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

[Simon Haslam <simon_haslam@xxxxxxxxxxx>]

You can work it out. The heat loss of the cylinder is proportional to
the t=
emperature difference between the water and the room, and the amount of
ins=
ulation. Therefore the higher the average temperature of the water the
more=
heat you will lose so keeping it at 60C for 24/7 will always lose more hea=
t than heating it on demand (when the average temp may be 30 or less).

Most larger new cylinders lose around 2kWh per day when hot (depending on
s=
ize and insulation), and take a few kWh (e.g. 6.1kWh for 210l from 10 to
60=
C) to heat up the water from cold (I haven't investigated smaller
cylinders=
). So the heat loss may be a significant part of the energy used, though
of=
course in the winter the heat will go into your apartment so isn't really =
"lost". To do more calculations you need to know the size of your
cylinder,=
level of insulation (preferably manufacturer's data) and whether there's a=
ny extra insulation (doesn't do any harm!).

That said buying something to control the load may not be cheap - you need
=
something that will safely dual-pole switch >13A. Even a Smiths digital
imm=
ersion timer is about =C2=A325, and I don't know what HA compatible
devices=
are available. (Please post what you find as others on the list may be int=
erested)

HTH


Simon

--- On Fri, 10/9/10, Dave McLaughlin <dave_mclaughlin@xxxxxxx> wrote:

From: Dave McLaughlin <dave_mclaughlin@xxxxxxx>
Subject: [ukha_d] 24/7 versus limited on and off time for water heating
To: ukha_d@xxxxxxx
Date: Friday, 10 September, 2010, 18:56







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Hi all,

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Anyone have any real data that says that keeping your immersion water
heate=
r

on all day is more wasteful of energy than say, switching it on in the

morning and then the evening for showers etc.

=20

The apartment I live in, the hot water is only available in the bathrooms

for shower and sink. The kitchen only has a cold water feed.

=20

Would it be considerably cheaper to switch it on in the morning for say 2

hours to heat the water and then off until about 8pm in the evening?

=20

I was looking to build a timer circuit (with HA interface to Homeseer via a

wireless link to allow me to control it and be able to switch it on if we

wanted hot water during the day)

=20

The thermostat is set low anyway to about 60 deg C as we don't really need

very hot water here.

=20

=20

Cheers,

=20

Dave...

---

Very funny Scotty, now beam down my clothes!!!

---

<http://www.embeddedcomputer.co.uk/>
http://www.axoninstruments.biz

---

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