First, if you are not 100% comfortable (and confident of your skills) doing DIY (Do It Yourself) with this then you should call an electrician.
I Shelly Pro 3EM, and only one for the whople house. Instructions for wiring it up are with the manual and can be found online. Here is a link to it:
Note although I have 150amp service the 3EM I use only goes up to 120amps. However, as empty nesters we never get usage that high. Inoticed since my prevoud post there is a 400amp model not (but that is almost twicve the price and overkill).
How many leads come into your home power panel from outside? Mine has 3. You may have two (read through the whole conversation below).
I only use two of the three transformers that came with it. I have what they call a split-phase system (look at #2 at the end of the chat gpt conversation at the end below). I used ChatGPT to help with with setting it up, I have posted the copnversation below:
ChatGPT said:
ChatGPT
In a three-phase power system in the USA, the voltages between phases are typically 208 volts, and the voltage between any phase and neutral is 120 volts. So, for a residential private home with three-phase power:
- The voltage between any two phases (A-B, B-C, or C-A) is 208 volts.
- The voltage between any phase and neutral (A-N, B-N, or C-N) is 120 volts.
3.5
You said:
How can that be true because when I use a voltmeter, for the three cables coming into the home, A-B is 208 volts, A-C is 120 volts and B-C is 120 volts, so how are all three cables 208 volts?
ChatGPT said:
ChatGPT
I see the confusion. Let me clarify:
In a three-phase system, each phase is 120 degrees apart from the other. The voltage between any two phases is 208 volts.
So, if you measure:
- A-B: 208 volts
- A-C: 208 volts
- B-C: 208 volts
These readings are correct for a balanced three-phase system.
The 120 volts you’re measuring might be between one phase and neutral. In a three-phase system, the voltage between any phase and neutral is 120 volts. So:
- A-N: 120 volts
- B-N: 120 volts
- C-N: 120 volts
3.5
You said:
No, A-C and B-C are each 120 volts
ChatGPT said:
ChatGPT
I see the confusion now. You are describing a split-phase system, not a true three-phase system.
In a split-phase system, you have two phases that are 180 degrees apart. The voltage between these two phases is 208 volts. The third “phase” is actually a center tap on one of the phases, which gives you 120 volts to neutral.
So, in a split-phase system:
- A-B: 208 volts
- A-C: 120 volts
- B-C: 120 volts
This is a common setup in residential homes in the USA. Thank you for clarifying.
3.5
You said:
I have a Shelly pro 3EM for measuring whole-house power. It is a three phase energy meter. Can that still be used if I have split phase rather than three phase?
ChatGPT said:
ChatGPT
Yes, the Shelly Pro 3EM can still be used even if you have a split-phase system instead of a true three-phase system.
In a split-phase system, the Shelly Pro 3EM would be installed to measure the two hot lines (usually labeled L1 and L2) and the neutral line. It can still provide accurate measurements of your whole-house power consumption, even in a split-phase setup.
You would connect L1 to one phase, L2 to the other phase, and the neutral to the neutral line. This way, you can monitor the power consumption of your entire home.
3.5
You said:
So the cables coming into the house where A-B is 208 volts, A-C is 120 volts, and B-C is 120 volts - for the Shelly Pro 3EM, cable A connects to the A terminal, cable B connects to the B terminal, and then cable C connects to the N terminal (not the C terminal)?
ChatGPT said:
ChatGPT
Yes, that’s correct. In a split-phase system, you would connect:
- Cable A (phase A) to the A terminal.
- Cable B (phase B) to the B terminal.
- Cable C (neutral) to the N terminal.
This configuration allows the Shelly Pro 3EM to accurately measure the power consumption of your entire home.
3.5
You said:
So what do I connect to the C terminal on the Shelly Pro 3EM?
ChatGPT said:
ChatGPT
In a split-phase system, you only have two hot lines (phases) and one neutral line. Therefore, you would not connect anything to the C terminal on the Shelly Pro 3EM.
You will only use the A, B, and N terminals:
- Cable A (phase A) connects to the A terminal.
- Cable B (phase B) connects to the B terminal.
- Cable C (neutral) connects to the N terminal.
There is no need to connect anything to the C terminal in a split-phase setup.
3.5
You said:
What gauge wire should be used for 208 volts?
ChatGPT said:
ChatGPT
The gauge of wire you need depends on the current (amps) that will be flowing through it and the length of the wire run.
