John Powell wrote:

One potential problem for me is the apparent low flow rate into the
house from the mains

I did a check at the nearest cold tap to the water inlet, ( the cold
water is at mains pressure) - I filled a 2 litre jug and timed it

it came out at about 15l/min

would that change the optimum choice of boiler?

I had this concern myself since we have a poor (ish) mains feed. I found
I actually got the best flow rate at the cold bath tap however (the
kitchen tap is a monobloc mixer with microbore feed, and was giving a
misleading impression that the feed was capable of 5 or more l/min less
than was actually the case). So it might be worth repeating the test at
another tap if possible. Use a larger container and time say 10 litres
to get a more accurate picture.

If the limit really is 15 l/min then you have three choices:-

1) live with it, since it is plenty good enough for a shower, and is not
going to restrict the performance of any combi below 38kW (i.e. quite large)

2) Upgrade the mains feed

3) Fit a mains pressure unvented cylinder, and heat it like you would a
conventional hot water cylinder.

Option 2 is worth doing if you are looking for a very high end combi
system (or multiple combis).

Option 3 will outperform the combi systems for things like bath filling
but cost as much or more than IMM's "a boiler for every room of the
house" scheme.

--
Cheers,

John.

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