Thermal - PV and diff controller + dump control... [RE-wrenches]

[Geoff Greenfield]

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Thanks Tom-

I also like the el sid's and have had no failures.  I am also curious about
their variable speed injector control.  I wish they had more "solid" looking
stuff rather than exposed boards.

I am now knee deep in a much better version of Tom Lane's book - my earlier
edition was rough, this is more polished.  It is still a lot of info (all
things to all applications) but I can focus only on freeze region technology
now, as well as res HW and larger approaches.

Here is a further question I have about my future system and a customer's -
\

D U M P    L O A D S!

I am looking forward to a system sized for radiant heating assist, and plan
on a combined dump load/secondary storage/rejuvination station:  An
insulated hot tub (concrete stock tank) with a big copper coil HE under a
bench seat!  The added complexity of being able to store and remove heat may
or may not be worth the effort.

My question is:  are motorized valves reliable?  worth the electrical load
(I'm off grid) Or would I be better off with dedicated pumps and check
valves?.

Second question:  is there an easy way for existing GL-30 to kick in this
dump load at storage tank high temp or do I need a seperate GL 30 or
aquastat?  A-stat or control Recomendations (I don't have an immersion well
available so prefer a thermister approach).


Date: Mon,  1 May 2006 12:21:04 +0000
From: Tom DeBates <habitek83 at yahoo.com>
Subject: RE: Thermal - PV and diff controller?



good day Geoff,
 ...sorry about the delay in replying.
  This Winter I installed a PV-powered solar thermal system for my
residence.  I have a 32 watt Unisolar powering 4 ElSid pumps. Currently
there are only 3 pumps installed as I have not completed the small
radiant heating loop. There is a 10 watt pump on the collector loop, a 5
watt on the storage tank loop, and a 5 watt on the heating loop (HX
side). The other 5 watt pump will be on the heating side of the HX.
  Although I need to do more insulating and fine-tuning, so far I am
satisfied with the performance of the system. Initially I felt that I
was "missing" some late afternoon gain as the collectors had more
"thermal inertia" than the PV could extract during that period. I
considered adding a small module facing west, but have decided that the
storage tank and collectors are almost at equilibrium at that point
anyway and I am not losing much gain.
  ElSid does make a differential controller. It is a small board that
attaches to the side of the pump. It is set for ~ 8 to 10 degrees
(non-adjustable) and seems to work well....nice and simple. I inquired
as to a set-point controller and Dan (ElSid) said that he could do this.
  I can send a schematic and pics if you want.
good luck,
Tom


geoff at third-sun.com wrote:
>
> I like the PV direct approach for typical residential solar thermal...
> nice
> 20 watt panel and an el-sid and away we go.  Flow rate increases with
> sunlight (and collector temp in theory?). Usually an 80 gallon with
> built in
> HE.
>
> My question - how may of you add a differential controller to the
> system?  I
> didn't have a good answer for a savvy customer who asked the somewhat
> obvious question... "What keeps us from dumping heat on a sunny but
> super
> cold day?"
>
> For a brighter energy future,
>
> Geoff Greenfield
> NABCEP Certified Energy Practitioner
>
> THIRD SUN SOLAR & WIND POWER Ltd.
> 340 West State Street
> Athens, OH 45701
>
> www.third-sun.com
> (740) 597-3111
>
>

For a brighter energy future,

Geoff Greenfield
NABCEP Certified Energy Practitioner

THIRD SUN SOLAR & WIND POWER Ltd.
340 West State Street
Athens, OH 45701

www.third-sun.com
(740) 597-3111

-


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