"Christian McArdle" wrote in message
. net...
Two combis win on:

1. Low capital cost of installation

********. One boiler with no pipework
changes will be less than half the
capital cost of two boilers with substantial
changes to pipework.

But the gains are terrific.

2. Running cost, upstairs heating can be off most of the day.

Subzoning is easily achieved using a single boiler.

It is NOT. You require zone valves, which take up space and the control
wiring and knowledge to do it to boot. Two combi's achieves this much
simpler with virtually no wiring worth talking about. To avoid Part P you
can even connect them up to a 3 pin socket.

3. No waiting for showers

Have you ever used a storage system? There is no wait for showers.

They run out though. No waiting for showers with a combi eiether. Ever used
one? And "two" high pressure showers can be running all day. Can't get
that with a storage system.

4. Showers don't run out of hot water

A shower will not run out of hot water,
provided the usage is below the
capacity of the coil.

Which means a large boiler and a new larger space consuming cylinder, in
this case. Getting expensive now. Two comb's is looking far more attractive.

5. Simple zoned heating system
with independent time zones.

Subzoning is easily achieved using a single boiler.

It is NOT. See above.

6. Different rad temperatures on different floors.

Which serves what purpose when
you have TRVs and subzoned thermostatic
control?

Economy and safer with kids about in the playroom with no exsessively hot
rads. The lower the boiler temp the more efficient. Turn upstairs to 61C
flow.

7. Less controls to go wrong, with
accompanying down time and expense.
(no zone valves and the likes)

But multiple pumps and boilers,
all of which can go wrong.

Two integrated pumps that do CH and DHW. As two boilers, the load is shared
and they both have an easier life. W-B Junior is simple with no 3-way valves

8. Always heat and hot water. Two combi's
means built-in redundancy.

About the only advantage.

You lack common reasoning.

9. Release valuable space for storage.

Where are you putting the new boiler?
The cylinder and tanks are often in
otherwise unused locations.

What sort of house do you have? Most British houses are far too small with
cylinder taking up valuable cupboard space.

You'll need to run a new gas line as well. The
existing 22mm won't be enough.

One for each. Not a great thing.

Only disadvantage is slightly more
expensive on regular servicing, which
is overwhelmingly offset by the above points

Which is why every house in the country
has 2 combis. The case is so compelling.

Most houses have a tank in the loft, a cylinder taking up cupboard space, a
shower you run around in to get wet, TWO taps on a basin so you are moving
your hands from one too hot tap to the other cold tap when washing them and
a boiler in the KITCHEN. Most other countries laugh at us. The British are
renowned for bad plumbing. Talk to an American who have been backpacking
around the UK. They can't wait to get home for a decent shower.

In the US many are going over to multi-points that output 200,000 plus
BTUs/hr. On-demand hot water is regarded as much superior to stored water.
Bosch, Takagi and Rinnai are the big players. Two combi's is roughly the
same output. The largest output multi-point in the world is a Takagi.

Read what I write and take it in, instead of thinking you know it all.



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