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Old 09-24-12, 01:45 PM   #29
opiesche
Helper EcoRenovator
 
Join Date: Jul 2012
Location: Rohnert Park, CA
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Quote:
Originally Posted by AC_Hacker View Post
Vlad,
He is trying to determine the total thermal response characteristic of his house, which could be expressed in a simple mathematical expression... this could have utility far beyond just heating his house against the winter cold.
Yes, I'm hoping this will prove useful for other things - like I've already seen that I should install some radiant heat barrier in my attic to reduce summer heat gain

As for the heat loss calculations I'm doing, these are primarily about

-sizing my heater properly to get the best efficiency I can

-find out what water temperatures I'll need to reduce experimentation

-find out what flow rates I'll need (I'm still working on that) with a given water temperature, so I can pick the right circulation pump

-make the system smart enough to turn on and off the pump at the right times, maximizing efficiency and keeping temperatures comfortable

The last point goes further than just setting parameters and forgetting - the controller should be able to adjust to changing exterior temperatures because it knows the relationship between heat loss and temperature difference (which follows a simple equation I'll be able to generate from the heat loss data once I've got a few days worth).
It can also learn the delay of the system when it turns on the pump, and make a decision based on that information to turn the pump on sooner or later - that timing will change with different i/e temperatures and current heat loss, and if it does it right, efficiency of the system can be further increased (the later I can start turning on the pump, the later the water heater will need to fire, further reducing short cycles of the heater).


Once I've got all the data and formulas right (I can verify them on my own system), I'm hoping to put everything into an SD card image for the Raspberry Pi for people to use and extend. Then anyone could solder a few wires together, leave a small box running for a couple of weeks, input a few values (floor area, heating loop density, air volume, etc) into a web site, and have the software spit out a range for flow rates and water temperatures to pick the right heaters and circulation pumps - all for less than 50 bucks in parts
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