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.
Note that the program in the current version, but still unfinished, occupies more than 110% of the Flash memory of the Arduino Pro mini.
Therefore, I have divided [depending on the FIRST_USE directive] the program into a part for programming the Dallas thermoments and a program for operating the heat pump.
Procedure: first program the Dallas thermometers by setting the [FIRST_USE] directive. After programming the thermometers, the [FIRST_USE] directive should be commented out and the Arduino Pro mini should be programmed again. This will free up more than 3kB of Flash memory! (Waldek)
Works from ground heat collectors (loops) to radiant in-floor heating system.
Driving:
- EEV,
- Heat Pump Compressor (1kW electrical power),
- Circulating Pumps,
- Compressor Heater,
- Three-way valve for domestic hot water heating,
- Four-way reversing valve for chilled water cooling.
Temperature sensors installed:
- Before/After Evaporator,
- Cold In/Cold Out,
- Hot In(used as Target)/Hot Out,
- Outdoor temperature,
- Compressor,
- Domestic hot water tank.
Controlled via both RS-485 and 16x2 display with buttons.
- 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: a lot of DS18B20 inputs
- 17 May, 2019: PCB 1.3 tested, assembly instructions added
- 24 Nov 2022: (Waldek)
- added half-steps to the EEV increasing accuracy
- delay added, Cold WP turns on first and compressor turns on later
- same when the compressor is turned off, after [COMPRESSOR_DELAY] shuts down Cold WP
- 15 sep 2023: (Waldek)
- added heat pump cooling capability (four-way reversing valve needed)
- [RELAY_4WAY_VALVE] relay controls [valve4w_state]
- moved [T_setpoint_cooling] to eeprom
- added possibility to heat domestic hot water (three-way valve needed)
- [RELAY_SUMP_HEATER] relay controls [valve_cwu_position] ATTENTION!!!!! No sump heating in this!!!!! The heat pump must stand in a room with a minimum temperature of 10 degrees Celsius!!!!!
- [T_TARGET_CWU] was moved to eeprom, [CWU_INTERVAL] - every how many hours in milliseconds to start a water heating cycle, [CWU_MAX_HEATING_TIME] - how many hours in milliseconds to heat water in one cycle
- added [CWU_HYSTERESIS] and moved to eeprom
- transferred [T_EEV_setpoint] to eeprom
- overload error handling
- lack of start handling
- added buffer charging procedure
| Usage. | Brief description. | Application examples | Available protections |
|---|---|---|---|
| 1. Thermostat. | Precision thermostat. Simple and cheap. Only one relay and one temperature sensor required. |
Room heat control. A 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). Protect system from an 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 applications. | 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. Require two T sensors. | Upgrade your system from capillary tube to EEV. | Protects from liquid at suction line by design. |
For more information about Heap Pumps look at Wikipedia about HP
- Up to 13 T sensors (see "T sensor abbreviations" for full list)
- 5 relays (Compressor, Hot CP or Air Fun, Cold CP or Air Fun, Compressor 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
- On board or off board power supply
None: Target temperature uploaded to board with firmware and not changed anymore. System used as an fixed thermostat. You can change target temperature with firmware re-upload.
0.96 OLED or 1602 LCD screen + buttons: Simple, local screen controlled system.
Remote computer terminal over RS-485 line. Target temperature and running conditions under remote control. A 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 the prototype 485 network).
Both screen + buttons and RS-485. Combination allowed.
* RS-485 specification. The hardware test succeeded on 400 meters line.
Example: day/night setpoint control and data visualization with JSON communication way.
Only one Relay: drive an electric heater (any)
5 Relays, drives all you need:
- Compressor (relay can be used as external relay driver for High Power systems)
- Cold Circulating Pump (CP)
- Hot CP
- Compressor Heater (optional, recommended for outdoor HP installations)
- and one reserved to support 4-way Valve
- 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)
- 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, assembly instructions here
- install firmware CHPC_firmware.ino
- install CHPC at your system
- enjoy
These abbreviations used in the 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 Compressor Heater Compressor 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) | |
| Tcwu | domestic hot water tank | |
| Ts2 | additional sensor2 |
PCB v1.1
This is prototype 2 (PCB v1.0). 1602 is the best choice.
EEV development started here, PCB v1.0.
Prototype 1. Say v0.0.
History ) But worked well for a 2018-19 season.
gonzho АТ web.de (c) 2018-2019
If you have any comments or questions, please do not hesitate to contact me.