differential controllers [RE-wrenches]

Sat Jan 11 06:27:26 PST 2003

  Upon further reflection, and with the helpfull advice of many I will keep
my closed loop space heating system as is. I think the minor temporary
temperture drop (one degree) on morning startup (around 20 degrees outside
temps and 100 degree storage tank temp) is not worth the installation of a
snap switch to let the collectors pre heat a little before circulating
through the immersed heat exchanger in the storage, although I will use a
snap switch in future work in various applications, same with the heat
actuated 3 way valves, its good to get this input and learn from others that
have been there.  I won't drain my panels come summer, or cover them like I
did last year, which as I mentioned due to the 14' height of the array is
real awkward and a big pain. Last summer I used some shade cloth, which is
available in various percent of exclusion, the stuff I got is cheap (100
bucks for more then enough to cover 6 panels) and keeps out 85% of the suns
rays. Its UV resistant, made out of recycled poly propelyne, and has little
holes that let the wind blow through so it won't flap in the breeze.  For
those covering their systems in the summer these beat the heck out of
plastic blue tarps. Poultry farmer supplier (www.FarmTek.com also call
1-800-327-6835 for a free catalog) sells the stuff, plus other goodies like
radiant floor heat inulation (Tek-Foil).
  For temperture control in the summer I will leave the glycol loop as is,
but I will tee off of the 500 gallon tank supply and return lines, and rig a
used truck radiator, a used circ pump, a 16" used box fan and a used
aquastat to turn on the pump and fan when storage tank temps reach 160
degrees or so.  This means I won't have to mess with the glycol loop at all,
the panels won't stagnate,and the whole thing will operate automatically
with no labor, once installed, like the rest of the system. It'll use a
little power but in the summer I have an excess anyway, especially in the
middle of the day.  This plan also meets the criteria I hold to when working
on my own thermal system of "I already have the needed parts laying around
in the shop, and they're paid for"! Also the next space heating system I
install I  will consider laying some K copper or PEX tube around the
foundation to use as a heat dump. I'm also going to keep my eyes open at the
metal scrap yard for steam radiators or other surplus heat exchange items to
use as heat dumps.

Tom Simko
Skyline Solar

on 1/10/03 9:20 AM, sunwise at sunwise at cheqnet.net wrote:

> Greetings Tom,
> 
> That sounds like good advice and I have seen damaged (browned and
> disintegrated) insulation on collectors.  I have also seen a number of
> collectors where that absorber plate has pulled away from the collector
> tubing (perhaps desoldered?), mostly at the top and bottom ends of the
> collector, and have often wondered if this is in part the result of high
> stagnation temps.
> 
> Kurt Nelson
> 
> -----Original Message-----
> From: Tom Lane, Energy Conservation Services [mailto:tom at ecs-solar.com]
> Sent: Friday, January 10, 2003 7:24 AM
> To: RE-wrenches at topica.com
> Subject: Re: differential controllers [RE-wrenches]
> 
> The problem with stagnation is degradation of the insulation  IF the
> iscosyanurate sheet DOES NOT have binderless fiberglass     ---
> stagnation
> will char the iso about an half inch down----if you drain out the glycol
> fill again with a solution of water and baking soda -- circulate an
> hour --drain  ---flush with water leave the air vent off  and open all
> valves to allow air to vent itself --- this will keep the collectors a
> little cooler during summer stagnation  gator tom
> ----- Original Message -----
> From: "Tom Simko" <tom at skylinesolar.com>
> To: <RE-wrenches at topica.com>
> Sent: Friday, January 10, 2003 12:18 AM
> Subject: Re: differential controllers [RE-wrenches]
> 
> 
>> Brad,
>> My intention this spring is to drain the system fully down from
> inside my
>> shop, saving the fluid, and then open a ball valve on top and one on
> the
>> bottom of the 6 panel array.  I'll leave the valves open for a little
>> ventilation, ands screen them against bugs. At my latitude my tilt
> angle
> for
>> winter is 60 degrees, I set my panels at 70 (and true south) to
> encourage
>> snow to slide off and lessen summer temps.  Having only dealt with
> closed
>> loop systems in the past I'm with you on the stagnation thing, its to
> be
>> avoided at all costs, but if the panels are empty of fluid its a
> different
>> deal I suppose? The drainback systems must spend much of the summer in
> a
>> similar situation, repeatatly filling and draining ,and it doesn't
> seem to
>> be a problem. Not a bad idea to flush with water, I'll do that also.
> BUT
>> others also say even IF empty its a concern. What say Gator Tom?
>> 
>> I've dealt with about half a dozen of the El Cids, and all have been
>> silent.
>> Tater Tom
>> Skyline Solar, Idaho
>> 
>> on 1/9/03 1:35 PM, Brad Bassett at bsbassett at earthlink.net wrote:
>> 
>>> Lots of good info in this thread! I'm not a fan of letting
> collectors
>>> stagnate. If you do end up draining collectors for the summer that
> have
>>> had antifreeze in them, I think it would be a good idea to
> thoroughly
>>> flush with water before letting them stagnate. Otherwise you may end
> up
>>> with some residue of antifreeze that will decompose at the high
>>> temperatures and might leave a highly acidic deposit on the insides
> of
>>> the collector tubes, not desireable!
>>> 
>>> One disadvantage of a drain back system is the much higher pumping
> power
>>> necessary to overcome static head all the time. A closed loop
> requires a
>>> much smaller circulator. One advantage of a drainback system, when
>>> powered by the grid, is that if there is a power outage, the fluid
>>> drains out of the collectors instead of stagnating and decomposing
> or
>>> boiling and losing the charge. PV powered pumps avoid this problem
> of
>>> course.
>>> 
>>> One other note, if the PV module powering the circulator is mounted
>>> facing west to reduce early moring cold starts, it is likely to keep
>>> running after there is heat to collect, and will cool the solar
> heated
>>> water that has been collected during the day. Probably not a big
> issue
>>> with a closed loop system, more so with an open loop system. I
> usually
>>> face the PV east a little, though with the El Cid the start up
> current
>>> is so low that it's probably not cecessary.
>>> 
>>> Does anyone have experience with ElCid pumps that are noisy? I have
> one
>>> that I've replaced the driver, impeller, and impeller shaft and
>>> confirmed that the impeller is not hitting anything, and it still
> ticks
>>> in time to rpm when not at full speed. Is this common, I've been
> told
>>> they are nearly silent.
>>> 
>>> Brad Bassett
>>> 
>>> 

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