[Greenbuilding] [BULK] Solar water heater

[Morgan McDonald]

Lawrence,

I think you're referring to draindown systems and the problematic
draindown valve. Drainback is different. Drainback systems typically do
not require any special valves but instead allow the system to drain
whenever not circulating by way of an air gap in the solar return line
just before the drainback tank. Very reliable -- only thing you need is
gravity!

Cheers,

MM

_______________________________
Morgan McDonald, B.Eng.(Mech)
Design Manager
Taylor Munro Energy Systems, Inc.
11-7157 Honeyman Street, Delta BC (Canada) V4G 1E2
T: 604.946.4433 x223   F: 604.946.3804
mcdonald at taylormunro.com
www.taylormunro.com
 

-----Original Message-----
From: greenbuilding-bounces at listserv.repp.org
[mailto:greenbuilding-bounces at listserv.repp.org] On Behalf Of Lawrence
Lile
Sent: March 10, 2008 10:02 AM
To: Clarke Olsen
Cc: greenbuilding at listserv.repp.org
Subject: Re: [Greenbuilding] [BULK] Solar water heater

There are advantages to drainback, yes.  One of the recurring problems,
I am told, is with the drainback valve - this is a valve that admits air
at the top of the collector.  They tend to stick open or freeze shut
after a while.  If they freeze shut, your collector can't drain, and it
freezes and busts.  

Like I say, I have no direct experience with this, and there are
companies that have specialized in drainback, so presumably they have
worked on these bugs.  

Lawrence Lile, PE, LEED AP
Project Solutions Engineering

-----Original Message-----
From: Clarke Olsen [mailto:colsen at fairpoint.net] 
Sent: Thursday, March 06, 2008 7:51 PM
To: Lawrence Lile
Cc: Ian Remmler; greenbuilding at listserv.repp.org
Subject: Re: [Greenbuilding] [BULK] Solar water heater

     Shouldn't one of the positive features of drainback be the  
reduction of mass
     to be heated? That is, the liquid that cools in the collector,  
though it isn't
     frozen, still represents more mass that has to be brought up to  
temperature
     by the next sunshine, delaying (reducing) output.
     Clarke Olsen
     Spencertown, NY

On Mar 6, 2008, at 6:10 PM, Lawrence Lile wrote:

> I'm looking at some of the same issues right now, and also looking for
> some recommendations.
>
> Drainback systems, I have read, are the most problematic of all solar
> systems, and many companies don't recommend them.  If you have  
> freezing
> issues, go with non-toxic propylene glycol and a heat exchanger.
>

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