Carlo Gavazzi EM24

Carlo Gavazzi · three-phase energy meter, DIN rail · EM24

what it is

A three-phase energy analyzer for DIN rail, four modules wide. Enclosure made of self-extinguishing PA66 nylon, 90 mm high, weighing about 400 g. IP50 protection on the front and IP20 at the terminals. Powered from the measured voltage — it does not need its own supply.

There is not a single port on the front panel. There is a liquid crystal display (three rows, character height 7 mm), a joystick for entering settings, a page selector knob and a red LED that flashes in proportion to the measured energy. All connections are on the top and bottom faces, under covers with sealing eyelets.

The variant decides whether it can be read remotely at all. The designation consists of segments, one of which describes inputs and outputs: E1 is Ethernet with the Modbus TCP/IP protocol, IS is digital inputs with RS485, M1 is M-bus, and XX means there is no communication at all. These are not different enclosures, only options of the same device — you cannot tell them apart by appearance.

There are also two measurement ranges: direct, up to 65 A, and via current transformers. The second has different terminal numbering.

what we read from it

Reading goes over Modbus TCP — the device has no other path: no web panel, SNMP or SSH. The meter reports almost every quantity separately for each of the three phases. On a three-phase grid this is the difference between "something is wrong with the supply" and "phase L2 is sagging".

Voltage:

• Line-to-line — L1-L2, L2-L3, L3-L1 — and line-to-neutral on each of the three phases.
• Average values separately for line-to-line and line-to-neutral voltages.
• Phase sequence, also given in words. A reversed phase sequence can damage a motor, and it is one of the few things visible only on the meter.

Current and power, on each phase separately and in total:

• Current on L1, L2 and L3.
• Active power — the one we pay for.
• Reactive power — the one that circulates between the grid and the load and burdens the installation without doing work.
• Apparent power — the geometric sum of both, used to size conductors and protection.
• Power factor on each phase and in total. A falling power factor is a sign that the installation carries current that does no useful work — and with larger loads it can be a line item on the bill.

The meter itself reports reactive power, apparent power, power factor and line-to-line voltages; the Victron controller that reads the same meter does not pass these quantities on.

Energy:

• Imported and exported energy — two separate counters, so an installation with its own generation is visible on both sides.
• Imported energy separately on each phase — shows whether the load is evenly distributed. The meter reports exported energy only as a total.

Grid frequency and a full set of link data: speed, duplex, error and drop counters, a link quality rating.

port layout

The drawing shows the front panel, because it is the only one dimensioned by the manufacturer: a large display window on the left, and on the right a subpanel with the joystick at the top and the knob below. Above and below the display run the terminal cover strips, each with a sealing eyelet.

The terminals are on the top and bottom faces, under covers, and the network port — in the variant with Ethernet — on the lower step of the enclosure on the left. The manufacturer dimensions none of them; their count and numbering follow from the wiring diagrams, their position does not.

what to watch out for

• At most 64 registers in one request. With a longer one the meter responds with an "illegal address" error, even though it is the size that is wrong, not the address.
• The model code (1648 for the EM24) is returned only by a single-register read. In a longer request the same address holds part of the L3–L1 voltage and the model comes out as "code 0".
• 32-bit numbers are stored low word first — the reverse of many other meters.
• The sign of the power factor does not indicate the direction of flow. Measured: a phase exporting energy had a positive power factor, and an importing one — negative. The sign describes the nature of the load; the direction follows only from active power.
• The per-phase energy counters do not add up to the total counter. Measured: phase sum 8457.9 kWh against 7022.6 kWh in the total counter. This is a property of the device, not a reading error.
• The serial number and firmware version are not in the known Modbus registers.
• The meter handles two readers at once — for example an energy storage controller and separate monitoring. The upper limit is not worth testing on a working installation: cutting the controller off from the meter stops storage management.

what we cannot read

• Which load draws current — the meter measures the point where it is connected, not what hangs behind it.
• Measurement history — values are instantaneous and the energy counters cumulative; the trend has to be recorded separately.

full parameter list

A full parameter list for this model is not here yet — the ones described above are those we have read and verified. A missing list does not mean the device exposes nothing more.