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poor performance and condensation

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Posted by Tom on April 8, 2006, 3:01 pm
I bought and installed a Heliodyne Gobi 410 on the roof of my house in
Los Angeles. At optimum tilt and facing true south the panel was making
just 120 degree water. My conversations with their tech support amounted
to me explaining the problem and they telling me that I must have done
something wrong.

When we uncarted the panel the first thing I noticed was condensation
under the glass. I reported it immediately to the manufacturer. The
condensation never goes away. Finally, I unscrewed the glass plate and
propped it open a quarter of an inch on the upper corner. The
condensation exits almost immediately and I get a twenty degree jump in
performance in one hour (140 degrees).

I reported this to the manufacturer and they immediately said I had
installed improper freeze protection (I had a pro install the protection
specified by the Heliodyne rep), and why would someone jump to that
conclusion when the discussion was about condensation and performance,
not leakage.

Heck, I don't want to sue anybody, I just want the danged thing to work.

So, anyone have any ideas? Here are more specs:

Insulation under the tube is bone dry from top to bottom.

No leaks visable.

Max output so far for 4 by 10 collector is 140 degree water from a open
loop 75 gallon tank, insulated lines, about a gallon a minute calibrated
flow from a PV powered Hartell pump, which was also recommended by the
manufacturer. Best delta p to date at 1 gpm is about 12 degrees
(yesterday when the top of the panel was askew)

Any ideas? All would be welcome.



Posted by SJC on April 8, 2006, 4:52 pm

  Tech support people sometimes do not solve the problem but anger the =
It is as difficult for them to diagnose the problem as any of us. =
Neither we nor they
can actually see the problem, we only hear/read about it. Not the best =
way to trouble
   My first guess would be an air leak in the case that allowed the =
moisture to
get in at night, but not out in the daytime, even when it warms up.Once =
you opened
the case, you allowed enough space to get the moisture out, but that =
also let out heat.
Maybe try a blow test to see if you can spot any leaks in the case. =
Force some air in
and use a spray bottle to see if you can spot the leak. Just a first =

Posted by Tom on April 8, 2006, 6:05 pm
 SJC wrote:


nor they



out heat.

air in

Many thanks for the idea. I will try it this afternoon. I have noticed
this morning that for the first time there is no condensation on the
inside. Is there any chance at all that moisture that was shipped with
the unit could not escape until yesterday when I opened the case and let
it breathe?

Posted by Solar Flare on April 8, 2006, 10:04 pm
 One thing people have a hard time with is that items with air in them
have to breathe or withstand changes in atmospheric pressure. If they
don't a large face of glass is going to bend a lot or break.

Usually some venting has to occur in order to prevent the above and to
control the venting is the trip. Here is what happens to some of our
gauges on equipment exposed to the sky.
You get this extreme hot sunshine on the gauge, some manufacturuer has
tried to seal. Now you have a build up of internal pressure and it has
to leak around the seals or the glass cracks. Suddenly it rains and
the cold rain hits the gauge causing the air inside to contract and
the seals now suck in the rain.

This can all be prevented by not sealing the chamber in the first
place. This takes, usually, a fine screen breathing vent that won't
allow liquids in but gaseos moisture is free to come and go.

house in



jump in




the customer.

Neither we nor they

best way to trouble

the moisture to

up.Once you opened

that also let out heat.

case. Force some air in

first guess.


Posted by Tom on April 9, 2006, 5:17 am
 Solar Flare wrote:

Thanks for the thoughts. Do you feel that the collector frame should be
sealed to the collector. Are the vent holes provided enough to allow the
  collector to adjust for pressure differences?

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