Making use of Belgium's digital electricity meters with my-PV

How did you come to my-PV?

“It's very simple: We came across my-PV on Google. There are different brands, but my-PV's AC•THOR was the only brand compatible with the P1 interface of the digital meters S211 or T211-D. That's an exclusion criterion for us here in Belgium because of the regulations regarding digital electricity meters,” John Michale concludes.

Obstacles/specialities during the installation

The customer from Belgium carried out the installation by himself. The only obstacle was that the boiler had intelligent control for the input of the heating element. This had to be removed to avoid conflict with the AC•THOR's linear power control; Safety temperature limiter (STL) also had to be in place as a protection. This way, the AC•THOR can regulate the output of the heating element directly and use excess photovoltaic power for hot water preparation.

“The setup was easy and very straightforward. Another important point was the cable from the digital meter to the AC•THOR. It had to be a twisted pair and shielded 'RJ-12' cable. I found one with 4 cable pairs that had very thin wires due to the fact that the AC•THOR’s RTU gateway has small terminals that were difficult to insert into the AC•THOR connector,” the Belgian reports.

It is also important to mention that the P1 port of the digital meter must be activated at the respective energy supplier, in this case it was at "ENGIE". Otherwise, the P1 port remains disabled by default and there is no communication and therefore no surplus power detection.

Brief explanation of the system – what should be mentioned?

“In 2021 we installed photovoltaic modules with 7.9 kWp and a home battery with 8.5 kWh. Shortly thereafter, the energy supplier installed a digital meter that does not run in reverse when surplus power is injected into the power grid. With the surplus electricity during the summer months, we wanted to do more and consume more of it by ourselves. Then it occurred to us that the central heating needs gas to heat the water, while we feed a lot of surplus electricity into the public grid, especially during the summer,” John Michale says, explaining the considerations. "We wanted to save this gas and use the electricity from the photovoltaic system on the roof to heat the hot water in the future."

In order to reduce the amount of electricity fed into the grid, the owner decided to use the surplus PV electricity to heat the water. There are many systems that can do this, so finding a suitable solution was not easy.

The customer wanted a system which would be compatible with the grid operator’s meter. So he found my-PV's AC•THOR, which uses a P1 interface to connect between the P1 port of the T211-D digital meter and the AC•THOR's RTU gateway. The PV power diverter ‘AC•THOR’ uses every excess watt linearly for hot water preparation in the 200 liter boiler. This works even though a battery storage is also installed in the house – there is enough surplus electricity available during the summer months.

The entire system consists of two boilers connected in series. The 150 liter boiler is the central tank that is supplied with 200 liters of hot water, which is mainly heated by surplus PV power in the summer months. From the largest boiler of 200 liter, heated to +/- 70°C by the AC•THOR, the water is piped to the other 150 liter boiler, set at 55°C by the central heating, so there is always hot water at a temperature of at least 55 °C available.

Due to the battery storage, the system works great between April and October. In the months with less sun, the hot water has to be heated conventionally due to the battery storage and the settings made there, since there is not enough photovoltaic surplus for the battery and hot water preparation.

Is hot water backup with mains power used?

In the 4-person household, only surplus photovoltaic power is used for hot water preparation, i.e. without activated hot water backup, which my-PV offers. So far there has always been enough hot water in the tank.

Any cost changes/ROI?

The AC•THOR has only been installed since March 2022 – where gas prices have increased drastically. The saving is therefore calculated as follows: A saving of about 15-20 kWh, which corresponds to 1 m³ of gas and 10 kWh of electricity, with 1.5-2 kWh used to heat the water. This saves around €150 on the gas bill in summer. The boiler costs €1,000 and the AC•THOR also €1,000.

"I think that it will amortize in 2-3 years", the Belgian customer concludes satisfied.