same main panel labels 120/208 3 phase 4 wire wye also 120/240 3 phase 4 wire delta

[Designer101]

3 SolarEdge single phase inverter 11.4 kw is used to make three phase connection

SOME questions I am confused
I thought the wiring diagram shows 120/240 3 phase 4 wire delta( high leg) in the main panel

our guys at the site says they didn't measure any unusual voltage ( L- N to be 208 VOLTS)
they Said they measure
208 208 208 and 120 120 120
but I designed it to be 240 240 240 and 120 120 208 thinking high leg and skipping high leg

so this means the connection at main panel depends on what's coming from transformer ?? it has nothing to do in the main panel side and main panel as such can be configured to any configuration 120/208 3 phase 4 wire wye or 120/240 3 phase 4 wire delta??

also next question
Looking at the pictures of main panel
there are two pole breaker at the bottom panel this Means those two pole breaker will read 208 volts when measure between two phases if connected as 120/208 3 phase 4 wire wye??


Please look pictures attached.

 

[Carultch]

The way I read this nameplate, is that the equipment is built to be used for any of the above grid types that are labeled on it, and they have special instructions for what to do if you have a high leg system. It indicates that the equipment is rated for either 120/208V wye, 120/240V high leg delta, or 240V straight delta (either ungrounded or corner-grounded). In other words, as long as the voltage is AC and 240V or less, you are good to go.

If I were a manufacturer, there is no reason I would ever make special equipment for 208V, when I would also be making otherwise-identical equipment for 240V. I would standardize, because there is no significant advantage to making your equipment with slightly less insulation, slightly less space between components, and slightly less arc quenching, for the 208V application. You are better off standardizing, and this is exactly what Square D/Eaton/Siemens/GE all do. They use the same family of equipment for 208V as 240V, and therefore, the fact that 240V is labeled on the equipment will not necessarily indicate that your grid type has 240V.

Obviously, you couldn't have all grid types simultaneously in the same device. In this case, your description tells me that it is a standard 120/208V wye system, that is 120V to neutral and 208V between phases.

The current rules require the high leg to be identified with orange, and I don't see an orange wire in your system. This is another clue that it is a 120/208V wye system, instead of a 240V high leg system. Of course, checking voltages is something you indeed should do, just to confirm that this is the case, since a previous installer may have not known about the requirement, or built it before it was a requirement.

 

[ggunn]

Of course, checking voltages is something you indeed should do...

This. Always.

I have encountered mislabeled panels and incorrect conductor color coding many times, including one site where the service was changed by the utility at the transformer from 208/120V to 240 delta high leg but the color taping of the customer end of the service conductors and the labeling of the MDP were never changed. I once encountered a school where they used all 480/277V equipment in the electrical room for the 208/120V service; that one got me and it was an expensive and embarrassing error. In fairness (to me) it was one of 10 schools in the project; all the rest had 480/277V services and all their MDPs including this one looked alike.

ALWAYS verify the voltage at the point of interconnection with a meter at the site survey. It takes seconds to do, and the later you discover an error the more of a PITA it will be to correct it.

 

[Carultch]

also next question
Looking at the pictures of main panel
there are two pole breaker at the bottom panel this Means those two pole breaker will read 208 volts when measure between two phases if connected as 120/208 3 phase 4 wire wye??

I realize I didn't address this question.

Two pole loads on this grid, means you have single phase or multiwire branch circuits that are 208V line-to-line, and are each 120V line-to-ground. If you draw this visually, it looks like a triangle with two legs that are 12 cm long, a 120 degree angle between them, and the remaining side being 20.8 cm long. The two 120V waveforms are a third of a cycle apart, and if you play with the sine functions that define the waveforms, you can show that this means the the difference between two phase-shifted waveforms of equal amplitudes will have an amplitude that is 173% the amplitude of the original two waveforms, since sqrt(3) is about 173%.

Current doesn't simply add when you combine single phase inverters across pairs of phases of a 3-phase grid. There is a square root formula from vector math for combining phase-to-phase currents, to get the total current per line conductor, which is Ia = sqrt(Iab^2 + Ica^2 + Iab*Iac), and equivalent formulas for other phases. Three identical inverters would have sqrt(3) times the nominal current of each one, among all 3 phases. Every group of 3 identical inverters forms a balanced 3-phase power source on this grid, when they are connected to staggered pairs of phases of the system (AB, BC, and CA). My term for this setup is triplexing.

For the Solaredge 11.4H-US inverters, they are built to have a rating of 11.4 kW on a 240V split-phase grid. However, since the current can't be increased, the power reduces when you connect it to a 208V grid instead. This means it acts as a 10kW inverter on this grid. Cut the voltage to 83% while keeping the current constant, and you also cut the power to 83%.

Back when transformers were in single phase inverters, you could adjust the taps on the transformer, and correspondingly increase the current to maintain the same nominal power, to adapt to both 208V and 240V grids. Some inverters allowed you to adapt to 277V grids, and triplex inverters line-to-neutral for 277/480V grids. Now that we have transformerless inverters, what happens instead, is that you just adjust the voltage while current is constant. You adjust the setpoints on the internal relay, that turns off the inverter when the grid voltage is too far from nominal.

 

[Designer101]

This. Always.

I have encountered mislabeled panels and incorrect conductor color coding many times, including one site where the service was changed by the utility at the transformer from 208/120V to 240 delta high leg but the color taping of the customer end of the service conductors and the labeling of the MDP were never changed. I once encountered a school where they used all 480/277V equipment in the electrical room for the 208/120V service; that one got me and it was an expensive and embarrassing error. In fairness (to me) it was one of 10 schools in the project; all the rest had 480/277V services and all their MDPs including this one looked alike.

ALWAYS verify the voltage at the point of interconnection with a meter at the site survey. It takes seconds to do, and the later you discover an error the more of a PITA it will be to correct it.

well we encountered so many High leg system here, thats not color coded, so i assumed it be be another high leg,
this time I as wrong.