On 20/05/2017 13:35, Terry Casey wrote:
I note it says in the wiki that: "I need a new one, what should I get!" comes
up in some form almost every day on uk.d-i-y, but couldn't find enough
information to clench the deal, one way or the other.

My wife and I are living in a two bedroomed bungalow - there's nobody else
living there except the cat! The central heating is old - if the pencilled
date on the back of the controller I replaced recently is anything to go by
it dates from 1996.

We had a quote recently from a local plumber who advocated a combi - which
I've always been convinced from various things I've read (probably here) that
they can be problematic - but he said that modern combis are much better than
their predecessors and would be highly suited to our needs. He also pointed
out that he has a combi in his 4 bedroom property and has no problems with
it.

We then got another quote from someone who is clearly prejudiced against
combis! Apart from additional strain on the old pipework - which we are well
aware of - he said that the increased pressure can damage the non-return
valve in dual fill washing machines (ours is currently a dual-fill Hotpoint)
but that we wouldn't be able to run hot water from two taps at the same time!

This could be a worry if we couldn't wash our hands (or whatever) every time
the washing machine was filling or the other is running a bath. Can this
really be true?

Quote No. 1 includes an Ideal Logic+ 30kW boiler whilst No. 2 is for a
Worcester Bosch 15ri boiler. No. 1 includes quotes for both combi and non
combi options (but does give any indication of which non-combi boiler would
be fitted) and No. 2, as might be expected, doesn't have a second option!

How do these boilers compare - assume No. 1 would use a non-combi version of
the same boiler?

All comments gratefully received!

Terry

The first question is do you actually *need* a new boiler? What's wrong
with the existing system? There's no point in replacing it just because
it's "old" if it works ok and if spares are available. [My boiler is far
older than that - and still going strong - although I have updated the
controls.]

A new boiler will almost certainly by be more efficient than an old one
- but the payback time until you have broken even is likely to be quite
a few years, particularly if the new one require more frequent
maintenance. If the controls need updating to make sure that the boiler
doesn't waste energy keeping itself hot when there's no heating or hot
water demand, you can do that for far less than the cost of a new boiler.

If you are convinced that you *do* need a new boiler, the choice between
conventional and combi depends on many factors.

Firstly, do you bath or shower? Even a good combi will take a long time
to fill a bath with hot water compared with a stored hot water system.

Are you desperate to get rid rid of your hot water cylinder in order to
redeploy the space for some other purpose?

Have you got decent pressure and flow from your cold water mains. I
think the figure often quoted is that the mains needs to be able to
deliver at least 14 litres per minute at the point of entry - often the
kitchen tap.

Is your gas pipework up to the job. A combi will consume gas at a very
high rate when heating the hot water (as opposed to the radiators) so
the internal gas pipework may need upgrading.

In my view, there *are* some circumstances in which a combi represents a
good solution - but they're few and far between. I've stayed in one or
two holiday lets in the summer where a combi has been ok, but when I've
stayed with friends and relatives who have a combi in a normal
household, the hot water supply has always been dire!
--
Cheers,
Roger
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