General duty disconnect switch

[peter d]

I didn't want to hijack this thread but you have to tell that story.

Nothing to it really other than the instructor was adamant that a GD disconnect could not be installed in a dwelling for the aforementioned reasons. But, nothing new for this guy as he had a tendency to make up code rules as he went along. He also said that die cast EMT connectors were not listed for grounding. :roll:

 

[Carultch]

It means nothing, it is just marketing. You could use it in any location.

General duty switches will usual be 250 volts or below and heavy duty safety switches 600 volts or less.

So other than the measurable ratings of the switch (voltage, current, fault current, etc), what is the difference between a general duty switch and a heavy duty switch?

What would be the essential differences between Square D's H222n & D222n disconnects, since they both have the same volts, poles, amperes and NEMA enclosure rating?

 

[Jraef]

It's a lot of little things that if you could see them in person side x side, would be obvious. Lighter gauge sheet metal, fewer bends/folds for stiffening, a little less (but still minimum) copper in the current carrying parts*, the handle is easier to bend, stuff like that. And apparently Dq D are ones who don't put the cover interlocks on any of the GD switches; if it were Siemens the 60A switch would have that.

*Sq. D (and others) uses what's called a "live hinge" type of mechanism that is basically a bar with a pin in one end that acts as the pivot point and when closed, wedges between two bars forming a slot on the other side. Current must flow though the moving parts, so the hinge parts must be kept tight with spring pressure. In the GD switch, everything about this arrangement is lighter, less tight etc. as time goes on and the switch sees more operations, that live hinge on the GD switch will loosen up and start getting hot. On the HD switch, the parts are stronger, stiffer and the springs are better. It's the difference between barely passing test requirements and exceeding them.

All that said, if it's a resi installation that will likely not see 10 operations per year, you may never notice. In other words HD would be overkill.

 

[iwire]

So other than the measurable ratings of the switch (voltage, current, fault current, etc), what is the difference between a general duty switch and a heavy duty switch?

What would be the essential differences between Square D's H222n & D222n disconnects, since they both have the same volts, poles, amperes and NEMA enclosure rating?

jaref gave a great description.

What I was getting at was as far as the code there is no difference. It becomes a design issue as jaref points out in some instances a general duty is going to have a short lifespan.

 

[kwired]

Can you guys provide some background information for those of us that are not so experienced? What are the switches you are discussing? I have no experience of this topic! What is a general duty disconnect switch? What are the seismic issues you are mentioning?

The switches under discussion are those that typically have a lever handle on the side of the enclosure to operate the switching mechanism - typically called a "safety switch". Most of the time they also contain a fuse holder though they are also made without fusing provisions. Some of us almost never see the general duty other then maybe in the 30 and 60 amp 240 volt versions, though there are higher current models in most manufacturer's catalogs.

 

[FionaZuppa]

so can a SIEMENS LNF222R disco be used in residential if you lock it? this is a tiny/small 60A 2-pole 1ph disco, but does not have a shield like the GE Model# TFN60RCP 60A blade style disco.

 

[kwired]

so can a SIEMENS LNF222R disco be used in residential if you lock it? this is a tiny/small 60A 2-pole 1ph disco, but does not have a shield like the GE Model# TFN60RCP 60A blade style disco.

Seems to me the absence of a line shield would have more impact on what you can or can't do with the door open while the line side is energized more so then whether or not the switch can be used at all, in any occupancy type.

 

[petersonra]

I think it is all about making something as cheap as possible to fill the requirement for a disconnecting means for things like HVAC units out back of one's house.

 

[FionaZuppa]

Seems to me the absence of a line shield would have more impact on what you can or can't do with the door open while the line side is energized more so then whether or not the switch can be used at all, in any occupancy type.

not a lock on the switch, a lock on the door.

I think it is all about making something as cheap as possible to fill the requirement for a disconnecting means for things like HVAC units out back of one's house.

the GE model i listed, is $4.88 retail. but this style is not "fast" compared to external lever style. lever vs covered blade for pools ??

 

[The Smashing Electrons]

General duty vs heavy duty

General duty vs heavy duty

You could get the exact definition if you purchase NEMA's document that covers this, but I think it depends heavily on how many times it is switched under load and how much load at that. There are some factories out there that use large disconnects like you and I use light switches. If your installing something that is intended to be left on or has a contactor of some sort that does all the make/break general duty would likely be fine, I you are switching heavy loads frequently then use heavy duty.

 

[iwire]

not a lock on the switch, a lock on the door.

Where is the requirement to have a lock?

 

[kwired]

not a lock on the switch, a lock on the door.


the GE model i listed, is $4.88 retail. but this style is not "fast" compared to external lever style. lever vs covered blade for pools ??

Lock on the door is pretty effective as a line shield.

What about all the cheap pull out style disconnects commonly used for air conditioning equipment? Seems the user is commonly exposed to at least some more hazards with those then with a safety switch. Plug the pullout in when there is a short circuit vs. closing a safety switch with door closed into same fault condition and tell us which one more likely leaves you needing to change your pants

 

[FionaZuppa]

Where is the requirement to have a lock?

it was mentioned that the disco's w/o shields are no-go for residential. but if you can lock the door then is having no shield such an issue?

 

[iwire]

it was mentioned that the disco's w/o shields are no-go for residential. but if you can lock the door then is having no shield such an issue?

It was mentioned that during a code update class the instructor, who was also inspector made the claim it was a code violation to use a general duty safety switch at a dwelling unit because it does not have a cover interlock.

I did not agree with him then or now.

 

[templdl]

It was mentioned that during a code update class the instructor, who was also inspector made the claim it was a code violation to use a general duty safety switch at a dwelling unit because it does not have a cover interlock.

I did not agree with him then or now.

Is it an NEC violation or
Local code requirement? Is not a general duty safety switch is UL listed?

 

[kwired]

The safety switches with a door interlock usually still have a bypass to allow opening the cover, it just takes a little bit better idiot to figure out how to use it:happyyes:

 

[iwire]

Is it an NEC violation or
Local code requirement? Is not a general duty safety switch is UL listed?

If I recall he cited NEC 110.27(A)(2)

 

[Jraef]

If I recall he cited NEC 110.27(A)(2)

Kind of an extreme viewpoint of what it is saying if you ask me, so I see why you treated it as almost a joke.

110.27 starts out:

"... shall be guarded against accidental contact by approved
enclosures or by any of the following means: ..."

Enclosed safety switch UL listed = "approved enclosure". No need to read further. And I think the "screens" they are referring to in A2 are referring to things like FENCES, not shields WITHIN an approved enclosure.

But again, you know that, hence the chuckle.

 

[templdl]

Kind of an extreme viewpoint of what it is saying if you ask me, so I see why you treated it as almost a joke.

110.27 starts out:


Enclosed safety switch UL listed = "approved enclosure". No need to read further. And I think the "screens" they are referring to in A2 are referring to things like FENCES, not shields WITHIN an approved enclosure.

But again, you know that, hence the chuckle.
View attachment 15529

That's my point. These screens may be referring to barriers of something e type to prevent contacting live parts with the for open. This may be options available from the manufacturer.