The people I work with are not electrical people.
I run into this struggle almost every other week on why I choose to use 24VDC. I have some arguments listed below, if anyone has anything else to add or refute, I'd love to hear them!
120VAC is lethal. The danger does not just lie in the controls enclosure, but also to any instrument, valve, or other equipment that is running 120V.
24VDC has a near-zero chance of being lethal.
120VAC requires conduit to be run to any sensors, valves, etc up meet code.
24VDC doesn't require conduit to be run to valves, sensors, etc. Cables are acceptable. (Cables may still need to be routed in a tray)
120VAC requires PPE while working on any enclosure or wiring. (anything above 50VAC)
24VDC does not require any PPE
120VAC requires shielding for any analog signals and has a greater risk of inducing voltages on incoming/outgoing signals
24VDC does not induce any voltage on analog signals.
120VAC does have some advantages.
It tends to work better in very dirty areas, since the voltage can overcome resistance created by dirt.
When there is a short, it will burn up a wire or pop a fuse, so you can find problems quicker. When 24VDC shorts, usually the power supply gets pulled ‘low’ and the supply will be damaged. You don’t always find the short/issue at the point of failure.
I run into this struggle almost every other week on why I choose to use 24VDC. I have some arguments listed below, if anyone has anything else to add or refute, I'd love to hear them!
120VAC is lethal. The danger does not just lie in the controls enclosure, but also to any instrument, valve, or other equipment that is running 120V.
24VDC has a near-zero chance of being lethal.
120VAC requires conduit to be run to any sensors, valves, etc up meet code.
24VDC doesn't require conduit to be run to valves, sensors, etc. Cables are acceptable. (Cables may still need to be routed in a tray)
120VAC requires PPE while working on any enclosure or wiring. (anything above 50VAC)
24VDC does not require any PPE
120VAC requires shielding for any analog signals and has a greater risk of inducing voltages on incoming/outgoing signals
24VDC does not induce any voltage on analog signals.
120VAC does have some advantages.
It tends to work better in very dirty areas, since the voltage can overcome resistance created by dirt.
When there is a short, it will burn up a wire or pop a fuse, so you can find problems quicker. When 24VDC shorts, usually the power supply gets pulled ‘low’ and the supply will be damaged. You don’t always find the short/issue at the point of failure.