CHPC: Cheap Heat Pump Controller v1.x

The CHPC 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 system.

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.

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

Changelog

• 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. Actial versions: PCB v1.1, firmware v1.3.
• 02 may, 2019: PCB v1.3 coming up, main feature: lot of DS18B20 inputs

Applications:

Usage.	Brief description.	Application examples	Available protections
1. Thermostat.	Precision thermostat. Simple and cheap. Only 1 relay and 1 temperature sensor required.	Room heat control. Chicken coop climate control. Distillation column. Else.	N/A
2. Heat pump (HP) control.	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 running conditions.	DIY heat pump system. Repair module for commercial system. Water heater, house heating systems and same.	Compressor: cold start or overheat. Discharge and suction lines protection. Short-term power loss. Anti-freeze. Power overload protection.
3. EEV controller.	Only drives EEV, no relays. Requires 2 T sensors.	Upgrade your system from capilary tube to EEV.	Protects from liquid at suction line by design.

For more information about Heap Pumps look at Wikipedia about HP

Features:

• 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
• RS485 or Serial(UART 5V) support
• Automatically turns on/of system when heating required
• Takes care of system components health
  
  

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:

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

Temperature sensors:

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

Temperature sensors installation example (medium scheme)

Get your own CHPC:

• download PCB gerber file, CHPC_v1.x_PCB_Gerber.zip
• search google where to order PCB or make your own at CNC machine
• order electronic components, see BOM (Bill Of Materials) list, CHPC_v1.x_PCB_BOM.html
• solder
• install firmware CHPC_firmware.ino
• install CHPC at your system
• enjoy
  
  

T sensors abbreviations:

This abbrevations used in interface during sensors installation procedure

Abbr.	Full name	Required for
Tae	after evaporator	EEV Anti-liquid protection at suction line
Tbe	before evaporator	EEV
Ttarget	target	Thermostat Thermostat+EEV
Tsump	sump	Automatic Sump Heater Sump overheat protection
Tci	cold in	Antifreeze protection
Tco	cold out	Antifreeze protection
Thi	hot in	Hot CP automatic control
Tho	hot out	Overheat protection
Tbc	before condenser	Discharge overheat protection
Tac	after condenser
Touter	outer (outdoor)
Ts1	additional sensor1
Ts2	additional sensor2

Photos:

Upcoming PCB v1.3, untested now. Lot of small changes here.

PCB v1.1, actual version.

This is prototype 2 (PCB v1.0). 1602 is the best choise.

EEV development started here.

Prototype 1. History ) But worked well for a season.

Author:

gonzho АТ web.de (c) 2018-2019

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