Power cable 16AWG, NEC


#21

I feel like that is entirely non sequitur as there are probably few if any inspections inside the panel after Sense has been put in place.

I think the ask here is entirely reasonable and in the best interest of customers to avoid even the faintest of worry. It isn’t the kind of thing you want to be “good enough” until someone does something in a way that screws it up and draws attention to it.


#22

Well, I will say that the minimal cost to use 14AWG leads instead of 16AWG at product design time probably would have been justified to avoid this compliance issue. However, I still maintain that the chances of anyone having any sort of practical problem (property damage or injury) due to this conductor sizing issue are so low that it’s essentially zero risk. I have yet to see any plausible explanation for how landing a 16AWG cable on any commonly available residential MCCB would pose any sort of hazard, especially when it’s carrying tens of mA.


#23

I don’t disagree on this point.


#24

So, digging in a bit more here:

The connector used for the power input on the monitor is a Molex microfit, according to this teardown:

Looking at the terminal options, 18AWG appears to be the largest cable size that is supported by this connector family:

https://www.molex.com/molex/products/listview.jsp?query=&path=+inmeta:promotable%3Dyes+inmeta:CollectionName%3DImpulse+inmeta:category%3DCrimp%20Terminals%26requiredfields=(productseries:43030|productseries:46235)&offset=0&autoNav=0&sType=z&filter=&fs=productseries:or(43030||46235)&channel=products&key=undefined&encode=true

So likely this is the reason they’re not using a 14AWG cable assembly, for what it’s worth.


#25

Lots of added comments here:

As mentioned, installing more than one wire under a breaker terminal is generally not allowed. I have seen maybe only one manufacturer of breaker that allows more than one wire under a terminal. For those though I suspect you have to have the same size wire under both terminals (or with one gauge perhaps). While the Sense wire carries a trivial amount of current, the other wire that might be connected to that breaker may carry a considerable amount of current. I would not make the assumption that if there was a poor quality connection that the heat would cause the breaker to trip. That is likely, but nothing you should ever depend on.

I believe the only code compliant way to install a Sense today is by building your own pigtail and just wire nutting a the Sense wire to a properly sized wire to go into the breaker. While yes, if you land the Sense on a breaker directly which is not rated for that small size wire it is unlikely to ever be an issue (and this is how I have installed mine), but when it comes to inspections and NEC, the code is the code and what the breakers are UL rated for is what they are rated for. It is pretty cut and dry.

Note that the “ask” for solid core wire vs. stranded is not a big deal. I get how that might be hard with the molex connector. The actual critical “ask” is around wire gauge and electrical code.

FWIW, there is no way I would install the Sense wire and a much larger gauge wire under a breaker terminal that was not rated for two wires. That is asking for issues. You are either going to be crushing (and damaging) the Sense wire or you are not going to put enough clamping force on the larger wire to flow enough current across it (or both).

I figured the Molex connector probably had a wire size limitation. I am not sure how to deal with that other than having Sense build a wire with a butt splice in it from the factory, or select a connector that can accommodate a larger gauge wire.

This is obviously not a showstopper for most folks as clearly people are installing Sense units, but it might stop getting a UL listing or something (is Sense UL listed btw? - I did not look)


#26

On the website:

Sense, if properly installed, also meets all requirements laid out in the 2017 National Electrical Code (NEC). This means the Sense Home Energy Monitor has been through an extensive set of industry standard safety tests to ensure that it is safe to use when plugged into electrical power and safe to use inside an electrical panel. Per section 312.8, the Sense monitor and its current transformers are listed as a system, designed for field installation in a switch enclosure.

Sense also meets FCC Class B standards for electromagnetic interference. All electrical devices emit electrical “noise” (in fact, the electrical noise emitted by the devices in your house is one of the things Sense uses to identify them!) — and the FCC has a strict set of limits and requires extensive testing to make sure they are not exceeded. Sense has passed those tests and should not cause interference with other devices in your house.

Certified to CSA STD C22.2 No. 61010-1

Conforms to UL STD 61010-1

Conforms to UL STD 61010-2-032

Conforms to CAN ICES-3(B)/NMB-3(B)

Conforms to CISPR 32

Conforms to CISPR 35


#27

I Wanted mine external so here is how I installed mine, which I think fixes the issue of code compliance.