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Newbie Ignorant Questions - Page 3

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Posted by LarenCorie on May 2, 2004, 3:38 am

With Solar, you need a tank. That tank might be inside of the
collector up on the roof, in a passive thermosyphon or batch
type collector, or in the house where your present standard
tank is, with an active system.  Either way it needs to be big
unless you are in a climate that has sunshine every day. Tanks
of 80 gallons or more are standard.

  Instead of screwing up the looks of your house, and lowering
its resale value, with an unprofessional tacky collector installation
up on racks above your roof, have your collectors mounted flush
to your west or east roof.  The efficiency will be lower, than on
a southern exposure, so you will need to compensate by increasing
your collector area by 50-100%, depending on your latitude, how
far they are aimed from south, and the pitch of the east/west roof
where you mount the system.  But, you will also not have the costs
involved in a complicated tilt rack mounting.  That will give you a
much more professional installation, that will look like skylights,
not an ugly piece of machinery.  In most cases the end cost of
extra collector, instead of extra tilt racks and labor, is close.
I worked with a company that installed thousands of hot water
systems. That was the best way for a house without an optimum
south facing roof.  Tilt racks on weird angles are really tacky.
Most people who make that mistake, end up paying to have the
collector system taken down, especially when they want to sell
the house for top dollar.

-Laren Corie-

Posted by Benign Vanilla on May 3, 2004, 1:54 pm


I am hoping to replace my current 50 gallon gas fired unit, but feed it with
solar, so I use less gas. I don't have room for an 80 or up.

That's a good piece of advice, and I intend to follow it. If the array looks
like hell, my wife will kill me.


Posted by Gary on May 5, 2004, 2:00 pm
 Benign Vanilla wrote:

I think that this is basically good advice, but with your fairly low
pitch roof, and your fairly high latitude, you should be aware that you
will not get much sun on the collector panel during the mid winter
months.  The sun just does not get high enough in the winter to put a
lot of useful sun on a panel with low tilt.

The table below compares the daily total solar radiation received by 1
square foot of panel for a horizontal panel to a panel tilted at an
angle equal to latitude and aimed south (the ideal case) -- this is for
a latitude of 48degrees (Northern US).  These numbers are for sunny days.

    Horizontal    Tilted 48 deg to South
Jan     596            1478 BTU/ft^2-day
Feb    1080            1972
Mar    1578            2228
Apr    2106            2266
May    2482            2234
Jun    2626            2204
Jul    2474            2200
Aug     2086            2200
Sep    1522            2118
Oct     1022            1860
Nov    596            1448
Dec    446            1250

So, the horz panel does fine in the summer, but is not so good in the 3
or 4 months of winter.  As suggested, you could increase the panel area
to partially offset this.

Good Luck -- Gary

Posted by Chuck Yerkes on May 9, 2004, 6:45 am
 Ecnerwal wrote:

When the sun is in the west, it's usually warmer.  For all that means.
In your area (you don't say) that might mean it clouds up.  I get fog
around 4-5PM everyday.

What area?  Got a state?  Oregon hard freezes, but not like Michigan.

Is it possible to just run empty in the winter with these (turn it off)
and use it when the water isn't going to freeze and screw the heat
exchange? It's not quite AS effective, but for 7-8 months/year it means
you don't need anti-freeze and a big tank.

Well, some tank to do heat exchange.  In my non-hard freeze area (or
rare), I can get away with a 10-20 gallon tank in front of a tankless
heater.  Showers will likely not use more than that.  If something does,
then I'm in a "no solar" state and the tankless heater just does what it

I just picked up a bunch of info at a Green Fair in Berkeley today
(small, in a small park).  Was looking at a Japanese tankless (50 years
in .ja and 10 years in the US) on display.  It heats the water UNTIL
it reaches the set point (110, 115).

Tomorrow AM, I meet with a solar contractor.  He had an issue with a
client who was storing water that was TOO hot.  Water sits around and
recircs and heats and recircs and heats and comes out at Tea making
temps.  I think the solution was just a bigger (25gal) storage tank).

I'd suggest that it's size.  I have room for either my 50 gal tank or
a tankless with a little bitty solar tank (eg, 100 gallons?  Perhaps in
the guestroom).

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