Heat only boilers are normally installed as a direct replacement, that is replacing an older boiler that has an expansion tank in the loft space which automatically keeps the heating system topped up.

A System boiler doesn’t have an expansion tank, they have an expansion vessel which means that the heating system is sealed and has to be topped up manually.

An upgrade to a sealed system is normally preferable as a sealed system is more economic to run as it is less likely after the system has been flushed that sludge will build up in the system preventing it from working properly

All the boilers we install are condensing boilers to recover as much heat as possible.