Dave Fawthrop wrote:

| overstated the requirements slightly

is the understatement of the year. You posted

Not really....

| Not really. If you replace it and don't go the combi route, you will
| need to replace the hot water storage cylinder as well with a fast
| recoivery one to comply with the building regs.

Which is outright wrong.

It should read, "you will need to replace the hot water storage cylinder
with a part L1 compliant one (or better) to comply with the building regs"

(This does make the (fairly safe) assumption that a 1960's installed
system will not already have a compliant cylinder)

My error was in describing this as "fast recovery" which in fact is a
bit faster still than the "ordinary" part L1 compliant ones.

On a more practical level, cylinders don't have an unlimited lifespan,
so if you are replacing an ancient boiler and the cylinder is also as
old, now would be a good time to replace it before it leaks.

If you are using a condensing boiler, then there is no reason to not use
a fast recovery cylinder.

(there used to be the issue that the load they placed on the system
could drop the return temperature too far, and cause condensing on non
condensing boilers - this would either damage the boiler, or require
more a complex install to add blending valves on the return to keep the
return water temp above the dew point)

As I am putting a combi system in specifically to get rid of the hot water
cylinder, and have worked out that the smallest combi will provide more
liters per min of hot water than the present system, and more importantly
will provide one bath after another, which the present system struggled
with.

The smallest combis (typically 24kW) will deliver water at 9 lpm (at 45
degrees) in warm weather (less in winter). So there is something
seriously wrong with your storage system if it can not match that. A
badly designed an implemented one should do 20 lpm (at 65 degrees), and
a good one 40+ lpm (to which you can also in addition add cold water at
a significant rate).

As for "one bath after another", yes it will, so long as you don't mind
it taking 15 mins to fill each one.

I will stay with the combi.

Fine by me, by we wern't talking about you ;-)

Most DIY domestic combi installations will have the same requirements as
myself.

You are IMM and I claim my five pounds!

That seems like a rather presumptuous statement...




--
Cheers,

John.

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