Pressurised boiler

[Boto]

I am buying a new house that has a pressurised boiler. The vendor says that it is similar to a combi boiler. What is a pressurised boiler, is there constant hot water like a combi? How does it differ from a convential boiler?

[buildersmate]

It is not that the boiler is different (between a 'pressurised' and a 'conventional') - its that the HW and CH system pipes are pressurised. A pressurised system may have a hot water tank store (also pressurised) or it may not. That's the main difference really.
If it doesn't have a hot water tank, it uses a Combi boiler, which heats the HW only as it is needed (no separate hot water storage tank).
If it has a hot water tank, this tank is contained inside a steel vessel for safety. Megaflow is one such brand name you may have come across but there are others. With this system, the HW is stored ready for future use, and the HW is at the same pressure as the cold water mains coming into the house.
Both of the above systems are pressurised to about one bar.
Ask the vendor to show you the components, perhaps?
A conventional system has a cold water storage tank in the loft space, and the HW and CH system is only 'pressurised' by the weight of the head of water in the cold tank above.

[gasman]

If i may also add to buildersmate very good reply. that the pressurised systems are much more economical. Will save you ���s

[Boto]

Buildersmate and gasman - many thanks.