Posted by caraug on May 22, 2005, 2:32 am
Here is a question for you all. Thermo-Dynamics, N.S. Canada, is
marketing a solar hot water heating system using propylene glycol as the
heat transfer fluid. This liquid is claimed to be non-toxic and used in
the food industry for high speed freezing of meat (...) through direct
immersion (...) etc. This allows to pass the solar loop directly into
the storage tank unlike the older systems which, I believe, used a
separate loop to prevent the leaks into the storage tank. (These older
systems were using normal car antifreeze liquid, I think) Is there
anyone out there who has seen this before? Is this relatively new? Is
there a catch somewhere?
Posted by Duane C. Johnson on May 22, 2005, 2:54 am
Yes, this stuff is often used as antifreeze in potable water
systems for over winter. Often used in RVs. It's labeled as
> This liquid is claimed to be non-toxic and used in the food
> industry for high speed freezing of meat (...) through direct
As opposed to it's cousin Ethylene Glycol as is often used
as car radiator antifreeze. Which is poisonous!!!
> This allows to pass the solar loop directly into the storage
> tank unlike the older systems which, I believe, used a
> separate loop to prevent the leaks into the storage tank.
> (These older systems were using normal car antifreeze liquid,
> I think) Is there anyone out there who has seen this before?
> Is this relatively new?
Not new at all.
> Is there a catch somewhere?
I don't think so.
The main reason to us it is for safety reasons.
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Posted by Gary on May 22, 2005, 3:47 am
Duane C. Johnson wrote:
All that Duane says is true, but I believe that most building codes
still require double wall heat exchangers to be used whenever a
non-water fluid (eg Propylene Glycol) is used in the collector loop.
You can get more detailed info from Home Power Magazine issue 92 from
the www.homepower.com site. The article on heat exchangers in this
issue says that "The Uniform Solar Energy Code (USEC) requires
double-wall heat exchangers for use in solar hot water
systems when a fluid other than potable water is used
for the collector loop fluid. ... Although almost all systems
today use nontoxic propylene glycol mixtures as the
heat transfer fluid, anyone could mistakenly add car
antifreeze to the system, so the code remains in effect
The double wall heat exchanger is designed so that two walls separate
the potable water from the collector fluid, and is built in such a way
that if either wall leaks, the leaking fluid drains to a point where
it can be detected by the owner -- thus allowing it to be replaced
before both walls fail.
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Posted by DJ on May 23, 2005, 1:55 am
I guess the Canadian codes give a little more credit to the user in
being able to tell neon green from whitish-clear fluids ;-).
Might be, also, that the non-toxic nature of the propylene glycol gives
them the option. I do know that the manufacturers up here use single
wall exchangers, near as I can tell.
Posted by DJ on May 23, 2005, 1:40 am
Actually, all the major manufacturers are now. TD, Enerworks, etc. And
they've been doing it since the 80's...
It's food grade, yes. It's also one of the main ingredients of Dairy
Queen soft ice cream ;-). Yummy ;-).
Well, either through the little heat exchanger in the Thermo-Dynamics
Solar Boiler, or in a larger shell and tube heat exchanger mounted on
the exterior of the storage/preheat tank, yes.
I install them all the time, yes.
New, if you think twenty year old technology is new ;-).
De nada ;-).