emonTx V4, emonVS in North America

brandock · 2024-03-18T17:18:43.520Z

The firmware for the emonPi2 uses the EmonLibDB library. It looks to be almost identical to the emonTx4 firmware.

There are two flavors of firmware available for both emonPi2 and emonTx4 – single phase and 3-phase.

In the single phase versions we have the number of voltage inputs hard-coded to 1.

#define NUM_V_CHANNELS 1                                   // SET TO 1 FOR SINGLE PHASE

In the 3-phase version of the firmware for each board, the number of voltage channels is hard-coded to 3.

All the above (1- and 3-phase) have the same code block for setting up the relationship between the power-monitoring channels and the voltage inputs.

  #if NUM_V_CHANNELS == 3
    
    EmonLibDB_set_pInput(1, 1); // Phase 1
    EmonLibDB_set_pInput(2, 1); // Phase 2
    EmonLibDB_set_pInput(3, 1); // Phase 3
    EmonLibDB_set_pInput(4, 1); // Phase 1
    EmonLibDB_set_pInput(5, 1); // Phase 2
    EmonLibDB_set_pInput(6, 1); // Phase 3
    /*
    EmonLibDB_set_pInput(1, 1, 2);               // CT1 between V1 & V2    
    EmonLibDB_set_pInput(2, 2, 3);               // CT2 between V2 & V3  (etc)
    EmonLibDB_set_pInput(3, 3, 1);  
    EmonLibDB_set_pInput(4, 1, 2);  
    EmonLibDB_set_pInput(5, 2, 3);
    EmonLibDB_set_pInput(6, 3, 1);
    */
  #else
    for (byte ch=0; ch<NUM_I_CHANNELS; ch++) {
      EmonLibDB_set_pInput(ch+1, 1);
    }
  #endif

My thought is that an experienced/technically-inclined user in the US could use an emonVS 3-phase, installed as discussed above, and modify the firmware to use 2 voltage inputs, and change the channel setup code to something that matched their setup, such as

  #if NUM_V_CHANNELS == 2  //one channel for each leg of split-phase US voltage
    
    EmonLibDB_set_pInput(1, 1); // Leg 1 -- modify these to match the leg used by the monitored circuit
    EmonLibDB_set_pInput(2, 2); // Leg 2
    EmonLibDB_set_pInput(3, 2); // Leg 2
    EmonLibDB_set_pInput(4, 1); // Leg 1
    EmonLibDB_set_pInput(5, 1); // Leg 1
    EmonLibDB_set_pInput(6, 1); // Leg 1
    /*

That said, all the recommendations for US users I have seen in the forum and in the docs seem to suggest the single-channel emonVS. This makes sense for the non-technical user for sure, I think. For those that take this route, they only need to connect the device to one leg. It strikes me that they could use the NEMA 15-5 cable mentioned above and plug it into a standard household near the breaker panel.

In the later setup, I would think that some error would be introduced by the fact that voltage can actually vary between the legs. There is also the fact that the phase angle is 180° different than between the legs, but a motivated non-technical user could compensate using the Phase Correction tool in the configuration utility.

Am I on the right track with these two paths? (Technical path: 3-phase tools stepped down to 2-channel, split-phase configuration. Non-technical path: 1-phase tools with phase correction and some loss of accuracy due to voltage difference between the legs.)

Robert.Wall · 2024-03-18T17:46:54.760Z

brandock:

My thought is that an experienced/technically-inclined user in the US could use an emonVS 3-phase, installed as discussed above, and modify the firmware to use 2 voltage inputs, and change the channel setup code to something that matched their setup,

This is exactly the intention and why the library calls are provided the way they are. There’s no fundamental difference between a single phase UK setup, a split-phase N.American setup and a 3-phase UK or elsewhere setup, as far as the emonLibDB library is concerned, they’re handled most of the time as one, two or three single-phase channels. With a 3-phase emonVs and two or three phases, you can specify the line-line voltage rather than the (implied) line-neutral voltage.
So to the library (I had no control over the sketches that have been uploaded or appear on Github) all you suggest is catered for.

However, I would suggest adding a 180° phase “error” is a bad idea, far better to use a negative amplitude calibration or point the c.t. in the other direction.

