Identifying strings

[DEfusion]

Hi there,

I have an East/West install with 5 panels on the East side and 14 panels on the West and I was told they were installed as 3 strings.

I was looking at Energy Stats app and seeing that had an option to show breakdown by strings, however it was only showing 2 as having power, even went the sun is overhead and hitting both sides of the roof.

So I hit the API myself to make sure it's not the app and that does look to be the case:

Code: Select all

/op/v0/device/real/query

{
  errno: 0,
  msg: 'success',
  result: [
    {
      datas: [
        {
          unit: 'kW',
          name: 'PVPower',
          variable: 'pvPower',
          value: 4.273
        },
        {
          unit: 'kW',
          name: 'PV1Power',
          variable: 'pv1Power',
          value: 0
        },
        {
          unit: 'kW',
          name: 'PV2Power',
          variable: 'pv2Power',
          value: 2.166
        },
        {
          unit: 'kW',
          name: 'PV3Power',
          variable: 'pv3Power',
          value: 2.107
        },
        {
          unit: 'kW',
          name: 'PV4Power',
          variable: 'pv4Power',
          value: 0
        }
      ],
      time: '2024-08-30 16:32:14 BST+0100',
      deviceSN: '************'
    }
  ]
}

I requested these variables via the API and the above is all it sent back:

Code: Select all

"variables": ["pvPower", "pv1Power", "pv2Power", "pv3Power", "pv4Power", "pv5Power", "pv6Power", "pv7Power", "pv8Power", "pv9Power", "pv10Power", "pv11Power", "pv12Power", "pv13Power", "pv14Power", "pv15Power", "pv16Power", "pv17Power", "pv18Power"]

So to me it looks like only 2 strings have been set up, which doesn't seem right unless they put the East panels on a string with some of the West -- which doesn't seem a good idea. Is there any way to actually confirm that by looking at the inverter or something?

[Dave Foster]

That api response is showing strings 2 & 3 being used (i’m assuming you must have a KH inverter)

Can you check your PV voltages, typically depending on your panels during the day you’ll get 33V per panel so if you are seeing 460 volts (ish) you have 14 panels on one string.

[DEfusion]

Thanks for your reply. Do the volts depend on the generation? Right now it's very cloudy so I'm only getting ~1kw generation. Here are the responses for the PV volts:

Code: Select all

 {
          unit: 'kW',
          name: 'PVPower',
          variable: 'pvPower',
          value: 0.996
        },
        {
          unit: 'kW',
          name: 'PV1Power',
          variable: 'pv1Power',
          value: 0
        },
        {
          unit: 'kW',
          name: 'PV2Power',
          variable: 'pv2Power',
          value: 0.502
        },
        {
          unit: 'kW',
          name: 'PV3Power',
          variable: 'pv3Power',
          value: 0.494
        },
        {
          unit: 'kW',
          name: 'PV4Power',
          variable: 'pv4Power',
          value: 0
        },
        { unit: 'V', name: 'PV1Volt', variable: 'pv1Volt', value: 0.8 },
        {
          unit: 'V',
          name: 'PV2Volt',
          variable: 'pv2Volt',
          value: 227.2
        },
        {
          unit: 'V',
          name: 'PV3Volt',
          variable: 'pv3Volt',
          value: 227.4
        },
        { unit: 'V', name: 'PV4Volt', variable: 'pv4Volt', value: 0 }
 

[DEfusion]

I guess if it's always 33v then that suggests 2 strings of 7 panels each with the other 5 not being connected properly?

[Dave Foster]

I guess if it's always 33v then that suggests 2 strings of 7 panels each with the other 5 not being connected properly?

The string voltage will fall on dull days but if you are generating power that 227V per string looks like 2 equal strings - the panel specs will give you the precise voltage you would expect but 227V for 7 panels looks about right for a dull day.

Which as you say suggests the 5 panels may be un-connected or there is a wiring fault - PV1 isn’t showing any volts?

[DEfusion]

Thanks for that, it's gotten slightly brighter now and string 1 is showing 1.4 volts (was 0.8 earlier):

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{ unit: 'V', name: 'PV1Volt', variable: 'pv1Volt', value: 1.4 },
{ unit: 'V', name: 'PV2Volt', variable: 'pv2Volt', value: 229.5 },
{ unit: 'V', name: 'PV3Volt', variable: 'pv3Volt', value: 229.4 },

229.5 divided by 7 = ~32.78v which is stated as the Maximum Power Voltage (Vmp) on the datasheet.