I found some older threads discussing this dating back to 2014 (one even to 05), but is it still legal for solenoids to share negative/ ground wires? For example, one manifold we are looking at contains a spot for each individual solenoid to plug in, then one common wire to come off, 4 positives, and one common negative. Would this setup be legal as long as the wire gauge of the one single wire is enough to handle the load rating of 4 solenoids?
The main question here is “why and how would you want to”? The PCM provides connections for positive and negative, so the incentive seems minimal; probably legal, but why? If you’re planning to use a bunch of small relays taking advantage of the #1 superscript in the third-to-last row of R37, then sure, why not?
We were looking at purchasing some manifold mount solenoids from Automation Direct. The manifold that goes along with it has plugs for each solenoid to plug into, directing the wires into one cable, which contains 4 positives and one common negative. It isn’t something we designed or even really want to do, but we just want to know if using a setup like this is legal. This approach we are looking at seems to be more affordable for a manifold setup than the SMC products available from Vex. We were just going to do double wire ferule mounts for the negative and connect all those from the solenoid together on the PDP side.
As I read R37, controlling multiple soleniod valves from through relays is perfectly acceptable, but controlling them through the PCM this interface requires that one solenoid valve be controlled through one pair of outputs. This could easily be construed to prohibit wiring multiple solenoid valves through a manifold, but I consider it likely (far from certain) that if you combine all of the appropriate ground wires together to feed to the manifold’s ground, you’ll pass inspection. To be a more certain, I heartily recommend bypassing the electrical portion of the manifold and wiring each valve directly to a port pair on the PCM.