I understand using Table 250-122 in selecting the minimum size equipment grounding conductor based on the size of the OCPD. But when it is required to bond a steel structure such as a steel vessel (with no electrical devices on it) how would you select the proper size bonding jumper? In the industrial plant where I work we have an underground grid system which we tie into.
Bonding
- Thread starter drivetr.
- Start date
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Re: Bonding
The plant uses the rebar and other underground material as a ground. Conduit is brought up through the concrete and ground conductors attached to the grid is fed through the conduit and connect to terminal bars. Many motors will have a bonding conductor attached to the frame and the other end will be terminated to a ground bar located nearby.
The plant uses the rebar and other underground material as a ground. Conduit is brought up through the concrete and ground conductors attached to the grid is fed through the conduit and connect to terminal bars. Many motors will have a bonding conductor attached to the frame and the other end will be terminated to a ground bar located nearby.
- Location
- Illinois
- Occupation
- retired electrician
Re: Bonding
drivetr,
These connections are not required by the NEC and therefore there are no rules for their installation in the NEC. In most cases, there is no real electrical or safety advantage in connecting the motor frames to the grounding ring. The required EGC must be installed in the same raceway or cable as the motor circuit conductors.
Don
drivetr,
These connections are not required by the NEC and therefore there are no rules for their installation in the NEC. In most cases, there is no real electrical or safety advantage in connecting the motor frames to the grounding ring. The required EGC must be installed in the same raceway or cable as the motor circuit conductors.
Don
- Location
- Bremerton, Washington
Re: Bonding
Derek, Art 250 limits the length of external bonding jumpers to 6 ft.
Derek, Art 250 limits the length of external bonding jumpers to 6 ft.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Bonding
Tom would that apply to the bonding jumpers we install for pools?
I beleave that the intent of section V of 250 artical 250.102 exception is to ensure electrical continuity and the capacity to conduct safely any fault current likely to be imposed. as taken from 250.90. this bonding jumper would not serve as a fault path and if any thing it would be another gec that is not required by the nec so I dont think artical 250.102 would apply. There would have to be a egc ran with the circuit conductors. but this is a seprate conductor and not the bonding conductor that was discribed by Drivetr
Tom would that apply to the bonding jumpers we install for pools?
I beleave that the intent of section V of 250 artical 250.102 exception is to ensure electrical continuity and the capacity to conduct safely any fault current likely to be imposed. as taken from 250.90. this bonding jumper would not serve as a fault path and if any thing it would be another gec that is not required by the nec so I dont think artical 250.102 would apply. There would have to be a egc ran with the circuit conductors. but this is a seprate conductor and not the bonding conductor that was discribed by Drivetr
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Bonding
I need to read a little better as I was thinking this was for a motor. as I now see it. It is for the likely hood of a ungrounded conductor possibility coming into contact with the tank and energizing it. But if this bond is not allowed then what happens when we bond the water piping in a house that doesnt have a connection to the underground waterpipe like when you have a well we have to bond the water pipes. how can we keep this bond under 6'?
I need to read a little better as I was thinking this was for a motor. as I now see it. It is for the likely hood of a ungrounded conductor possibility coming into contact with the tank and energizing it. But if this bond is not allowed then what happens when we bond the water piping in a house that doesnt have a connection to the underground waterpipe like when you have a well we have to bond the water pipes. how can we keep this bond under 6'?
Re: Bonding
Wayne: This is where the ground electrode conductor becomes a multi-task conductor. Change the name and the length increases.
On a 200 amp service, run a #4 from the neutral/ground bus to the ground rod then to the water pipe. The system is grounded, bonded, and earthed.
Bonding for fault clearing is a different game than bonding for potential equalizing.
Wayne: This is where the ground electrode conductor becomes a multi-task conductor. Change the name and the length increases.
On a 200 amp service, run a #4 from the neutral/ground bus to the ground rod then to the water pipe. The system is grounded, bonded, and earthed.
Bonding for fault clearing is a different game than bonding for potential equalizing.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Bonding
So artical 250.102 exception is only for fault clearing paths and this bond could be longer?
I have always been taught to follow the path of current to know what the purpose is for a wire. and install acordingly to the NEC for that type of circuit like if this wire is for fault path as an egc then it would have to be shorter than 6' as per 250.102 but if it is a bond for water pipe that does not connect to earth like in a well then what it is still for fault clearing? or is it it could be called to prevent voltage differances between the metal parts like in a pool but even that would have to have fault clearing capacity. so it would be limited to the 6' rule. The question I have is when a bond is used to prevent voltages on other metal should it be limited to the 6' rule or does the 6' rule apply as it is for fault clearing only as it says in 250.90? :roll:
So artical 250.102 exception is only for fault clearing paths and this bond could be longer?
I have always been taught to follow the path of current to know what the purpose is for a wire. and install acordingly to the NEC for that type of circuit like if this wire is for fault path as an egc then it would have to be shorter than 6' as per 250.102 but if it is a bond for water pipe that does not connect to earth like in a well then what it is still for fault clearing? or is it it could be called to prevent voltage differances between the metal parts like in a pool but even that would have to have fault clearing capacity. so it would be limited to the 6' rule. The question I have is when a bond is used to prevent voltages on other metal should it be limited to the 6' rule or does the 6' rule apply as it is for fault clearing only as it says in 250.90? :roll:
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