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September 21, 2002: Added 2 more solar collectors

This week I built a structure for 2 additional 4 X 8 ft. SunEarth
Empire series solar collectors.  These are identical to the
original 2 units except that the absorber plates are coated
with black chrome rather than black paint which has
much lower emssivity - 12% vs 56%.  See their detailed
spec. sheet for the details. (235K pdf file)

So now I have more than doubled my solar heating capacity.

 I did leave the system running through the summer with the
Dow Frost HD propylene glycol (50% solution) in the collectors.
The highest temperature that I observed was 245F, which
is not hot enough to worry about degrading the glycol.
I'm told that anything over 325F is cause for concern.
Perhaps with the additional panels I will have to
drain and flush the system next summer.

In the process of installing the new collectors, I drained and
stored the antifreeze mixture, then flushed out the plumbing
with fresh water until it ran clear.  This seems like prudent
maintenance to clear out old deposits etc.  The antifreeze
mixture looks to be in good shape, the typical Gatorade
green and clear, not murky.  For now I am leaving plain
water in the collectors, until the weather turns cold.

I made a few other minor system corrections.  I had
originally placed an automatic air vent at the top of the
collectors outside.  I was warned that these units aren't
rated for the weather extremes, so I moved inside to just
above the water storage tank in the floor loop.  Then I
installed a coin type air vent in the "T" to the new collectors:

before                                               after

Here is the inside air vent - before and after moving the
automatic air vent inside and putting the original coin
vent outside:

before                                  after

Removing air from the system is essential to maintain good
fluid flow through the system.  When I fill the system,
I am extra cautious to purge all air by circulating the
fluid at high pressure (with either a pump, or house
water pressure of 30psi) to push all the air bubbles through.
Then after the system has settled and run for a day or so
I bleed air from the top vents where air may
have become trapped.

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