MR-1 Spindle uses 10-30, N connected to ground inside machine

I was looking at how to wire up my spindle outlet. I thought it was an odd choice to use a 10-30 given this is a ungrounded split phase plug. Opened the the machine, and the neutral wire from this 10-30 is connected to ground, which creates an unintentional N-G bond, will mess with GFCI’s etc.

I bet we have a mix of people using a 10-30 as if the N is a ground pin (most folks), 10-30 wired correctly with N-N (these folks are at risk of N-G problems), and some folks leaving the N open.

Some conflicting info from langmuir as well in this thread (2nd hand) “I was speaking with Langmuir tech support and they did say it should be wired hot, hot, neutral.” Spindle wiring help - #8 by MichaelBarker

That makes it sound as if the machine is expecting a correctly wired 10-30 outlet, but when you open the machine, you can see very clearly the N pin on the 10-30 is wired to ground.

My money is on the 10-30 should have been a 6-30.

I cut off the stock spindle plug and installed a new 6-50p plug, so that I can use the same receptacle as my welder.

In my case both ground and neutral terminate on the same bus bar, so there shouldn’t be any difference. The third prong on my 6-50 spindle plug is nominally a ground, but I ran it using shielded wire in the conduit anyway just in case I ever want to change the receptacle type. And it ends up in the same place in tht panel.

Ground and neutral should not terminate on the same busbar, except for in your main service panel, and only in that one location for the whole electrical service.

There is also a reason for running a dedicated ground on grounded plugs, and not just rely on the shield or metal conduit to be the ground - and that is to carry fault current. If you rely on a shield/conduit to be your ground circuit, and there is a ground fault which fuses a weak connection in your conduit or shield, then a metal enclosure can become live - and this is a shock hazard.

I have a thread going with Langmuir and will update when they respond - I’m pretty sure this spindle is supposed to be connected to ground, and not neutral.

Yes, that circuit goes to the main panel and therefore terminates on the same bar.

I’m not using the conduit as ground. I’m using a wire in conduit, which happens to be shielded, as ground. 6-50 has a dedicated ground wire, as does the spindle.

Response from Langmuir:

“” After some conversation with the design team, here’s what they’ve told me.

“So the final answer to his original question is that yes, the spindle, for best practice, should be wired to a 240 V, single phase, grounded outlet. You can pretty safely use a NEMA 10-30 outlet or the voltage converter from our website, but replacing the cord with a NEMA 6-50 or other single phase grounded outlets with sufficient current is the most correct by NEC standards.”

I’m sure this will be an important topic in our next design review meeting so we might be making a design revision in the future. “”

So based on this I (this is coming from me, not Langmuir) would encourage everyone to wire this in to a single phase grounded outlet such as a NEMA 6 series or similar, and if your machine happens to be installed near a pre-existing 10-30 outlet, do not use it because you will be connecting neutral where the machine is expecting ground, and this could cause electrical gremlins, at best.

@dyno Here I was feeling like a cowboy for cutting up my spindle wiring. Feels good to be validated! :rofl: