Here is the latest entry to the recap given above in March, which provided a timeline of what happened between April 2023, when I started the thread, and March 2024.
June 2024
emonTx5 was introduced to the OEM Shop. A new “N. American split-phase” option for the EmonVs was introduced to both the emonTx5 and the emonPi2 ordering options. This option provides the components for the “technical user” configuration discussed above: an emonVs with 2 input channels and firmware for monitoring both legs of North American split-phase power. Here is the announcement topic. emonTx5 transmitter node & emonPi2 (12 CT expansion) available in the shop - Hardware - OpenEnergyMonitor Community
In that announcement topic @Bill.Thomson pointed out that we still may not have solved the question of what a safe, up-to-code installation will look like for this split-phase monitoring.
The National Electrical Code (NEC 725.136A) specifically excludes any low voltage wiring from being installed in an electric panel, raceway, or box used for high voltage (120/240V) circuits.
Low voltage in this context, means less than 50 Volts.
I suggested in that topic the shop could offer a “non-technical” configuration like the one we discussed in this topic, and @TrystanLea said he would discuss it with @Gwil.
I would like to further discuss here the safe, code-compliant installation of a split-phase-monitoring emonVs.
My next thought would be to run a length of Romex (residential branch wiring) from a 2-pole breaker, out of the electric panel, and into the emonVs, so that the emonVs would be outside the electric panel but have each input connected to a leg inside the panel.
That would be an option if a user has an unused 4-pole receptacle near the electrical panel already.
The majority of users will not. Those receptacles will be in the garage (EVSE), behind the dryer, behind the oven, and so on, and typically they will already be in use.
One could be installed by a technical user (AKA “electrician”). The receptacle part costs about $13 US, and the plug with cable at least $32 US. I would personally prefer to have my electrician run the Romex directly to my emonVs without the bulky intervening receptacle, plug, and cable. But if the experts on US code (looking at you @Bill.Thomson) tell me I have to have the receptacle, so be it.
That’ll work as long as it’s in a conduit.
(this is where something like flexible PVC - often sold under the name “liquid tight” - works really well. (much easier to install compared to metallic conduit)
It doesn’t even have to be Romex. As we’re speaking of running the wiring in conduit, individual wires are OK and cost quite a bit less than Romex.
In the UK, the emonVS can be permanently connected - either the single-phase or the 3-phase version, but will of course need a 2-pole or 4-pole isolator and appropriate over-current protection in the form of a single-pole or 3-pole linked mcb, and connected following normal wiring practice.
I should’ve mentioned the fact I was speaking of a US installation.
That said, It’ll need overcurrent protection (can be a circuit breaker or fuses) and although not required, it’s never a bad idea to use some form of disconnect device. (US term for isolator.)
It should work OK. Although the fit would be a little “sloppy.” The thread diameter of the gland you linked to is 20 mm and the threads of a 3/4 inch gland should measure ~19.1 mm
(a difference of about 0.035 inches)
Fuses? That surprises me, because the fuse on one leg could operate, leaving the other leg live and the emonVs would still be live to one leg. In the UK, fuses would not be acceptable for that reason – a linked circuit breaker would be required.
Double pole fusing was normal in the UK in the dim and distant past, and was made illegal for exactly the same reason - the neutral fuse could operate while still leaving the apparatus live though the line fuse and thus potentially dangerous.
As an example, both the WattsOn and WattNode specify circuit breakers or fuses as OCP for their mains inputs.
I did give some incorrect info about the need for a disconnect device. (I forgot about the rules regarding permanently connected equipment.)
The use of a disconnect is required when a device is considered permanently connected. i.e. hardwired. That’s mentioned in the CCS WattNode manual excerpt shown below.
Thanks, Bill. I contacted Continental Control Systems, described the use case (and provided a link to this topic) and asked if they could recommend a package for North American users that would include an enclosure and circuit breakers. Something like this: WattNode Meter Enclosure Brochure (ctlsys.com)
In the meantime, as I was searching, I noticed that Sense suggests users can install their unit inside the electrical panel. My search found many images of people having done so. Are they non-compliant? Installation – Sense.com
It’s a nice enclosure, but they’re mighty proud of that bad boy.
As it’s a UL 508 listed assembly, from what I’ve read, the NEC does not apply.
However, there are rules specific to 508 type devices.
Ref:
The cost for that item alone will more than likely be a showstopper for most users.
WRT the Sense device being installed inside of a load center…
There must be something in the NEC that allows them to do that with a device that
uses a radio link vice a wired connection. (the NEC is a large document)
As a retail company, they have too much to lose if it wasn’t legit to install their
device in a load center.
I have had a chance to try out some of the suggestions above regarding how to install the emonVS beside North American service panels.
First, here is the New/Non-Technical User that might want to use a NEMA 5-15P cable for simplicity, despite the error introduced by monitoring only one leg.
Next, some options we’ve discussed for the Experienced/Technically-Inclined User. Here is Romex 14-3 with pigtails running into the emonVS. This option cost me about $70US at a local hardware store, with most of the cost being the Romex. The convenience is not needing conduit, as I understand it.
We discussed that the emonVS itself might need to be in an enclosure. Here is a Stahlin enclosure and some pictures of the way the Romex would be enter the service panel and the enclosure through NM clamp (here 3/8" clamps are shown, which use a 1/2" knockout). This enclosure costs about $123US.
Next here is THHN wire with conduit. This option cost about $15US at a local hardware store, with most of the cost being the conduit. The first photo shows that the emonVS knockout could probably be widened to accommodate the conduit (this is 1/2" Cantex in the photo). If the emonVS enclosure was considered sufficient with conduit, it could potentially work.
Finally, here is an image showing how the conduit would run to the Stahlin enclosure, be secured by the locking nut, and the THHN wire could then be run directly into the emonVS within the enclosure, or to pigtails, depending on the stiffness of the THHN wire.
This is where national standards and practice diverge. In the UK, those thimbles on twisted wires (IMG_5005) are a definite no-no, a screw connector, a crimp or a lever connector (e.g. https://www.screwfix.com/p/wago-221-413-32a-3-way-lever-connectors-50-pack/2803r) would be OK, but it would be normal to replace the supplied cable gland with one to suit the cable being used and make the terminations directly into the screw connector on the p.c.b. You’d also need a label on the outside of the emonVs, stating “WARNING Isolate elsewhere before removing this cover” or words to that effect, and it could, but wouldn’t need to, go in another bigger enclosure.
You obviously could not use a fixed conduit because of the location of the fixing screws for the case of the emonVs (and I would say not acceptable because it would prevent inspection and maintenance of the emonVs), but flexible conduit would be acceptable.
I like the function of the emonVs. The function is well thought out, particularly because it can be used with many devices.
I mounted just outside the panel (load center) see similar thread 21 Jul 25 Yes, it will be a challenge to inspect and maintain.
Connecting the AC to the emonVs is awkward for North America. For example, please note " … form the wires to minimize the stress on the connector" I would propose a cover redesign. The top cover could be two parts, basically splitting it to be able to expose the connector on one part and the main part much the same.
The main part would have 3rd and 4th screws.
The connector cover is more of a challenge. I’m thinking the 12.5mm hole extending to the edge will a filler coming up? Two parts, one permanently attached to the base with the hole in this part? or the main part? The other part is just a hatch to access the connector?
Definitely center the hole on the connector, putting two mounting tangs in the corners.
I have no idea how to incorporate a strain relief, but this should be done.
Or, just forget the box completely and mount into a 3-gang box.
