Disconnect Switch Secondary Side Xfrmr

[mstrlucky74]

Is a disconnect switch always needed on the secondary sideof a transformer per code?

 

[jumper]

No, but the conductors connected to the secondary need to be protected according to 240.21(C).

 

[mstrlucky74]

Ok the secondary side conductors are feeding a panel 200 feet away so disconnect is needed if I'm reading 1-6 correctly. Transformer is delta to wye

 

[ron]

Ok the secondary side conductors are feeding a panel 200 feet away so disconnect is needed if I'm reading 1-6 correctly.

That is the way it works out most of the time

 

[petersonra]

Ok the secondary side conductors are feeding a panel 200 feet away so disconnect is needed if I'm reading 1-6 correctly. Transformer is delta to wye

a disconnect is not required on the secondary side, however it often works out that it is a convenient place to put the OCPD that may be required.

you might also need it for other reasons, such as the disconnect feeding a separate structure.

 

[jumper]

a disconnect is not required on the secondary side, however it often works out that it is a convenient place to put the OCPD that may be required.

you might also need it for other reasons, such as the disconnect feeding a separate structure.

:thumbsup:

 

[mstrlucky74]

That is the way it works out most of the time

But we are trying to determine if a mcb in the panel 200' away can serve as the means of disconnect. Some are saying not because of he distance away from the transformer.

 

[jumper]

But we are trying to determine if a mcb in the panel 200' away can serve as the means of disconnect. Some are saying not because of he distance away from the transformer.

As stated above, what you need is protection of the secondary conductors and your breaker is too far away, so you need a disconnect that provides protection/OCP for the conductors not the xfrmr.

 

[infinity]

But we are trying to determine if a mcb in the panel 200' away can serve as the means of disconnect. Some are saying not because of he distance away from the transformer.

You need to have the OCPD with no more than 25' of the secondary conductor length so no 200' away won't work with a main in the panel.

 

[mstrlucky74]

Thanks

 

[mstrlucky74]

You need to have the OCPD with no more than 25' of the secondary conductor length so no 200' away won't work with a main in the panel.

So the disco has to be within 25' of the transformer and not at the panel 200' away? Thx

 

[GoldDigger]

So the disco has to be within 25' of the transformer and not at the panel 200' away? Thx

The issue is not the disco itself but the overcurrent protection it provides for the wires.
Until they reach an OCPD the wires are taps and subject to the applicable tap rules. That is the issue, not the disconnecting of the circuit.

 

[infinity]

The secondary conductors require over current protection within 25' of their origin at the transformer. They do not require a disconnecting means although a fused disconnect would accomplish both of those actions.

 

[petersonra]

what if it is outside?

 

[infinity]

what if it is outside?

Different scenario, is this installation outside?

 

[petersonra]

Different scenario, is this installation outside?

Don't know. Op did not say.