This is a work-in-progress page for a monitoring system being developed by Megni, a small company who are developing energy monitoring systems http://megni.co.uk/

Read below for explanation, CLICK HERE TO VIEW LIVE DATA

This particular logging is on a 5kW Mitsubishi Ecodan air source unit background-heating large radiators in a large old building. No DHW.

The monitoring system collects the following live data:

• Electrical input pulses from a standard kWh meter with modified (increased) pulse rate
• Flow temperature at heat pump
• Return temperature at heat pump
• Water flow through heat pump
• frequency of compressor

There is also a 2.8kW electric heater fitted immediately up-stream of the heat pump. This is used periodically for calibration of the logging system. It uses all the same sensors as the heat pump does.

From the above, an Embed microprocessor is used to calculate the heat output and COP. This is sent to : http://power.openenergymonitor.org/emoncms/pages/heatpump.php

How to view the live data

By default, you will probably see the COP and ambient temperature, however, you should change the viewed graphs by checking/ un-checking in the boxes.

Try this:

Un-check the COP (top left), and check : Flow temperature, Return temperature, Air-off temperature. (ambient is already ticked)
Note 'air-off' means chilled air out from the heat pump.

You can now see the working temperatures of the air-on(ambient) and air-off (air-in and air-out) and also the water in and out. This gives a feel for what its doing. Click on the HOUR button to see the last hours results -Is the unit running or stopped? - have a play.

Now either open a new window (keep the one you have already set up), or modify the one you are already playing with.

Try looking at the electrical power input, and the heat output. The COP is the ratio of these two.

Try looking at the kWh/day electicity and kWh/day heat over a month. Add the ambient temperature.

You can also look at the compressor speed. 100% relates to maximum speed.

Important notes :
1) Real time COP readout has its issues: - the power reading is instant, but temperature readings have a delay. As the compressor modulates (changes frequency) the COP deviates considerably. This explains the saw-tooth appearance of the graph. When the compressor stops, the COP could approach infinity for an instant. However, the average reading is accurate. Furthermore, COP goes negative when there is a defrost. Total kWh heat divided by total electricity is used for average COP readings over a period.
2) Occasionally this system may be used for experiments; i.e. simulating winter by covering the heat pump etc.
3) This particular installation is only for back-ground heating. This is why the COP is high. Wood stoves are used most evenings, and a gas boiler is used when ambient temperatures are particularly low.
4) The all time average COP is high, in part, since it omits a winter period, but also because of the gas boiler use in mid winter.

Accuracy and calibration

It is always very important to know how accurate your equipment is. The flow meter used is a Grundfoss VFS sensor. This is a low-cost device. It there fore requires calibration. I have been carrying this our regularly. The use of the electric heater for calibrationr is very important since we know that electric heaters have a COP of 1.

The following is a snap-shot of the live data is from a calibration taken at about 6:30pm in 11th November 2011. There are periods of no heat for testing the sensors, and a period where the electric resistance heater is switched on.

After the calibration, showing the heat pump running again. (sorry, line colours not consistent with graph above)