Now that my heating controller is nearly done I've been using it to collect
data. Some of it is quite surprising, at least to me.

We have a ~25 year old 120L HW cylinder with foam insulation. Over a period
of 6 hours with no heat input (and just a couple of handwashes) the
temperature dropped from 61.5 C to 56.5 C. Measurements have a resolution of
0.1C. According to my calculations that represents a loss of ~2.5
megajoules, which over 6 hours is an average of ~115W.

I daresay modern cylinders could do a lot better than this, but somehow I
was expecting the losses to be higher.

Steve S
--

Steve S wrote:
Now that my heating controller is nearly done I've been using it to collect
data. Some of it is quite surprising, at least to me.

We have a ~25 year old 120L HW cylinder with foam insulation. Over a period
of 6 hours with no heat input (and just a couple of handwashes) the
temperature dropped from 61.5 C to 56.5 C. Measurements have a resolution of
0.1C. According to my calculations that represents a loss of ~2.5
megajoules, which over 6 hours is an average of ~115W.

I daresay modern cylinders could do a lot better than this, but somehow I
was expecting the losses to be higher.

If you've got the space, an extra wrap of loft-insulation can be a good
plan.

In article k
Steve S wrote:
Now that my heating controller is nearly done I've been using it to collect
data. Some of it is quite surprising, at least to me.

We have a ~25 year old 120L HW cylinder with foam insulation. Over a period
of 6 hours with no heat input (and just a couple of handwashes) the
temperature dropped from 61.5 C to 56.5 C. Measurements have a resolution of
0.1C. According to my calculations that represents a loss of ~2.5
megajoules, which over 6 hours is an average of ~115W.

I daresay modern cylinders could do a lot better than this, but somehow I
was expecting the losses to be higher.

I expect there are regions of colder water that you're not measuring.

Steve S wrote:
Now that my heating controller is nearly done I've been using it to collect
data. Some of it is quite surprising, at least to me.

We have a ~25 year old 120L HW cylinder with foam insulation. Over a period
of 6 hours with no heat input (and just a couple of handwashes) the
temperature dropped from 61.5 C to 56.5 C. Measurements have a resolution of
0.1C. According to my calculations that represents a loss of ~2.5
megajoules, which over 6 hours is an average of ~115W.

I daresay modern cylinders could do a lot better than this, but somehow I
was expecting the losses to be higher.

Steve S
--

That fits well with my observation that I can heat our DHW all summer
and barely be able to measure the oil used (hand washing, washing
machine and dishwasher). Come autumn and the start of the CH season we
use about 1cm a day.
It really makes me wonder how these solar systems which basically just
do DHW can ever be justified.

"Rob Morley" wrote :

I expect there are regions of colder water that you're not measuring.

I don't think so. Sensor is 3/4 of the way down the cylinder.

Steve S

--

On Mon, 09 Jan 2006 16:38:58 +0000, Steve S wrote:

Now that my heating controller is nearly done I've been using it to collect
data. Some of it is quite surprising, at least to me.

We have a ~25 year old 120L HW cylinder with foam insulation. Over a period
of 6 hours with no heat input (and just a couple of handwashes) the
temperature dropped from 61.5 C to 56.5 C. Measurements have a resolution of
0.1C. According to my calculations that represents a loss of ~2.5
megajoules, which over 6 hours is an average of ~115W.

I daresay modern cylinders could do a lot better than this, but somehow I
was expecting the losses to be higher.

I beleive that a modern Part-L compliant cylinder would do a bit better
but these numbers are not very far out.

To improve this, make sure that all the hot pipework is insulated the
losses from 1m of HW pipework is about 20W

The hand basin uses may have taken out a fair bit from the cylinder even
if you did not wait for the WH to come through.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html