Detecting if the AirCon is running...

[toftat]

I would like to optimize the setting of the thermostats in my house (I have programmable ones) to do this I need to detect if the AirCon is running. The idea being that a better setting will end up with lower runtime

I can't connect directly to either the AirCon or the thermostat so I need to observe the effect of it running, to this end I have come up with 2 ideas and am hunting for more

1) measuring a thermal delta between the vent outlet and "somewhere else" in the room. Somewhere else probably being against the ceiling to make sure that there _is_ a delta

2) measuring airflow. I have successfully done this using an old processor fan and measuring the voltage coming from the motor during hurricanes but I suspect the vent output is not forceful enough to generate anything significant...

As this is a hobby project, cost is a significant consideration...

Thanks for any further ideas!

[Simon]

so you simply want to know when the AC is running ? do you have access to any low DC voltages in the AC unit ? if you want to detect the differnce in air temp putting a sensor on the top or in front of the intake and one in front of the outlet will certainly get you your delta C

[tecman]

1.  Clamp on current sensor on air handler or compressor circuit

2.  Temp sensor on vapor line

3.  Airflow "sail" switch

All are relatively simple and cheap to use.

paul

[XynxNet]

4. You could put a hall sensor near your aircondition fan.

[gbowne1]

I don't know but you could set up a small PLC to control this.  AllenBradley Micrologix 1500's are nice for this.
You can set up all kinds of things on it, relays, sensors, switches, etc.

In my case, I'm adding a small GE FANUC 90-30 to my home control for the HVAC requirements of heating and cooling.

Greg