heatpump

README

Chiltrix CX34 dashboard software

This project is used to communicate with a hydronic heating system that uses the Chiltrix CX34 air-to-water heat pump. The components of the system are as follows:

1. A Raspberry Pi.

2. The Chiltrix CX34 heat pump chiller. The Pi communicates with the chiller using using serial communication, which is used natively by the CX34 to talk with its controller per the wiring diagram and ProtoAir FPA-W44 manual.

3. A USB-to-RS484 dongle that connects the Raspberry Pi to the Chiltrix. This device should show up as /dev/ttyUSB0.

4. Optional DS18B20 temperature sensors, which can now be bought for about $2 each. Several temperature sensors can be connected to single GPIO port on the Pi. I followed this guide to get up and running and then wrote the github.com/gonzojive/heatpump/tempsensor Go package to read the sensor values.

Implementation notes

This project is written in Go.

Setup

Software installation

Install go on the Raspberry Pi according to the official instructions.

Install the collector binary:

go get github.com/gonzojive/heatpump/cmd/cx34collector github.com/gonzojive/heatpump/cmd/cx34install

Install the systemd service so the service runs at boot.

sudo `which cx34install`

Inspect the logs with

journalctl -u cx34collector.service

CX34 control

General development tips

Wiring

The Chiltrix uses RS485 to communicate with its controller. I have a USB-to-RS484 with a ch340T chip and pins labelbed "A / D+" and "B / D-".

TODO: more info

ssh access with password login disabled

My ~/.ssh/config has a section like

Host waterpi
    HostName 192.168.86.22
    User pi

and the Pi's ~/.ssh/authorized_hosts and /etc/ssh/sshd_config has a section with

# To disable tunneled clear text passwords, change to no here!
PasswordAuthentication no

sshfs

Mounting the Raspberry Pi's OS can be helpful for developing on a workstation. I followed this guide and ran these commands:

sudo mkdir /mnt/waterpi
sudo chown <YOUR_USERNAME> /mnt/waterpi
sudo sshfs -o "allow_other,default_permissions,IdentityFile=/home/<YOUR_USERNAME>/.ssh/id_rsa" pi@192.168.86.22:/ /mnt/waterpi