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tracking btus

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Posted by geogeek on January 27, 2006, 3:04 pm
 
I'd like to track the number of btus that enter my house through my
solar hot water system daily.  Besides recording the change in
temperature each day and doing a little math, what are my options?  I
use a Tekmar 155 controller.  This units gives me delta T hours, which
I don't think is very useful (am I wrong?)....

Any help or advice would be greatly appreciated.


Posted by Ecnerwal on January 27, 2006, 11:27 pm
 


I that's hours of pumping times (average temperature difference while
pumping) all you need to figure out (might be difficult, might not,
depending on collector loop design) is how much water moves per hour
while the pump pumps (for ease of BTUs, you want to know how many
_pounds_ of water), and you're there - multiply (delta T hour) by
(pounds per hour), you have BTUs (if the delta T in in Farenheit -
otherwise one more unit conversion).

--
Cats, coffee, chocolate...vices to live by

Posted by Mitch Dickson on January 29, 2006, 3:35 pm
 
I love cats myself.  Want my new cat Burgou recipe?  It starts, "Shoot 6
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Posted by Steve Shantz on January 28, 2006, 4:45 pm
 
geogeek wrote:

An accurate measurement of flow rate is one of the biggest problems
here.  If you have an AC pump connected to a differential controller,
you could make a fairly educated guess as to your flow rate.  If you
know the amount of time the pump is on, and the Delta T, BTU/hr is a
straightforward calculation:

Pumping Time per day (minutes) x Gallons per minute x 8.77 lb per
gallon x Delta T (degrees F)  x 0.87 BTU/lb F = BTU per day

The density and specific heat factors are for 50% propylene glycol.  If
you are pumping water, the density is 8, and specific heat is 1.0

However, if you have a DC pump powered by solar panels (as is my
system), an accurate estimation of flow rate and pumping time is
impossible.  A flow meter is the only way around this problem.  I have
yet to find a good inexpensive one.  If anybody knows of one, please
let me know.

One of my goals it to see if I can get a PIC controller, interface it
to temperature sensors and a flow meter, and voila... BTUs / day.

Steve


Posted by schooner on January 28, 2006, 7:49 pm
 Check out the OneWire temp sensors if your looking for a simple solution.


geogeek wrote:

An accurate measurement of flow rate is one of the biggest problems
here.  If you have an AC pump connected to a differential controller,
you could make a fairly educated guess as to your flow rate.  If you
know the amount of time the pump is on, and the Delta T, BTU/hr is a
straightforward calculation:

Pumping Time per day (minutes) x Gallons per minute x 8.77 lb per
gallon x Delta T (degrees F)  x 0.87 BTU/lb F = BTU per day

The density and specific heat factors are for 50% propylene glycol.  If
you are pumping water, the density is 8, and specific heat is 1.0

However, if you have a DC pump powered by solar panels (as is my
system), an accurate estimation of flow rate and pumping time is
impossible.  A flow meter is the only way around this problem.  I have
yet to find a good inexpensive one.  If anybody knows of one, please
let me know.

One of my goals it to see if I can get a PIC controller, interface it
to temperature sensors and a flow meter, and voila... BTUs / day.

Steve



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