no its not the installer problem he did as manufactures said
manufactures offers the warrenty their fault
It is the installer's problem.
The customer will usually know zilch about boilers and heating, that is why they've employed a heating contractor. Mr Customer has a contract with Mr. Installer that says Customer hands over £XYZ pounds, Mr. Installer supplies and fits boiler and heating as per contract. Mr Customer can reasonably expect Mr. Installer to know a good boiler from a bad boiler.
The manufacturers will usually fix such problems under the warranty because they know that they're at the end of the contract chain and will have to supply a new boiler if they don't fix it on site.
You may disagree but a 5 day course on contract law says you'd be wrong; very boring it was too.
So are you saying that the manus terms of warranty is given to the installer ? or it is given to the custumer ? who purchased the boiler from the installer ??