i work in electrical maintenance for a college, we work on lights, switches, receptacles, motor starters,branch circuits, you name it, we work on it.etc. we do not install new services, we maintain existing premisies wiring systems, all of the elec distribution is from 480 delta xfmrs sec
208/120 wye, we have one service 12.5 kv coming into the mech room, from there it is distributed thru 7 mv switches to 7 xfmrs 12470/480 to the existing bldgs.
the wiring was installed in 77 in the bldg i am describing,, no egc's were installed in the 208/120 distribution panels, they are primarily receptacle circuits, the emt was the egc,
the lighting panels are 277v
when checking certain 208/120 distribution panels i see some neutral to ground connections, others i dont, some wiring added over the yrs
on a sds system , the xo terminal at xfmr secondary is bonded to the case of the xfmr, a system bonding jumper,
so there should be no neutral to ground connections, after this connection correct?
this one point has been difficult for me to understand, and to keep it clear in my mind. because i see so many different sds's and their respective wiring, some of the wiring in these bldgs was done in 63 and later in 77, so i see a lot of different methods and old panels, they have some old fp panels that were added by others years ago.
thanks for any light you can shed on this question concerning sds's,
anyone that works in old schools/colleges and has seen it all, please pass on some helpful info,
thanks
steve
208/120 wye, we have one service 12.5 kv coming into the mech room, from there it is distributed thru 7 mv switches to 7 xfmrs 12470/480 to the existing bldgs.
the wiring was installed in 77 in the bldg i am describing,, no egc's were installed in the 208/120 distribution panels, they are primarily receptacle circuits, the emt was the egc,
the lighting panels are 277v
when checking certain 208/120 distribution panels i see some neutral to ground connections, others i dont, some wiring added over the yrs
on a sds system , the xo terminal at xfmr secondary is bonded to the case of the xfmr, a system bonding jumper,
so there should be no neutral to ground connections, after this connection correct?
this one point has been difficult for me to understand, and to keep it clear in my mind. because i see so many different sds's and their respective wiring, some of the wiring in these bldgs was done in 63 and later in 77, so i see a lot of different methods and old panels, they have some old fp panels that were added by others years ago.
thanks for any light you can shed on this question concerning sds's,
anyone that works in old schools/colleges and has seen it all, please pass on some helpful info,
thanks
steve
