Illuminated E-Stop wiring

[f16bmathis]

I'm sure I know the answer, but...

Can you wire an illuminated E-Stop 120 VAC so the power to the E-Stop when removed (button pushed) from the E-stop circuit, will then power the LED illuminated E-Stop light?

I only have the two wires coming to the E-Stop, though I could run the power to the LED then to the conduit ground, but that sounds unsafe also.

I think I need to run a third wire to do this correctly.

Thanks!

 

[JesperMP]

I think I need to run a third wire to do this correctly.

Yeah. No other way about it.

edit:

I only have the two wires coming to the E-Stop

Just have to comment, that you can then have only 1 channel in the E-stop button, and the safety can only be at a low category.

 

[OdinIII]

I could run the power to the LED then to the conduit ground, but that sounds unsafe also.

and a 4th wire for the neutral/negative side of the light assuming the two existing wires go to the E-Stop.

The E-Stop wiring needs to be completely independent from any indicator lighting.

 

[dogleg43]

With all due respect, if you are asking this question then you have no business designing or wiring this circuit.

 

[Plastic]

Agreed

With all due respect, if you are asking this question then you have no business designing or wiring this circuit.

An old-school, single channel e-stop may actually satisfy the application... If a proper risk assessment, and safety performance level (PL) identified.

BUT, the use of Ground for return path of circuit is a sure method to create a possible lethal hazard to persons. An automation engineer does not make you a licensed electrician.

PLC In/Out at 24vdc limited to 240watts typically won't hurt anyone.

120vac often does injure and kill.

Don't want to come off as harsh, actually the opposite, I care deeply about families being able to never incur a loss of a loved one due to an electrical installation made in short-judgement or non-qualified choices, and inspection by AHJ.

Best Regards

Plastic

 

[jraef]

It may be hard to find now, but there used to be a type of pilot indicator device that used a neon bulb and you can wire them so that the neon bulb is going around the switch (parallel) and connected to the load. When the switch is closed, that is the least resistance circuit so the lamp is off. When the switch is opened, a small amount of power flows through the neon lamp to the load, making the neon glow, but the neon lamp acts like a current limiting resistor (or has one in series) so that only enough energy flows to excite the neon. That is a way of having an indicator without having a neutral wire.

Mind you this was very very old school and was not something you would use on anything that was an electronic circuit, because SOME energy is getting through that neon lamp, so it might be enough to trigger a solid state device on the other side, and you don't want that on an E-Stop. But if your load is a relay coil or something like that, it can work.

 

[simpleman]

Old machine with a 120 v e-circuit yes, if you can add a NO contact ( will close when button is pushed ) to feed the light & YES you will need a neutral wire. ( pull a system ground while you're at it, we never should rely on the conduit anymore ) Should you do it - probably NOT unless you follow OdinIII's advice.
Newer machine then OdinIII is right on the money. Sadly whenever we change the safety circuits we also seem to own the future liability for that change. Weather or not your change caused the issue, you will still have to hire your own lawyers to defend your changes.

 

[JasonTheSparky]

Old machine with a 120 v e-circuit yes, if you can add a NO contact ( will close when button is pushed ) to feed the light & YES you will need a neutral wire. ( pull a system ground while you're at it, we never should rely on the conduit anymore ).

+1

PSA:You should NEVER use any conduit, enclosure or frame of equipment for a return path to a circuit, regardless of the voltage. Should anyone ever come in contact with it, it has the potential to make them a part of the circuit, which then can cause injury or even death. At the end of the day we all want to go home in the same (or better) condition in which we walked in the door. Depending on your location (I can only speak to Michigan electrical codes and practices) you sometimes see your conduit used as your grounding conductor (no ground wire inside the conduit). Here in MI, MEC (Michigan Electrical Code, adapted from NEC) used to allow it (for certain installations), then they didn't, last I checked they allowed it again. It's not a practice I follow. Always pull a separate grounding conductor!

Using an additional N.O. contact block on your switch will accomplish what you are looking for.

. Sadly whenever we change the safety circuits we also seem to own the future liability for that change. Weather or not your change caused the issue, you will still have to hire your own lawyers to defend your changes.

Also +1

One lesson I learned working for an electrical contractor years ago: Once you touch it, you own it. It had better be safe and work correctly when you are done.