Gofinity is a library for interacting with the Carrier Infinity / Bryant Evolution communicating residential HVAC systems.
This library exports
The code in this repository can loosely trace it's heritage back to Andrew Danforth's Infinitive project which aims to emulate a SAM device.
This project has evolved out of my desire to data-log everything on my HVAC system. I'm particularly interested in:
Longer-term, I want to be able to:
I have a fancy hybrid heat pump & variable throttled furnace, and my utility company costs fluctuate enough that given specific environmental factors, it may be less expensive to use gas or electricity (heat pump) for heating. I also live in a very temperate zone of the north american continent, where for roughly 8 months of the year the outdoor ambient air could be used for cooling with a fan rather than running the compressor on the heat pump.
My night-time 'set back' with the thermostat in 'auto' mode results in my heat pump compressor activating, when I could economize with just ambient air from outside.
The HVAC company solution to outdoor air involves a heat exchanger to try to equalize incoming ambient air temperatures to the same temperature as the conditioned space. Using this system to try and 'cool' a home would result in the fan having to blow for considerably longer than otherwise necessary if conditioned air were simply exhausted and exchanged for ambient outside air.
This all came about, as a consequence of talking with my HVAC tech (whom I also know outside of his professional life) about my economizer idea. Turns out, there are commercial products out there that do this kind of thing, but they're pretty expensive and don't do a great job of integrating with the Carrier / Bryant communicating systems. My friend did the opposite of trying to talk me out of it.
Challenge Accepted.
Half Duplex RS-485 + 24VAC = ABCD
Inside Carrier Infinity / Bryant Evolution systems there's a set of screw terminals labeled, "ABCD". These are the very wires which connect the thermostat, air handler, and any outdoor units (heat pump, air conditioner).
The A & B terminals carry RS-485 serial data at 38400, 8n1. The C & D Terminals provide 24VAC.
You'll need some way to communicate with the RS-485 bus of the ABCD connectors on your HVAC system. Instead of dealing with the shortcomings of common USB transceivers and looking more toward my final goals of embedded custom hardware & software, I designed and built pi485, a TTL Serial to RS-485 transceiver for Arduino and Raspberry Pi type devices. These are not difficult to make, and a full BOM will cost about $15 USD (2017 prices) in single quantities. You could probably do it for less than that if you have a bunch of things in your 'junk drawer'.
Or, you could go the RS-485 -> USB Converter route. Any of these can work.
Beware hardware that doesn't have a way to disable termination resistors, as that will cause issues with your ABCD bus. Also, devices which don't properly bias the AB lines with the DC supply voltage and 'ground', may have issues as well. These issues (and I wanted to use the UART rather than USB) were why I created pi485.