Grounding pv panels, safety switch and midnite dc surge protector.

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Cheap 4-life

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Aug 3, 2020
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372
Thanks in advance for your assistance.
When I installed my roof mount array (metal roof) I had the understanding that the array should be grounded to its own ground rod. I understand now that might not be correct.
Now I’m planning to add an outdoor pv safety disconnect switch and a dc surge protector. I do not have a ground wire running with the pv wires. The pv wires are in plastic conduit in the attic space.
How do I ground the safety disconnect and the dc surge protector?
I was hoping to mount the dc surge protector directly onto the pv disconnect switch. The combiner for the pv is inside the house. I want to put the pv disconnect after the combiner on the outside of the house.
Do I have to disconnect the array from it’s ground rod and run a ground wire along with the pv wires then into the pv disconnect. I was thinking that I don’t want to bring the dc surge/lightning into the attic on the ground wire. I guess I could mount the dc surge protector in the soffit instead of on the safety disconnect. That way surges are stoped before entering the house..
Thoughts?
Additional info. I am connected to the grid that also has a ground rod for the main panel
 
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italianuser

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Feb 25, 2020
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335
I wanted to ground solar circuits, too, and add an SPD. From my little understanding, my building should have a main ground (it doesn't), and each apartment should have its own ground wire connected at the main control panel to a ground bar; the ground bar is then connected to the building's ground.

But @Roland W surely has the correct answer, he has many videos about grounding.
 
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Roland W

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Joined
Oct 9, 2017
Messages
136
Thanks in advance for your assistance.
When I installed my roof mount array (metal roof) I had the understanding that the array should be grounded to its own ground rod. I understand now that might not be correct.
Now I’m planning to add an outdoor pv safety disconnect switch and a dc surge protector. I do not have a ground wire running with the pv wires. The pv wires are in plastic conduit in the attic space.
How do I ground the safety disconnect and the dc surge protector?
I was hoping to mount the dc surge protector directly onto the pv disconnect switch. The combiner for the pv is inside the house. I want to put the pv disconnect after the combiner on the outside of the house.
Do I have to disconnect the array from it’s ground rod and run a ground wire along with the pv wires then into the pv disconnect. I was thinking that I don’t want to bring the dc surge/lightning into the attic on the ground wire. I guess I could mount the dc surge protector in the soffit instead of on the safety disconnect. That way surges are stoped before entering the house..
Thoughts?
Additional info. I am connected to the grid that also has a ground rod for the main panel
As the PV DC is an isolated system, I would keep a separate grounding for the frames and mounts for lightning protection. That energy will then be directed directly to ground, and if you did it right, and there is no other rod or metallic objects like pipes within 5m of that PV rod, which are grounded to PE of your service, that is ideal as you will not import a surge to the rest of the house via the soil.

The SPDs (AC and DC) are a must next to the inverter, you can use the regular PE system of your house to bleed of surges coming through power lines as those are just momentary connections to ground. If your array is more then 10m away from the inverter, then you need a DC SPD at the array as well. Just connect it to the PV rod. No problem, as it might have advantages of 2 rods having less impedance then just one.

SPDs are no concern in the grand scheme of grounding because they are just providing that short time path to ground...
 
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Cheap 4-life

Member
Joined
Aug 3, 2020
Messages
372
As the PV DC is an isolated system, I would keep a separate grounding for the frames and mounts for lightning protection. That energy will then be directed directly to ground, and if you did it right, and there is no other rod or metallic objects like pipes within 5m of that PV rod, which are grounded to PE of your service, that is ideal as you will not import a surge to the rest of the house via the soil.

The SPDs (AC and DC) are a must next to the inverter, you can use the regular PE system of your house to bleed of surges coming through power lines as those are just momentary connections to ground. If your array is more then 10m away from the inverter, then you need a DC SPD at the array as well. Just connect it to the PV rod. No problem, as it might have advantages of 2 rods having less impedance then just one.

SPDs are no concern in the grand scheme of grounding because they are just providing that short time path to ground...
Is the pv dc isolated? I’m using the same grid tie inverters you use. They are grounded to the grids ground in the main panel.
 

Roland W

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Joined
Oct 9, 2017
Messages
136
Is the pv dc isolated? I’m using the same grid tie inverters you use. They are grounded to the grids ground in the main panel.
DC is always isolated if not deliberately bonded to ground. There is no advantage in giving up DC isolation, as you only have the array and the inverter. You cannot shock yourself in such a circuit other then touching both plus and minus at the same time. The inverter ground is for AC only.
 
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Cheap 4-life

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Joined
Aug 3, 2020
Messages
372
DC is always isolated if not deliberately bonded to ground. There is no advantage in giving up DC isolation, as you only have the array and the inverter. You cannot shock yourself in such a circuit other then touching both plus and minus at the same time. The inverter ground is for AC only.
Thanks for your time
 
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