harakumar
Member
- Location
- Peoria,AZ,USA
I have some questions regarding grounding and I like to take your inputs.
System description:
1. The system is a 6.4 KW solar PV.
The system uses enphase inverter.
The ground for the enphase (Green wire) goes through the conduit all the way to the service entrance ground.
2. The panels are grounded using weeb clips , WEEB-DMC is used for equipment grounding for enphase inverter. WEEB bonding jumpers will be used to electrically connect spliced Unirac rail.
WEEB grounding Lug will be used to connect system to equipment ground.
3. Aluminium J-box is mounted on the rail and a conduit runs between the j-box and PV sub panel. The conduit will be connected to service entrance ground. The conduit runs in the attic of the building.
Goal:
1. Provide grounding for the equipment. The rails, metal parts etc..
2. Like to provide a safe path in case a power surge in rails etc due lightning near by.
3. Ensure over current protection devices operate properly.
Questions:
1. Can the rails be connected to a separate grounding electrode ? ( not connected to the service entrance ground). This gives a safe path in case of a lightning surge. The electrode will be close to where the panels are installed. This avoids the need for a separate equipment ground wire to service entrance for the equipment ground through the attic. The most important idea here regarding separate equipment ground is, if the metal parts picks up a lighting surge then it will go quickly to the separate ground and will not go through the attic to the service entrance ground. Shorter path and is safely routed to ground (separate ground).
2. Do I need a non-conducting spacer ( breaks the path) in the conduit so that the service ground and the separate equipment ground are separated( with out the non conducting spacer the conduit makes a continuous path from rail to the service entrance ground) .
a) Is separation safer approach as the surge will not have a path through the conduit ? But I think this is against NEC - am I correct?
Separate isolated ground is not allowed.
b) Is it a good thing to have the conduit conducting that is with out the non conducting spacer in the conduit? Using this method there will be a grounding electrode System as described in NEC 250.50 (2005). The exhibit 250.21 shows a metal fame connected to a grounding rod which is also connected to a concrete encased electrode. The conduit connected to service entrance ground will serve the path from the rack to the concrete encased electrode. The ground rod connected to the rack (the solar rack and metal parts) serves as another grounding method and they are both connected through the conduit. Need to ensure that the conductivity from the rack to j-box to conduit to service entrance ground exists.
Which approach is better?
I am thinking approach (b) is good. If a 4 AWG CU is used for rack to ground rod then this will work like a shunt path when there is a surge even though there is a path through the conduit (cannot guarantee it) or at least there are multiple paths to ground and a system of ground is better than just one service entrance ground.
c) A variation of method B is to keep the insulating spacer and remove the connectivity to ground through the conduit but have a separate wire run to the service entrance ground but around the building (not through the attic). This connects the ground rod (just for the rack) and the service entrance ground forming a grounding system.
Please give me your inputs. Which one is the best approach?
3. Like to know if the over current protection devices will operate OK with this arrangement.
Since the enphase ground comes to service entrance ground it should be OK - is this a correct statement?
Please give me you inputs.
Thank you
System description:
1. The system is a 6.4 KW solar PV.
The system uses enphase inverter.
The ground for the enphase (Green wire) goes through the conduit all the way to the service entrance ground.
2. The panels are grounded using weeb clips , WEEB-DMC is used for equipment grounding for enphase inverter. WEEB bonding jumpers will be used to electrically connect spliced Unirac rail.
WEEB grounding Lug will be used to connect system to equipment ground.
3. Aluminium J-box is mounted on the rail and a conduit runs between the j-box and PV sub panel. The conduit will be connected to service entrance ground. The conduit runs in the attic of the building.
Goal:
1. Provide grounding for the equipment. The rails, metal parts etc..
2. Like to provide a safe path in case a power surge in rails etc due lightning near by.
3. Ensure over current protection devices operate properly.
Questions:
1. Can the rails be connected to a separate grounding electrode ? ( not connected to the service entrance ground). This gives a safe path in case of a lightning surge. The electrode will be close to where the panels are installed. This avoids the need for a separate equipment ground wire to service entrance for the equipment ground through the attic. The most important idea here regarding separate equipment ground is, if the metal parts picks up a lighting surge then it will go quickly to the separate ground and will not go through the attic to the service entrance ground. Shorter path and is safely routed to ground (separate ground).
2. Do I need a non-conducting spacer ( breaks the path) in the conduit so that the service ground and the separate equipment ground are separated( with out the non conducting spacer the conduit makes a continuous path from rail to the service entrance ground) .
a) Is separation safer approach as the surge will not have a path through the conduit ? But I think this is against NEC - am I correct?
Separate isolated ground is not allowed.
b) Is it a good thing to have the conduit conducting that is with out the non conducting spacer in the conduit? Using this method there will be a grounding electrode System as described in NEC 250.50 (2005). The exhibit 250.21 shows a metal fame connected to a grounding rod which is also connected to a concrete encased electrode. The conduit connected to service entrance ground will serve the path from the rack to the concrete encased electrode. The ground rod connected to the rack (the solar rack and metal parts) serves as another grounding method and they are both connected through the conduit. Need to ensure that the conductivity from the rack to j-box to conduit to service entrance ground exists.
Which approach is better?
I am thinking approach (b) is good. If a 4 AWG CU is used for rack to ground rod then this will work like a shunt path when there is a surge even though there is a path through the conduit (cannot guarantee it) or at least there are multiple paths to ground and a system of ground is better than just one service entrance ground.
c) A variation of method B is to keep the insulating spacer and remove the connectivity to ground through the conduit but have a separate wire run to the service entrance ground but around the building (not through the attic). This connects the ground rod (just for the rack) and the service entrance ground forming a grounding system.
Please give me your inputs. Which one is the best approach?
3. Like to know if the over current protection devices will operate OK with this arrangement.
Since the enphase ground comes to service entrance ground it should be OK - is this a correct statement?
Please give me you inputs.
Thank you