<b> The Valden Heat Pump controller is a platform to precisely control heat
pumps. Controller can be easily used for newly designed heat pumps (HPs), including series, as repair controller or as control system for experiments with refrigeration equipment.</b>
- find in Google, [where to order a printed circuit board](https://www.google.com/search?q=order+pcb+gerber) (keywords: order pcb gerber), place an order,
For arduinos with old bootloader you need to update it. (Tools-> Burn Bootloader).<br>
For successful compilation, you must have "SoftwareSerial", "OneWire" and "DallasTemperature" installed (see Tools -> Manage Libraries).<br>
As a first try it's enough to simply upload firmware without any tunings. Think of it as of commercial closed-source controller, where you cannot change internal options.
## Self-tests
QA tests are available to test the assembled board.<br>
Self-test helps you check relays, indicators, speaker and temperature sensors.<br>
To check EEV, you can use a stepper motor as shown in the video. If you are testing a real EEV, it should be closed after the first "beep" and partially opened after the second "beep".<br>
To check temperature sensors connectors prepare one array of sensors. Connect it to all sensors connectors one-by-one and check results in a serial console.<br>
{-Photo: PCB with connected arrays of sensors (I have enough sensors, so all 3 arrays are connected except Ts2 and Treg) -}<br>
{-Screenshot: serial console with temperature readings: -}<br>
- connect the "power inlet" wire to one of the "phase" connectors,
- and connect the second "phase" connector to the AC input of the 12V power supply,
- connect the "Compressor" relay output to the Compressor input,
- connect the relay output "Hot CP" to the input of the Hot Circulation Pump (pump of the water floor heating system or the fan input of the indoor unit if you are using an air system),
- connect the relay output "Cold CP" to the input of the Cold Circulation Pump (ground loop pump for geothermal systems or the inlet of the outdoor unit air fan if you are using an air system),
- when using a compressor heater: connect the "Crankcase heater" output to the heater cable input (highly recommended for outdoor installation and year-round use)
- SCT013 sensor (the only low-voltage device in the circuit with interchangeable contacts), connect and install on the phase inlet wire,
- RS485 through a wire of the desired length to the remote control display (if used, another control method is a local computer with a USB-UART converter, you may like it for the first time). Note that A is connected to A in the display, B to B and GND to GND,
- you can power the display from a 12V controller, the board has 12V and GND secondary pins,
- connect the outputs of the pressure sensors: 1st wires together to the right pin, 2nd cold side wire to the left terminal, 2nd hot side wire to the middle terminal; use the dummy when pressure sensors are not in use.
You may prefer to solder the wires over using connectors. But in this case, it will be more difficult to disassemble the system if you want to change something. The choice is yours.<br>
{-Photo: T sensors with abbreviations and full names-}<br>
At this example: "hot in" ~30 °C, compressor ~80 °C and so on. Heat Pump (HP, compressor) ON, Hot water pump ON, Cold water pump ON. Power consumption 980 watts.
End user do not wat to know much about refrigerants, evaporation, cycles and so on, so this display designed as simple as possible. See [display page](https://github.com/openhp/Display/) for datails. And yes, this display is also DIY non-commercial product with opened gerber and source code.<br><br>
One day i'v realised that notebook with a serial console is very good diagnostic tool, but i want more compact tool to get maximum available information from heat pump. So this "Quickly Assembled Service Display" appeared. It fits everywhere and with a good power bank it can works 2-3 days long, without any additional power source. The diagnostic display is build from scratch, no PCB and housing here (and no plans to create it), because i do not see this device as a permanent-mounted display for the end user.<br>
- for single-component refrigerants: slightly open the valve of the HVAC gauge manifold to start adding refrigerant through the gas phase on the cold side,
- for multi-component refrigerants: turn over the refrigerant cylinder, VERY SLIGHTLY open the HVAC manifold valve to start adding a VERY LITTLE amount of refrigerant through the liquid phase,
- carry out charging until the suction temperature (according to the suction pressure on the manometer) is ~ 10 ... 15 °C lower than the temperature of the heat source (example: the temperature at the inlet of the mixture of water and antifreeze from the closed ground loop is + 8 °C, so the suction temperature should be -2 ..- 7), then close the manifold valve,
- carry out the final charge when the system is stable and the heat pump stops normally (setpoint is reached), this may take 12 hours or more, and now the target difference between the suction pressure temperature and the temperature from the T sensor should be 3 ... 6 °C.
