I came across a situation where a customer is running a service lateral from a pad mounted x-former to a pedastal containing metering device and a 200A outdoor disconnect. The pedastal is approx. 15 ft. away from the transformer and the disconnect is grounded using two 8ft. ground rods 6 ft apart. The customer has to run a feeder from his disconnect to his house panel which will be a 200a mcb panel approx 300ft. away. My question is do you have to run 4 wire or can you run 3 wire from disconnect to house and ground panel in house according to 250.32. It would make more sense to me to run 3 wire and install new ground rods at house which will be a shorter grounding source to house panel than running 4 wire (4th wire as egc) and relying on ground rods 300ft. away as your grounding means. There will be no potential between the two grounding sources since the 3 wire feeder will be run in pvc pipe. The house water pipe will also be used as a grounding electrode.
Grounding residential building
- Thread starter MichaelF
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- Bremerton, Washington
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- Master Electrician
Re: Grounding residential building
Grounding electrodes are required at pedistal and the house. A neutral to ground connection on the load side of the service disconnect is allowed per 250.32(B)(2) but this is not recommended. If you are in washington state the grounded conductor can not be used in place of the equipment grounding conductor.
Grounding electrodes are required at pedistal and the house. A neutral to ground connection on the load side of the service disconnect is allowed per 250.32(B)(2) but this is not recommended. If you are in washington state the grounded conductor can not be used in place of the equipment grounding conductor.
Re: Grounding residential building
250.32 is the code section that you need to study. Any time a building contains more than one circuit you will be required to connect and/or install a grounding electrode at the building (or structure). The conductors between the pole and the building are "feeders". Whether you are required to install a ground wire with the feeder is determined by whether or not there are other "continuous metallic baths bonded to the grounding system in each building or structure". These paths could be a telephone or cable TV line, or a metallic waterline for example. If you KNOW there are no other metallic paths you may install three conductors (2 hots and 1 grounded (neutral) conductor) from the pole to the building. Tie the neutral and grounds together just as you would in a new service. Otherwise run four conductors and separate the grounds and grounded (neutral) conductors just as you would in a sub-panel. It is never wrong to install the four conductors and it "future-proofs" your installation against someone in the future installing a metallic path between the two structures. I usually recommend the four conductors, but you need to understand why you are doing it. With only three conductors and another metallic path available you will have neutral currents travelling on "conductors" that are not meant to carry current.
250.32 is the code section that you need to study. Any time a building contains more than one circuit you will be required to connect and/or install a grounding electrode at the building (or structure). The conductors between the pole and the building are "feeders". Whether you are required to install a ground wire with the feeder is determined by whether or not there are other "continuous metallic baths bonded to the grounding system in each building or structure". These paths could be a telephone or cable TV line, or a metallic waterline for example. If you KNOW there are no other metallic paths you may install three conductors (2 hots and 1 grounded (neutral) conductor) from the pole to the building. Tie the neutral and grounds together just as you would in a new service. Otherwise run four conductors and separate the grounds and grounded (neutral) conductors just as you would in a sub-panel. It is never wrong to install the four conductors and it "future-proofs" your installation against someone in the future installing a metallic path between the two structures. I usually recommend the four conductors, but you need to understand why you are doing it. With only three conductors and another metallic path available you will have neutral currents travelling on "conductors" that are not meant to carry current.
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