Phase coupler

Is it appropriate to install phase couplers in electrical panels?


Yes, you can certainly compliantly install a phase coupler device in a panel as long as the gutter fill does not exceed 40% (which doesn’t seem to be the case) and as long as the overcurrent device is appropriate (which it seems to be). You can install many things compliantly in the gutter space of a panel. The objection to a doorbell transformer is the low voltage wire inside the box without a barrier.

I guess my general feeling is that I wouldn’t do it this way, but I’d be hard pressed to tell you why this is either non-compliant or unsafe. Just ugly. Some companies make phase couplers that mount on a 4-square and some that just plug in a receptacle. I’d go that route if it was me.


Thanks Marc.

2008 NEC - 312.8 Enclosures for Switches or Overcurrent Devices.
Enclosures for switches or overcurrent devices shall not be used as junction boxes, auxiliary gutters, or raceways for conductors feeding through or tapping off to other switches or overcurrent devices, unless adequate space for this purpose is provided. The conductors shall not fill the wiring space at any cross section to more than 40 percent of the cross-sectional area of the space, and the conductors, splices, and taps shall not fill the wiring space at any cross section to more than 75 percent of the cross-sectional area of that space.
Most enclosures are intended to accommodate only those conductors connected to terminals for switches or overcurrent devices within the enclosures themselves. Where adequate space is provided for additional conductors, such as control circuits, the total conductor fill in the enclosure may not exceed 40 percent of the cross section of the wiring space in the enclosure and no more than 75 percent if splices or taps are necessary.

I disagree, and I can do the math to prove it.

AGAIN NO! :twisted: :twisted: :twisted: :roll: :roll: :roll: :mrgreen: :mrgreen: :mrgreen: :wink: :wink: :wink:

110.3(B) Installation and Use. Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling.

Find me any panel instruction that prohibits items like a heating contactor or a phase coupler in the gutter space. Plainly put, there isn’t one, thus no 110.3(B) violation. They might not have intended for these items to be there, but they sure are not prohibited. They don’t even come close to approaching the gutter fill limitation. I don’t mind saying that this is a stupid installation, I wouldn’t do it this way, but it’s not prohibited. The second line of that PPC instruction says “or equivalent enclosure”. All they want is for it to be in a box of some kind, which it is.

Where is a device like this used? i.e. what can it be used for?

It’s for some of the home automation stuff that “communicates” between devices with a radio type signal over the wiring. The phase coupler just bridges those communication signals from one hot wire to the other to make sure the whole home is covered. It could really be installed anywhere in the home that both hot legs are present.

From the instructions for this product:

The PPC-1 is designed to install in a suitable junction box and wire to two phases (circuits) of the circuit breaker panel.

Here is the real quote from the instructions with the “or equivalent enclosure” text:

Cabinet. An enclosure that is designed for either surface mounting or flush mounting and is provided with a frame, mat, or trim in which a swinging door or doors are or can be hung.

Enclosure. The case or housing of apparatus, or the fence or walls surrounding an installation to prevent personnel from accidentally contacting energized parts or to protect the equipment from physical damage.

FPN: See Table 110.20 for examples of enclosure types.

Panelboard. A single panel or group of panel units designed for assembly in the form of a single panel, including buses and automatic overcurrent devices, and equipped with or without switches for the control of light, heat, or power circuits; designed to be placed in a cabinet or cutout box placed in or against a wall, partition, or other support; and accessible only from the front.

A panelboard cabinet is still an enclosure. It’s just a specific type of enclosure.

If I was called to put in a phase coupler, I’d put it in a seperate box. If the homeowner was to ask me why I didn’t just stick it in the panel cabinet, I’d lie and tell them it was a code violation just to get them off my back, since it seems totally believable. I still maintain, however, that this phase coupler as pictured is a legal install. Dumb, but legal.

Hmmmmmm a battle of the giants. Don’t get many of these. Normally it’s just an exchange of self-congratulatory statements on these threads.

This will keep the viewing figures up!

Again, no. This time I have an email message from this company supporting my previous reply.

Doesn’t matter what they say in an email. All you can go by is the documentation.

I’d bet my bottom dollar that the manufacturer never intended for these phase couplers to be mounted in the panel, and I’ll bet they don’t even like it one bit. Their documentation, as written, does not prohibit this installation.

I received permission from the company to post the first message as follows:

"Joe -

The product is not installed to the National Electrical standards. It should be mounted in a Junction box out side of the Main breaker panel with the connections made in that box and then wired into the Main panel.

I have attached the installation manual for your records.

Will it work. the answer is yes. PCS builds these items with a plastic enclosure because we know what the installers do in the field.

Who installed this item for you?

[FONT=RotisSemiSans][FONT=‘Myriad Pro’]Regards,[/FONT]
[FONT=RotisSemiSans] [/FONT]
[FONT=‘Myriad Pro’]Scott Klodowski[/FONT]
[FONT=‘Myriad Pro’]Director of Sales & Marketing[/FONT]
[FONT=‘Myriad Pro’]Powerline Control Systems, Inc.[/FONT]

[FONT=‘Myriad Pro’]P: 818.701.9831 ext. 105[/FONT]
[FONT=‘Myriad Pro’]F: 818.701.1506[/FONT]
[FONT=‘Myriad Pro’]C: 562.506.7046[/FONT]


[FONT=RotisSemiSans]This e-mail and any attachment are intended for the above named recipient(s) only and may contain confidential or privileged information. If you are not an intended recipient, please notify the sender and delete the message. Failure to maintain the confidentiality of this e-mail and any attachment may subject you to penalties under applicable law."[/FONT]

I would stand behind this and avoid the embarrassment in a court of law!


What they said in the email is exactly what I fully expected they’d say. The fact remains that this installation is not expressly prohibited by the manufacturer’s instructions, and the NEC does not prohibit things other than the actual panelboard to be mounted in a panelbaord cabinet as long as long as the gutter fill is not exceeded. Unusual installations always strike people as “wrong”, and this one is unusual. I would call it wrong from the standpoint that I wouldn’t do it, but still not illegal or non-compliant. The panelboard cabinet is still an enclosure. Remember, it’s only residential “loadcenters” that package all three pieces in one convenient package for installation. The panelboard (the guts), the cabinet, and the cover are three distinct pieces. They are ordered seperately for commercial work. It’s only resi panels that come all put together. You could just as easily use a panelboard cabinet (no guts inside) as a cutout box (junction box with hinged cover) if you wanted to. If you happen to have a also have the panelboard itself mounted in a panelboard cabinet, that’s no reason to prohibit other devices in the panelboard cabinet. The NEC certainly gives no reason, save for max gutter fill.

I still say: dumb, but legal.

I think the better thing to do would be to educate the manufacturer to the fact that a panelboard cabinet is still an “enclosure” in the truest sense of the word so that they might reword their documentation to reflect what they intend.

After looking at some Eaton panels at the NC Electrical Institute today I looked up this on their web site. Can someone tell me what that is in the bottom of that panel?

Click here


Looks like it might be surge protection.