Best Control Voltage for a 30' Run

[fifty60]

I need to run 30' of wire between an HMI/PLC and a piece of lab equipment. My immediate options are 24VDC and 115VAC. This is well within the capabilities of 24VDC right? The only current through the wires will be enough to activate the coils on relays located inside of the equipment.

I like the 24VDC because its source will be a Class 2 power supply located within the equipment. Is there anything else to consider?

 

[Jraef]

Class 2 implies that your total relay load is fairly low, ie under 100W worst case, so I would agree with you.

 

[petersonra]

I don't think it makes any real difference other than if it is a class 2 circuit the wiring options might be a little more appealing.

 

[dereckbc]

My two cents worth. If it were me using 24 volts I would check on voltage drop @ 24 vdc. 30 feet-one-way (60 loop feet) could be problematic depending on the current. Use a gauge of wire that results in 3% or less voltage drop. Assuming 4 amps (100 watt load) at 30 feet 3% max will require a minimum 14 AWG copper.