Quote:
Originally Posted by jeff5may
What is it and how is it used?
Are there any standard control schemes or algorithms that are commonly used?
I am trying to integrate the control into an arduino sketch.
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I'm certainly not the final word on the issue, but here's what I think I know:
ODR's are designed to compensate for the thermal mass of the building + high mass floor if high mass radiant is used.
In a scenario without ODR, the heating system gets its command to begin heating when the indoor temp falls below the minimum set point. If the thermal mass of the house & thermal mass, etc. is very large, the heating system will be in a constant time-lag of overshoot/undershoot.
In a scenario with ODR, the heating system monitors the outdoor temperature as well as indoor temperature, and can "anticipate" the need for heat... thereby eliminating the problem with temperature lag.
Vlad had some kind of uber-smart controller on his hydronic heating system that was able to do ODR functions and also monitor the heat of the thermal storage tank, and with all that information, it would inject controlled pulses of hot water into the circulating water stream, to smoothly maintain optimum temperature.
It had a "learning" function too, that allowed it to learn the thermal mass of the house it was heating.
Cheap Chinese PID controllers also have a learning function built in. The way the learning function works is the controller go "ON" (and start measuring a time interval) until the temperature of the water, as an example, reaches the set point, then they turn "OFF" (and start measuring this time interval), and wait until the measured temperature returns from overshoot, and hits the set point again. So, by just knowing the time it takes to reach a set point, and the time to return from overshoot, back to the set point, the effective thermal mass can be calculated.
There are PID routines available for the Arduino... maybe even learning routines also, so you won't have to re-invent the entire wheel.
This might help, too:
http://tekmarcontrols.com/solutions/...y-savings.html
I don't think that ODR's are needed if the house + heating system is low mass, or if severe sudden temperature changes are not an issue.
Good Luck.
-AC