On 05/12/2011 22:36, Lieutenant Scott wrote:
On Mon, 05 Dec 2011 22:18:25 -0000, Roger Chapman
wrote:

On 05/12/2011 21:50, Lieutenant Scott wrote:

But getting hot isn't enough with condensing boilers, the rads
have to
drop
the return temp to about 50C so the boilers condense while still
providing
enough heat to do their job.
This can be somewhat difficult if a lot more water is going through
one rad
than another.

Then don't use a condensing boiler.

These days you don't get much choice.

Worst case scenario it doesn't condense, so you get less efficiency?

For it to condense first get a condensing boiler.

I don't think I have one, there is no fan or condensate piping. It was
fitted in about 1995.

If yours does not have a fanned flue, then its probably fairly basic,
and unlikely to exceed 70% efficiency. Hence it wastes 30p of every £
you spend on gas.

With a natural gas fired boiler the difference can be considerable - up
to 10%.

I don't call 10% considerable. It's not even enough to make a pig stop
you for speeding.

Compared to yours, a modern boiler is likely to be 25% better.

And why does all the water going to one radiator cause a problem? The
water would still cool by 15C or whatever it is. I assume a condensing
boiler can handle only one radiator being switched on, which would have
the same effect.

You seem to be making a lot of very strange assumptions. The heat loss
in any radiator is a function of the volume of water flowing through the
temperature drop across the radiator. The bigger the radiator the more
scope there is to give out heat and the narrower the pipework the less
water you can force through it.

If you actually want to get a 15C drop across the radiator you have to
slow down the throughput and sacrifice some of the heat output you would
have got had you the means to push water through the radiator so fast
you only get a very small temperature drop.

With condensing boilers you need bigger radiators so you can get the
return temperature to below IIRC 53C to get the condensing process
started but you need the return temperature a good way below that in
order to get a 10% advantage over a non condensing boiler.

Sounds like a lot of hassle, one of these things where people spend
1000s of pounds to save a few pennies. Kinda like solar panels.

Much depends on the size of your gas bill. There is often no point in
ripping and replacing a working system unless you have very high bills.
However when you are forced to replace, you may as well go for the best
available at the time.

I will probably rip out and replace my boiler on the grounds of
efficiency, but only because a new one will pay for itself in two to
three years due to the current size of the bills.

Except for certain very limited
exceptions condensing boilers are mandatory both as new installations
and as replacements.

Mandatory energy savings - whatever next. It's MY money.

You want to replace your window you have to have double glazing using
special (ie) expensive glass.

Do I hell. I replace it with what *I* want.

Depends on if you can do it yourself again. A FENSA register installer
will only be able to install stuff that complies with modern building regs.

You want to improve the insulation of your
has you can't take any half measures, you must do it to new build
standards. Big brother is alive and well and living in your wallet.

Really? Does he watch what I put in the loft?

Yup.

I have what he called a balanced flu.

So do most people these days. You could well have a condensing boiler
without knowing it.

I think you need to read up on the basics of central heating design
which should include inter alia boiler types, heat output, circuit
design, pipe sizing, etc.

Then there is the more sophisticated stuff - programmable thermostats,
zoning, weather compensation, heat recovery ...

Ever heard of the acronym KISS?

Well if you want to be considered stupid I will oblige in future and not
bother you with inconvenient facts.

I was trying to tell you that overcomplicating thongs is pointless.

More of a Y front person myself, so can't really comment.


--
Cheers,

John.

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