GFDI issue

[sunnybai]

No could be about it. The fault is in your inverter.

Confirmed, Kaco technical support agrees that it is the inverter. New inverter gets shipped out tomorrow.

A bit of history; this particular string has been operating trouble free for approx. just over a year.

No mature trees or squirrels around and I was meticulous in making sure wires are routed properly. Although I still performed a thorough inspection of all conductors.

Sunkings approach is based on FACTS. I appreciate that.

I will confirm operation when new inverter is installed.

Thank you all for your insight and factual information. This forum is excellent.

[inetdog]

Could you explain in further detail what is in red and how this is connected and how it determines where in the string it goes away?

Sure: Let us say that we have six panels in series which each have a Voc of 40 volts. The total voltage across the string when disconnected from the inverter is therefore 240 volts. But when measuring from either + or - to ground with no fault present, we see zero volts from each of them individually to ground.
The 100kohm resistor is to force some current to be drawn so that we will not read a voltage which results from a very high resistance, not relevant, leakage.

Now, if the ground fault is at the + of the top panel, the meter will still read 0 volts to ground from + and will read -240 volts to ground from the - lead of the bottom panel.

If the ground fault is anywhere inside the top panel, we will read between 0 and +40 on the + lead and between -240 and -200 on the - lead. We have set up a simple voltage divider, where the earth ground is connected in the middle of the previously isolated panel array.

If the ground fault is somewhere in the fourth panel from the bottom, the - lead will show between -160 and -120 (the voltage from the fault point to the - end of the string.) And the voltage from the + lead to ground will be between 80 and 120.

But any of this assumes a strong, not intermittent or-heat related ground fault. It is possible from the description that if the fault is in a panel it is dependent on the temperature of the panel in that case the test will still show 0 volts from both leads to ground until the panels heat up. The panel temp should be about the same whether they are delivering current or not, so the test may have to be done during full sun.

This is not related at all to the more direct and conclusive test of removing one panel at a time looking for the fault to go away, but it does not require diving as far into the wiring harness right at the start.

[Sunking]

The voltage goes away when I disconnect the leads from the inverter, and test to ground. So you are saying there could be an internal problem with the inverter?

No could be about it. The fault is in your inverter.

[sunnybai]

Do NOT put a megger on the panels. It can/will create a fault where none existed before! If you need to use a megger (megohmmeter) to check the wiring, you will need to disconnect the panels and the inverter first.

To check the panels, one good way is to take each one in turn out of the series string and replace it with a jumper. When the GF goes away, you have found the panel.
Also, if the voltage to ground that you see is a solid one (carefully put a 100K ohm 1 watt resistor in parallel with your meter leads) then the value of the voltage will tell you where along the string the fault is. Do all of this with the GT inverter disconnected from the panels. If the voltage goes away when you disconnect the inverter, then look for an internal problem there.

The voltage goes away when I disconnect the leads from the inverter, and test to ground. So you are saying there could be an internal problem with the inverter?

Thanks.

[Naptown]

Do NOT put a megger on the panels. It can/will create a fault where none existed before! If you need to use a megger (megohmmeter) to check the wiring, you will need to disconnect the panels and the inverter first.

To check the panels, one good way is to take each one in turn out of the series string and replace it with a jumper. When the GF goes away, you have found the panel.
Also, if the voltage to ground that you see is a solid one (carefully put a 100K ohm 1 watt resistor in parallel with your meter leads) then the value of the voltage will tell you where along the string the fault is. Do all of this with the GT inverter disconnected from the panels. If the voltage goes away when you disconnect the inverter, then look for an internal problem there.

Could you explain in further detail what is in red and how this is connected and how it determines where in the string it goes away?

[inetdog]

True. I have seen those phantom voltages. Is it possible to meggar a dc pv circuit at night?

Do NOT put a megger on the panels. It can/will create a fault where none existed before! If you need to use a megger (megohmmeter) to check the wiring, you will need to disconnect the panels and the inverter first.

To check the panels, one good way is to take each one in turn out of the series string and replace it with a jumper. When the GF goes away, you have found the panel.
Also, if the voltage to ground that you see is a solid one (carefully put a 100K ohm 1 watt resistor in parallel with your meter leads) then the value of the voltage will tell you where along the string the fault is. Do all of this with the GT inverter disconnected from the panels. If the voltage goes away when you disconnect the inverter, then look for an internal problem there.

[Jairo]

ok thanks..

[sunnybai]

No that is not True, in fact digital meters lie all the time when used on voltages. Fluke makes great meters, very accurate. But all digital meters have one major flaw built into them, very high input impedance in excess of 20 M-Ohms. The problem or error it will give you is Ghost or Phantom voltages where there is none on an open circuit. That is why all Electricians use a meter called a WIGGY which is an ole fashion solenoid volt meter. To trougle shoot what you are looking for will take an analog meter or a Meggar.

True. I have seen those phantom voltages. Is it possible to meggar a dc pv circuit at night?

[Sunking]

Yes, FLUKE series 780 digital.

No that is not True, in fact digital meters lie all the time when used on voltages. Fluke makes great meters, very accurate. But all digital meters have one major flaw built into them, very high input impedance in excess of 20 M-Ohms. The problem or error it will give you is Ghost or Phantom voltages where there is none on an open circuit. That is why all Electricians use a meter called a WIGGY which is an ole fashion solenoid volt meter. To trougle shoot what you are looking for will take an analog meter or a Meggar.

[sunnybai]

But did you see the products en solarmurals.com..
there are three...

What's up with high jacking my thread. Please start a new one. This thread is addressing a GFDI issue.

[Jairo]

the products

But did you see the products en solarmurals.com..
there are three...

[Naptown]

Good afternoon,

i Am new here..i want to know the difference between the products that you can see in the nex page..

What dou you think is the best??

Thanks very much...

Both will be very low producing items. Not worth the effort or expense as the absorber area is so small.
Could not be used for a direct exchange in a pool as the copper pipes would self destruct in rapid order with the pool chemicals.
The one shown wouldn't be enough to heat a bathtub much less a large swimming pool unless you used like 500 of them.

[Jairo]

Solar Murals

Good afternoon,

i Am new here..i want to know the difference between the products that you can see in the nex page..

What dou you think is the best??

Thanks very much...

[sunnybai]

What kind of meter? Digital?

If you are reading a voltage from ground to either negative of positive polarities is confirmation you have a ground fault. It can be anywhere. Most likely candidate is a chaffed wire and Mr Tree Rat aka squirrel. It can also be an internal fault in a panel.

Hi,

Yes, FLUKE series 780 digital.

I agree the meter does not lie. I will get up on the roof now, and start inspecting my way through each module. I will inform you guys of my findings.

What is the procedure for eliminating internal fault in a module? Check negative and positive to frame of module?

Thanks.

[Sunking]

It is ungrounded. I agree there shouldn't be any voltage on the - side of the circuit, but I am reading a voltage with my multimeter. This tells me there is leakage somewhere (is this correct?), I guess I have to pull each module?

What kind of meter? Digital?

If you are reading a voltage from ground to either negative of positive polarities is confirmation you have a ground fault. It can be anywhere. Most likely candidate is a chaffed wire and Mr Tree Rat aka squirrel. It can also be an internal fault in a panel.