Introduction: Hot Water Pump Recirculating Control System in a Solar Thermal Plate


The purpose of this Instructable is to show how works my Hot water pump recirculating control system.

I use a solar thermal plate, that save the hot water in a thermal tank, and I have installed at home a system that allow us enjoy of hot water once you open the pipe, without waste cold water waiting for the hot water, saving many liters of water.

The problem is that if I allow the pump to work continuosly, it cold the water stored in the tank. So, I have desing a little system with Arduino that allow us control automatically the pump in relationship with temperature and also with remote control for custom activation of pump. Also, I can also control the internal resistence of thermal tank to heat water in cloudy days in winter.

Moreover, current status of system is monitorizing by wifi with help of an ESP8266 module.

Step 1:

Step 2: ​Materials:

- Arduino Nano

- Regulated power supply 220AC to 12VDC

- Relay module

- ESP8266 ESP-01 module

- Temperature probe LM35DZ

- 4 channels wireless remote control (chip PT2272-M4) (

- Recycled LEDs for current status monitor from a LED Strip (RGB LEDs at 12V)

- Some resistors, capacitors, transistors and plugs

Step 3: Scheme and Assembling

The idea in the code is that pump automatically switch ON when temperature is higher than 70ºC and switching OFF when temperature is lower than 60ºC.

Thus, I can control function of pump and internal resistence with the remote control, stablishing different working times for each button, 5min for button A and 10min for button B. Button C switch ON 15min the internal resistence of tank, and D button is configured as STOP both pump and resistence.

So, I can stop the pump and resistence in any moment and system would be controlled by temperature probe.

The ESP8266 was mount over an accesorial board, with an LM7805 and voltage divider to yield 3.3V from 12V power supply.

The probe was coupled with two capacitors and one resistor, together a shielded wire, as detailed in the datasheet of LM35 to avoid noise because of length of wire (about 3m).

Step 4:

Step 5: Video

The Red led indicates that system is OK (It is switched ON during void setup step in Arduino code)

Blue led indicates that relay (pump)is OFF, and Green Led indicated that Relay (pump) is ON.

Such leds are controlled in the video with help of remote control.

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