Parallel path's??

[GMc]

Morning,

I just ran into something today that has me scratching my head.

We have at our facility many TS-400-W switches made by The Watt Stopper that control lights in mechanical rooms and interstice area's. I went to replace one this morning and found that the ground (egc) is used to power the electronics of the switch. I set one up on the bench and found that my meter wouldn't even read the current because it was so minimal. I have never read any where in the NEC that allows the egc to be used as a return path.

Thanks for any input,

Gary

 

[GMc]

I grabbed a meter that had a lower scale. The current is .7 micro amps.

Gary

 

[480sparky]

How are they getting powered by the ground? By the manufacturer's wiring diagram, it's not being used as a neutral, as some installers like to do.

 

[GMc]

480sparky,

The switch itself is getting powered by 277v and returned through the ground. Meaning if I disconnect the ground the switch will not operate.

Gary

 

[GMc]

480sparky,

I re-read my post and I agree I didn't word it quite right but I hope now you understand what I was saying.

Thanks,

Gary

 

[ron]

You will find that most light switches that are internally illuminated when the switch is off, do the same thing.
I'm not sure of the code implications.

 

[480sparky]

Using the grounding conductor (ground) as a grounded conductor (neutral) is a violation. This installation shows why the low-voltage and control industries have tried for years to require the neutral to be present at switch locations.

The CMPs always respond that not having the neutral present at the switch is a design choice but not a hazard. What is a hazard is someone who KNOWS using the ground as a neutral is a violation, but does so anyway.

My guess is, since it's 277v lighting, it's in a commercial setting. And commercial settings are generally run in conduit. Pull the lighting circuits' neutral to the switch and use the proper wire to power the switch.

 

[GMc]

480sparky,

Pull the lighting circuits' neutral to the switch and use the proper wire to power the switch.

I won't even be able to do that. Running the neutral down to the switch I would have to land it on the green screw and I would be creating the same hazard.

I guess we would have to go to another manufacturer.

Thanks for all the responses,

Gary

 

[480sparky]

I looked at the wiring diagrams again. There is no neutral connection for the switches. I guess they are designed to use the ground. I don't understand why they don't work in you remove the ground unless they are made so if they are not grounded, they will not operate. In other words, if they cannot 'find' a ground, they will not turn on. Maybe it's designed that way for safety?

 

[GMc]

Ron,

You will find that most light switches that are internally illuminated when the switch is off, do the same thing.

Never thought of that until you mentioned it. How can UL approve such devices and then the NEC says your in violation. Hmmmm

Thanks,
Gary

 

[GMc]

I guess they are designed to use the ground. I don't understand why they don't work in you remove the ground unless they are made so if they are not grounded, they will not operate. In other words, if they cannot 'find' a ground, they will not turn on. Maybe it's designed that way for safety?

They don't work when I remove the ground because the guts of the switch need a return path to light up the display, turn the timer on and control the tiny relay inside. Safety for the manufacturer and a violation in the eyes of the NEC.

Whats one to do?

Gary

 

[cschmid]

this makes the ground a functional ground..how many water lines carry voltage is there really any difference..(devil advocate on this) :grin:

 

[ELA]

They don't work when I remove the ground because the guts of the switch need a return path to light up the display, turn the timer on and control the tiny relay inside. Safety for the manufacturer and a violation in the eyes of the NEC.

Whats one to do?

Gary

That is very interesting. As already mentioned many manufacturers require the neutral be at a switch location to power their devices.
I also do not understand how UL could list such a device that instead uses the equipment ground conductor.
If this were legal then I wonder why other manufacturers don't use the ground and instead require the neutral?

I wonder how it would survive a Hi-Pot test :smile:

 

[GMc]

ELA,

I surely don't get it. I thought that I was missing something thats why I posted it here. Now that I seen it I can't ignore it. If I call the manufacturer they will just tell me it's fine of course.

Gary

 

[ELA]

I grabbed a meter that had a lower scale. The current is .7 micro amps.

Gary

My first reaction is like yours, how can they allow current to purposely flow through the EGC?

NEC aside , on a strickly theoretical basis, is it really a problem for a device to conduct 0.7 uamps through the EGC?
It would take an awful lot of such devices (~7000) to trip at GFCI at 6ma.

That current seems very low in order to power the device but if that value is accurate then would it really ever cause a problem?

Makes me wonder if UL allows this as it is below the maximum it allows for EMI filters to leak to ground?

All EMI filters allow a constant current to flow through the EGC due to capacitances from Line and Neutral to ground. I don't remember the values exactly but I think it may be permissive to leak up to 500ua?
It would take ~700 of these devices to exceed that.

 

[crossman]

If you have one of the devices at your workbench with it wired up to work properly, but then remove the equipment ground, does the equipment ground terminal on the device have a measurable voltage to the disconnected EGC?

 

[brother]

My first reaction is like yours, how can they allow current to purposely flow through the EGC?

NEC aside , on a strickly theoretical basis, is it really a problem for a device to conduct 0.7 uamps through the EGC?
It would take an awful lot of such devices (~7000) to trip at GFCI at 6ma.

That current seems very low in order to power the device but if that value is accurate then would it really ever cause a problem?

Makes me wonder if UL allows this as it is below the maximum it allows for EMI filters to leak to ground?

All EMI filters allow a constant current to flow through the EGC due to capacitances from Line and Neutral to ground. I don't remember the values exactly but I think it may be permissive to leak up to 500ua?
It would take ~700 of these devices to exceed that.

I had this discussion before, about the manufacturers getting away with violating the NEC using the egc as a neutral, others use the 'load' as the neutral.
check out the thread

http://forums.mikeholt.com/showthread.php?t=97093

 

[charlie]

This is an interesting thread and I am surprised that someone didn't know that UL does permit this type of construction. You will find a lot (most, all?) of occupant sensors and similar devices use the equipment grounding conductor for the current return path to operate their devices.

Now the question of Code enters the minds of most of you. Consider that it is a listed device in the same manner as devices that have more load than they should have to be plugged into a 15 ampere receptacle and they are listed with a 15 ampere plug. Because the device is listed and used in a manner consistent with the manufacturer's instructions, it is fine and does not violate the NEC. The products have been tested and no danger has been found.

The question I now have, do you know of any injuries or deaths caused because of this practice?

 

[quogueelectric]

They don't work when I remove the ground because the guts of the switch need a return path to light up the display, turn the timer on and control the tiny relay inside. Safety for the manufacturer and a violation in the eyes of the NEC.

Whats one to do?

Gary

Take them all out and mail them to me they are very expensive.:smile:

 

[quogueelectric]

this makes the ground a functional ground..how many water lines carry voltage is there really any difference..(devil advocate on this) :grin:

Oh I might ask a plumber changing a water main or maybe that would be a bad idea.