Elk M1G Can grounding with no outlet

[Linwood]

Retrofit install, 28" can (plus another small one) on a wall in a closet. There is NO outlet in the can, the transformers are mounted on outlets nearby.

I understand one does not ground the panel itself.

Should I ground the can? Is there any code requirement to do so (generally, in the US) with no line voltage inside? Is there any technical reason? (With the panel not grounded and not connected to the can, and no RF inside the can, it is hard to see that it matters)

Perhaps more importantly if so - how? Partly esthetics, I hate to run a wire over to the outlet and do something like run it under the face plate. I am not sure that's even legit. Was thinking of a cord, only connect the ground wire, and plug it in. Sounds safe and also not legal?

There's a small ground wire lug on the transformers, I could run plug it in, but 18g ground wire feels a bit wrong.

There's no other good ground source nearby other than the protective ground inside the outlets.

Is there a normal practice in such cases? Or do people just not bother grounding the can if there is no line voltage inside?

 

[video321]

No ground needed.

 

[ecborgoyn]

I'm NOT a grounding/bonding expert. BUT leaving the 'can' floating just sounds wrong to me. I understand that Elk does NOT want the power supply reference tied back to ground. But I don't agree with leaving the 'can' ungrounded. I worry about ESD, RFI, EMI, and just plain safety. Even though I don't intentionally put line voltage into the 'can', I can't determine what a device or wiring fault would do. It seems prudent to make sure the 'can' has a low impedance path to ground (and not via a plug/receptacle).

I'd like to hear comments from any grounding/bonding experts out there.

 

[Del91574]

Not entirely true regarding grounding.

The NEC does mandate there is supposed to be a ground in article 250. The code, however does recognize certain requirements and if the circuits are being installed as a class 2 or class 3. Generally, most systems are being installed as a class 2, mainly because of it's limited nature.

The enclosure, at minimum is supposed to be grounded and includes a nice green screw for such. The panel, however, does cover such requirements on pg. 11 regarding it's connection to EG, which supercedes the code, as the equipment is being installed I/A/W manufacturer's instructions.


Do you see many pros and those "in the know" not ground the enclosure, sure.

Your individual grounding conductor needs to be 14AWG as a minimum, and as a generalization, needs to be green or bare copper. There's specifics on how you're supposed to bond to EG, however using the center pin of a grounded outlet is an acceptable practice, however bonding directly to the building's ground is the preferred method.

 

[Linwood]

Your individual grounding conductor needs to be 14AWG as a minimum, and as a generalization, needs to be green or bare copper. There's specifics on how you're supposed to bond to EG, however using the center pin of a grounded outlet is an acceptable practice, however bonding directly to the building's ground is the preferred method.

No middle screw. :blink:

I've never liked that anyway, face plate removal (e.g. painting), might not get put back right.

From a NEC perspective can I run a ground under the face plate and connect to the screw terminal on the outlet where the actual grounding conductor is? It's esthetically unpleasing to have bare wires running across the wall, but not unusual. I would bound the two panels together then to that outlet ground I guess.

I admit it does not feel right having metal panelboards without grounding even if no line voltage inside.

 

[Del91574]

No middle screw. :blink:
I've never liked that anyway, face plate removal (e.g. painting), might not get put back right.
From a NEC perspective can I run a ground under the face plate and connect to the screw terminal on the outlet where the actual grounding conductor is? It's esthetically unpleasing to have bare wires running across the wall, but not unusual. I would bound the two panels together then to that outlet ground I guess.
I admit it does not feel right having metal panelboards without grounding even if no line voltage inside.

I thought you were referring to using an Elk 1640 transformer with 3 screw terminals that has all 3 pins for a normal recepticle, not a standard 2 blade transformer.

No, you are not allowed to extend wiring from inside the box to outside the box, as it would be possible for the conductor (albeit other things would happen first) become energized.

The best option would be to homerun a grounding conductor to where it can be properly bonded to the building's ground, typically a ground rod. There's other options, but without knowing the specific layout and runs, would open up a can of worms that should be addressed via other means.

 

[Linwood]

I'm sorry, I misunderstood you. So you are saying that while I ran 18g for the AC from the ELK 1640, if I ran 14G to the middle screw of the transformer I could use it?

Running to the building ground would be quite a challange from where I am. Not impossible, but a challange.

