Understanding periodic verification

[SharpSparks]

I had been sent on the NIC Solar PV course last year to learn how to test the DC side of solar installations as my company are testing solar panels in social housing. Due to obvious circumstances the testing work has only started this week and as I completed the course a year ago i'm struggling to fill out the documentation for periodic verification. Therefore I have a few questions that I need help with before I continue:

On the PV array test report is the string over-current protective device a fuse for each string? Or do I instead input the protective device for the AC side? i.e. 61009 type B 16a 230v
Same for the wiring. Is this the solar cable (PV1-F) or the AC wiring? What about earth? Is it n/a for DC wiring with no earth?
Earth continuity - is this referring to equipotential bonding?
I don't have access to any of the original specification sheets for the panels or inverter, so I can't fill out this section of the form. (What do I do?!)
Do I need to use Solar PV system inspection report for periodic verification? If I do then how do I tick 'Array frame correctly fixed and stable?' without a scaffold to check this?

If anyone has any help or guidance they could give me it would be much appreciated, thank you

 

[TJ Anderson]

On a Domestic PV system you won't have overcurrent protection devices on the DC side. Even on a 4 kw system with parallel strings, the max current even under fault is less than the cable rating.

Earth continuity can only refer to the AC final circuit to Inverter and also the array if inverter does not have an isolating transformer (you will find many are not earthed though). If the inverter does have an isolating transformer then the array may be bonded if installation conditions require it.

Also, ask your company how they expect you carry out a PV inspection and test if you are not inspecting the roof top panels, frame mountings and external DC wiring? Kind of important if they are asking you to sign it off.

 

[SharpSparks]

On a Domestic PV system you won't have overcurrent protection devices on the DC side. Even on a 4 kw system with parallel strings, the max current even under fault is less than the cable rating.

Earth continuity can only refer to the AC final circuit to Inverter and also the array if inverter does not have an isolating transformer (you will find many are not earthed though). If the inverter does have an isolating transformer then the array may be bonded if installation conditions require it.

Also, ask your company how they expect you carry out a PV inspection and test if you are not inspecting the roof top panels, frame mountings and external DC wiring? Kind of important if they are asking you to sign it off.

Thank you for clarifying the protective devices. So far I have not found any to be earthed but will check to see if they have isolating transformers. From what I understand they just want the readings but without the manufacturers data I can't make any calculations. Do I ignore the inspection checklist as I can't just tick the items for the sake of it?

 

[TJ Anderson]

AC side is simple, just deal the circuit like you are doing an EICR. Regarding the DC side, Check with your company what the scope of this maintenance check is. If they just want readings then do that. Do you have a DC clamp meter and W/M2 meter? The owner of the system would have been provided with MCS handover pack documentation which will include the panel info and array wiring layout diagram (that diagram and shutdown procedure should also be on the wall near AC Isolator). If you have all that, then you can still attain some meaningful results.

 

[SharpSparks]

AC side is simple, just deal the circuit like you are doing an EICR. Regarding the DC side, Check with your company what the scope of this maintenance check is. If they just want readings then do that. Do you have a DC clamp meter and W/M2 meter? The owner of the system would have been provided with MCS handover pack documentation which will include the panel info and array wiring layout diagram (that diagram and shutdown procedure should also be on the wall near AC Isolator). If you have all that, then you can still attain some meaningful results.

I haven't been testing the AC side (should I?), just shut off the isolator to complete the DC tests. I do have the equipment to do the tests no problem: clamp meter (DC) for the Isc and been using the multimeter for the voltage and insulation tests. The owner is the social housing firm that i'm guessing has the documentation, I've mentioned it to my manager but been told to just provide the results, which i'm struggling to on my own when the sun is in and out (having to run out of the loft to get the irradiance reading). There have been no wiring diagrams present on site in the houses I have tested so far.

 

[TJ Anderson]

I haven't been testing the AC side (should I?), just shut off the isolator to complete the DC tests. I do have the equipment to do the tests no problem: clamp meter (DC) for the Isc and been using the multimeter for the voltage and insulation tests. The owner is the social housing firm that i'm guessing has the documentation, I've mentioned it to my manager but been told to just provide the results, which i'm struggling to on my own when the sun is in and out (having to run out of the loft to get the irradiance reading). There have been no wiring diagrams present on site in the houses I have tested so far.

Again, not sure what the scope of your works is. Really, the AC side would come under the EICR anyway I suppose. Just do what they are asking for then (Isc, Voc and Irradiance reading I guess). Without panel data you can't compare it with STC for the panel, but if they are not asking for it then don't worry about it. At least you can prove the system operates which is maybe all they want. Only issue I could foresee is if you have 2 parallel strings (with Y connections under panels) with one down on a dull day, you could mistake the low current for lack of sun when in fact one is open circuit.