RE: 24/7 versus limited on and off time for water heating

["Dave McLaughlin" <dave_mclaughlin@xxxxxxxxxxxxx>]

The element on my water tank is inserted from the bottom. As an aside,
the =
tank itself seems to well insulated as there is a metal cover on the
outsid=
e and it hardly gets warm when the water is at the max temperature.
=20
Reference your PS. I see nothing wrong with this. You are into HA are you
n=
ot? SWMBO=E2=80=99s the world over will never understand us=E2=80=A6
=20
=20
From: ukha_d@xxxxxxx [mailto:ukha_d@xxxxxxx] On Behalf Of S=
imon Haslam
Sent: 14 September 2010 14:28
To: ukha_d@xxxxxxx
Subject: RE: [ukha_d] 24/7 versus limited on and off time for water heating
=20
=20=20
Agreed - the thermostat will turn the element off after the preset temp is
=
reached (it should 60C to kill Legionella bacteria).

One other consideration though is where the heating element is placed: if
i=
t is at the top of the cylinder, diagonally pointing down (the traditional
=
design) then the top, say, quarter of the cylinder is heated quickly - I
us=
ed to find that a relatively short burst would be enough for a quick
shower=
. Larger tanks may have the immersion element horizontally mounted about
ha=
lf-way down - in this case you have to heat half the tank to the
temperatur=
e you want at the top - I can't quite work out why they do it like that
(pe=
rhaps it puts less thermal stress on the element?).=20

One thing I am finding is that heat loss, even from a modern insulated
cyli=
nder, is significant - currently about 1C an hour for me - so for maximum
e=
fficiency you don't want to heat it for much more than you use. Of course
i=
t might not be so bad in the tropics ;-)

Simon
PS. I've got my 1-wire sensors on my new cylinder and think I might be=20
turning into a DHW bore! SWMBO is not convinced that you should have to=20
look at a graph on the kitchen computer to judge if the water is hot=20
enough for a shower!




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