For more information about Heat Pumps look at [Wikipedia about HP](https://en.wikipedia.org/wiki/Heat_pump).<br>
If you are interested in questions like "how refrigeration systems works" read Patrick Kotzaoglanian books.<br>
If you want more technical details, sophisticated scmemes, "how EEV can be driven by temperature" diagrams, etc. refer to vendors manuals (you can find a lot in Alfa Laval brochures, Danfoss guides, and so on).<br>
For refrigerants and oils types comparison see wiki.<br><br>
## Personal experience
Note that the SCT013 sensor and the current monitoring scheme cannot be used for accurate measurements and accurate COP calculations. Use wattmeter for accurate power measurements.<br>
Measuring the temperature of a warm floor with sensor at one point is a bad idea - it's better to deal with temperature of the "hot in" water coming from all over the floor, as implemented in firmware.<br>
The weather-dependent (both outdoor and indoor temperature dependent) system does not work fine for 30-150 m2 buildings. The system turns out to be difficult and works bad due to unpredictable ventilation. And also due to the unpredictability of heat emitted in the house by other sources.<br>
I tried the scheme with a flooded evaporator in 2019 and found it extremely problematic, then refused to use it.<br>
Deep regeneration schemes are useful only for some refrigerants and only in certain temperature ranges. I also tried deep regeneration, I was convinced that the theory coincides with the practice and then also refused this idea.<br>
In general, it is possible by complicating the refrigeration scheme to win somewhere 1%, somewhere 3%, but all this leads to significant time and money costs, compared to not very much profit.<br>
Summary: If you want experiments - Experiment. Want reliably and quickly - make system simple.<br>
<br>
## License
GPLv3. <br>
This product is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.<br>
| **P.Tcrc** | Protective stop. "Compressor" temperature is too high. Overheat protection. This is an ordinary situation during long runs. See **T_CRANKCASE_MAX** option and compressor manual if you want to tune it (~115 °C for wide-available compressors). |
| **P.Tae** | Protective stop. "After evaporator" temperature too low. Preventing cold loop from freezing and protecting suction line from liquid. See **T_COLDREF_MIN** option. |
| **P.Tbe** | Protective stop. "Before evaporator" temperature too low. Preventing cold loop from freezing. See **T_BEFORE_EVAP_WORK_MIN** option. |
| **P.Tbc** | Protective stop. "Before condenser" temperatire is too high. Overheat protection. This is an ordinary situation during long runs. See **T_BEFORE_CONDENSER_MAX** option. |
| **P.Tci** | Protective stop. "Cold in" temperature is too low. Preventing cold loop from freezing. See **T_COLD_MIN** option. |
| **P.Tco** | Protective stop. "Cold out" temperature is too low. Preventing cold loop from freezing. see **T_COLD_MIN** option. |
| **#Thi>Setp.** | "Hot in" temperature > setpoint, so no reason to start. |
| **#Ts1>Setp.** | "Ts1" temperature > setpoint, so no reason to start, see **SETPOINT_TS1** option to switch betwees Thi and Ts1 as setpoint sensor. |
| **HWP_OFF** | Setpoint sensor temperature > setpoint, so after some time (**HOTCIRCLE_STOP_AFTER** option) hot side pump powered off and gone to power saving mode. |
| **HWP_ON_by_ev** | Hot side pump started after power saving. See **HOTCIRCLE_START_EVERY** option. |
| **#HotPrp:_seconds_** | Hot side pump is on, waiting for T stabilisation. Countdown, seconds. See **HOTCIRCLE_CHECK_PREPARE** option. |
| **#HotSlp:_seconds_** | Hot side pump in power save mode (sleeping). Waiting for next startup. Countdown, seconds. See **HOTCIRCLE_START_EVERY** option. |
| **#CPp:_seconds_** | Cold side pumping. Preparing system to start compressor. Countdown, seconds. **COLDCIRCLE_PREPARE** option. |
| **#Tho>Max** | "Hot out" temperature is too high. See **T_HOT_MAX** option. |
| **#Thi>Max** | "Hot in" temperature is too high. , see **T_HOT_MAX** option. |
| **#CaseCold** | Compressor crankcase temperature is too low. Can't start. This situation occurs if the outdoor installation when AC power was lost for a few hours. Wait, while the crankcase heater stabilizing your compressor temperature. See **T_CRANKCASE_MIN** option. |
| **#CaseHot** | Compressor is still overheated, waiting. See **T_CRANKCASE_MAX** option. |
Are you still reading? If yes, your are interested in and this appendix is for you.<br>
About sensors: do not use cheap "waterproof epoxy-covered" sensors. "Waterproof" lasts for a short time.<br>
Buy DS18B20s chips. Cheap or not cheap doesn't matter - I've never seen "bad" DSes. Solder sensors to the wires and cover the sensors with a two layers of 2-component epoxy resin as pictured below.<br>
To get precise temperature readings sensors must be insulated from ambient air temperature influence with additional thermal insulation. Temperature readings from most of sensors are interesting, but +/- few degree does not matter. So most of sensors can be covered with insulation as you wish. But 2 sensors "Before evaporator" and "After evaporator" are critical to EEV and needs extra attention. Temperature of this sensors must be as close to the temperature of copper tube as it possible. So install Tae and Tbe sensors as pictured below. You can use thermal paste, but there is no significant difference with much more available silicone.<br>
Water(glycol)<->refrigerant heat exchangers. You can use plate heat exchangers. Pros: best efficiency. Cons: costs money. And requires oxygen brazing with "(20%+)silver-copper" solder.
