Code Requirements

[jap]

The short circuit ground fault protection is an overcurrent device.

Yes it is, so, why label the rule as only applying to a circuit breaker as an "overcurrent protection" device?

JAP>

 

[Strathead]

Because the rule for manually and automatically opening is for a circuit breaker used as an "overcurrent device"
On a motor load or air conditioner you're allowd to size your wire smaller because of the "overcurrent protection device" incorporated into the motor's overload, and, the circuit Breaker ahead of it actually then becomes the Short Circuit Ground Fault protection.
JAP>

I don't actually know the nuance of the "why" motors can have wiring smaller than the overcurrent protection, but I don't think it is exclusively for the reason you listed. I actually think it is because the nature of a motor is that it inherently can't short out and have an overcurrent that damages the conductor insulation before the head end breaker trips. And a wire short will reach instantaneous trip area anyway.

 

[Strathead]

Yes it is, so, why label the rule as only applying to a circuit breaker as an "overcurrent protection" device?

JAP>

Because nothing prevent a circuit breaker from being used as a switch, maybe. Nothing says I can put a 200 amp breaker with #2 wires on it, on the load side of a 100A circuit breaker. I am just guessing, by the way.

 

[jap]

I don't actually know the nuance of the "why" motors can have wiring smaller than the overcurrent protection, but I don't think it is exclusively for the reason you listed. I actually think it is because the nature of a motor is that it inherently can't short out and have an overcurrent that damages the conductor insulation before the head end breaker trips. And a wire short will reach instantaneous trip area anyway.

Sounds good.


JAP>

 

[jap]

Because nothing prevent a circuit breaker from being used as a switch, maybe. Nothing says I can put a 200 amp breaker with #2 wires on it, on the load side of a 100A circuit breaker. I am just guessing, by the way.

Ok.

JAP>

 

[jap]

Because nothing prevent a circuit breaker from being used as a switch, maybe. Nothing says I can put a 200 amp breaker with #2 wires on it, on the load side of a 100A circuit breaker. I am just guessing, by the way.

Where motors with overload protection are concerned I beg to differ.

JAP>

 

[busman]

Common trip tandem 2 pole
View attachment 2566597

Just bought one of these the other day. Look for the "C" in the part number. Link to the one I bought below. I had a "full panel" and needed to add a 2-pole, so I joined the existing compressor (40) and air handler (20).

Eaton BQC220240​

 

[don_resqcapt19]

Yes it is, so, why label the rule as only applying to a circuit breaker as an "overcurrent protection" device?

JAP>

The definition if overcurrent in Article 100 includes short circuits, ground faults and overloads. The sizing permitted for branch circuit overcurrent protective deices results in the OCPD only providing short circuit and ground fault protection, while a second device provides the overload protection.

 

[don_resqcapt19]

Because nothing prevent a circuit breaker from being used as a switch, maybe. Nothing says I can put a 200 amp breaker with #2 wires on it, on the load side of a 100A circuit breaker. I am just guessing, by the way.

The 2 AWG, assuming it is copper, is properly protected by the 100 amp breaker, and the 200 amp is just a switch. There is nothing in the code that says you can't do this.

 

[mtnelect]

But, on an Air Conditioner is the Circuit Breaker actually considered the "Overcurrent Device" ? or is it the "Short Circuit Ground Fault" protection?

If the circuit breaker feeding an air conditioner is actually considered the "Overcurrent" device, then I don't see how we could you ever size our wire to a motor load with integral overload protection smaller than the OCPD feeding it.

JAP>

If you are using just a circuit breaker, it would be the maximum fuse amps or HACR type circuit breaker. with the minimum circuit amps for the wiring. Then just a non-fusible disconnect at the unit.

 

[don_resqcapt19]

If you are using just a circuit breaker, it would be the maximum fuse amps or HACR type circuit breaker. with the minimum circuit amps for the wiring. Then just a non-fusible disconnect at the unit.

If it just says fuse on the nameplate, you can't use a breaker.

Many breakers are no longer marked HACR because a change made in the 90s to UL 489 requires all listed breakers to be suitable for HACR installations.

Also for larger equipment, you have to be note the available short circuit current at the disconnect as well as the equipment. Most non-fusible disconnects can only be used where the available short circuit current is 10,000 amps or les.

 

[mtnelect]

If it just says fuse on the nameplate, you can't use a breaker.

Many breakers are no longer marked HACR because a change made in the 90s to UL 489 requires all listed breakers to be suitable for HACR installations.

Also for larger equipment, you have to be note the available short circuit current at the disconnect as well as the equipment. Most non-fusible disconnects can only be used where the available short circuit current is 10,000 amps or les.

On this forum, I have seen many electricians question how can a 50-amp breaker protect a 33.1 wire ?

The compressor's internal safety's "Hermetic/Scroll provides the protection needed to prevent it from any damage, like over current and over pressure. All compressors are manufactured to the highest degree possible than any other motor. That is why they can tolerate more than any common motor.

 

[don_resqcapt19]

On this forum, I have seen many electricians question how can a 50-amp breaker protect a 33.1 wire ?

The compressor's internal safety's "Hermetic/Scroll provides the protection needed to prevent it from any damage, like over current and over pressure. All compressors are manufactured to the highest degree possible than any other motor. That is why they can tolerate more than any common motor.

Not sure anyone was talking about how conductors are sized for motors and air conditioning equipment, and what is 33.1 wire?

So you have never replaced a hermetic compressor because the motor had burnt up?

There is cheap junk on the market for all types of equipment, including air conditioning equipment.

 

[mtnelect]

Not sure anyone was talking about how conductors are sized for motors and air conditioning equipment, and what is 33.1 wire?

So you have never replaced a hermetic compressor because the motor had burnt up?

There is cheap junk on the market for all types of equipment, including air conditioning equipment.

In California "Cheap Junk" will not fly.

 

[electrofelon]

On this forum, I have seen many electricians question how can a 50-amp breaker protect a 33.1 wire ?

The compressor's internal safety's "Hermetic/Scroll provides the protection needed to prevent it from any damage, like over current and over pressure. All compressors are manufactured to the highest degree possible than any other motor. That is why they can tolerate more than any common motor.

I'm not sure I follow your reasoning. Even a standard simple motor is allowed to have a standard breaker for the short circuit and ground fault protection set at 250% plus next size up.

 

[mtnelect]

I'm not sure I follow your reasoning. Even a standard simple motor is allowed to have a standard breaker for the short circuit and ground fault protection set at 250% plus next size up.

You also have motor control heaters to protect the wiring. In HVAC protection there is none, it is internal. That's what confuses people on this forum.

 

[Strathead]

Where motors with overload protection are concerned I beg to differ.

JAP>

I meant can’t put.

 

[Strathead]

The 2 AWG, assuming it is copper, is properly protected by the 100 amp breaker, and the 200 amp is just a switch. There is nothing in the code that says you can't do this.

Yeah I meant can’t . It was a typo.