Is it better to have one control unit with more relays, or several smaller ones?

There’s no answer that fits every case: it depends on the cable routing on site, so it’s always the installer who can give the correct indication based on a site survey.

A concrete example: if the only connection required is Wi-Fi, with a maximum of 100 concurrent users and 4 access points to manage, you can choose between 2 control units with 2 relays (e.g. LK-LH-CU2) or 1 control unit with 4 relays (e.g. LK-BS-CU4). Since each reader still needs to be connected to a control unit, the question is: is it more convenient to bring the cables of the 4 readers together at a single point (4-relay control unit), or is it more practical to route them to 2 separate points (2 control units with 2 relays)?

If the cable routing makes it simpler and cheaper to split the connections across 2 points, installing 2 control units can be worthwhile even with a slightly higher hardware cost, because it reduces cable length, installation time, and system complexity. In the most extreme cases, when each access point has a completely separate cable route from the others, it can be more convenient to install 4 readers with 4 independent control units, one per access point.

For details on the available models, see Control Unit Types; for the electrical wiring, see Electrical Connection.