We are specifying a 112.5 kVA Transformer, 2400V:208Y/120V, Impedance = 2.4. We have an existing 50 amp fuse (type SC-3)for the primary protection and a 350-amp main breaker for the secondary protection. Table 450.3(A) says max primary fuse protection of 300% transformer rating (300% * 27 amps) = 81 amps. The secondary protection max OCP according to the NEC is 125% * 312amps = 390 amps. The contractor says he talked to GE and they would void the warrantee if the transformer is installed with this OCP devices. We called GE and told them about our design. They saw no reason why the installation would void the warrantee and wanted to know the name of the person that told the contractor that. The contractor refuses to say who told him that.
Does anyone see a reason why the design would void the transformer warrantee? The only thing I found so far is that the fuse manufacturer (Ferraz Shawmut) says the Type CS-3 series are "typically sized at transformer rated current of 133%, thereby providing superior overall protection"
As always, thank you for your input.
Does anyone see a reason why the design would void the transformer warrantee? The only thing I found so far is that the fuse manufacturer (Ferraz Shawmut) says the Type CS-3 series are "typically sized at transformer rated current of 133%, thereby providing superior overall protection"
As always, thank you for your input.