The first part of this guide explained how to set up the necessary hardware for temperature monitoring. This second part explains how the recorded data can be processed further and what conclusions can be drawn from it.
Measuring correctly
To ensure the measurement provides meaningful results, two measuring devices are needed.
- Measuring device 1 records the flow and return temperatures of the heating system.
- Measuring device 2 records the room temperature in the living area and the outside temperature.
It is only possible to draw the correct conclusions with these four measured values. This is because the room and outside temperatures must be known to correctly interpret the heating system’s measured values.
The measurement approach can be explained as follows:
With a room temperature of 22°C and an outside temperature of -2°C, the heating system must deliver a flow temperature of 69°C. Of the 69°C supplied, 27°C remains in the return flow.
This quickly reveals which heating technology is suitable for the building and which is not. Thus, the old heating system helps determine its successor.
An important factor in the measurement is the time of year, as it makes little sense to measure in summer. The ideal times for measurement are January and February, when the heating system is working hardest. The best time of day for measurement is at night, between 10 p.m. and 8 a.m., as this is when the coldest periods are recorded. For this purpose, any night-time temperature reduction should be deactivated.
One more point to consider is that hot water preparation can lead to measurement errors if there is no return flow barrier between the hot water heating circuit and the normal heating circuit. This can cause the heating water from the hot water system to heat up the sensor in the return pipe. If this is the case, the hot water system must be switched off during the measurement. This means that you will have no choice but to take a cold shower on this occasion.
Recording and reading measurement data
Once the four temperature sensors have been correctly positioned, the measurement cycle can be started either directly on the measuring device or via the website. The temperature sensors will then report the measured values every 60 seconds, which will be transferred to a CSV file. As the date and time come from an NTP server, both measuring devices are synchronised. To read out the recorded data for further processing, the measurement cycle must first be stopped. The data can then be transferred to a PC using an FTP programme via the FTP protocol. WinSCP, a free Windows programme, is a good choice for this. It can be downloaded here.
After installation, the two measuring devices must be entered as FTP servers. To do this, you will need the IP address, username and password. The IP address is displayed when the measuring device is switched on. The username and password are entered in the sketch. These can be changed in line 151 of the sketch.
Here’s how to proceed:
- Start WinSCP
- Open ‘New tab’ (Neuer Tab)
- Open ‘New connection target’ (Neues Verbindungsziel) and enter the data
- Save the entered data
- Click on ‘Login’ (Anmelden)
- The connection to the FTP server will open
- Click on the file ‘Messwerte.csv’ (measurements) and then on ‘Download’
The data can now be imported into a programme such as Excel or LibreOffice that can process .csv files.
Importing data using Excel (Excel 2010) as an example:
- Open an empty Excel file
- Open the ‘Data’ menu (Datei)
- Click on ‘From Text/CSV’ (Aus Text) and open Messwerte.csv (measurements)
- The import dialogue box will open and accept the entered values. Click on ‘Next’ (Weiter) to open the next dialogue box.
- In dialogue box 2, select ‘Semicolon’ (Semikolon) as the separator and delete ‘Tab stop’ (Tabstopp).
- Click ‘Next’ (Weiter) to open the next import dialogue box
- Click ‘Finish’ (Fertig stellen) to complete the data import
- Specify the location in the table for the imported data (Existing worksheet/bestehendes Arbeitsblatt)
Note: The Arduino IDE outputs floating-point numbers using a dot as the decimal separator, which is standard in English-speaking countries. Therefore, no adjustment is required when importing the data into Excel.
Application example
Once all the data has been collected, you can sit down with the heating engineer and compare the heating system quotes with the determined values. Without the heating engineer’s expertise, it will be difficult to select the right system.
One project in which this measuring device was used involved replacing a 30-year-old gas heating system in a building dating from 1959 with three residential units. The energy consultant made the following recommendation:
- Complete replacement of the building’s insulation
- Replacement of all piping and radiators
- Installation of underfloor heating
- Construction of a pellet bunker for the recommended pellet heating system
The total cost was approximately €120,000.
Following measurements and a consultation with the heating engineer, it was decided to install a gas hybrid heating system consisting of a heat pump and a gas heater (prepared for hydrogen operation) to cover peak loads. No changes were required to the building, including the piping and insulation. The total cost was approximately €38,000.
The example shows that measuring is better than guessing.
