SteveBB
Member
- Location
- United States
Hello,
For whatever reasons throughout my career, circumstantial I presume, I've not been involved in any projects at a facility that has utilized a high resistance to ground. I have a project that just kicked off for a client. I've yet to visit the site personally, but am asking for some base feedback prior to my visit from you knowledgeable folks here.
A question that came up, in regards to an equipment vendor that has a machine SCCR rated at 25kA, is that one of the facility electrical engineers has basically stated that he prefers a higher rating but that the upstream OCPD through coordination efforts would mitigate the "low" SCCR.
That struck me as odd, because if the facility has an HRG system, wouldn't any fault currents be essentially negligent? I was under the assumption that was one of the benefits of HRG. Unfortunately for me project schedule and cost is not going to give much wiggle room for coordination efforts after the fact as most distribution equipment is going to be ordered and installed likely before we get final vendor equipment ratings.
Granted, I'd rather the asset be higher than 25kA simply because the particular client has an established track record of moving equipment to other facilities, which are, in my experience usually not an HRG implementation.
Assuming I am correct above, my feedback to the team is that essentially the 25kA is fine because the facility is HRG. I'm not going to hinge project success on being able to coordinate on the fly during installation. Either the HRG is going to determine the 25kA is fine or I'm going to push the vendor to up the SCCR.
Any feedback is appreciated.
For whatever reasons throughout my career, circumstantial I presume, I've not been involved in any projects at a facility that has utilized a high resistance to ground. I have a project that just kicked off for a client. I've yet to visit the site personally, but am asking for some base feedback prior to my visit from you knowledgeable folks here.
A question that came up, in regards to an equipment vendor that has a machine SCCR rated at 25kA, is that one of the facility electrical engineers has basically stated that he prefers a higher rating but that the upstream OCPD through coordination efforts would mitigate the "low" SCCR.
That struck me as odd, because if the facility has an HRG system, wouldn't any fault currents be essentially negligent? I was under the assumption that was one of the benefits of HRG. Unfortunately for me project schedule and cost is not going to give much wiggle room for coordination efforts after the fact as most distribution equipment is going to be ordered and installed likely before we get final vendor equipment ratings.
Granted, I'd rather the asset be higher than 25kA simply because the particular client has an established track record of moving equipment to other facilities, which are, in my experience usually not an HRG implementation.
Assuming I am correct above, my feedback to the team is that essentially the 25kA is fine because the facility is HRG. I'm not going to hinge project success on being able to coordinate on the fly during installation. Either the HRG is going to determine the 25kA is fine or I'm going to push the vendor to up the SCCR.
Any feedback is appreciated.
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