Secondary Heat exchange cleaning

[how2]

Hi Guys.

Need some Help. Ideal Logic combi 24

I got Insurance with Scottish Power for my boiler but started playing up on the 20th December 2016, they replaced a few parts but boiler still not working. Then they told me it's the secondary heat exchange. Was getting code L2 and F2, after the PCB was replaced got code FA.

CH works but no DHW, the guy told me to use "one shot" which I found to be drain cleaner(91% sulphuric Acid). I am going to take out the secondary heat exchange

I have put Sentinel X400 into the heating system and will also use X100.

How will I know which is the CH holes and which are the DHW holes?

Which holes will have black deposits? - CH assumption

Which holes will have Limescale? - DHW assumption

I am assuming the DHW is blocked.

I have access to a wide range of acids which should I use and for how long?

Are any of these not Acids suitable fro the secondary heat exchange?

Should i use Fernox DS3 which is about 90% or more Sulphamic acid
Citric acid,
Hydrochloric acid
Sulphuric acid
Sulphamic acid

Thank you

 

[bernardgreen]

Acetic acid ( vinegar ) deals with limescale.

 

[gas112]

the side that will have black deposits in is the side you clean 20 mins with brick acid in it is enough think brick acid is around 10/15 % hydrochloric

 

[Agile]

Is this not a room sealed boiler that he should not even be opening?

 

[how2]

Had a look at the seconary heat exchange, there was no black gunk in the CH side and the DW side had little limescale. Poured water thought it and only a bit of lime scale came out. accacheed hose pipe and water flow through with ease.

Some why am I getting very little Hot water CH is working fine.