DPDT to switch Hot and Neutral in motor application

[andy s.]

This one threw me for a loop. I actually seen an application where the hot and neutral conductors are separated by a DPST toggle switch to a motor and additional receptacle on a vacuum cleaning device. Albeit, this application may be exposed to damp locations, I was nonetheless stunned to see this.

Can anyone shed some light on this?

If this is wrong, please advise, for this methodology seems to have gone on for quite some time.

Let me know what's wrong with this picture....should I go back to school again after a few decades in the arena?

 

[infinity]

I have seen this too on fan power boxes that have a factory wired DPST switch with tails for the connection of the ungrounded and grounded conductors. This is permitted by the exception in 404.2(B) if the switch disconnects both the ungrounded and grounded conductors simultaneously.

 

[George Stolz]

Andy, I just replied to your PM, I didn't see this thread.

I'm sure everyone would be curious as to why someone preferred to switch the neutral as well as the hots, I can't envision a scenario where this is beneficial. Can you elaborate as to some of the details, and how you came into the picture, and all that?

We all love stories.

 

[andy s.]

Sorry for the SNAFU It is a DPST!

I was hired on to do some work for Company @#%@(&^.

They are in the business of manufacturing vacuum cleaners, and other floor care devices. Because of my dual discipline (Electrical and Mechanical) I thought I'd give these bloaks a shot. Much to my surprise, as I was evaluating a piece of equipment, I noticed the DPST toggle switch. The line cord, DPST, motor and an additional receptacle which is used for wand applications paralleled.

16/3 line cord-----DPST===motor and receptacle in parallel.

ROTFLMAO when I saw that the line had the hot and neutral attached to the DPST switch. From the switch, the motor and receptacle are attached, thus breaking both the hot and the neutral. Fortunately the ground is attached to the housing.

My quandry is, in event of this device being accidentally wetted, (wet/dry vac) would this provide a greater potential for shock hazard, not to mention if this was on a GFCI circuit, how would this come to be if the GFCI senses the difference in potential. And how would this be applicable to AFCI. I tried it on AFCI while slowly trying to toggle (very slowly) and my results were rather odd. Sometimes it would trip and sometimes not.

Come on folks! What's your input. IMHO, I feel that this may be a good sticking point for a change. I like to keep the neutrals tied together.

Their response was, since the plug was not polarized, and the motor being universal, that's the way they do things, because of the nature of the beast, these guys (the consumer) loves pulling that ground off and the potential of flipping the plug, (maybe saving it for a brass collection? Who knows). Period!

 

[iwire]

I can't envision a scenario where this is beneficial.

Check out 2005 514.11(A).

It has to due with circuits supplying gasoline dispensing equipment.

That section requires the grounded conductor to be broken with the ungrounded conductors.

 

[iwire]

ROTFLMAO when I saw that the line had the hot and neutral attached to the DPST switch. From the switch, the motor and receptacle are attached, thus breaking both the hot and the neutral.

No need to laugh there is nothing wrong with that and if they sell that unit in a country that does not use a grounded conductor it will be fine there as well.

First lets start by call the conductors by the proper names.

What you called 'Hot' is the ungrounded conductor.

What you called 'Neutral' (It's not) is the grounded conductor.

And what you called 'ground' is the grounding conductor.

Fortunately the ground is attached to the housing.

That is all that really matters.

My quandry is, in event of this device being accidentally wetted, (wet/dry vac) would this provide a greater potential for shock hazard,

No.

As long as the ungrounded conductor is switched with the grounded conductor there is no problem at all.

not to mention if this was on a GFCI circuit, how would this come to be if the GFCI senses the difference in potential.

The GFCI will work fine, all the GFCI senses is the amount of current on the two circuit conductors, if the current is different by more than 6 or 8 ma the GFCI will operate.

And how would this be applicable to AFCI.

The AFCI will not 'know' the difference either.

I tried it on AFCI while slowly trying to toggle (very slowly) and my results were rather odd. Sometimes it would trip and sometimes not.

Try the same test with the neutral spliced through solid and I bet you get the same random results.

Come on folks! What's your input. IMHO, I feel that this may be a good sticking point for a change. I like to keep the neutrals tied together.

I don't see any need for a change, there is no safety issue as long as both circuit conductors are switched together.

Their response was, since the plug was not polarized, and the motor being universal, that's the way they do things, because of the nature of the beast, these guys (the consumer) loves pulling that ground off and the potential of flipping the plug,

Well that does happen and by switching both conductors they guarantee that the neutral will not be switched separately if the cord is supplied reverse polarity.

So if that is the reason they did it I say good thinking on their part.

 

[andy s.]

Thank you all for shedding light on this. Looks like I have to get back into the books again. It just struck me odd in the application, but after wrangling with this all night long, I guess it makes sense.

Thanks again.

Andy

 

[al hildenbrand]

but after wrangling with this all night long, I guess it makes sense.

This is an extraordinary place for that "wrangling".

Having a community to converse with improves the more solitary work in the field!