# Thermosyphoning freeze protection - Page 2

Posted by daestrom on July 11, 2003, 6:32 pm

If freeze protection is the goal, keep in mind the density of water stops
increasing with dropping temperatures when you get to about 39 degF.  From
there on down to 32, the density actually decreases (i.e. 34 degree water
'floats' above 39 degree water).  If your water nears 39 degF, your
thermosyphon will stop, allowing the water in upper section to freeze.

daestrom

Posted by Nick Pine on July 11, 2003, 7:57 pm

That might happen when 60-sqrt(Q/43) = 39, ie Q = 43x21^2 = 18,963 Btu/h
= (60-T)4, ie T = minus 4,686 F :-)

Nick

Posted by andy on July 12, 2003, 1:32 am
And don't forget that they system thermosyphons ONLY when the pump
fails. It is not a regular operational thing.

Posted by Nick Pine on July 12, 2003, 6:39 pm

Perhaps you are trying to say "I do not understand your calculation," or
"I have no short-term memory." See my posting of yesterday (at 4:53 EDT
on 7/11, to which you responded :-) for an explanation of the gibberish.

Nick

Posted by andy on July 14, 2003, 1:03 am

the idea is that the energy picked up by the internal piping 'losses'
will offset the external header losses. The BTUs required to feed the
thermosyphon cycle are picked up from the internal envelope of the
building. This also presumeably where Nick gets his 68F from. As long
as the building is warm the pipes in the building won't freeze...type
of thing.