Power meters and cutouts

This page documents some examples of analogue power meters, formerly used (and still in service to this day in some countries) to measure the electricity consumption of an installation, as well a supplier's cutouts: fuses or breakers intended to protect the supply wires going into a building.

Types of meters

European-style meters - common in most 230V countries - are mounted to the wall (or a specific type of plastic box) with screws; one is on the top and slots into an indent on the housing of the device, while two other screws are used to secure it in place and prevent it from moving around. The wire connections are under a cover, sealed by the electricity company.

On the other hand, North American-style power meters are installed using special types of sockets, which enable for easy replacement of the meter. These may also be combined with breaker panels.

1980s ENEL power meter

This is a common type of analogue power meter, used in Italy before they were replaced entirely by smart meters. It was manufactured by Costruttori Associati Meridionali for ENEL, the former nationalised electricity company in Italy.

The front of the device shows its various specifications: the platter spins at 600 revolutions per kWh, it's meant for a 230V single-phase supply and has a maximum current rating of 40A (more than enough for a typical Italian supply). There's also a logo indicating the presence of an anti-tamper mechanism: if the meter is connected to spin in reverse, a special gear will automatically stop the platter from spinning.

Italian 125V meter

This old meter was made by Officine Galileo and is quite interesting as it was designed for 125V supplies, which were common for lighting and small devices back in the day. 125V were on a different (and cheaper) tariff, and the lower voltage was used to prevent people from using it for appliances.

Its intended use also helps explain the low current rating (and high revolutions per kWh) of the meter. The voltage rating of 125V is derived from the then-common three-phase 127/220V transformers. Other voltages were also in use, but starting from the 50s-60s these were standardised into 125V, 220V and 380V.

Support for power meters

As mentioned previously, European meters are often mounted on a special plastic junction box. This is an example of one of them, bought at a hardware store in Germany. It's a very simple item, with slots for three screws that can be adjusted to be positioned as required. A hole is present for the connection wires, as on continental European meters these are fed from the back of the meter (in the UK, instead, they're fed from the bottom) and thus hidden from sight.

ENEL limiter breaker

This is an old Italian supply limiter breaker. While they look similar to other types of breakers used in Italy back in the day, limiter breakers were specifically meant to limit the maximum power allowed for an installation. This is because in Italy you pay different rates depending on the maximum power specified in your contract - going above the limit for more than a few seconds will cause the breaker to trip and shut off your power.

While nowadays this is all done inside the meter, with an electronically-controlled breaker, in the era of analogue meters this function was accomplished using a separate breaker placed next to the meter.

Schneider supplier's breaker

This is a supplier's breaker, made by the French company Schneider Electric. It's a single-phase model, though three-phase versions also exist, and it was built relatively recently, as there's a 2012 date code stamped on the plastic case.

Aside from the two covers for the terminals, there's a third one on the front which can be used to adjust the trip current of the breaker, from 10 to 32A. This is done by placing a screw at different points along a metal strip. The current rating that's been set is visible from the front using a small transparent window.

Breakers like this one are very common on French electrical installations (unlike Italy they aren't integrated into power meters). However, the ones typically used there also have a low-sensitivity RCD, required due to the TT earthing system used in France. This model, instead, doesn't have an RCD of any sort - and that's made very clear in the front label - as it was found in Slovenia, which tends to use the TN-C-S earthing system.