Fitting new combi boiler using existing single pipe system

[MartynH]

I am in the process of getting quotes for replacing my old back boiler with a combi boiler and the first heating engineer to call has said that I will need to convert my existing single pipe system to a dual pipe system! Is that correct? No combi boilers will work with a single pipe system!

 

[ChrisR]

Some manufacturers explicitly forbid it, nobody recommends it. If you system's that old you probably have rads which are due for replacement? TRVs are a problem too.
Converting to 2 pipe is not that hard when you look into it, and well worth it.

 

[Agile]

By the time that you consider whats required then its almost worth replacing all the rads anyway.

Many of the rads on one pipe systems were undersized by current standards.

Tony

 

[gasmataz]

i have fitted 2 combi's on one pipe in last 2 weeks and they both worked fine but chris had it right that it's not recommended and i also didnt recommend it but customers choice