Cheap Heat Pump Controller - CHPC

CHPC: Cheap Heat Pump Controller v1.x

The CHPC is a minimal cost heat pump (HP) controller, which can be used as provided, or can be adopted to nearly all use cases due to open source nature.

Real life installation:

Works from ground heat collectors (loops) to radiant in-floor heating systems.

Driving:

• EEV,
• Heat pump compressor (1kW electrical power),
• Circulating pumps,
• Sump heater.

Temperature sensors installed:

• Before/after evaporator,
• Cold in/cold out,
• Hot in (used as target)/hot out,
• Outdoor temperature,
• Sump.

Controlled via both RS-485 and 16x2 display with buttons.

Photos:

Change log:

17 May, 2019: PCB 1.3 tested, assembly instructions added.

• 13 Apr, 2019: EEV support development started.
• 16 Apr, 2019: Standalone EEV (no thermostat) with only 2 T sensors written and debugged.
• 30 Apr, 2019: HP system updated to CHPC.
• 01 May, 2019: CHPC fully tested and released.
• 02 May, 2019: PCB rev.1.3 coming up, main feature: lot of DS18B20 inputs.

Applications:

1. Thermostat

Brief: Precision thermostat. Simple and cheap. Only 1 relay and 1 temperature sensor required.Application examples: Room heat control. Chicken coop climate control. Distillation column. Else.

2. Heat pump (HP) controller

Brief: Heat pump controller. Controller drives HP system components: compressor, cold and hot side Circulating Pumps (CP). Protects system from overload, overheat and freezing up. Drives EEV to optimize HP running conditions. Application examples: DIY heat pump system. Repair module for commercial system .Water heater, house heating systems and same. Available protections: Compressor: cold start or overheat. Discharge and suction lines protection. Short-term power loss. Anti-freeze. Power overload protection. Others.

3. EEV controller

Brief: EEV driver, no relays. Requires 2 T sensors. Application examples: Upgrade your system from capilary tube to EEV. Available protections: Protects from liquid at suction line by design.

For more information about heat pumps look at Wikipedia about HP.

Features:

Takes care of system components health

• Up to 13 T sensors (see "T sensors abbreviations" for full list)
• 5 relays (Compressor, Hot CP or Air Fun, Cold CP or Air Fun, Sump Heater, 4-way valve)
• 4 inputs
• 5/6 pin EEV connection
• 1602 display support
• RS-485 or Serial (UART 5V) support
• Automatically turns on/of system when heating required

Control interfaces:

None: Target temperature uploaded to board with firmware and cannot be changed. System used as fixed thermostat. Target temperature can be changed later with firmware re-upload.0.96 OLED or 1602 LCD screen + buttons: Simple, local screen controlled system. Remote control is not possible. Remote computer terminal over RS-485 line. Target temperature and running conditions under remote control. User can get stats from all T sensors. Up to 1.2 kilometer line.* Remote automated control/stats via RS-485. Firmware was written with Python scripting in mind (and real scripts at prototype 485 network). Both screen + buttons and RS-485. Combination allowed.

* RS-485 specification. Hardware test succeeded on 400 meters line.

Example: day/night setpoint control and data visualisation with "pythonic rs485" way

Relays:

"Thermostat:"

Only 1 relay: drives electric heater (any)

"Heat pump" capillary tube, TXV, EEV:

5 relays, drives all you need:

4-way Valve (support coming up: autumn 2019)

• Compressor (can be used as external relay driver for High Power systems)
• Cold circulating pump (CP)
• Hot CP
• Sump heater (optional, recommended for outdoor HP installations)

Temperature sensors:

3 sensors needed for "HP with EEV" (absolute minimum scheme)

• Up to 13 temperature sensors can be connected to CHPC to control all processes that you want.
• Only 1 sensor needed for "Thermostat" or "Heat Pump capillary/TXV"

Temperature sensors installation example (medium scheme):

Get your own CHPC:

• Actual versions: https://github.com/gonzho000/chpc
• Download PCB gerber file, CHPC_v1.x_PCB_Gerber.zip
• Order electronic components, see BOM (Bill Of Materials) list, CHPC_v1.x_PCB_BOM.htmlinstall firmware CHPC_firmware.ino
• Search Google where to order PCB or make your own at CNC machine
• Solder, assembly instructions here
• Install CHPC at your system
• Enjoy

Somephotos, older revisions and prototypes:

PCB v1.1

EEV development started here.

Prototype 1. History, but worked well for a season.

More info and sources here: https://github.com/gonzho000/chpc

Author:

gonzho АТ web.de (c) 2018-2019

If you have any comments or questions, please do not hesitate to contact me.