For right now I did something half right -- I ran it under the face plate to the screw that holds the outlet into the outlet. That might not be right, but it doesn't come off for painting, and it will do for a while until I either get more creative, or get time to pull a new ground. I'm way on the opposite side of the house from the service entry ground. And I don't trust separate grounds that aren't bonded, I've seen two ground rods 100' apart have quite a high voltage between them.

No, you are not allowed to extend wiring from inside the box to outside the box, as it would be possible for the conductor (albeit other things would happen first) become energized.

Can I do it behind the wall?

I mean, I could pull romex from the box into the can and put an outlet there. Is there a requirement that if you do so you run all conductors? I would really have thought the protective ground could leave the box to ground other equipment (though coming out the front sounded wrong).

 

[Sandpiper]

Not entirely true regarding grounding.

The NEC does mandate there is supposed to be a ground in article 250. The code, however does recognize certain requirements and if the circuits are being installed as a class 2 or class 3. Generally, most systems are being installed as a class 2, mainly because of it's limited nature.

The enclosure, at minimum is supposed to be grounded and includes a nice green screw for such. The panel, however, does cover such requirements on pg. 11 regarding it's connection to EG, which supercedes the code, as the equipment is being installed I/A/W manufacturer's instructions.


Do you see many pros and those "in the know" not ground the enclosure, sure.

Your individual grounding conductor needs to be 14AWG as a minimum, and as a generalization, needs to be green or bare copper. There's specifics on how you're supposed to bond to EG, however using the center pin of a grounded outlet is an acceptable practice, however bonding directly to the building's ground is the preferred method.

Your statements here are somewhat misleading. I agree that this is covered in Article 250 of the NEC. Please note that section 250.112 states that equipment is to be grounded except for equipment supplied by Class 1 power-limited, Class 2 and Class 3 power sources. [250.112(i)]. No equipment ground is needed.....because residential alarm systems are fed by a Class 2 transformer. Also, I see nowhere in the ELK manual that states the can must be grounded. It does specifically state (on page 11) that the control is not to be grounded.

Now if there were a 120V outlet installed in the bottom of the can, that's a different story.

 

[Del91574]

Your statements here are somewhat misleading. I agree that this is covered in Article 250 of the NEC. Please note that section 250.112 states that equipment is to be grounded except for equipment supplied by Class 1 power-limited, Class 2 and Class 3 power sources. [250.112(i)]. No equipment ground is needed.....because residential alarm systems are fed by a Class 2 transformer. Also, I see nowhere in the ELK manual that states the can must be grounded. It does specifically state (on page 11) that the control is not to be grounded.
Now if there were a 120V outlet installed in the bottom of the can, that's a different story.

Not to argue a point, but your reference is missing a key important point: NEC 2008, 250.20(A):2. If you go to the section you referenced, it states that circuits shall be grounded where system grounding is required by Part II (250.20 specifically) or Part VIII of article 250. Grounding is required in the section I noted, which is in Part II, since the transformer itself is ungrounded.


Specifically, the system itself used to be covered in 725.6 which would state that all class 1,2 and 3 circuits would need to be grounded in regards to article 250. The M1 itself would not, however, since it is stated within the manufacturer's installation manual.

In regards to the OP, I would recommend ditching the 2 blade transformers and getting a 3 prong transformer, such as a 1640 and then run appropriate single conductor grounding back to the enclosure.

 

[Sandpiper]

Not to argue a point, but your reference is missing a key important point: NEC 2008, 250.20(A):2. If you go to the section you referenced, it states that circuits shall be grounded where system grounding is required by Part II (250.20 specifically) or Part VIII of article 250. Grounding is required in the section I noted, which is in Part II, since the transformer itself is ungrounded.


Specifically, the system itself used to be covered in 725.6 which would state that all class 1,2 and 3 circuits would need to be grounded in regards to article 250. The M1 itself would not, however, since it is stated within the manufacturer's installation manual.

In regards to the OP, I would recommend ditching the 2 blade transformers and getting a 3 prong transformer, such as a 1640 and then run appropriate single conductor grounding back to the enclosure.

