We just recently installed a 7200/12470V Pad mount XFMR, which steps down to 277/480V. We installed 3- 3/4 inch grounds rod (coupled together) within the XFMR pad, to a depth of about 22-23 ft, and that is our XFMR ground. That sounds like overkill, but hard to get a good ground reading in North Florida. Anyway....We are installing a 600 Amp service which ultimately feeds a sandblast booth among other things. The main question I have is, one of our engineers states that we need to pull in a ground from the XFMR into the new 600A service. He also said if we did this, we would not need to put in more ground rods for the service. We (us actually doing the work) are planning to install at least 2 ground rods, either coupled or paralleled, plus bond to a nearby facility beam for the new service. We cannot figure out any logical reason why they want us to pull in a ground with the secondary coming from the XFMR. We are pulling parallel runs of 500kcmil, and they want us to pull parallel 1/0 grounds. The conduit feeding the new service is Schedule 80 PVC. Is this right? wrong? Overkill? Any guidance would be great. Thanks!
HV XFMR Grounding/Service Entrance Grounds
- Thread starter gk351
- Start date
- Status
- Location
- Illinois
- Occupation
- retired electrician
Is this a utility owned transformer or a customer owned one? Most utilities do not permit an EGC run with the service conductors. If this is customer owned, then the EGC may be required by the code rules, but in either case a grounding electrode is required at the building.
charlie
Senior Member
- Location
- Indianapolis
If The USAF owns it and they are a US Government agency, I would make the assumption that they are the electric utility and treat the lateral as service conductors. In that case, you would not install a grounding conductor with the service lateral but you will be required to install a normal service as well as the grounding at the building.gk351 said:
With that said, find out who the AHJ is for that facility and find out if they agree with me. They could say that the service begins at the primary disconnecting means that is close to the cash register (primary meter) where the USAF receives power from the serving electric utility. You need to know what rules you are playing by and this forum can't answer that question for you. The rules for that building may be from Article 225 or 230, depending on the answer from the AHJ. :smile:
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