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Solar collectors plumbed Parallel vs. Serial - Page 3

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Posted by Nolan Tucker on October 21, 2004, 12:19 am
 
Thanks Gary-
    This is great stuff.  I'm new to maintaining my own system and learning
a lot.
nolan


Posted by Nolan on October 21, 2004, 12:08 pm
 


     It is definitely oriented more for a late morning/early afternoon sun.
The second panel is currently clogged with something - maybe a due to the
serial plumbing and having the anti-freeze too hot.  I've been trying to
work on it as time permits and my knowledge of the system increases.  The
pump may have been weakened by working against the clogged second panel - I
don't know how long it was running while clogged. If I wanted to plumb in
parallel what kind of valve would I use to slow the flow?


Posted by Niels Lyck on October 21, 2004, 8:25 pm
 The valve is, in Europe anyway, known under the name "Tacosetter". The
setter allows for monitoring (it has a small glass part where a floater
indicates the flow rate) and limiting the flow by increasing the resistance
in the loop, just as would a serial connection, by the way. I do not,
however, see any use of it in your system. The controller will stop the
pump, once the heat is brought down into the boiler, so Tacosetters/flow
restrictors are merely used in systems where one wants a slower flow for
specific boiler layouts (mantle boilers, for stratification purposes) (=low
flow systems).
Greetings from Niels, Copenhagen, Denmark (www.vvfs.removethis.dk)


plumbing


Posted by Gary on October 22, 2004, 1:08 am
 Nolan wrote:

Its best if the panel faces South, and is tilted up at an angle about
equal to your latitude, but you can vary from ideal by a fair bit and
still get good performance as long as the collectors get 5 or 6 hours
of sun per day.  This web site has a great sunchart maker that gives
you the path of the sun at your location for the full year -- it helps
to visualize how well your panels are aimed:
http://solardat.uoregon.edu/SunChartProgram.html

For the flow restrictor, I guess any valve thats in the piping that
goes too/from the collector could be used to restrict the flow, and
slow the flow rate -- just shut it part way.  There may already be a
valve in the system that can be used for this.
The one Neils describes sounds nice in that it gives a visual
indication of what the flow is.  As Neils says, you may not need this
as the differential controller will turn the pump on when the
collector water is hot, and off when not.  One exception might be that
if the pump turns repeatedly on and off in very short intervals, this
could be due to too much flow cooling the collector very quickly.
Anyway, I would try it without the flow restriction and see how it goes.


One thing to check:
The differential controller that turns the pump off and on reads one
temperature sensor on the bottom of the storage tank, and one
temperature sensor at the outlet of the collector.  When the collector
outlet temperature is about 10 degrees (F) greater than the bottom of
tank temperature, the controller turns the pump on (because there
collector has water hotter than the tank).  The controller turns the
pump off when the collector sensor temperature gets close to the
bottom of tank sensor temperature.  If the sensor is mounted on the
output of the 2nd collector, and you have it disconnected, the
controller will not be getting correct collector temperatures.  You
would want to move the temperature sensor to the outlet of the
collector that is hooked up.  It is usually just attached to the
outside of the collector outlet pipe with a pipe clamp, and covered
with a bit of insulation.

Gary








Posted by Nolan on October 22, 2004, 9:22 pm
 Thanks Gary.  I'll check that.  We've had a terrible week for sun here in
PA.  Last weekend we had a decent day and the reading from the sensor inside
the top tank read 100, but the pump wasn't running.  Maybe because of the
sensor you're indicating.  I don't remember seeing any wires on those pipes,
but I'll check tomorrow - we're supposed to get some sun!
Another question - the hose connections I took off appeared to be sealed
with silicon caulk and required me to cut them off to flush the collectors.
I replaced (temporarily) with auto heater hose, but they may be leaking as
I'm now losing pressure.  When I put these back together permanately, do I
use a silicon hose and silicon caulk?
nolan

plumbing

panel - I


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