How water keeps overheating - Ravenheat 84F Combi

[scottb]

The CH had been on a hour or so yesterday evening when I decided to run a bath. After getting out of the bath later I notiched that there was water around the bottom of the boiler (housed in another room)

The boiler appears to have overheated.

When I tried to pressurise the boiler back to 1 bar, water started dripping from between the silver motor housing and the unit its bolted onto.

Questions:

Do I need to replace the pump of are there gaskets that I can just replace.

Would it be the D.H.W. sensor that has gone or the D.H.W. Potentiometer

I replaced the CH sensor about 6 months ago and wondered whether I should have done the D.h.W. but chose not to due to more cost - oh well...

Thanks for any advise

 

[Llan1observer]

they didn't make an 84F but i can find 84E or 84ET on ravenheat site.

sounds like the O/H stat to me. but if you have a look here

http://www.ravenheat.co.uk/pdf/RSF841Print.pdf

go through the diagnostic it'll give you a better idea.

the leak is probably a blown fiber washer which also needs replacing.

you should use a gas safe registered engineer (as you are entering the combution chamber of the boiler) to replace these sensors

 

[scottb]

Thanks for the fibe washer info. I will sort that out.

It is an 84ET, sorry about that.

The diagnostic flow chart suggests that I replace the potentiometer and not the O/H stat as you suggest - I only say this because the boiler did not trip.

Would you still stick with the O/H stat or agree with the pots - just want to make sure the money is spent in the right place.

Aybody else any suggestions.

Thanks

 

[Llan1observer]

if the DHW temp is higher than stated in flow chart then change the pot

sorry i assumed it locked out.

 

[Slugbabydotcom]

water started dripping from between the silver motor housing and the unit its bolted onto.

Pump is knackered. Thats how they go. Dont faff about with washers, put a new one in.
Overheat stats go on these as well but sort the pump out first unless the OH stat isn't resetting. You dont need to get into the combustion chamber on these but even if you did the boiler has 13 idiot proof screws on the CC and even if an idiot managed to screw that up then the boiler wouldn't fire anyway because the APS wouldn't operate.

 

[Agile]

I dont know why you are all ignoring the most likely part.

With the boiler cold measure the resistance of each sensor!

It sounds like a failed DHW sensor.

Try tightening the pump head screws and see if that stops it leaking ( if the pump is still working --- it will not be for long though---also check the big screw in the centre is also tight as these can leak and allow water into the motor part ).

Tony

 

[gas4you]

The DHW sensors are fairly reliable on these. The CH one is the most often one to go. This controls the overheat as well.

I would go for the new pump first, then once you have the circulation proved correct, start looking for any further possible faults.

Tony, good to meet up with you again Saturday night and a pleasure to meet Martha

 

[Slugbabydotcom]

When I tried to pressurise the boiler back to 1 bar, water started dripping from between the silver motor housing and the unit its bolted onto.

I take it you mean between the pump head and the pump 'body'
Sort the pump out first and then post back if theres any other issues

the boiler did not trip

The boiler appears to have overheated.

No it probably cut out on the low water pressure switch because the water had leaked out of the pump.