New install wire size

[mmiller]

I work in an injection molding shop and they continue to constantly move machines around all the time. This makes it difficult for me to re-run wire and breakers and what not.

So here is the question. Can I run a wire size the covers my highest amperage needs to all locations and then just swap out the breakers as required for the piece of equipment ?

 

[iwire]

So here is the question. Can I run a wire size the covers my highest amperage needs to all locations and then just swap out the breakers as required for the piece of equipment ?

Yes.

The way I see it done is run large feeders and tap fused disconnects from it as needed. Easy to make changes.

 

[charlie b]

Yes you can. The key requirements are that (1) The wire size be big enough to handle the load current associated with the equipment it is serving, and (2) The breaker's rating be no higher than the ampacity of the wire.

The function of the breaker is to protect the wire from overcurrent. The breaker does not protect the equipment itself. So if for example you want to put a 20 amp breaker to serve a wire that could handle up to 50 amps, that is acceptable. Next week, when you connect a different piece of equipment to this circuit, you can replace that breaker with a 30 or 40 or 50 amp version, as called for by the equipment manufacturer.

 

[infinity]

We commonly do this for copier receptacles in commercial spaces. Run 2 pole, 3 wire 30 amp circuit and then install CB and receptacle accordingly when the equipment shows up.

 

[iwire]

The breaker does not protect the equipment itself.

I have to disagree.

For instance 422.11 seems to imply we are also protecting the equipment.

There is also 424.22

 

[peter d]

I work in an injection molding shop and they continue to constantly move machines around all the time. This makes it difficult for me to re-run wire and breakers and what not.

Perhaps you could talk to the management about installing a busway system.

 

[haskindm]

I have to disagree.

For instance 422.11 seems to imply we are also protecting the equipment.

There is also 424.22

422.11 states that the branch circuit for an appliance "shall be protected in accordance with 240.4". It goes on to explain that in some limited circumstances the branch circuit overcurrent protective device MAY also protect the appliance, but this is incidental to its main function of protecting the branch circuit.
424.22 says about the same thing for space heating equipment. The equipment "shall be permitted to be protected" by the branch circuit over current device, if it meets the specific criteria of this section, but again this is incidental to its main function of protecting the branch circuit.
The reason we install branch circuit over current protection is to protect branch circuits. If it happens to also protect the equipment in limited applications, that is a happy coincidence, not the purpose of the protection.

 

[Southpaw]

I worked in a similar situation for serveral years.

Finally I talked management to go for a wireway.

However I aggree with my manager's comment " We have paid for the buse system but still don't have one"

Do a cost analysis and justify a busway system. In my previous employment we installed busway as this resulted in lowest total cost and often used SO type cable drops for the "frequent interchange of equipment"