# Power Supply Sizing and Distribution

The Voldeno Bus carries 24 V DC on the same connector as the CAN-FD signal pair. This page covers how much supply an installation needs, how to distribute it so voltage drop stays under control, and how to confirm the result once the panel is live.

# What the 24 V rail powers

The bus rail powers module electronics only. Field loads never draw from it:

Circuit	Supply
Module electronics, relay coils, sensor front ends	24 V DC from the bus
Lights, heating, blinds, sockets	Own supply, through the L/N group terminals on the I/O and RELAY modules
Push buttons and dry contacts	The 24V sensing terminals on the I/O input banks

The 24V terminals on the I/O input banks are a reference for input sensing. Do not power field devices from them.

# Sizing the supply

Take the current draw of each module from its datasheet and add them up. Two things to allow for beyond the idle figure:

• Relay coils. Size for the worst case, where every output on the bus is energized at the same time, not for the typical case.
• Headroom for expansion. Modules get added to installations; a supply chosen with no margin has to be replaced when they are.

If the total exceeds what a single supply can deliver, use several. Connect their grounds together so all modules share one reference; without a common GND the CAN-FD differential pair has no stable common mode and communication becomes unreliable.

# Distribute one feed per cabinet row

Do not daisy-chain 24 V and GND across the entire bus. Every module in the chain adds its current to the conductor upstream of it, so the last module in a long chain sees the accumulated voltage drop of everything before it.

Instead:

1. Run a dedicated 24 V DC feed, positive and GND return, from the supply or from a fused distribution block to the first module of each cabinet row.
2. Connect that feed to the Input (left) positions of the 24V and GND pairs on that module.
3. Daisy-chain 24 V and GND only within the row: Output (right) of module N to Input (left) of module N+1.
4. At the last module of the row, leave the 24V and GND Output positions disconnected, capped or insulated.

Repeat for every row. Each row then carries only its own current, which is what keeps the drop small.

The CAN-FD pair is wired differently: BUS+ and BUS− daisy-chain continuously along the whole installation as one linear chain. Only the power is split per row. See Bus topology and wiring.

# Conductors

Parameter	Value
Recommended conductor	0.5 mm² (20 AWG) copper
Terminal range	0.2 … 0.75 mm² (24 … 18 AWG), single wire
Stripping length	9 … 10 mm
Connector	WAGO 235-454/331-000, push-in

Going below 0.5 mm² on the 24 V distribution buys nothing: the terminals accept the larger size, and the drop scales directly with conductor resistance.

# Verify the voltage that arrives

The 300 m bus length limit is a signal integrity limit for the CAN-FD pair. The length of the power run is limited by something else entirely: voltage drop. That means it has to be measured, not calculated once and trusted.

Read the module terminal voltage in Voldeno Studio, or measure at the connector with a multimeter, at the last module of each row and under worst-case load, with every relay on that row energized. If the reading at the far end sags, the fix is a shorter run, a larger conductor, or an additional feed point, in that order of preference.

Repeat the check after adding modules to an existing installation. A row that was comfortable with four modules is not necessarily comfortable with eight.

# Common mistakes

• One supply daisy-chained across every row of the panel, so the far end browns out under load.
• Multiple supplies with grounds left unbonded, producing intermittent bus errors that look like a wiring fault.
• Field devices powered from the I/O input-bank 24V sensing terminals.
• Voltage checked at the supply rather than at the terminals of the farthest module.