Definition of Feeder

[kwired]

430.62 ..............

I don't see that requiring it be larger for every case, many instances yes, but not all. A 15 amp feeder could easily supply several motors that only draw an amp or two and they could all have 15 amp circuit breakers as the branch circuit devices.

 

[Dennis Alwon]

I don't see that requiring it be larger for every case, many instances yes, but not all. A 15 amp feeder could easily supply several motors that only draw an amp or two and they could all have 15 amp circuit breakers as the branch circuit devices.

That wouldn't be a feeder would it

 

[kwired]

That wouldn't be a feeder would it

If each motor had an additional branch circuit device (as I tried to describe) it has to be a feeder by definition.

 

[Dennis Alwon]

If each motor had an additional branch circuit device (as I tried to describe) it has to be a feeder by definition.

Yes but then the feeder is serving more than one piece of equipment. My statement was about the case of one feeder to one motor. You are changing the premise of the statement

 

[Dennis Alwon]

Here is new wording

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. Circuit conductors to the disconnect of an individual piece of equipment's field installed disconnect with an overcurrent protective device shall be considered a branch circuit.

 

[kwired]

Yes but then the feeder is serving more than one piece of equipment. My statement was about the case of one feeder to one motor. You are changing the premise of the statement

Sorry about that, I still don't see where you couldn't have same size overcurent device on the feeder as you have on the branch circuit though.

In the case of an AHU with two or three breakers installed in the unit either at the factory or via listed field installed heat kits, IMO if it is designed to accept a single supply circuit, that is a branch circuit. If you put a loadcenter next to the AHU and drop two/three breakers to it you have a feeder and 2/3 branch circuits.

 

[Dennis Alwon]

Sorry about that, I still don't see where you couldn't have same size overcurent device on the feeder as you have on the branch circuit though.

In the case of an AHU with two or three breakers installed in the unit either at the factory or via listed field installed heat kits, IMO if it is designed to accept a single supply circuit, that is a branch circuit. If you put a loadcenter next to the AHU and drop two/three breakers to it you have a feeder and 2/3 branch circuits.

Yes if you have conductors that feed a disconnect with 2 or 3 sets of conductors feeding a single unit then by definition it is a feeder-- may applies to one overcurrent protective device in the disconnect. "an overcurrent protection" are the words I used.

Last time

430.62 states that the overcurrent protective device for a feeder is calculated by using the flc of the unit times 250% (from table 430.52)for an inverse time plus the sum of the other motors. In my case, there are no other motors.

Let me point out that one motor overcurrent protective device still falls under 430.62 if there is overcurrent protective device in the disconnect because those conductors are a feeder. so a 100 amp motor would have an overcurrent protective device at 250 amps but the branch circuit conductors from the disconnect to the motor itself may be sized a max of 175% of the flc. So the overcurrent protective device in the disconnect must be sized no more than 175 amps.

The point is there is no reason for this because imo, the entire run is a branch circuit

 

[kwired]

Yes if you have conductors that feed a disconnect with 2 or 3 sets of conductors feeding a single unit then by definition it is a feeder-- may applies to one overcurrent protective device in the disconnect. "an overcurrent protection" are the words I used.

Last time

430.62 states that the overcurrent protective device for a feeder is calculated by using the flc of the unit times 250% (from table 430.52)for an inverse time plus the sum of the other motors. In my case, there are no other motors.

Let me point out that one motor overcurrent protective device still falls under 430.62 if there is overcurrent protective device in the disconnect because those conductors are a feeder. so a 100 amp motor would have an overcurrent protective device at 250 amps but the branch circuit conductors from the disconnect to the motor itself may be sized a max of 175% of the flc. So the overcurrent protective device in the disconnect must be sized no more than 175 amps.

The point is there is no reason for this because imo, the entire run is a branch circuit

I get your point that entire run is a branch circuit. I don't get where you are coming up with the feeder must be higher setting then the branch circuit. 250% plus zero sum of all other motors is still 250%.

Branch circuit conductors only need to be 125% of motor FLA (most instances)- you mean to say something other then conductors there?

 

[al hildenbrand]

Here is new wording

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. Circuit conductors to the disconnect of an individual piece of equipment's field installed disconnect with an overcurrent protective device shall be considered a branch circuit.

This new wording is better, but it doesn't address the subpanel (not Service Equipment) as the origin of the last leg of conductors.

When your individual piece of equipment is supplied by an OCPD in a subpanel (not Service Equipment) your Definition forces the conductors between the subpanel and the Service Equipment (which is a Feeder) to be a Branch Circuit.

You still need to call out the first upstream OCPD closest to the "field installed disconnect with an overcurrent protective device".

 

[Smart $]

Here is new wording

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. Circuit conductors to the disconnect of an individual piece of equipment's field installed disconnect with an overcurrent protective device shall be considered a branch circuit.

Alternative???

Branch Circuit, Individual. A branch circuit that supplies only one utilization equipment, including one with a disconnecting means and overcurrent protection device at the outlet.

 

[al hildenbrand]

First, lets re-look at the words in 430.62:

430.62 Rating or Setting — Motor Load.
(A) Specific Load. A feeder supplying a specific fixed motor load(s) and consisting of conductor sizes based on 430.24 shall be provided with a protective device having a rating or setting not greater than the largest rating or setting of the branch circuit short-circuit and ground-fault protective device for any motor supplied by the feeder [based on the maximum permitted value for the specific type of a protective device in accordance with 430.52, or 440.22(A) for hermetic refrigerant motor compressors], plus the sum of the full-load currents of the other motors of the group.

The rule is a SHALL BE. So, it is "required". WHAT is required? ? ? The OCPD rating or setting NOT BE GREATER THAN. The rule does NOT say BE EQUAL TO, only "not be greater than". With this in mind, let's revisit your example from earlier:

I believe here is the issue. 430.62 speaks of feeder for fixed motor load(s). This states that a feeder should be based on the largest overcurrent protective device for a motor plus the sum of other motors. We have only one motor so a 3 phase 20 hp motor @ 208 volts is 59.4 amps. Table 430.52 tells us to take 250% of the load for a polyphase inverse time breaker-- 148.5 amps

This means the feeder technically should be 148.5 amps instead of a conductor size for the branch circuit at 125% 74.25 amps

For that 3 phase 20 hp motor @ 208 V, is the OCPD "next size" of 80 Amps "not greater than" 430.52's 148.5 Amps? ? ? Yes.

Or, the OCPD could be 90, 100, 110, 125, etc. as all are "not greater than". The actual OCPD chosen is a design choice. All that the language of 430.62 does is prevent the OCPD rating or setting from going ABOVE your example's 148.5 Amps.

Your argument that the cost of the largest OCPD is too great isn't a SAFETY issue, is it? Isn't the CMP primarily interested in safety only?

 

[Dennis Alwon]

Well, we will see what they say as I had already sent in the second re-wording. I am tired of it- the whole thinking is that the entire run is really a branch circuit and IMO, to call it otherwise feels wrong. There are differences so.... I realize this isn't a major change but I thought it worthwhile. The only reason, IMO that the cmp doesn't want to change this is that it complicates things

 

[Bob V]

Another way one could look at this is that a feeder usually (but not always) terminates in a load center or panelboard where the downstream wiring becomes branch circuits. If the wiring provides power to more than one load (multiple motors for example), it could be considered a feeder even if it originates in a panel of some type. I am all for clarifying things that are ambiguous but I have seen clarifications that generate more confusion than they solve.