>Can anyone clarify the requirements regarding the fusing of both line >and neutral supply conductors? >It seems that where ( 230V) equipment is powered from a supply where the >neutral is connected to earth then a fuse should not be fitted in the >neutral. This is the situation in Europe. >In the US this equipment may be powered from a 208V supply which does >not earth the neutral (often the situation in labs). Should both line >and neutral be fused in this case? > >Appreciate any comments, >Philip Tatterton > > >
Note that with 208V in the USA, there are two possibilities when operating with standard mains (the neutral is earthed). If the equipment is single phase equipment, there is no neutral. Both poles are live to earth and therefore both poles must be protected from earth faults. If the equipment is three-phase, there may or may not be a neutral. All of the poles must be protected from earth faults. The neutral, if it is used, is not to be fused and no earth fault protection is required. I am unaware of locations that generate 3-phase 208V and do not earth the neutral. I would consider such a site to be in non-compliance with the electrical code. This is my opinion and not necessarily that of my company. Richard Woods Sensormatic Electronics
