Drainback vs. Closed Loop Circulators [RE-wrenches]

Tue Jun 6 04:25:54 PDT 2006

Hey Conrad

Would you describe the type and manufacturer [s] , as well as the
contractors involved  , of drainback systems you have encountered in your
area ?
Drainback is a generic term and there are significantly different ways of
achieving it.

Thanks, Ken

----- Original Message -----
From: "Jeff Clearwater" <clrwater at earthlink.net>
To: <RE-wrenches at topica.com>
Sent: Tuesday, June 06, 2006 1:55 AM
Subject: Re: Drainback vs. Closed Loop Circulators [RE-wrenches]

>
> Hey Conrad,
>
> Is the drainback of the '80s a fair comparison to the drainback of today?
>
> It's the failures of '80s glycol that pushes us to drainback.  But
> then again is the glycol of the '80s a fair comparison to the glycol
> of today?
>
> The debate goes on.
>
> Travis, you said "all the benefits of drainback" - Want to spell that
> out for us?
>
> Conrad, game to do the same for glycol?
>
> Still Learning,
>
> Jeff C.
>
>
>
> >Jeff, Travis and other Drainheads,
> >
> >If you want to cut the power use more you can use two smaller
> >circulators, cutting the second one out after 5 minutes (once you
> >know you've filled the collector).
> >Tek-Mar controller provides for this through a programmable second
output....
> >.
> >BTW, out of the several hundred 80's systems that we've serviced
> >here in the northeast, there is yet to be one surviving drainback.
> >Some day I'll try to catalog this in the hopes of solutions.
> >for starters:
> >-corrosive drainback water?-circulators failing quickly and
> >collectors corroding
> >-freeze ups
> >
> >Those glycol loops sure hold up....
> >
> >Conrad Geyser
> >Cotuit Solar
> >
> >----- Original Message ----- From: "Travis Creswell, Ozark Solar"
> ><ozsolar at ipa.net>
> >To: <RE-wrenches at topica.com>
> >Sent: Monday, June 05, 2006 3:52 PM
> >Subject: RE: Drainback vs. Closed Loop Circulators [RE-wrenches]
> >
> >>
> >>Hello Jeff,
> >>
> >>We just did a drain back system with six 4x10 flat plates.  Calculations
> >>showed that we had to use Grundfos 26-96 to overcome the head and total
> >>pressure drop.  I carefully added up every foot of pipe, valve, elbow
etc to
> >>make sure I didn't oversize it.
> >>
> >>It's rated at 215 watts but we choked the flow down to ~9 gpm (1.5 per
> >>panel) and dropped the wattage to 135 as measured with a Brand power
meter.
> >>
> >>The pump would do almost 20 gpm with out reducing flow which was higher
then
> >>the charts said it would do so I assume there was a siphon effect adding
to
> >>the flow.  But you can't factor that into the pump sizing as you have to
> >>overcome the head initially.  And the next smaller pump left no room to
> >>safely overcome the head plus it didn't use much less wattage.
> >>
> >>I'll gladly use the extra energy to get all the benefits of drain back.
In
> >>the morning I saw a 20f delta t at 9 gpm.  Of course the Delta T drops
as
> >>the days goes on but stays above 10.  That's 90,000 BTU's of heat for
460
> >>BTU's worth of electricity.  So the average of the day that's 1% of the
> >>energy collected is used to pump.  Share that with the "thermal
engineer"
> >>and see what he says.
> >>
> >>The common circulation pump is centrifugal which is not a positive
> >>displacement type.  Very low wattage positive displacement pumps are
> >>available that can handle the temp but their flow rate limits them to a
max
> >>of several panels.  Ken Schaal of Commonwealth Solar can speak with
direct
> >>knowledge of them.
> >>
> >>Best,
> >>
> >>Travis Creswell
> >>Ozark Energy Services
> >>
> >>
> >>-----Original Message-----
> >>From: Jeff Clearwater [mailto:clrwater at earthlink.net]
> >>Sent: Friday, May 19, 2006 7:56 AM
> >>To: RE-wrenches at topica.com
> >>Subject: Drainback vs. Closed Loop Circulators [RE-wrenches]
> >>
> >>
> >>Hi All,
> >>
> >>We have been getting back into offering Solar DHW - mostly due to two
> >>factors that make it a doable business model in terms of
> >>installation, service and liability.
> >>
> >>The first is switching to evacuated tube collectors.  They are light,
> >>easy to ship and handle and easy to install - I don't have to worry
> >>about cranes or major racking weight and it eases safety factors with
> >>my installers.
> >>
> >>Second is going with drainback instead of closed loop glycol.   This
> >>eliminates having to service the glycol every 2-3 years and actually
> >>gives a chance that the system might live on when the folks sell the
> >>house etc.
> >>
> >>However, I recently suggested drainback, closed loop to a low income
> >>zero energy home development we are working with and the thermal
> >>engineer came back with data saying that the drainback circulators
> >>used up to 1/3 of the energy harvested by the system in terms of
> >>electrical cost vs. gas saved!  I find that hard to believe. He
> >>claimed the closed loop circulators use less but still was showing a
> >>significant percentage.  I'm not sure whether he's just finding an
> >>excuse to go with what he is used to or whether there is a
> >>significant difference here.
> >>
> >>So the questions for my esteemed wrenches are:
> >>
> >>1)  Does anyone have KWH use figures for solar DHW circulators?
> >>2)  Does anyone know of the most efficient circulators?  (are
> >>circulators positive displacement pumps?) - any models to suggest for
> >>drainback?
> >>3)  Do folks recommend using PV direct pumping for drainback?  What
> >>controller would one use then?
> >>
> >>Thanks!
> >>
> >>Jeff C.
> >>
> >>--
> >>~~~~~~~~~~~~~
> >>Jeff Clearwater
> >>Village Power Design
> >>Sustainable Energy & Water Solutions for Home & Village
> >>http://www.villagepower.com
> >>gosolar at villagepower.com
> >>NABCEP (tm) Certified Solar PV Installer
> >>
> >>530-470-9166
> >>877-SOLARVillage
> >>877-765-2784
> >>72 Baker Rd.
> >>Shutesbury, MA 01072
> >>425 Nimrod St.
> >>Nevada City, CA 95959
> >>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`~
> >>
> >>
> >>- - - -
> >>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
> >>
> >>
> >
> >
> >- - - -
> >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
>
>
> --
> ~~~~~~~~~~~~~
> Jeff Clearwater
> Village Power Design
> Sustainable Energy & Water Solutions for Home & Village
> http://www.villagepower.com
> gosolar at villagepower.com
> NABCEP (tm) Certified Solar PV Installer
>
> 530-470-9166
> 877-SOLARVillage
> 877-765-2784
> 72 Baker Rd.
> Shutesbury, MA 01072
> 425 Nimrod St.
> Nevada City, CA 95959
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`~
>
>
> - - - -
> 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
>

- - - -
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
--^----------------------------------------------------------------