Are the wires feeding a transformer primary considered feeders or branch circuits?

[jaggedben]

I'm going to turn the question around: What difference does it make if the primary conductors are considered a feeder vs a branch circuit?

Do different rules come into play which would mean a different installation, or do you end up with the exact same requirements other than the name?

I found a few things, but perhaps the most notable is that if you had a 1000A circuit feeding a transformer and you claimed it was a branch circuit, that apparently would get you out of 215.10s requirement for GFP.

 

[kwired]

I'm going to turn the question around: What difference does it make if the primary conductors are considered a feeder vs a branch circuit?

Do different rules come into play which would mean a different installation, or do you end up with the exact same requirements other than the name?

Different rules do apply Art 210 vs Art 215.

Some the rules in either section are similar if not the same though.

 

[Space]

Article 100 Definitions

Feeder. All circuit conductors between the service equipment, the source of a separately derived system, or other power supply source and the final branch-circuit overcurrent device.
Transformer. Equipment, either single phase polyphase, that uses electromagnetic induction to convert current and voltage in a primary circuit into current and voltage in a secondary circuit.
Utiliziation Equipment. Equipment that utilizes electric energy for electronic, electromechanical, chemical, heating, lighting or similar purposes.

There are multiple types of branch circuits/definitions, but they are essentially defined as the circuit conductors between the final overcurrent protection device and the utilization equipment or outlets.

A transformer isn't utilization equipment and therefore the primary and secondary conductors are feeders in my opinion.

 

[don_resqcapt19]

I found a few things, but perhaps the most notable is that if you had a 1000A circuit feeding a transformer and you claimed it was a branch circuit, that apparently would get you out of 215.10s requirement for GFP.

But 210.13 would apply and still require GFP for that branch circuit. That was added in the 2014 code.

 

[rojodo3030]

This is similar to how we do not treat conductors as utilization equipment even though they have losses and voltage drop.

I like this, good point.

 

[rojodo3030]

I'm going to turn the question around: What difference does it make if the primary conductors are considered a feeder vs a branch circuit?

Do different rules come into play which would mean a different installation, or do you end up with the exact same requirements other than the name?

Feeders and branch circuits have different rules for voltage drop. Feeders allow up to 5% voltage drop while branch circuits only allow 3%.

 

[rojodo3030]

I think we have also concluded a feeder and branch circuit are not mutually exclusive.
For example you could have a 50A receptacle on a branch/ feeder circuit that also supplies a 50A panel.

Well, you would need taps for this. Regardless this is an interesting point however, doesn't apply to the discussion

 

[jaggedben]

Feeders and branch circuits have different rules for voltage drop. Feeders allow up to 5% voltage drop while branch circuits only allow 3%.

This is not in the NEC. Do you have a state energy code that requires this?

 

[jaggedben]

I think we have also concluded a feeder and branch circuit are not mutually exclusive.
For example you could have a 50A receptacle on a branch/ feeder circuit that also supplies a 50A panel.

Can you give an actual example of a 50A receptacle load for which the code doesn't require an individual branch circuit? Also wouldn't this likely be a load calc violation?

 

[wwhitney]

Can you give an actual example of a 50A receptacle load for which the code doesn't require an individual branch circuit?

If a 50A OCPD supplies both a main load directly, as well as a 15A OCPD to a secondary load, one could argue that is still an individual branch circuit with respect to the main load. The nature of the common conductors with respect to supplying the 15A OCPD is as a feeder, which usage perhaps does not contradict the definition of individual branch circuit. I.e. the branch circuit supplying the main load and the branch circuit supplying the secondary load have no conductors in common.

On the other hand, the definition of individual branch circuit refers to "suppl(ying) only one utilization equipment." So you could say that covers supplying both as a branch circuit and as a feeder. In which case it would not be an individual branch circuit.

Also wouldn't this likely be a load calc violation?

Not if the secondary load is a small load. Then the conductor and OCPD sizing for the feeder and for the main load branch circuit may coincide.

Cheers, Wayne

 

[jaggedben]

...

On the other hand, the definition of individual branch circuit refers to "suppl(ying) only one utilization equipment." So you could say that covers supplying both as a branch circuit and as a feeder. In which case it would not be an individual branch circuit.
...

This is really the only sensible thing one can say.

 

[wwhitney]

This is really the only sensible thing one can say.

Yet it is also the case that turning one redundant OCPD into a switch is not a meaningful change.

Cheers, Wayne

PS To spell that out, you could have (1) a 50A OCPD supplying (a1) a 15A OCPD and (b1) a 50A OCPD, each of which supplies one piece of utilization equipment. Or you have (2) a 50A OCPD supplying (a2) a 15A OCPD and (b2) a disconnect, each of which supplies one piece of utilization equipment. The only difference in case (1) is that in the event of an overload on the 50A piece of equipment, you have to check two OCPDs to see which needs to be reset.

 

[kwired]

Can you give an actual example of a 50A receptacle load for which the code doesn't require an individual branch circuit? Also wouldn't this likely be a load calc violation?

cooking appliances? Many are often connected to individual branch circuits but certainly can have more than one on a branch circuit in some cases.

Often those are hard wired but I can't think of any restriction either unless the appliance isn't listed for cord and plug connection or it's instructions state an individual branch circuit.

 

[kwired]

Feeders and branch circuits have different rules for voltage drop. Feeders allow up to 5% voltage drop while branch circuits only allow 3%.

This is only a suggestion in an informational note and not a requirement. Local rules could make it mandatory though.

 

[tortuga]

Can you give an actual example of a 50A receptacle load for which the code doesn't require an individual branch circuit? Also wouldn't this likely be a load calc violation?

When I encountered it was like a 7kw commercial oven on the receptacle and a 4.5 kw water heater & 120V GFCI out of the sub-panel.

 

[jap]

Transformers are not a load.

I'd have to politely disagree with that.

Jap>