Dave Liquorice wrote:
On Wed, 09 Sep 2009 21:22:22 +0100, The Natural Philosopher wrote:

Like other posters, my boiler rarely runs over the summer.

I get the impression that you live on your own or use another means
of heating water. When I lived on my own I put the boiler on for HW
when I needed it which was about every two days. The water stayed hot
enough in the well lagged tank for washing. I started this when the
time switch broke and the (much reduced) gas bill arrived before I
got around to fixing it, so I didn't bother...


Not at all. two of us who dont take baths the whole time, and a well
insulated tank.

Plus dishwasher and washing machine with cold only feeds.


All I am pointing out is that hot water here, a large and very under
occupied house - is the least of my worries, and barely takes any
energy at all. I probably have more hot water via the coffee kettle,
than via the hot taps.


Lets say I have to use 100 liters of 60C water every day. and it comes
in at say 10C. so that's 5MJ a day? a bit over a kilowatt hour. now on
oil thats about 5-10p a day. Depending on oil price and boiler eficiency.

DOES ALL YOUR HOT WATER (nearly) claim the solar guys.

Big ****ing deal. I've got a 12 KW boiler, so it fires up for just ten
minutes a day to heat the tank.

Compare and contrast the energy calcs for the whole house at -5C
outside. 10Kw, or 240Kwh/day. something like TWO HUNDRED TIMES more.

My oil bill is about £2000 a year of which about £1300 is in December
January and February. The rest is in the spring and autumn, and in
summer,(June July and August) it uses almost nothing. At the most I
estimate my hot water is £100 a year.

My father in law was conned into a £3k solar water installation. Even
using the MOST optimistic figures from the SUPPLIERS THEMSELVES his
rather largest three generation household, with great addiction to
showers, saves £180 a year.

And he is delighted when he sees 70C influx temperatures, despite my
saying that he can see 240v on his mains without drawing any power off
it at all..


The fact that a boiler fails to fire up in summer to heat water is
totally unsurprising. heating water is utterly trivial in the quantities
we use it, and takes almost no power at all. Its about 30p a bath I
would say.

Now, lets go back to that hot water. Aa kilowatt hour per day. so about
50W continuous.

I wonder how many of these stupid solar installations would sell if they
said 'produces enough energy to keep a single 60W lightbulb burning day
and night, all year round' 'saves you 30cc of oil EVERY DAY'.

Mind you,its more than a domestic windmill does.



I'd be happy to still work on that system now but the with a SWMBO'd
and two kids it wouldn't work. They are far to used to hot water as
and when they want not in 30 to 60 mins time.


So get a bigger tank and fit an immersion heater.

If I want to save 50W, I simply turn off the computers overnight..