Not true. I didn’t mention it because it doesn’t apply in this case. 250.20(A)(2) applies to systems supplied by transformers when the transformer supply is ungrounded. The transformer supply, in this case, is a 120VAC branch circuit from the residential panel. Residential systems are grounded as I am sure you are aware.
Your argument, while paraphrasing for “clarity”, goes like this:
Equipment must be grounded (Article 250.112), except for when supplied by Class 2 transformers but not when system grounding is required (Article 250.112(I)). System grounding is required for AC system of less than 50 volts when the transformer is ungrounded (Article 250.20(A)(2).
If this is true, then why have the exception for Class 1, 2 and 3 power limited circuit in the first place? That is not what 250.20(A)(2) means. Again, it is referring to the supply circuit for the transformer being ungrounded.
I had to go to my ’96 code book to find the 725.6 reference you mentioned. Article 725.6 of the ’96 NEC merely says that class 1, 2 and 3 power limited circuits are to be grounded per Article 250. But if you look at Article 250 you find the same things we have just been talking about. Essentially there is no change from the grounding requirements for power limited circuits from the ’96 code to the 2008 code.
You obviously have a lot of experience and energy which is helpful to many of the neophytes here. But please, you don’t have to continue the baffling narrative in order to keep from saying you made a mistake and maybe you learned something today.
Residential alarm panels (and equipment enclosures) powered from Class 2 transformers are not required to be grounded!

 

[Del91574]

The code section you're ignoring says everything in it, not stating there was a point where I mispoke, as alluded to by yourself.

I'm not arguing your point regarding the section 250.20:A(2) as what you are stating is an interpretation and not what it actually says within the code. Paraphrased, what the article is stating is the system shall be grounded if the transformer supply system is ungrounded, which it is, unless you have a grounded transformer on the system. The HV feed of the branch circuit is covered elsewhere within 250. In many cases, the manufacturer's instruction and not the code modifies and relieves the requirement for a system ground, as they (Elk included) state a EG is only required for extra transient protection.

What the article is stating is the system is required to have a ground if the conditions are met, and elsewhere, like 250.112i), however most systems get further restrictions removed in 250.162:2 and 3.

250.162:2 relieves the requirement to ground the DC portion of system covered under article 725.

The code doesn't separate a commercial panel vs. residential, however a panel is a different item than an enclosure. If you disagree, I will chalk it up to how your AHJ's are looking at the NEC and enforcing such. Up here, since NFPA is written one state away, I believe we're enforced tighter than you may be. The bold statement at the end you make is not true across the board.

 

[SIMKO]

So in plain English... Do I have to run a ground to the green screw on the panel if I put an outlet in the bottom of the can. I am currently in the process of hooking up my panel (drywall cut, power stubbed into bottom of panel). If so, can I run a ground out of the outlet at the bottom of the can to the screw?

 

[Linwood]

In regards to the OP, I would recommend ditching the 2 blade transformers and getting a 3 prong transformer, such as a 1640 and then run appropriate single conductor grounding back to the enclosure.

Done. Thank you. I'll leave the "must I really" to the experts, but it seemed prudent to ground it. I tied the two cans together with 14g and then grounded it at the outlet.

One reason by the way, for people to do this is if you use a surge supression device for the phone line, e.g. the Elk device that I think comes with the M1G. You need a good ground for it to work properly. One can debate lightning and surge suppression all day, but in my professional life running data centers, practically every piece of equipment damaged by lightning has been over communication lines not power (I love fiber for that reason alone).

 

[Sandpiper]

So in plain English... Do I have to run a ground to the green screw on the panel if I put an outlet in the bottom of the can. I am currently in the process of hooking up my panel (drywall cut, power stubbed into bottom of panel). If so, can I run a ground out of the outlet at the bottom of the can to the screw?

In plain english......Yes.

The longer explanation......
If the outlet box is metallic, then it must be grounded. And since the outlet box is in contact with the panel, then the outlet box must be bonded to the panel enclosure. There are several ways it could be bonded, but the easiest sure way is to run a pigtail grounding conductor from the outlet grounding conductor to the green terminal in the panel.

If the outlet box is nonmetallic (if you can find one that can mount there), the outlet (mounting) strap will likely be in contact with the panel enclusure, so there is a strong case for saying the panel enclosure must be grounded in this case also. I believe it would be wise to ground it in either case (metallic or non-metallic outlet box) when there is an outlet at the bottom of the panel enclosure.

 

[SIMKO]

I have a Leviton 42" panel along with the surge suppressing outlet made to drop into the bottom. The metal box that came with it does not have any screw for a ground, but it is obvious that they made sure that the point were the outlet mounts to the panel was bare steel to make a good connection to the panel when installed.

I am assuming that the panel must be grounded in this case because if it isn't then the metal outlet box will not be grounded.