Mezani
Member
- Location
- Washington
The issue is that the secondary has to be grounded in compliance with the NEC but in your case you will now have a hot and a grounded conductor going the the appliance instead of 2 hots. This will be a problem in some equipment that may have fuses in the appliance as you can't fuse a grounded conductor. It is also non standard and will be confusing to anyone working on this.The only way to derive a center tap is to send it back to the manufacturer. Texie, what would complicate this. It seems as though 240.21(C)(1) would allow going directly from the transformer to the equipment without overcurrent protection on the secondary. (#4 Cu secondary conductors) I did consider 250.20(B) (1) not allowing it as it is 208 to ground.
That is correct, as the system would be greater than 150V to ground.Hopefully Texie or another member will correct me if need be.
As I read 250.21, you could operate this as an un-grounded system and install a grounding-electrode system per 250.32(B), a SSBJ per 250.32(A) and a ground detector per 250.21(B)
This is feeding a cooking appliance that only requires 2 wires.
Well, yeah, you could do this but seems far more complicated and expensive than just getting the correct transformer.Hopefully Texie or another member will correct me if need be.
As I read 250.21, you could operate this as an un-grounded system and install a grounding-electrode system per 250.32(B), a SSBJ per 250.32(A) and a ground detector per 250.21(B)
No; it's labeled 480-208 and calls the HV the primary in the tap table.It almost looks like this transformer is meant to be a single phase STEP UP transformer instead of being a STEP Down transformer. But it does have the TAPS to adjust for the Primary voltage.
OP stated this feeds a two wire cooking appliance. He must be in a building that has existing 480. Looks like he needs to run two wires to appliance. A neutral and hot. This transformer will work.
This is feeding a cooking appliance that only requires 2 wires.
Should read:It could also could be fed by 2 ungrounded 208V conductors.
How is this any different than a glorified Buck/Boost Transformer?
250.21 (B) Alternating-Current Systems of 50 Volts to 1000 Volts.
Alternating-current systems of 50 volts to 1000 volts that supply
premises wiring and premises wiring systems shall be grounded
under any of the following conditions:
(1) Where the system can be grounded so that the maximum
voltage to ground on the ungrounded conductors does
not exceed 150 volts
(2) Where the system is 3-phase, 4-wire, wye connected in
which the neutral conductor is used as a circuit conductor
(3) Where the system is 3-phase, 4-wire, delta connected in
which the midpoint of one phase winding is used as a
circuit conductor
what if the appliance had a circuit breaker that was only slash rated?A 2-wire 208v load should have no issues with one line grounded.
A 2-wire 208v load should have no issues with one line grounded.