i would like to replace my conventional boiler with a combination boiler
has
anyone got inst instructions ?please

In order to fit gas appliances, you need to be what is described in the
legislation as a "competent person". For professional installation, this is
defined as being a member of CORGI, with, possibly an exception for BG.
However, for installations within your own home, it is permitted to DIY,
provided you can hold your head up high in a court of law and justify your
competence.

Unfortunately, the level of expertise that appears to be present from the
nature of your query would indicate that the court would be unlikely to
accept that you did comply with the competence requirement, and such an
installation would be illegal, and probably highly dangerous.

The court would be looking to ensure that you were able to perform and
understand all the calculations required to design the system. They would
also need to be convinced that your understood all the safety precautions
and systems required to do a professional installation.

Finally, the replacement of the boiler would come under building regulations
and require you to make a building application to your local authority to
ensure that the system as installed would comply with Part L1, for energy
efficiency and heating controls.

I would suggest ringing around in the Yellow Pages and asking for
recommendations for a CORGI installer in your local area. There is no need
to pay the high prices that BG and the other national companies charge.

Christian.