I suggest you download and look at the emonLibDB documentation published on this forum.

EmonLibDB - Version 1.0.2 emonTx

EmonLibDB is a Continuous Monitoring library specifically for the EmonTx4 energy monitor. It is able to monitor continuously 3 voltage channels and 12 current/power/energy channels, three pulse inputs (or two pulse inputs and one low voltage analogue input). It has has not been possible to include temperature measurement. Like emonLibCM, emonLibDB will always give an accurate measurement of the average over the reporting period of the voltage, and for each current/power channel the current, r…

rupert · 2024-03-18T18:01:43.839Z

Apart from the firmware, the emonTx4 replacement (an emonPi2 without the Pi) and the original emonTx4 both use a 433MHz band radio to communicate with the emonPi2 or emonBase.

Wikipedia says that the 433.05 - 454.79MHz ISM band is legal in ITU Region 1 i.e. mostly Europe & Africa. The Americas (ITU Region 2) use 902 MHz-928 MHz.
Wikipedia says that the 433.05 MHz - 434.79 MHz ISM band is legal in ITU Region 1 i.e. mostly Europe & Africa. The Americas (ITU Region 2) use 902 MHz-928 MHz.
[Corrected by post no.59 below]
Hence the 915MHz versions of the RFM69.

This might be worth considering?

brandock · 2024-03-19T01:03:36.213Z

My advice for US users would be to use the 433MHz radio that is currently offered by the OEM shop.

I’ve always used the 433MHz radios in my US installation. I started in 2015 with an emonTx, an RFM69Pi board on a Pi, and three emonTH sensors. I’ve since added on a second emonTx and several homegrown boards with 433MHz radios. I’ve had no issues. I asked a radio expert I know and he told me HopeRF, the maker of RFM69 transceivers, has an FCC part 15 grant for the 433MHz band. https://fccid.io/2ASEORFM380F32

The OEM shop doesn’t currently seem to offer the emonPi2 with the 868-915MHz option. If you have never tried to desolder one of these transceivers from a board let me tell you - it gets ugly. Felix Russo from LowPowerLab once described to me how he does so with a pair of chisel tips and a Metcal power supply that together cost more than a couple emonPis.

If someone did want the 868MHz option on an emonPi, I’d recommend checking with the OEM folks to see if they could make one that way or provide one without a transceiver. Felix Russo’s shop sells the transceivers and he has some online tutorials about soldering them in place, which is relatively easy. Transceivers

brandock · 2024-03-20T03:06:52.431Z

I’d like to recap this thread, including the timeline of what happened between April 2023, when I started the thread, and now (March 2024) as I look at all the new things that have been released in that span. This is to make sure I understand where we now sit.

Nov 2022

emonTx v4 (emonTx4) becomes available in the OEM Shop along with emonVS PSU single-phase. The 3-phase version is available as a hidden option in the Shop. There is not yet firmware that supports 3-phase monitoring. emonLib and emonLibCM are available, both of which are designed for one voltage input channel.

AVR-DB: emonTx V4, new hardware in progress - Hardware - OpenEnergyMonitor Community

April 2023

I started this thread and we envisioned two types of North American users of the new emonTx4+emonVS. The non-technical user could use the single-phase emonVS with NEMA 5-15P cable and a single-phase firmware available for emonTx4. The technical user interested in monitoring both legs of their split-phase power did not yet have an option, but they soon would.

May 2023

3-Phase Support came to OEM courtesy of Robert Wall’s emonLibDB.

EmonTx4 3-phase support with emonLibDB - Hardware / emonTx - OpenEnergyMonitor Community

The technical user could now use the 3-phase emonVS (or a 2-phase through special request?) mounted inside their breaker panel and an emonTx4 with 3-phase firmware configured for split-phase US power and the specific circuits monitored.

But this was only the case for a few months, because the emonTx4 was soon supplanted.

Dec 2023

The emonPi2 was released and the emonTx4 was discontinued. The next generation of emonTx will be based on this board but is not yet available per se as I write this.

https://community.openenergymonitor.org/t/emonvs-questions/

Non-technical users would continue to use the single-phase emonVS with NEMA 5-15P cable but would use the emonPi2 with single-phase firmware instead of an emonTx4.

