"Doctor Evil" wrote in message
...

snip

A domestic supply gas supply can provide 212 cu foot an hour, about
62kW
input. Two properly sized combi's can do the job no problem, with
the
average around 27kW.

This problem is crying out for two combi's as the solution.


It's also crying out from an up rated electricity supply and electric
showers, and if there is going to be more than one kitchen with full
cooking facilities then that alone will probably mean that the cost of
having the electric intake up rated has already been budgeted for.

It's also crying out for a storage tank so that there is at least some
hot water if there is a major breakdown of either boiler(s) or power,
also a storage tank will allow water to be heated in an emergency by
electricity (although expencive it will be cheaper than pitting up to
six tenants into a Hotel for how ever long.

This is not a clear cut plumbing decision, as someone else has said,
it's a planning / business decision as well.