Sime 102 DHW fault

[danncus]

Hi our 2008 sime 102 has a fault. when, say, filling a bath, the boiler works normally i.e. divert valve operates micro switch, fan & pump starts, pilot lights and crosslights main burner. hot water flows.

after about a minute the boiler shuts the main burner off, whilst micro switch, pilot, pump and fan are still on. water runs cold then after 20 seconds the main burner relights. this cycles until water is shut off. about 4 years ago i replaced the diaphragm. It has had a weep for some time from the valve, so i fitted a new assembly which has cured the leak, but not the DHW fault.

Help?

Thanks

 

[gingerbear]

hi ya , i have a simular prob with my sime super 90(how old i dont know) and someone told me yesterday clean out the dhw heat exchanger from lime scale and debris that maybe clogging it up. i to like you changed the divertor complete a year ago but it didnt seem to make a great deal of difference. if you do decide to try this, look for a cleaner that breaks down limescale that cloggs these up as i tryed something yesterday on a shower head i'd bin led to believe that does this and it didnt work, it was sentinel x800 jetflo but i later i tried a drain cleaner i have through work and f... me did it get rid of the limescale still yet to do the heat exchanger ! watch this space i hope this help in some way.

 

[danncus]

Thanks,
when the burner is on, water heat is good. we live in a area which has no limescale problems. it seems to me that there is some sensor somewhare which is shutting the main burner off?

 

[Agile]

How could you replace a part FOUR years ago on a boiler installed in 2008.

Your plate HE is probably blocked but it could be a gas fault needing an RGI.

Tony

 

[danncus]

Ah...

I was wondering who would be the first to see my deliberate mistake!

It was installed in 1998!

 

[danncus]

what would be the best course of action? a reverse flush?

thanks

 

[Agile]

The plate HE should be removed and cleaned or replaced.

Tony

 

[gingerbear]

mmm! me thinks that to! may be try that first! i took out my dhw heat exchanger out the weekend(f..... nightmare) and broke down what felt like a lump in there of i'm hoping that is limescale and debris. i ended up using a drain cleaner called 'knock out' (a bit strong so watch out) and touch wood today it seemed ok but talking to someone today they also tell me the next thing to go for if it aint worked is the thermister stat fitted to to hot water pipe internally. on my boiler, having looked this eve this is the same as the one fitted to the heating side of my boiler (inter changeable on my boiler)so i may be i'll give this a try if it aint worked properly.watch this space eh ! i'll let you know !

 

[gingerbear]

mmm ! i not fully convinced this has totally done the job or just partially worked ! only there has bin a couple of times where the boiler has done what it was doing before, that is shutting down.I'm gunna try changing the dhw thermister for the heating one as there identical and see what happens then. if this dont fully solve it then i'm at a loss cos i dont know what else to go for ? any other pointers most greatly received ! anyone ?