Technical users would continue to use the 3-phase emonVS (or perhaps a 2-phase emonVS through special request) mounted in their breaker panel, and would now use the emonPi2 with 3-phase firmware configured for split-phase US power and the circuits being monitored.

These are high-level outlines, of course. There are various flavors of the plan for each type of user, as we’ve discussed above. My intent is to summarize what devices would be used with what firmware and high-level configuration. Again, my hope is to make sure I understand where we now sit.

rupert · 2024-03-30T16:22:13.234Z

To correct my previous post:

Wikipedia says that the 433.05 MHz - 434.79 MHz ISM band is legal in ITU Region 1 i.e. mostly Europe & Africa. The Americas (ITU Region 2) use 902 MHz-928 MHz.

Sorry for the typo!

Robert.Wall · 2024-03-31T00:51:23.004Z

brandock:

If you have never tried to desolder one of these transceivers from a board let me tell you - it gets ugly.

My advice has always been - don’t try. I have considered getting a piece of copper busbar or equivalent, about 6 mm thick and bending it into a ‘U’ shape with the legs just wide enough to span the RFM, and the same length as the RFM, and attaching an insulated handle - to make a soldering iron capable of reaching and melting all 14 joints at the same time. It would need heating with a gas blowtorch or similar, and even then, I think it would be very tricky to pull off without damaging something.

brandock · 2024-06-06T15:25:36.764Z

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.

Robert.Wall · 2024-06-06T16:18:02.280Z

A 4-pole connector was mentioned earlier in this thread.

brandock · 2024-06-06T17:40:13.053Z

Robert.Wall:

A 4-pole connector was mentioned earlier in this thread.

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.

Bill.Thomson · 2024-06-06T18:05:18.949Z

brandock:

run a length of Romex (residential branch wiring) from a 2-pole breaker, out of the electric panel, and into the emonVs,

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.

Bill.Thomson · 2024-06-06T18:07:39.233Z

brandock:

run the Romex directly to my emonVs without the bulky intervening receptacle, plug, and cable

You will need some sort of enclosure. It can be as simple as a junction box or as elaborate as you wish.

brandock:

I have to have the receptacle, so be it.

AFAIK, it can be hardwired. i.e. no receptacle needed.

Robert.Wall · 2024-06-06T18:39:32.715Z

Bill.Thomson:

AFAIK, it can be hardwired.

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.

brandock · 2024-06-06T18:46:37.343Z

Bill.Thomson:

You will need some sort of enclosure. It can be as simple as a junction box or as elaborate as you wish.

Could the conduit (for example Liquid Tight) connect directing to the emonVs enclosure by replacing the M20 cable gland ( Cable glands for emonVs-PSU - Hardware - OpenEnergyMonitor Community) with a conduit fitting? (Something like this: Liquid Tight Conduit Straight Fittings (flexiblepvc.net).)

Bill.Thomson · 2024-06-07T05:06:12.336Z

Robert.Wall:

In the UK, the emonVS can be permanently connected

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.)

Bill.Thomson · 2024-06-07T05:15:31.587Z

brandock:

Could the conduit (for example Liquid Tight) connect directing (sic) to the emonVs enclosure by replacing the M20 cable gland

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)

Robert.Wall · 2024-06-07T10:46:25.456Z

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.

Bill.Thomson · 2024-06-08T02:59:58.497Z

Robert.Wall:

Fuses?

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.

image1126×443 220 KB

The WattsOn wiring is shown below. Note the use of a dead-front fuse block.

image1093×826 108 KB

Elkor Technologies is a Canadian company.
The WattNode is made by Continental Control Systems, a US company.

brandock · 2024-06-10T16:33:11.745Z

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

Bill.Thomson · 2024-06-11T00:13:33.296Z

brandock:

Something like this: WattNode Meter Enclosure Brochure (ctlsys.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:

Continental Control Systems, LLC

WattNode Meter Enclosure - Buy - Continental Control Systems, LLC

The WattNode Meter Enclosure is a UL 508A Listed, NEMA 4 rated, steel or polycarbonate enclosure for a single meter. It saves installation time and cost for installations where an enclosure is required. The meter enclosure price does not...

Est. reading time: 1 minute

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.