Choosing the correct multiconductor wire size

Question

I have multiple solenoid valves I want to supply control power via a multi conductor cable. Each valve draws .8 amps at 120v. I could use 22awg size wire in my cable for the wires operating each valve. My question is about the common wire. Since that wire is common to all the valves will I have to size my wire based on the current running through that wire? Am I correct in thinking that if all four solenoids were active at once then the common wire would be carrying a load of ~4 amps? (4 sol x .8 amps each) so the common wire would need to be sized at 18awg? This sounds like such a novice question I know. Any help would be appreciated!

Robert Peter Oakes · Accepted Answer

As far as your basic question, you are correct 4 relays consuming just under an amp each with a common return will result in 4 Amps flowing in the return wire when all are on so it must be sized to handle that load. what also needs consideration is the distance between the control point and the relay, if too far then you may need bigger gauge wire to compensate for losses in the wire You need to ensure you have protection across the load as well to protect back emf from blowing the control circuits, these may already be in the relays or the controller but make sure they exist, if not then add them (This is sometimes called a snubber network). If the Solenoids are DC then a Diode across the solenoid will work but I assume you're using AC due to being a common mains voltage, and in this case the snubber will be across the switch