find the fault.

Tony

 

[mcl07]

Thanks for information on the diverter Tony.

The engineer was hoping that a new PCB would resolve it, but unfortunately not. The day after he fitted it a fuse then went on that board, so I had no heating or water. Luckily he kept the old pcb so swapped a fuse off that.

I am inclined to agree with your comments on the engineer, although I know he is frustrated as I am (as he has been working for nothing the last two visits). Apparently he knows a Worcester Bosch engineer so hopefully he will call him in to investigate the problem with all the relevant tools. I was just hoping I could find some info on a few possibilites he could check.

Mark

 

[Agile]

Fuses dont just blow!

That implies there is a faulty component like a pump etc.

Just replacing a fuse does not fix the underlying problem.

If its a new PCB then it should be covered by the warrantee !

Are you sure it was a new PCB and not a rep[aired one?

Tony

 

[mcl07]

He did say it was a new PCB, and I paid the price of a new one (£130 inc vat). To be honest I will be asking him to get in touch with the Worcester Bosch engineer he knows as hopefully he can find the true cause of the problem.

I have my own concerns with regards to his investigational skills, which is why I am posted this message. Although from reading some of the posts on here (who have described similar issues with the 24i), he has started with two feasible causes (flow switch and PCB).

Will have to see what happens. In the meantime, thanks for your assistance Tony.

Mark

 

[Agile]

The two first suspects are the DHW flow switch and the DHW sensor.

Both are quite cheap as boiler parts go.

It does not sound as if he has checked the sensors. Maybe he does not even have a multimeter or know how to use it.

Hopefully the W-B engineer will find the problem!

Tony

 

[superdupergasman]

The thermistors on these are the disc type and normally very reliable but I would be out with the multimeter on Ohms to see what reading it was giving.

When you turn the tap what happens??? any noise?

and then you say its similar for CH.....what about when you turn on timer??

Air pressure switches are a bit iffy on these boilers and they have been changed to a different spec from the black originals.

 

[mcl07]

Update. As he is here now. Managed to have a look at some of the readings he has taken.

He has checked the voltage to the bolier and that is 241v, the old DHW Temp sensor was showing 14 ohms, he replaced with a new one and that shows 10 ohms. Unfortunately it doesn't appear to have made much difference.

I asked about the pump and he said that this was working ok as he 'tested' that previously.

The problem seems to be with the upstairs as the hot water now seems to firing on the kitchen tap. Yet when we run the shower (mixer shower, straight off the pipes no pump) the hot water doesn't always trigger.

Lots of head scratching going on.

 

[Agile]

Sounds something wrong here!

I think the sensors are about 13k or 13,000 Ohms !

I am surprised a staff engineer is having so much difficulty with a simple boiler!

Tony

 

[mcl07]

It could well have been 14k and 10k, I couldn't see what his measuring device was set to.

He thinks he knows why the fuse went on the new the PCB board as when he had put the new one in he had not connected something properly so there was an arc.

He's now gone and it did seem to be a bit better, however I am not convinced that it is fully sorted as if the hot water comes on downstairs then more often than not upstairs is fine. Will have to see what it is like in the morning when the heating\water has not been on for 9 hrs or so.

Out of interest does anyone know a Worcester Bosch or reputable engineer around the North Manchester area? Although i have not paid anything for the past 3 visits I do want this problem sorting. I'm not convinced my existing engineer will be able to resolve it satisfactory.

Regards,

Mark

 

[Gasguru]

Yet when we run the shower (mixer shower, straight off the pipes no pump) the hot water doesn't always trigger.

Has the flowrate been measured at the hot outlets upstairs? Have you considered there may be a problem with the mixer taps....perhaps there is too much cold mixing despite the shower temperature setting so there is insufficent hot flow to trigger the boiler. Can you isolate the cold feed to the mixer?

If he's plugged in a connector sufficient to blow a fuse I'd be suspicous of the boards condition.

 

[mcl07]

Gasguru:

I don't think he has checked the water flow rate. Although I'm not sure it is a shower mixer problem as the hot water tap to the sink upstairs behaves the same as the shower (not always triggering).

Out of interest can the water flow rate change over time? To me, the pressure feels the same as previous (4 yrs since the boiler was put in). The engineer even said that the pressure was good.

I may just see how it behaves tonight, as it will have been a good 6hrs since he had a tinker this morning. I'm hoping the PCB board is not knackered due to the fuse going, if it has then I will get him to change it. The heating still appears to be triggering on timer, which it wasn't doing before he changed it.

Thanks for all the assitance so far.

Regards,

Mark

 

[Gasguru]

Pressure has little to do with it....flowrate triggers the switch.

If the pcb, flowswitch, thermistors have been replaced/checked there is little else within the boiler to stop it from firing up with a demand. I am assuming it fires up ok for heating.

I was incinuating that if there was a problem with the shower mixer (ie cold flowing to hot even when not in use) then opening the hot basin tap (that I presume is not a mixer tap) could be a mix of hot water (via the boiler pipework) and cold water (via a faulty shower mixer into the hot pipework).

Therefore the actual water flowing through the boiler may be insufficient but the flowrate at the hot tap appears ok since water is flowing from the cold main through the shower mixer into the hot pipework to the hot tap as well as through the boiler.

That's probably confused you

If you can isolate the cold feed to the mixer valve(s) and then see what happens that would rule out that possible problem. Are there any isolating valves on the mixer?

 

[Agile]

Simple way to test what Paul is trying to describe.

Close the isolator on the cold feed into the boiler.

Then open each hot tap in turn.

Nothing should come out of any hot tap UNLESS there is a crossfeed problem ( which is usually in a thermostatic shower ).

Tony

 

[mcl07]

Update:
After a further visit (and call to Worcester Bosch), the only other thing he had not checked was the gas pressure. On tweaking this to the recommended pressure everything is now working fine.

Many thanks to Agile and Gasguru for your comments as they did help eliminate potential issues.

Cheers,

Mark