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Is My Solar Water Heater Working??? - Page 2

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Posted by SJC on April 29, 2006, 3:37 pm

  Let's say that your can get 20,000 BTUs per day out of your collectors =
average over the year and you use 50 gallons of hot water per day on =
Let's say the solar can heat 50 gallons of 50F well water up to 90F, =
(your tank
will lose some heat during the night) you will still have some final =
heating to do.
You have reduced your heating bill, but you have not eliminated it. As =
far as turning
off your gas heater in the summer, that would depend on several factors.

Posted by dold on April 28, 2006, 6:39 pm

Isn't 110F too low for safe storage of water?  

seems to be an easy to read correlation of data from sources that I would
consider valuable.  Page 12 speaks of DWH.

"Legionella colonized 60% of the hot water systems before monochloramine
... Increased prevalence of Legionella colonization was associated with
water heater temperatures <50C ...grows optimally at 35C and multiplies
between 25C and 42C"

Clarence A Dold - Hidden Valley (Lake County) CA USA  38.8,-122.5

Posted by SJC on April 28, 2006, 6:50 pm

  I would imagine that once he gets his system operating he might set =
water temperature higher.

Unless I miss my guess, this is probably the system that you bought.
  I would say that the 20 watt solar panel may not be adequate to power
your pump, especially if there are lots of bends in the lines and or =
of pipe length and or lots of vertical rise.

Posted by Steve Shantz on April 29, 2006, 1:59 am
 SJC wrote:

I have 2 4' x 8' AET collectors with 30 Watts of PV solar panel.  This
seems adequate.  I get about a 22 - 24 degree F rise through the
collectors at the best.  I would agree that 20 watts of PV seems low.
As for the pump, I'm assuming you are using an El Sid.  I think this
should be a 20 Watt pump for your size system.  (Thats what I have.)

Also, check that ALL of the air is out of your glycol system.  That
will absolutely clobber the performance of the low head circulators you
likely have.

As for the heater coming on in the evening... From your description, it
sounds like you are using LOTS of hot water.  Gas water heaters have a
mind of their own when used with solar pre-heaters. The hot water from
your pre-heaters 'floats' to the top of your gas tank if it is hotter
than the water in the tank (likely, as you have it set at 110.).  This
means that the water at the bottom of your gas heater just sits and
gets cooler and cooler until it trips the burner to come on.

My personal opinion on conventional gas water heaters is that they are
not an efficient way to finish off the heating.  However, alternatives
get expensive.  But I digress...

Put your hand on the pipe from the pre-heater to the gas water heater
when you are drawing hot water.  That will tell you quite a bit about
if your system is working or not.  It sounds like you don't have any
temperature gauges on the water side of your system.


Posted by Mary Fisher on April 29, 2006, 10:53 am

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