Ariston Combi Secondary Heat Exchanger

[Gham]

Hi,

Firstly thanks for everybody's help on here, you've been really helpful so far.

Quick summary of my problem - Ariston MicroGenus 27MFFI combi - when hot water is run the pilot light fires off then cycles on/off every 15 seconds or so, resulting in cold showers!

I was advised to have a powerflush and replace the secondary heat exchanger. I didn't go for the powerflush (as the guy didn't do anything other than remove the front of the boiler) and I was advised otherwise by another plumber. I adding Fernox central heating cleanser a few days back and will drain and refill tomorrow, adding inhibitor. (Interestingly when I drained the system it was pretty much all clear, no sign of black/sludge at all!?)

I'm now going to address the secondary heat exchanger and have a couple of questions:

1) In the manual, there's no mention or sign of disconnecting pipework - just removing two hex screws and popping it off - is that all there is to it?

2) It mentions draining down the boiler - I can't find any information on this at all. Any tips?

3) Is there anything I should look out for when doing this - (i.e. the manual says check the 'o' rings.

Thanks in advance,
Graham

 

[Rob]

hex screws are all that holds it in.

To drain boiler...close the htg return isolation valve and remove the cap which hangs down. When you reopen the valve it will drain the boiler. so have a bucket ready.

Then close CW inlet and open hot tap.

Boiler is now ready to be worked on.

Changed one fairly recently and dont remember having to use new o rings.

Job took about 15 mins.

 

[Gham]

Thanks very much Rob, I'll let everyone know how I get on!

Cheers
Graham

 

[Doctor Drivel]

I came across on e of these combis. When the DHW was shut off at the tap, it growned. Pump? I noticed the pressure guage was on zero. I was told it was duff (or so they thought)

Anyone any idea?

 

[Gham]

For anyone else looking at doing this...

Followed the above instructions, all fine. When I released the secondary heat exchanger some water came out, I fortunately had some dust sheets below!

Not enough room to get it out (after lots of trying), and couldn't get the side panel off the boiler due to where it was fitted. Took off the diverter valve (I think it was?!) and then I could.

Cleaned the heat exchanger with my jet washer for about 10 mins, put it back in and hey presto, I am fixed (for now!).

Thanks for all help,
Graham

 

[Doctor Drivel]

For anyone else looking at doing this...

Followed the above instructions, all fine. When I released the secondary heat exchanger some water came out, I fortunately had some dust sheets below!

Not enough room to get it out (after lots of trying), and couldn't get the side panel off the boiler due to where it was fitted. Took off the diverter valve (I think it was?!) and then I could.

Cleaned the heat exchanger with my jet washer for about 10 mins, put it back in and hey presto, I am fixed (for now!).

Thanks for all help,
Graham

Where was blockage? One the primary (CH side) or secondary (fresh water) side?

If on the primary, flush the system, add Fernox cleaner, flush a few times and add inhibitor.

If on the secondary, then was it scale? If not, then add a strainer on the cold mains pipes.

 

[Gham]

Sorry, just seen this. It looked to me like sludge - it was black when it was coming out. I had already done the Fernox cleaner, and inhibitor as you suggested.

Thanks
Graham

 

[Gham]

To follow up same problem has started occurring, as a number of people suggested would happen - however, I got a further 10 months life out of the secondary heat exchanger just by jet washing so I'm happy!

Thanks
Graham

 

[farenheit]

hex screws are all that holds it in.

To drain boiler...close the htg return isolation valve and remove the cap which hangs down. When you reopen the valve it will drain the boiler. so have a bucket ready.

Then close CW inlet and open hot tap.

Boiler is now ready to be worked on.

Changed one fairly recently and dont remember having to use new o rings.

Job took about 15 mins.

Hi there
I know this is an old post but I’m looking to do the same as mine is kettling at the mo, however I am unsure of some of the terminology.
First off, where can I find the heating return isolation valve
Second, which cap are you referring to?
Lastly, what is the CW inlet?
I’f anyone has any pictures they would really help.
Thank you

 

[endecotp]

Have you googled for the manual? They normally have nice exploded diagrams.

 

[farenheit]

Have you googled for the manual? They normally have nice exploded diagrams.

I did but without knowing what’s what I can’t pinpoint anything
I can manage the work it’s just knowing the steps. I’ve done work in the past in my system, for example I’ve drained the whole ch system and fitted new lsv and even fitted a magnetic filter however with replacing the secondary heat exchanger id like to know what’s what before I make a start
Just to add, mines an Ariston Microgenus 23 MFFI, not much different.

 

[farenheit]

Anyone?
Is there anyone in the Birmingham area that’s willing to help for a small fee if I get the secondary heat exchanger?

 

[farenheit]

Ok i think ive sussed it. Can someone please confirm that i have the correct valves highlighted in the attached image.
Thanks

 

[endecotp]

Those are probably the right valves. Not sure about the cap to unscrew; maybe someone else will comment.
The instructions you've quoted don't mention closing the CH flow isolation valve. I think you probably should, if the intention is to drain the boiler while leaving the rest of the system filled.
In any case, be prepared for water to escape whenever you unscrew something. Make sure the boiler electricity supply is off, and consider covering the electrics with something waterproof.

 

[farenheit]

Those are probably the right valves. Not sure about the cap to unscrew; maybe someone else will comment.
The instructions you've quoted don't mention closing the CH flow isolation valve. I think you probably should, if the intention is to drain the boiler while leaving the rest of the system filled.
In any case, be prepared for water to escape whenever you unscrew something. Make sure the boiler electricity supply is off, and consider covering the electrics with something waterproof.

The instructions from Rob above did say to close heating return valve.