Your advice is "anything but a combi". What if a combi is the best solution in this instance?
Actually the article points out reasonably fairly the advantages and disadvantages of each type of system. It doesn't really touch on an individuals specific use of the home, which ought to be a major part of the decision on the type of system needed. I would doubt many open-vented systems would be specified today, where there is presently no system at all.
Quoted from that article...
Where and where not to fit a Combination Boiler
The correct application of the combination boiler is most important, as an ill-fitted boiler will cause untold problems.
The mere fact that most combination boilers have the same output available to the central heating circuit as the domestic hot water can lead to the installation of the boiler in situations which are totally inappropriate for their use.
In a larger than average property the boiler would be suitable for the heating circuit but where numerous hot water outlets or where more than one outlet at a time is likely to be used it would not be suited. (E.G. If a downstairs tap was in use while the shower was in use upstairs the flow rate at the shower outlet would be little more than a trickle).
Another application problem that can occur is when a combination boiler is used as a replacement boiler on an existing system. The radiator valves, pipework and fittings would be subjected to an increased system pressure of two to three times of that before the system was pressurised and thereby lead to an increased risk of water leaks.
Many combination boilers incorporate a low water pressure switch which cause the boiler not to operate if the system pressure is too low for instance if there were a water leak on the system due to inadequate radiators. This would lead the customer to blame the boiler when the actual cause would be down to poor design.
Generally Accepted Sites for Combination Boilers
- Properties with a single bathroom.
- Flats.
- Bedsits.
- Starter homes.
- Offices with limited hot water outlets.
Generally Unacceptable Sites for Combination Boilers
- Large detached properties.
- Properties with multiple hot water outlets.
- Bedsits that use one combination boiler to supply several bedsits.
The exception to the above locations would be if the combination boiler were linked to a storage facility (cylinder). When this type of system is adopted it can be seen to defeat the object of the exercise.