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Insulation properties of PVC conduit. - Page 2

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Posted by crispin.proctor on May 3, 2008, 9:15 am

I am going at this on a whim I agree. This is why I am doing the
kennel first. Must cheaper to make mistakes. :)

I have not come across the trickle down collectors. I assume this is
what you are talking about?

How are they an advantage?
I really don't think I am going to go for the plastic option. While it
is cheaper, the copper option is not prohibitively expensive. I am now
trying to source some form of plate to use as a collector. I have a
few lengths of 20mm copper pipe lying around so will use that. I think
that they might be too thick but will see.

As for the storage, I was going to have a large, insulated, tub of
water. As I am building and designing the shed / workshop, I can
include this quite easily.

For both implementations, I am not looking to heat during the day but
store as much as I can during the day and heat at night. Suddenly the
size of the storage is scaring me. I don't want 1 cup of scalding
water but rather a large volume of tepid water. Any ideas on how I can
calculate this? I suppose there are too many variables in it such as
sun etc. Being in the UK, it'll be far less than my original South
Africa. Water in a garden hose could burn you!)


Posted by Jeff on May 3, 2008, 2:34 pm
crispin.proctor@gmail.com wrote:


  I'm not working on one, so I really don't know. Essentially all they
really need is water trickling down a roof, typically corrugated metal
with some kind of glazing. It's collected in a gutter and recycled. Your
only major cost is the glazing. You could do the glazing with glass, or
using two cheap layers. An inner layer that is tolerant to water vapor
and an outer one that is UV resistant, and perhaps tougher.

Potentially much lower cost.

There's a number of people that sell the absorber plate ready to go. You
provide the box. Easy. I made mine using a sandwich of aluminum flashing
but it is extraordinarily time consuming!

I have a

Collector design program:


Well, the heat in BTU's stored is easy to calculate. One pound of water
raised one degree F is one BTU. Similar equations for metric.

   The cheapest way to heat a home is not to lose heat. Tighten and
insulate is the most cost effective plan.

  There's a thread in this group titled "Tank Sizing", you may want to
read that.

I suppose there are too many variables in it such as

  Well, that can be a problem. I know there are some parts of the UK
where it's just too overcast.

   Google yields this:



Posted by crispin.proctor on May 7, 2008, 10:15 am

David / Jeff,

Thanks for the answers. 3.6 cubic meter tank is large. Larger than I
thought I would need.
Thanks also for the programme - I've downloaded and installed it. I'll
have a play around with it.

Due to the size of the storage tank required, I had another thought.
(We talking workshop here)
If I already plan on a concrete floor, why not make the base thicker
(200mm). As the rough size of the workshop will be 6 X 9 with a base
of 200mm, that gives me roughly 10.8 cubic meters. Making this thicker
has a huge increase.
As, from what I have read, concrete is roughly 4 times less efficient
at storing heat than water, this will be made up in bulk. There would
be a slight loss due to the piping in the concrete for heat transfer.

A major drawback would be the fact that I cannot control the
dissipation of the heat. Having such a large surface area I am sure it
would dump it rather quickly. (There is of course insulation on the
sides and underneath it.)

Maybe I'll just got get a 1300W heater from my local electrical
store :) Naa, this is more fun.


Posted by Jeff on May 7, 2008, 5:24 pm
 crispin.proctor@gmail.com wrote:


Go run your own numbers. I think you can probably get by with a tank a
third the size for 5kWHr.

   How much collector area are you planning on?


Posted by crispin.proctor on May 7, 2008, 7:29 pm
I'm confused by something. (Probably the most fundamental thing here)
When you say 5KWh, how would you compare that to a small heater?
I have a heater which is 1.1KW. Is that then, if used over an hour,
Your measurement is a rate. Or am I missing something? (Hangs head

Initially it was a series of 15mm copper pipes spaced about 30mm
apart. Height is 500mm and length 1.8m. There would be two of them.
However, after advice (from here) I will change it to use plates (from
underfloor heating) which will space the pipes further apart but
obviously have a much larger surface area.

Today was a "hot" day. Not a cloud in the sky and probably around 25c
(Yes, that is hot). The water (still) in my test collector, which is
not in a protective box and cooled by the breeze, was very hot. A
tepid cup of tea it would have made. I lost my temp probe so could not
get the exact temperature...


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