And also you can think "I'll take old AC parts... Housing... Slightly change... A hour or two, day of work maximum, and i'll got a refrigerant<->water heat exchanger in for a penny!" This idea is obvious. That was a first thing I've tried and do not want to try it anymore. You can also try this, but remember: to achieve "not very bad" performance it'll take much more than a day and much more than few $$, even if you have unlimited access to older ACs.
//#define RS485_JSON 1 //json, external systems integration
//#define RS485_HUMAN 2 //RS485 is used in the same way as the local console, warning: Use only if 2 devices (server and this controller) are connected to the same RS485 line
#define RS485_MODBUS 3 //default, Modbus via RS485, connection to the display (both sensor or 1602, see https://gitlab.com/valden/) or connection to any other MODBUS application or device
//#define EEV_ONLY //Valden controller as EEV controller: NO target T sensor. No relays. Oly EEV. Sensors required: Tae, Tbe, current sensor. Additional T sensors can be used but not required.
//#define NO_EEV //capillary tube or TXV, EEV not used
//#define T_sensor_2; //additional sensor, any source, for example: outdoor temperature, in-case temperature, and so on
#define T_crc; //if defined: enables crankcase T sensor and crankcase heater on relay 4
//#define T_regenerator; //an additional sensor, the regenerator temperature sensor (inlet or outlet or housing) is used only to obtain a temperature data if necessary
#define T_afrer_condenser; //after condenser (and before valve)
#define MAGIC 0x66; //change this value if you want to rewrite the T setpoint in EEPROM
#define T_SETPOINT 26.0; //This is a predefind target temperature value (start temperature). EEPROM-saved. The value can be changed using 1. Console 2. Changing the "setpoint" on a display 3. Changing this value AND changing "magic number"
#define T_SETPOINT_MAX 48.0; //maximum "setpoint" temperature that an ordinary user can set
#define T_SETPOINT_MIN 10.0; //min. "setpoint" temperature that an ordinary user can set, lower values are not recommended until antifreeze fluids at hot side are used.
#define T_CRANKCASE_MIN 8.0; //compressor (crankcase) min. temperature, HP will not start if T lower
#define T_CRANKCASE_MAX 110.0; //compressor (crankcase) max. temperature, overheating protection, HP will stop if T higher
#define T_CRANKCASE_HEAT_THRESHOLD 16.0;//crankcase heater threshold: heater will be powered on if T lower
#define T_WORKINGOK_CRANKCASE_MIN 25.0;//compressor temperature: additional check. HP will stop if T is lower than this value after 5 minutes of work. Do not set the value too large to ensure normal operation after long pauses.
