CHPC: Cheap Heat Pump Controller v1.0

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.

Development

State: active

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 or Yogurt maker t. control. 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.

* under development

For more information about Heap Pumps look at Wikipedia about HP

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

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 (medium scheme)

PCB Design

There are 2 PCB designs: type "F" and type "G".

Type "F" features:

• mostly SMD componens,
• internal power source,
• 10 output channels,
• 4 input channels,
• 5 relays: 1 * 16A + 4 * 7A,
• buzzer,
• EEV support,
• 16 bit i2c ADC: on board,
• i2c devices: allowed,
• T sensors: ds18b20 on one lane.

Type "G" features:

• no SMD components,
• external or board-placed power source,
• 5 output channels,
• 4 input channels,
• 5 relays: 2 * 16A + 3 * 7A,
• buzzer,
• EEV support,
• 16 bit i2c ADC: off board,
• i2c devices: allowed,
• T sensors: ds18b20 on one lane.

Type "F" PCB

Type "G" PCB

....

.... Drafts below.

Sensors abbreviations:

Abbr.	Full name
Tae	after evaporator
Tbe	before evaporator
Ttarget	target
Tsump	sump
Tci	cold in
Tco	cold out
Thi	hot in
Tho	hot out
Tbc	before condenser
Tac	after condenser
Touter	outer (outdoor)
Ts1	additional sensor1
Ts2	additional sensor2