A contactor follows two windows. There are five
The wiring that served for thirty years was designed for a grid with two states. The Walloon grid has five.
Updated on 14 September 2026
What the contactor does, and where it stops
A day/night contactor is a switch under command. It closes a circuit when the network signal says reduced rate and opens it when it says full rate. Two states, one module, a few tens of euros of hardware.
As long as a hot water cylinder is the only thing to shift, that is the right answer and we will propose nothing else. Laying a bus to control a single appliance is an expense nothing pays back.
It stops in two places. When several appliances have to be arbitrated against each other, and when the grid has more than two levels: the Impact tariff has three, and a switch does not know the difference between MEDIUM and PEAK.
Three levels of control, from simplest to most complete
- Day/night contactor
- One appliance, two states, driven by the network signal. The cylinder, and nothing else.
- Programmable time switch
- One or two circuits on fixed hours, independent of the signal. This is the answer when the meter does not relay the daytime off-peak window.
- KNX bus
- Every circuit becomes addressable, the rules change without touching the wiring, and a single logic arbitrates cylinder, charge point, heating and solar output.
KNX is justified by the number of circuits, not by home automation
The question is not whether you want to control your house from a phone. It is how many appliances have to share a limited supply capacity, against a grid with three prices.
At two appliances, a contactor and a time switch manage. At five, with a car, a heat pump, a cylinder and an output that varies hour by hour, fixed rules start to contradict each other and something has to arbitrate.
That arbitration is the product. The app on the phone comes with it, and it is not the reason for the purchase.
How we go about it
We start by surveying the existing board and its circuits. Plenty of houses already have a separate circuit for the cylinder without knowing it, and then half the work is done.
Then we price the lowest level that answers the need, and price the next one beside it with the difference between the two. It is for the client to decide whether to buy that difference, not for us to assume it on their behalf.
Tell us what is in your consumer unit
Describe what sits on your board and we will say what can be shifted and what cannot. By phone on +32 495 88 75 92 or through the questionnaire.
Sources for this page
- CWaPE, press pack, new low-voltage distribution tariffs for 2026Checked on 2026-09-14
- Public Service of Wallonia, the two-rate schedule changes on 1 January 2026Checked on 2026-09-14