For residential applications at 208 volts, typical wire sizes might include:
- For 15 amps: You could use 14 AWG wire.
- For 20 amps: You could use 12 AWG wire.
- For 30 amps: You could use 10 AWG wire.
Always ensure to consult with local electrical codes and regulations, as well as a qualified electrician, to determine the correct wire size for your specific application.
3.5
You said:
What if it is for a meter that takes 3 watts?
ChatGPT said:
ChatGPT
For the Shelly Pro 3EM energy meter, which typically operates on low power, you would use appropriately sized wires for low-voltage, low-current applications.
Since the Shelly Pro 3EM consumes only a small amount of power, you can use a small gauge wire such as:
- For low-power applications: You could use 18 AWG wire for connecting the Shelly Pro 3EM.
Always ensure to consult with the Shelly Pro 3EM user manual and local electrical codes for specific wiring requirements.
3.5
You said:
So what do I connect to the C terminal on the Shelly Pro 3EM?
ChatGPT said:
ChatGPT
Apologies for the confusion earlier. In a split-phase system, you would typically use only the A, B, and N terminals on the Shelly Pro 3EM.
The C terminal is used for a third phase in a true three-phase system. Since you have a split-phase system, you won’t be using the C terminal.
So, in summary:
- Cable A (phase A) connects to the A terminal.
- Cable B (phase B) connects to the B terminal.
- Cable C (neutral) connects to the N terminal.
There is no need to connect anything to the C terminal in a split-phase setup.
3.5
You said:
No I am asking for a split phase system, do I need to put the split core current transformer clamps on all three cables coming into the home, or just A and B but not C (the neutral)?
ChatGPT said:
ChatGPT
Apologies for the confusion. In a split-phase system, you only need to use the split-core current transformer clamps on the two hot lines (phases A and B), not on the neutral line (phase C).
So, you would use the split-core current transformer clamps on cables A and B, not on cable C (the neutral).
To clarify:
- Split-core current transformer clamp on cable A (phase A).
- Split-core current transformer clamp on cable B (phase B).
- No split-core current transformer clamp on cable C (the neutral).
3.5
You said:
So when three phase power is coming into residential home in the USA, there would be 4 cables coming into the home and one of those cables would be the neutral, but if it was just split phase service, there would be three cables coming into the home, one being a neutral?
ChatGPT said:
ChatGPT
Yes, that’s correct.
In a three-phase system:
- You would have three hot lines (phases) labeled A, B, and C.
- Additionally, you would have one neutral line.
So, you would have a total of four cables coming into the home.
In a split-phase system:
- You would have two hot lines (phases) labeled A and B.
- Additionally, you would have one neutral line.
So, you would have a total of three cables coming into the home.
To summarize:
- Three-phase system: 4 cables (3 hot lines + 1 neutral line).
- Split-phase system: 3 cables (2 hot lines + 1 neutral line).
3.5
You said:
For the Shelly Pro 3EM settings, if I have three cables coming into the home only, whch I believe means spllt phase, should the device profile be tri-phase or monophase
ChatGPT said:
ChatGPT
If you have a split-phase system with three cables coming into the home (two hot lines and one neutral), you should select the “Monophase” setting in the Shelly Pro 3EM device profile.
Even though you have two hot lines, it’s considered a single-phase (monophase) system because the two hot lines are derived from a single-phase power distribution system.
So, to set up the Shelly Pro 3EM for your split-phase system:
- Select “Monophase” in the device profile settings.
- Connect the split-core current transformer clamps to cables A and B, and connect cable C to the N terminal.
3.5
You said:
what is the difference between splt phase and single phase?
ChatGPT said:
ChatGPT
Split-phase and single-phase are often used interchangeably, but technically, they refer to slightly different things:
- Single-phase: A single-phase system has one voltage wave, typically with one hot wire and one neutral wire. This is the most common type of residential power in North America.
- Split-phase: Split-phase is a type of single-phase power distribution using two voltage phases, which are 180 degrees apart. In a split-phase system, there are two hot wires (phases) and one neutral wire. This system is used to distribute power in residential homes in North America. The voltage between the two hot wires is 240 volts, and the voltage between each hot wire and the neutral wire is 120 volts.
I might add - also that you might want to buy a 3-inch din rail to mount your pro 3-em on the wall next to your electrical panel like I did (not required). Also, for a more robust connection, I did not use the wifi feature for the unit but instead I plug ethernet directly into it.