IOT/HVAC controls thread

I'm breaking into the world of HVAC controls and IOT devices so I figured might as well start a thread for us that are into this.

I recently got my home server setup and will be getting home assistant setup therefore I will be adding little projects to justify having home assistant. I think my first project will be building my own BAS for the house to monitor the HVAC system and automatically alert me if there are any alarms (such as my condenser fan motor dying on me the other day) without me having to be home to catch it.

Tenative plan is to have supply, return, condensor, and evaporator temps, exterior temp, room temp, CT's on the compressor, condensor, and evaporator fans to ensure they're running when called and that amperage isn't higher than expected, and I would really like suction and supply line pressure and temp so I can auto calculate superheat/subcool, but I'm running into issues finding a pressure transducer that isn't obscenely expensive.

Plan is to run a Rasberry Pi in the air handler for the brain, the exterior sensors will be hard wired off the 110 on the unit but data will be wireless, and then I have the option to tie it into my home server and home assistant.

I'm hoping that this is compatible with refrigerant as it's somewhat reasonable
Absolute Pressure Transmitter, 0-5V DC, 0-665 PSI | McMaster-Carr

 

For whatever it's worth- I've always had better luck with a sensor(s) => Arduino(s) => Pi => {Recipient: Home lab server / API, etc...} architecture. I've built stuff for my garage doors, own weather station, some sensors for the front and back door over the years.

While you certainly can go IO from the sensor to the Pi, the Arduinos are just easier to work with the sensors at a closer hardware level, especially if you're using interrupts rather than polling...

Being able to 3D print is also nice.

 

I appreciate the tip of running through arduino to the PI and then to the home server, how has the reliability of the weather sensor been? I have been wanting to build one but it hasn't been a priority.
That makes sense to set an SOP of going from the sensor to the arduino on every sensor.

 

Been pretty busy lately but got some sensors installed in the ducts, got a sensor installed in the return, and long term I would like to put a CT on the blower motor.
All of this data is being fed back to home assistant and I’ll be integrating alarms, and long term goal is to build a thermostat with touch screen running on a Pi, if HA is down it will default to a built in sensor but if HA is active based on schedules and such I want the system to be fully automated and have bias towards comfort (humidity+temp levels) of occupied rooms and account for solar load based on time of day and such.
If I were doing a ground up install or rebuild I would make it a zoned system with VRV and VAV, and go that route.