mshields
Senior Member
- Location
- Boston, MA
Can anyone tell me what this part of 230.95, (Ground Fault on Services) means?
230.95 paragraph about fuses
- Thread starter mshields
- Start date
- Status
romex jockey
Senior Member
- Location
- Vermont
- Occupation
- electrician
possibly the fuse itself has a higher AIC rating than the switch it's in mshields
~RJ~
~RJ~
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
While not as common as it used to be, bolted pressure fusible switches were often used in the larger sizes in services. This is to ensure that the components are rated adequately for the available fault current in the event of a line to line fault where the GFP system would not be in play.
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
But that paragraph seems to link the rating of the fuse to the rating of the switch, rather than both depending upon the availability fault current.
??
Jon
??
Jon
victor.cherkashi
Senior Member
- Location
- NYC, NY
This is my vision of situation in example.
At the point of installation we have 100kA available S.C.
800A rated switch with a trip relay controlled by ground fault controller opens the switch at current between 1,100A - 10,000A.
At 10kA and above ground fault, the controller will allow fuses to open the fault.
At the point of installation we have 100kA available S.C.
800A rated switch with a trip relay controlled by ground fault controller opens the switch at current between 1,100A - 10,000A.
At 10kA and above ground fault, the controller will allow fuses to open the fault.
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
Ahh, so the trip relay operates in a limited range and does not attempt to open the switch if the fault current exceeds a certain amount, and the fuse has to be capable of opening anything above that.
Thanks for clarifying.
-Jon
Thanks for clarifying.
-Jon
Yep. Once, a vendor installed a motor controller (contactor switch) and routed the GF relay contacts to open the switch (contactor) if a ground occurs! The contactor switch contacts got damaged due excessive ground fault current experienced after a motor ground fault! The solution to the problem was routing the GF contact trip to the shunt trip contact of the supply breaker! The breaker has a higher interrupting rating than the contactor switch!
- Status