Ariston micro Genus 27MFFI

[Archie3cat]

I would like some help to solve a problem with my non condensing Ariston combi 27 MFFI, it could be over 4 yrs old. It works perfectly on CH but recently on DHW after about, say, 3 minutes the burner shuts off when the 70 temp. LED has been on for about 15 seconds. The 70 light goes off for about 30 seconds then the burner lights again...and so on.
I have done a rough check on the diverter valve by feeling the heating outflow pipe when this happens (heating off) and it remais cold so I think this one is operating OK. Water flow is fine.
Advice gratefully received.

 

[Rob]

Do a search on plate heat exchanger blockages. See if these symptoms match yours.

 

[superdupergasman]

I agree, DHW plate heat exchanger is blocked....

These can be removed and flushed, and refitted but its your donald duck if this will work.

If you do get a new one get a magnaclean filter fitted on the return to the boiler aswell as this will protect your investment. Helps to reduce the Carp floating about in the system water.

BG will do you a fixed price repair for £170 - 200 as the plate HE can be quite expensive.

 

[Archie3cat]

Many thanks chaps for your kind advices. I am a retired industrial engineer and used to whacking great coal burning boilers so these clever little units are a bit fiddly for me! I have got a local quote for a replacement exchanger which seems reasonable at £70 +vat so can I prevail upon you with the next questions :-

How is it attached to the other components?
Can it be changed in-situ or is it an off the wall job?
Would there be any success with a profesisonal chemical power flush?

I have been reading some other comments posted about siting boilers and can only say that mine is in a tight corner cupboard unit..Hey ho!
Best regards..Ivan.

 

[superdupergasman]

the DHW HE can be done in situ. just a couple of allan bolts and its out, some times the gas valve has to come out to allow it past.

A power flush would be a good idea as would be a magnaclean filter fitted on the return from the CH.

If you have debris in the system then after the abouve you will be sorted.

 

[Paul Barker]

You have a filling loop, so you have a way into the return pipe under the boiler. (sorry just thought ariston has that horrible little blue knob on the brass part which ends up letting by, fit an quality external filling loop and cap off the Ariston contracption for future reliability) If you now add a T to the flow pipe and put a gate valve beyond it to the system and shut this, then you can buy a magnaclean which you need anyway and install it in between these two entry points to the flow and return valves. Now you can buy a bottle of Sentinel X800 or Ferroquest whatever they are calling it this month, fill the magnaclean with it.

Now you have to have a way of t'ing the filling loop into this new loop between flow and return (remember gate valve on one side isolates rest of system.

Now pressurise system, and run boiler on hot water by running a tap. The chemical will do the job of cleaning the main heat exchanger and the plate heat exchanger primary.

drain take away your contraption put the magnaclean in the return pipework once again charged with the rest of the bottle of xleanser. Run heating for 3 hrs. Drain down refill with fresh water, run again 'till hot, drain down refill, drain down refil with X100 this time.

If that doesn't clean it then change the plate heat exchanger.

 

[Archie3cat]

Many thanks again for the replies. This type of informative help is like 'gold-dust' to me. I will post my results in due course...Regards, Ivan.

 

[Archie3cat]

Further to the recent valued advice I took the positive step of replacing the secondary heat exchanger. I found this very easy to do as I could take off the diverter valve actuator, it is only held in with a circlip.
Problem solved, hot water supply back to normal.

Can I perhaps pose another query? Ever since I have been the owner of this unit I have had some concern about the 'vwrump... thump' noise when the burner ignites. Is it normal? I see that the PCB has a rheostat denoted as 'soft start' is this one ajustable to smooth out this effect?
Some time ago I contacted the Ariston help line and was told 'yeah..they are all like that' but the man did not sound very convincing.

Thanks for all the help with the DHW problem.

 

[Rob]

Its not just a case of adjusting the pot. You need to see what your adjusting it to.

This requires a CORGI as you need to connect to gas valve.

The other problem is that these boilers are quite suseptable to ignition problems alot of the time because the ignition pressure is too low. So altering it may make it worse.

All this could be done on a service.

 

[Archie3cat]

Many thanks for your prompt reply,all things being equal I think I will leave well alone! Cheers, Ivan.