Thermal - PV and diff controller... and more! [RE-wrenches]

Thu Apr 13 07:13:57 PDT 2006

Your free subscription is supported by today's sponsor:
-------------------------------------------------------------------
Is your computer freezing up or slowing down?
Repair corrupt files and harmful errors - protect your PC
Take a 2-minute PC health check-up at no charge!
http://click.topica.com/caaeE3vbz8Qcsbz9JC9a/PC Powerscan
-------------------------------------------------------------------

Kurt, Tom and Kirk-

Thanks for the feedback.  I really should go back to school for thermal, or
not do it at all.  I am so busy with electrons that adding water to the mix
is silly.  That said, the economic/energy payback is so good that I feel
guilty not including it as an option for my customers (and the earth).  My
education consists of Tom Lane's informationally overwhelming and poorly
organized/edited (not edited?) book (sorry Tom if you are listening - thank
you for your book but please hire an editor for the second edition) and a
pile of HP articles/ mixed with and floating around with various
manufacturer's website info...  And of course there are many conflicting
bits of advice!

I want simple, I want reliable, I want effective.  I am in a NE hard freeze
locale. My target design is for residential families, using 40 SF to 96 SF
of collector area (and our grant program is based on SF) -  I have a bunch
of quotes out there based on PV direct/Solaraid (internal HE) tanks, but
after hearing this feedback I am reconsidering.

I am considering the following options - and soliciting wrench opinions on
them!:

A) PV direct sidearm HE with single pump.
B) PV direct sidearm HE with double pump.
C) AC sidearm HE with single pump.
C) AC sidearm HE with double pump.
D) Drain back system with reservoir HE
E) Drainback system with unpressurized storage
F) Insert your favorite here.

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

-----Original Message-----
From: RE-wrenches at topica.com [mailto:RE-wrenches at topica.com]
Sent: Thursday, April 13, 2006 7:04 AM
To: RE-wrenches at topica.com
Subject: Digest for RE-wrenches at topica.com, issue 2055

------------------------------

Date: Wed, 12 Apr 2006 11:18:16 -0500
From: "sunwise" <sunwise at cheqnet.net>
Subject: RE: Thermal - PV and diff controller? [RE-wrenches]

I like the Hartel MD10HEH pump with a 20 watt module, but that said,
they did have a bad run of pumps at one point and there may still be a
few out there.

Hey Geoff,

If you are using a side arm heat exchanger and thermo-siphoning the flow
into the tempering tank, there shouldn't really be any heat loss to the
tank.  Of course you have to have the HX lower than the tank to prevent
reverse flow as well as to promote productive heat transfer.  Any cold
fluid in the HX can't rise to the tank.

If you are using the tiny 3 watt el-sid to drive the HX (which can run
off the same 20 watt module), you can place a cheap snap switch on the
solar fluid supply into the HX that turns on the HX pump when it senses
useful heat (like a 120'/10' fan switch - $7).

Kurt

----------------------------------------------------------------

Kurt Nelson
PO Box 309
Cornucopia, WI 54827
715-742-3406
sunwise at cheqnet.net

------------------------------

Date: Wed, 12 Apr 2006 09:19:55 -0700
From: Todd Cory <toddcory at finestplanet.com>
Subject: Re: Thermal - PV and diff controller? [RE-wrenches]

My system has two DC circulation pumps. The one on the glycol closed
loop runs array direct with no controller.

For the pump on the potable side of the heat exchanger I  used an old
C-30 differential controller switching the DC to the pump through a 120
VAC relay.

I prefer to not use tanks with integral heat exchangers as they are more
expensive and it is easy to use the existing standard water heater as
the storage tank.

Todd
------------------------------

Date: Wed, 12 Apr 2006 18:38:59 -0400
From: "Kirk Herander, VSE" <kirk at vtsolar.com>
Subject: RE: Thermal - PV and diff controller? [RE-wrenches]

We made a business decision 6 months ago not to use a PV panel and DC
circulator unless we are installing off-grid SDHW. I have had very poor
luck with failing Hartell and El-sid circulators, not to mention the
snap switches.

If you are installing an incentivized system, at least in VT, you are
required to provide a five year bumper-to-bumper warranty on the system.
Do you really want to work for free, as I have, fixing DC driven SDHW?

Last weekend I worked (for free) to change a DC system (Hartell and snap
switches to AC (Taco 008 & Goldline GL-30 controller) because the
Hartell and switches had burned out twice in a 1 1/2 year period. It is
not my only example. I can think of 3 other DC circulator failures.

No more for me. AC is cheaper and much more reliable.

Kirk Herander
Vermont Solar Engineering
802.863.1202
fax 802.863-7908
NABCEP(tm) Certified Solar PV Installer
Xantrex Certified Dealer Charter Member
NYSERDA-eligible installer
VT Solar and Wind Partner

------------------------------

Date: Wed, 12 Apr 2006 17:17:57 -0700
From: Todd Cory <toddcory at finestplanet.com>
Subject: Re: Thermal - PV and diff controller? [RE-wrenches]

Kirk,

Were you using the electronic or brush version of the Hartel pump?
Did you feed it via a LCB?
Did you monitor the max input voltage during cloud effect events?

My pump has been running flawlessly for 4+ years now. I have an old LCB
and 5 diodes in series (.8 volt drop each) in the PV to pump circuit to
make sure the input voltage is well below the manufacturers max
recommendation. I think LCB's are important as I have heard these
sometimes have a hard time starting running PV direct.

I believe Tom Lane has info on how to best match the panel to pump to
make sure the pump does not get fried, although as I said, mine has been
fine and it is (over) powered by an ancient Arco M-55.

Todd

- - - -
To send a message: RE-wrenches at topica.com

Archive of previous messages: http://lists.topica.com/lists/RE-wrenches/read

List rules & how to change your email address: www.mrsharkey.com/wrenches/etiquette.php

Check out participant bios: www.mrsharkey.com/wrenches/

Hosted by Home Power magazine

Moderator: michael.welch at homepower.com
--^----------------------------------------------------------------
This email was sent to: michael.welch at homepower.com

EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Qcs.bz9JC9.bWljaGFl
Or send an email to: RE-wrenches-unsubscribe at topica.com

For Topica's complete suite of email marketing solutions visit:
http://www.topica.com/?p=TEXFOOTER
--^----------------------------------------------------------------