Hi all,

I have bought a few solar vacuum tubes, old model which gets filled
with water+antifreeze (not the heat pipe model), but I do not have the
installation instructions.

On the solar panel head there are 30 plastic screw threads, where the
tubes will be fixed. I have 2 questions concerning the installation of
the tubes, hope somebody can help.

How do I fix the tubes? I was thinking of using silicone on the thread
in order to hold and seal the tube.
Does anybody know if these kind of tubes can sustain a high pressure
(a few Bar)? That would be desirable, so that I can use a water tank
in the basement, via a closed-circuit connection and pump.


Thanks, Leodp

On May 3, 1:09*pm, leodp wrote:
Hi all,

I have bought a few solar vacuum tubes, old model which gets filled
with water+antifreeze (not the heat pipe model), but I do not have the
installation instructions.

On the solar panel head there are 30 plastic screw threads, where the
tubes will be fixed. I have 2 questions concerning the installation of
the tubes, hope somebody can help.

How do I fix the tubes? I was thinking of using silicone on the thread
in order to hold and seal the tube.
Does anybody know if these kind of tubes can sustain a high pressure
(a few Bar)? That would be desirable, so that I can use a water tank
in the basement, via a closed-circuit connection and pump.

Thanks, Leodp

What matters re pressure is where the solar tubes are relative to the
header tank. If the tubes are on the roof you've got next to no
pressure in them.


NT

What matters re pressure is where the solar tubes are relative to the
header tank. If the tubes are on the roof you've got next to no
pressure in them.

NT

Sure, but at low pressure vapor can form much more easily if temps are
high.
Do you think the silicone sealing is ok for keeping the tubes in
place?

Leo

"leodp" wrote in message
...
What matters re pressure is where the solar tubes are relative to the
header tank. If the tubes are on the roof you've got next to no
pressure in them.

NT

Sure, but at low pressure vapor can form much more easily if temps are
high.
Do you think the silicone sealing is ok for keeping the tubes in
place?

Leo

I have no idea how this type of tube works mechanically, but I would be
surprised if they were not designed to take several bar pressure.

In my case I have "heat pipe" type solar tubes which are about 7 metres
vertically above the pump and thermal store.

The (sealed) system has a capacity of about 9 litres, with a 7 litre
expansion vessel which is precharged to 1.25 bar with a 3 bar safety valve.
Fluid is 45% propylene glycol.

System is cold charged to 1.5 bar (measured at the bottom) which means ~0.7
bar at the manifold.

In test "stagnation" (ie pump "off" but sun "on") the manifold stabilises at
about 130C and system pressure 2.25 bar....so about 1.5 bar at the manifold.



D

On Mon, 3 May 2010 05:09:24 -0700 (PDT) someone who may be leodp
wrote this:-

I have bought a few solar vacuum tubes, old model which gets filled
with water+antifreeze (not the heat pipe model) [snip]
How do I fix the tubes? I was thinking of using silicone on the thread
in order to hold and seal the tube.

I imagine not the sort of stuff one sees in large orange sheds.
Vacuum tubes reach high temperatures, quickly. You will need to
investigate high temperature sealants. It might be worth looking at
suppliers of car sealants.

Is one available which will seal at high temperatures and pressures
yet not seal solid? No idea, when you find out let the rest of us
know. However, as you presumably don't have, and cannot find, spare
tubes this may not be a problem.

Does anybody know if these kind of tubes can sustain a high pressure
(a few Bar)?

The tubes should be able to. The joints may not unless made
properly.


You will need to consider the installation sequence carefully. The
controls and water circuit should be tested before inserting the
tubes. It would be sensible to shade the area from direct sunlight,
so that you can fiddle with getting the tubes in and sealed without
the pressure of things getting hot. When you think you are ready
remove the shading, but keep it handy in case heat shows up
problems.



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000...#pt3-pb3-l1g54