Hvac

[hhsting]

I have feeder breaker 30A feeds fused disconnect 25A which has branch circuit breaker which feeds condenser outside.

The condenser MCA is 17.2A. What size conductor between 30A breaker and the 25A fused disconnect #12 awg or #14 awg?

 

[petersonra]

I have feeder breaker 30A feeds fused disconnect 25A which has branch circuit breaker which feeds condenser outside.

The condenser MCA is 17.2A. What size conductor between 30A breaker and the 25A fused disconnect #12 awg or #14 awg?

What conductor gives you 17.2 amps of ampacity?

 

[augie47]

Your question could be expanded with "or a #10" as, the way it's worded, our inspectors would require a #10 since it's a "feeder".
If the max OCP for then unit is 25 amp and the panel had a 25amp breaker then #14 as they would consider the 2nd breaker , regardless of size, as a "disconnect.
No doubt, answers will vary,.

 

[infinity]

If the 25 amp OCPD is considered supplemental protection isn't the entire circuit a branch circuit?

 

[hhsting]

If the 25 amp OCPD is considered supplemental protection isn't the entire circuit a branch circuit?

No. Last overcurrent protection is the outside 25A fused disconnect so branch circuit is between the condensing unit and the outside fused disconnect

 

[hhsting]

Your question could be expanded with "or a #10" as, the way it's worded, our inspectors would require a #10 since it's a "feeder".
If the max OCP for then unit is 25 amp and the panel had a 25amp breaker then #14 as they would consider the 2nd breaker , regardless of size, as a "disconnect.
No doubt, answers will vary,.

Max ocpd is 25A. The fused disconnect has 25A fuse in it. The panelboard has 30A breaker feeding the fused disco.

Which has #14 awg?

 

[infinity]

No. Last overcurrent protection is the outside 25A fused disconnect so branch circuit is between the condensing unit and the outside fused disconnect

Look up supplemental protection.

 

[augie47]

I think if it was clear-cut, you might not have asked. I've seen it approached different ways. IF the outside disconnect was non-fusible then it would simply be that, a disconnect. Does adding fuses change it's nature ?? Does that make the circuit between the breaker and disconnect a feeder ? If one answers affirmative and the breaker is a 30 amp, I see the #10 requirement.
If you look at the outside disconnect as supplemental protection then you could make the case for a #14 but then it's difficult to allow a breaker over the MOCP of the unit,.
As I say, you will likely have comments beyond Bob and myself

 

[hhsting]

Look up supplemental protection.

Not in Article 100?

 

[augie47]

Not in Article 100?

Expand your mind a bit supplemental what ?? overcurrent protection !!!! Try that in definitions.

 

[hhsting]

I think if it was clear-cut, you might not have asked. I've seen it approached different ways. IF the outside disconnect was non-fusible then it would simply be that, a disconnect. Does adding fuses change it's nature ?? Does that make the circuit between the breaker and disconnect a feeder ? If one answers affirmative and the breaker is a 30 amp, I see the #10 requirement.
If you look at the outside disconnect as supplemental protection then you could make the case for a #14 but then it's difficult to allow a breaker over the MOCP of the unit,.
As I say, you will likely have comments beyond Bob and myself

Alight well in this case its not supplemental protection due to MOCP

#10 awg between breaker and fused disco however plans say #14awg. 240.4(D) applies only to branch circuits no? Also 240.4(G) would apply here no?

 

[Little Bill]

With the way it is now, a 30A breaker to a 25A fused disconnect, I see the 30A run to the 25A disconnect as a feeder and the conductor sizing should be sized accordingly, which would be #10 according to the table and referring to 240.4(D). The run to the unit from the fused disconnect can be sized according to 240.4(G) and could be #14. With the 30A breaker, I can't see any way of #14 being allowed from the breaker to the fused disconnect.
You could change the breaker to 25A and then use the #14.

 

[wwhitney]

Alight well in this case its not supplemental protection due to MOCP

Sounds like you're saying the MOCP is 25A, not 30A (information missing from the OP).

In that case I agree that the 30A feeder needs to be #10. But if you change the feeder breaker to 25A, then the feeder could be #14 just like the branch circuit.

Cheers, Wayne

 

[jap]

To run 14 ga. wiring to an outside 30 amp AC disconnect from a breaker in a panel is just plain dumb in my book.


JAP>

 

[hbiss]

IF the outside disconnect was non-fusible then it would simply be that, a disconnect. Does adding fuses change it's nature ?? Does that make the circuit between the breaker and disconnect a feeder ? If one answers affirmative and the breaker is a 30 amp, I see the #10 requirement.

That's the way I see it. It's a feeder. Save some money, use a non-fuseable disconnect and #12 wire and it's a branch circuit.

-Hal

 

[infinity]

No. Last overcurrent protection is the outside 25A fused disconnect so branch circuit is between the condensing unit and the outside fused disconnect

I should have said supplementary but the result is the same, the conductors between the panel and the disconnect are not always feeder conductors.

Overcurrent Protective Device, Supplementary. A device intended to provide limited overcurrent protection for specific applications and utilization equipment such as luminaires and appliances. This limited protection is in addition to the protection provided in the required branch circuit by the branch-circuit overcurrent protective device.

 

[wwhitney]

the conductors between the panel and the disconnect are not always feeder conductors.

I'm not following this emphasis on whether the conductors are feeders. If the OCPD does not exceed the MOCP, then a feeder supplying only one motor load/piece of HVAC equipment would be sized the same as a branch circuit, per my understanding of 430.62 (and as is only reasonable).

Cheers, Wayne

 

[infinity]

I'm not following this emphasis on whether the conductors are feeders. If the OCPD does not exceed the MOCP, then a feeder supplying only one motor load/piece of HVAC equipment would be sized the same as a branch circuit, per my understanding of 430.62 (and as is only reasonable).

Cheers, Wayne

The conductors between the 30 amp OCPD at the panel and the 25 amp OCPD at the disconnect can be by definition (OCPD at each end) a feeder. That means that they need to be a minimum of 30 amps but if the 25 amp OCPD is supplementary (Article 100 definition post #16) then the branch circuit begins at the panel and the conductors only need to be sized according to the MCA of 17.2 amps.

 

[wwhitney]

The conductors between the 30 amp OCPD at the panel and the 25 amp OCPD at the disconnect can be by definition (OCPD at each end) a feeder. That means that they need to be a minimum of 30 amps.

Again, only if the MOCP is under 30A. If the MOCP were 30A, then they only need to meet the MCA, regardless of whether they are a feeder or branch circuit. As per my understanding of 430.62, and as logic dictates.

Cheers, Wayne

 

[infinity]

Again, only if the MOCP is under 30A. If the MOCP were 30A, then they only need to meet the MCA, regardless of whether they are a feeder or branch circuit. As per my understanding of 430.62, and as logic dictates.

Cheers, Wayne

He stated that the MaxOCPD is 25 amps.