I am HVAC certified and wanted to throw out a couple of ideas that I have.
In my opinion the number one reason for Freon leaks in the system is either a failure of the blower motor or condenser fan motor. In which case create ice to build up on the a coil and creates stress and ends up shifting things around and creating leaks in the a coil.
My idea is to put a air pressure sensor above the furnace to indicate if a blower motor has failed and one also at the condenser fan. The one at the condenser fan I haven’t quite figured out yet in my mind.
You could use window sensors attached to the pressure sensors and then use rule machine. You could have the status of the sensors checked 3 minutes after startup and from there on out. If something fails you could have the system shutdown and then notify you.
True but very rare. In my case anyway. I’ve probably worked on a thousand units and have never come across it. I take that back. I had one that had the valves almost completely shut on the line set. but it didn’t ice up. But I haven’t been working on HVAC very long. First scenario anyway. The second one I would assume people would change there filters.
Edit. I miss read your comment. But you know what I’m saying
You could also monitor the fan amp current for both motors. This would be an indirect method for determining air flow or motor operation. The current draw would go down when the motors were not doing as much work due to something blocking the air flow and of course if the motor failed the current would be nada. I use to do that on large commercial units so technically it is certainly possible but I don’t know the specs on residential current monitoring devices for lower amp loads if the resolution is fine enough for monitoring gradual drops in load. You could always experiment and try the energy monitoring devices built in to outlets/switches now to track the power KW to see if that could do it as well?
Not to hijack, but one HVAC monitor I built was to receive a notification each time my heat pump went to the backup auxiliary heat (heat strips). I’ve had no way to see when the backup heat was being called for, and it was difficult to troubleshoot high energy bills. When I first moved in to the house, I had a refrigerant leak that was preventing the heat pump from operating properly, resulting in backup heat being used almost 100% and a $600 electric bill my first month.
It was very simple with a RIB relay on the heat strip call at the air handler, with a wired contact sensor (Monoprice) to send a signal to Smartthings; from there, a simple rule with notification. I’ve been able to log a pretty specific pattern that I can use as a baseline for future operation.
Interesting question about variable speed. If you have a specific application you could share let me know. Variable speed applications are certainly a little more complex.
That’s a good idea for the condenser fan motor. I could use this Aeon Labs AEDSB09104ZWUS Aeotec Z-Wave Smart Energy Monitor https://www.amazon.com/dp/B00DIBSKFU/ref=cm_sw_r_other_awd_0.ofxb1B1H35V the only issue would be whether proofing it somehow. Wait now that I think about it that probably wouldn’t work because it doesn’t read amperage. But you got my wheels turning.
I had something similar for monitoring my space heating using the Aeon Labs DSC06106-ZWUS - Z-Wave Smart Energy Switch. I was just monitoring the energy and when it spiked I knew my local electric heat was running. I ended up putting up the money for replacing the existing thermostat with the ecobee3 thermostat. I have never been more pleased with the better performing HVAC operation and automatic logging on the ecobee website not to mention the superior integration into SmartThings.
Not so sure abut that. Not a tech by any means. My new split unit supposedly does and the sales rep stated their new HVAC units did as well. (my AC is 5 years old - or ancient in the tech world)
Yeah - the split would be - but there are variable condensers - most are inverters, and the market will be 100% in a few years, at least for all but the bottom $$ ones.