Worcester Bosch 24cdi

[jestex66]

I know this has been covered in previous threads but I'm looking for a definitive answer.
My 24cdi had (and still has) intermittent hot water...ie 30 seconds hot (more warm actually) then 30 seconds cold.
Initially the rads were getting hot as well, without the c/h being on. Ok, diverter valve...changed that!
Unfortunately, the hot water problem persists. I've ruled out the dhw thermistor as i changed it with the c/h one. C/h still works but hot water problem is still present.
The heat exchanger was flushed through when it was out and seemed ok.
I'm thinking electrical fault, as everything mechanical seems to be working ok.
Any help would be greatly appreciated.
Thanks in advance

 

[scatmanjohn]

The heat exchanger was flushed through when it was out and seemed ok.

Seemed ok?

Flushed through? How?

Get ya self a new one

 

[Gas2Air]

I would hazard a guess jest and suggest the gas valve isn't modulating to low rate, simple to reset, but not for you. Have someone look at it for crikey sake.

PS how did the diverter change go? Easy eh?

 

[jestex66]

[Seemed ok?

Flushed through? How?

Get ya self a new one ]

had water flushed / passed through it. Purely to see if there was a blockage. nothing evident to suggest any blocks / resistance. oh and thanks for the really helpful advice!

[Have someone look at it for crikey sake]

Gas2air... thanks for the heads up on the gas valve. Hadn't tried that...and perhaps I misled you into thinking I'd done all this...yeah right.

It was a gas fitter who did it all, I just watched the proceedings making sure the kids weren't about everytime the air turned a bit blue.

 

[scatmanjohn]

had water flushed / passed through it. Purely to see if there was a blockage. nothing evident to suggest any blocks / resistance

Passing water through it may prove that it is not totally blocked but does not prove that it transfering heat from the primary side to the domestic side.

oh and thanks for the really helpful advice!

You are most welcome

It was a gas fitter who did it all

What does he "think" is up with it?

If he is stood in front of it but can't work out the fault i think you need a new "gas fitter"

Good luck with the gas valve

 

[Agile]

When I read all these kind of things, my mind starts wondering what kind of person is replacing loads of parts in a boiler when they dont cure the problem.

Obviously you dont expect to have to pay for parts which are not required so the poor inadequate is left with a loss of about £160 plus a lot of his time.

It would not take many jobs like that for him to become bankrupt !

Tony

 

[ollski]

The old cdi gas valves had a high and low solenoid.

 

[corgibloke]

Definitely partial blockage in plate heat exchanger!!

Needs pickling in acid solution, can't be pumped through as no threaded connections!

 

[Agile]

Definitely partial blockage in plate heat exchanger!!

Needs pickling in acid solution, can't be pumped through as no threaded connections!

I just half fill them and agitate. Later when the fizzing stops I fill them up to the top and leave them for a day or two.

Tony

 

[corgibloke]

Usually only takes half hour or so with Kamco FX Scalebreaker to clear completely in cold solution. Can also be speeded up by applying heat from blowtorch!!

 

[ChrisR]

Boiling water from a kettle into the other side of the hex is easier!

 

[corgibloke]

Boiling water from a kettle into the other side of the hex is easier!

Don't be such a pussy!

Go with the FIRE!

 

[spacethegas]

i'm with ChrisR.

full strength FX in primary side.

secondary boiling water.

then after 3-5 min increase boiling water to dilute.

generally 30 min max.

repeat if necessary.

 

[jestex66]

Thanks guys. I'll let y'all know how it goes.