#define T_BEFORE_CONDENSER_MAX 108.0; //discharge MAX, system stops if discharge higher
#define T_COLDREF_MIN -14.0; //suction min., HP stops if T lower, cold side (glycol) loop freeze protection and compressor protection against liquid
#define T_BEFORE_EVAP_WORK_MIN -25.5; //!!!before evaporator (after valve) min. T; can be very low for a few minutes after startup, ex: capillary tube in some conditions; and for all systems: after long shut-off, lack of reagent, 1st starts, and many others
#define T_COLD_MIN -15.5; //cold side (glycol) loop freeze protection: HP stops if inlet or outlet temperature lower
#define T_HOT_MAX 50.0; //hot loop: HP stops if hot side inlet or outlet temperature higher than this threshold
#define MAX_WATTS 1000.0 + 70.0 + 80.0 //power limit, watt, HP stops in case of exceeding, example: compressor: ~1000 + hot CP 70 + cold CP 80
#define POWERON_PAUSE 300000 //after power on: wait 5 minutes before the start of HP (protected from power faults)
#define MINCYCLE_POWEROFF 600000 //after a normal compressor stop: 10 minutes pause (max 99999 seconds)
#define MINCYCLE_POWERON 3600000 //after compressor start: minimum compressor operation time, i.e. work time is not less than this value (or more, depending on the setpoint temperature) 60 minutes = 3.6 KK 120mins = 5.4 kK.
#define POWERON_HIGHTIME 7000 //after compressor start: defines time when power consumption can be 3 times greater than normal, 7 sec. by default
#define COLDCIRCLE_PREPARE 90000 //before compressor start: power on cold CP and wait 90 sec; if false start: CP will off twise this time; and (hotcircle_stop_after - this_value) must be > hotcircle_check_prepare or HP will go sleep cycle instead of start
#define DEFFERED_STOP_HOTCIRCLE 1200000 //after compressor stop: wait 20 minutes, if no need to start compressor: stop hot WP; value must be > 0
#define HOTCIRCLE_START_EVERY 2400000 //while pauses: pump on "hot side" starts every 40 minutes (by default) (max 9999 seconds) to circulate water and get exact temperature reading , option used if "warm floor" installation (Thi as setpoint)...
#define HOTCIRCLE_CHECK_PREPARE 300000 //while pauses: ...and wait temperature stabilisation 5 minutes (by default), after that do setpoint checks...
#define HOTCIRCLE_STOP_AFTER (HOTCIRCLE_CHECK_PREPARE + COLDCIRCLE_PREPARE + 30000) //...and then stop after few minutes of circulating, if temperature is high and no need to start compressor; value must be check_prepare + coldcircle_prepare + 30 seconds (or more)
#define EEV_CLOSEEVERY 86400000 //86400000: EEV will be closed (zero calibration) every 24 hours, executed while HP is NOT working (milliseconds per cycle)
#define EEV_CLOSE_ADD_PULSES 8 //read below, additional steps after zero position while full closing
#define EEV_OPEN_AFTER_CLOSE 45 //0 - set the zero position, then add EEV_CLOSE_ADD_PULSES (zero insurance, read EEV guides for this value) and stop, EEV will be in zero position.
//N - set the zero position, than add EEV_CLOSE_ADD_PULSES, than open EEV on EEV_OPEN_AFTER_CLOSE pulses
//i.e. it's a "waiting position" while HP not working, value must be <= MINWORKPOS
#define EEV_MINWORKPOS 50 //position will be not less during normal work, open EEV to this position after compressor start
#define EEV_PRECISE_START 7.0 //(8.6 tube evaporator) precise tuning threshold: make slower pulses if (real_diff-target_diff) less than this value. Used for fine auto-tuning
#define EEV_EMERG_DIFF 1.7 //(2.5 tube evaporator) liquid at suction threshold: if dangerous condition occured: real_diff =< (target_diff - EEV_EMERG_DIFF) then EEV will be closed to min. work position //Ex: EEV_EMERG_DIFF = 2.0, target diff 5.0, if real_diff =< (5.0 - 2.0) then EEV will be closed to EEV_MINWORKPOS
#define EEV_HYSTERESIS 0.5 //(0.6 tube evaporator) hysteresis, to stop fine tuning: must be less than EEV_PRECISE_START, ex: target difference = 4.0, hysteresis = 0.3, no EEV pulses will be done while real difference in range 4.0..4.3
#define EEV_TARGET_TEMP_DIFF 3.6 //(3.6 tube evaporator) target difference between Before Evaporator and After Evaporator, the head of whole algorithm
#define EEV_REOPENLAST 1 //1 = reopen to last position on compressor start, useful for ordinary schemes with everyday working cycles, 0 = not
#define EEV_REOPENMINTIME 40000 //after system start: min. delay between "min. work pos." (must be > 0 in this case and > waiting position) set and reopening start
//#define EEV_MANUAL //comment to disable, manual set of EEV position via console; warning: this option will stop all EEV auto-activities, including zero position find procedure; so this option not recommended: switching auto/manual mode from console after startup is a better way
