RaveHeat LS80T Little Star DHW running cold

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Any help would be gratefully recieved

I have a ravenheat LS80/100 and for some reason the dhw doesn't work? the central heating works fine. If I have the central heating on and also run the taps at the same time the water is fairly hot but I can only let the water dibble out of the tap. and it takes forever to run a bath, in fact the water pretty much gets cold by the time the bath is run.

I tried turning the temperature down on the thermostat to almost the lowest level and the water was luke warm even though tap was running very slowly. At this point the boiler would fire up and stay fired up.

I tried turning the temp up on the thermostat and the boiler would fire up as per normal but would then cut out after about 20 secs, if I turned the thermstat down again the boiler would fire up again. the water thoughout was still only luke warm???

Is this a problem with the primary heat exchanger? Not really sure were to go with this?
 
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Most likely the diverter valve diaphragm.

But it can also be the saddle DHW demand switch.

If its the diverter valve then most professionals would usually replace the whole assembly as these are one of the troublesome ones.

Not a totally recommended DIY job.

Tony
 
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thanks for replies - how would i check for these ??

I have now noticed that the pressure is rising to 4bar when I have the CH on. I have drained the radiator to get the pressure down to 1-1.5 when cold but as soon as I put the CH on it gets up to 4ba in no time??

Anything else I can try??

Thanks
 
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more likley the sec heat ex or the dhw thermistor :idea:

OK I need to take this one step at a time.

Is there a way to test the dhw thermister?
and if it is fautly whats the procedure for replacing it?

Also I've just noticed that the dhw pipe (where the dhw sensor/thermo is located) is cold even when I got the hot water tap on - there is still very little hot water but the ch pipe is very hot?? Also when running the hot water tap, if I take the CH thermister off it cut the flame etc, is that right?

Pressure problem has been sorted
 
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And as tony stated above, problem is with diverter valve

I shall get the diverter valve replaced then, fingers crossed.
Tony mentioned that its not a totally recommended DIY job. Would it be "safe" to do myself, If I was very careful?
 
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You say you want to do one step at a time but you seem to have left out the expoansion vessel.

You also need to check the saddle switch before changing the diverter.

It would be easier for the professionals if you edited the subject to contain "Little Star" which is how most of us know this boiler.

Tony
 
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You say you want to do one step at a time but you seem to have left out the expoansion vessel.

You also need to check the saddle switch before changing the diverter.

It would be easier for the professionals if you edited the subject to contain "Little Star" which is how most of us know this boiler.

Tony

Thank Tony

I have checked the saddle switch (thats the microswitch on the diverter valve thats held on with a plastic clip) Yes? If I take the clip off then the boiler fires up, if I press the switch in the boiler cuts out.

How would I test the expansion vessel ?
 
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