IMM wrote:

My apologies to Mr. Orrett, but based on previous experience this may
degenerate... However due to the nature of the questions it is probably
worth cutting through some of the "spin" to get a more balanced view.

View two combi boilers. One doing one zone of space heating (upstairs) the

Remember the question here is can I have different bath taps! Chances
are using (a) combi boiler(s) of any sort is going to be a very
expensive way of doing what the OP wants.

A win, win, situation.

As long as you skip over the limitations...

Its advantages a

- cheap to install.

Not compared to changing a bath tap, and also much more expensive that
re plumbing the hot water cylinder to be heated by the existing boiler
rather than the immersion heater.

- quick to install.

Compared to what? Starting from the situation of having no CH and no HW
at all, then a combi may be quicker to install than a cylinder based
system. Most people don't start from this point however.

- space saving (releases an airing cupboard). Both can go in the loft, or
at the back of the existing airing cupboard.

Sometimes true.

- never without heat in the house as two boioers are used.

Sometimes true. Not sure this is a big issue since the things should not
fail that often.

- high flowrates (will do two showers and fill a bath in few minutes),

Better than one on its own yes. Compared to a heat bank solution then
probably not as good.

- No waiting for a cylinder to re-heat

True. Although a fast recovery cylinder driven from a decent sized
boiler will recover far faster than the immersion you are used to.

- Natural zoning, one does upstairs and one does down

Can be archived with some valves for less money.

- hardly any electrical control work (running a wire to a programmers/stat
and power to each,

Might be an advantage if you are fitting it yourself and are clueless
about wiring, otherwise a non issue.

- simple no brainer installation,

No more or less complicated than plenty of other options. Personally I
would have though changing the taps was _far_ simpler.

- minimal components used.
- less piping used

In the grand scheme of things not that much of an issue, sine you will
be paying far more for labour to fit them than you will for pipe.

- cheap to run overall as upstairs would be off most of the time
- etc.

Assuming you don't need the upstairs heated during the day etc.


IMM also forgot to include:

Some disadvantages/limitations a

You need a good cold mains flow rate

You may get longer bath filling times (especially in the winter).

You will have no stored water, so in the case of a boiler failure you
are without hot water. In the case of water failure you would be without
water. In the case of electrical failure you also loose HW as well.

Most combis can run the CH or the DHW, but not both at the same time. So
if people are having a number of showers one after another, the house
could start to get chilly. Also things like not turning off a hot tap
completely could result in the boiler turning off the heating.

If you CH system is getting on a bit, you may find it does not
transition to pressurised operation too well, and hence you start
incurring more cost replacing the bits that spring leaks.


So in summary a win win situation for some people, in some
circumstances. One size does not fit all.


--
Cheers,

John.

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