[Greenbuilding] [BULK] Solar water heater

[Lawrence Lile]

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.
>