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

["Dave McLaughlin" <dave_mclaughlin@xxxxxxxxxxxxx>]

Hi Simon,
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I have ordered a couple of 1-wire temp sensors and knocking up a small dev
=
board to log and record the temperature myself. Should have the parts and
t=
he code done by the weekend. The dev board has a small TFT LCD display so
I=
can show a graph on it of the temperature for the last 24 and 48 hours or =
so. Will be interesting to see how this water tank behaves.
=20
This same dev board will be able to control the heating times too and I
wil=
l add a wireless link back to Homeseer for the feedback and control if
requ=
ired. I can add a button to the Homeseer touch screen so that if a check
of=
the temp shows it to be too low, can request a boost for 15-30 mins or so =
(actual time to be determined after testing later) if someone wants a hot
s=
hower.
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Dave=E2=80=A6
=20
From: ukha_d@xxxxxxx [mailto:ukha_d@xxxxxxx] On Behalf Of S=
imon Haslam
Sent: 14 September 2010 20:00
To: ukha_d@xxxxxxx
Subject: RE: [ukha_d] 24/7 versus limited on and off time for water heating
=20
=20=20
Interesting - yes, mine's the same and I've also boxed in 3 sides with
25mm=
PIR board and rockwool. Once I got the 1-wire sensors hooked up though it'=
s quite clear - they're very sensitive - you can see from the middle
sensor=
when a just bowl of hot water has been run! We're currently using the imme=
rsion (as the boiler and solar aren't yet hooked up) so the obvious side
ef=
fect is that if you leave it at 50C without heating the water is too cold
t=
o shower a day later.

My suspicion is much of the loss is from the pipes at the top of the
cylind=
er - lagged in climaflex but probably not far enough. Apart from
convection=
from the copper, it could well be that little thermo-syphons are being set=
up in the vertical pipes taking heat out of the cylinder and radiating it =
up the pipe into the room above. Of course all of this is relatively small
=
beer (even at several kWh a day) compared to space heating.

Not quite sure how I got us so far off the HA topic ;-)

S




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