"Andy Hall" wrote in message
...
On Fri, 18 Jun 2004 01:18:47 +0100, "IMM" wrote:


"Colin eclipse 2" wrote in message
...

I know - done to death.. A customer has asked me this question. I have
come
up with the following list. Any other thoughts - sensible ones.. no
need
to
start a debate about the merits - just need a list!

Conventional
Pros
Stored hot water - so water (hot and cold)
available if mains supply fails

-This is so rare an event that is it is not worth taking into
consideration.

It happens to me every few months......

Stop making things up.

Immersion heater backup - hot water if boiler or gas fails
Warm airing cupboard

That can be achieved with any heating system, so not so.


Cons
Cylinder needs replacement (in this case to comply with building
regs)

-Cylinders may need replacing every 8 to 10 years in hard water areas.

One can use a water softener or phosphate
doser to avoid this.

Water softener at approx £400 just to buy then the cost of salt too and they
take up space. A de-scaler will only delay the inevitable.

If the water is untreated, then heat exchangers
on some combis are liable
to scaling.

Storing hot water not as energy efficient
More complex controls
More costly than combi to install

-Very poor shower pressure, having to use an expensive and noisy power
shower pump in some situations.

Flow from a combi can also be poor if it is not a large one.

You size accordingly. Many conventional boilers will not fully heat a house
and leave the occupants cold in winter. So, when you fit one you size to
suit. You don't undersize. The same with combi's.

-The cylinder takes up space.

So does a combi if of high capacity
and fitted with some form of
storage.

Such strange logic. A conventional system takes up two lost of space and a
cylinder takes up lots of space unless you go square like an Elson. You
obviously can't figure this out.

-Ugly zone valves and pumps around cylinder.

One can have a system boiler.....

You still need a 3-way vale or TWO 2-way valves.

Combi
Pros
High pressure showers without pumps
Only heats hot water you use
No stored water (flooding issue)
Frees cupboard space

-No wating for cylinder to reheat

This is irrelevant if the cylinder is adequately sized.

You mean oversized, taking up space and more standing heat losses.

-High pressure shower after shower can be taken.

That depends on the water supply
and temperature and rating of the
combi.

You size to suit. Duh...

-Have a high output, so house warms up faster.

Than what? A system boiler can be equally effective.

Combi boiler by their nature have outputs. Conventional boilers are sized
only for a particular house requirements. A combi in 90% of cases will have
spare heating capacity.

-All the system is inside the one white box.

A system boiler can achieve that as
well, with the exception of the
cylinder.

....and the cylinder takes up lots of space and has standing heat losses and
a 3-way va;lve has to be installed as well.

-No pipes to freeze in the loft

Irrelevant if they are properly insulated.

Which is more expense.

Cons
slower bath filling

High flowrate combi's are available, so not true.

We've had that debate and there are demonstrable limitations.

Stop babbling balls..."High flowrate combi's are available".

No warm airing cupboard

A small rad can be installed in the airing cupboard taking up no space.

A post suggesting that there are no
disadvantages to combis should be
regarded as suspect. Nothing is ever as clear cut.

You know nothing of combi's to come out with a ridiculous statement.