430.33

[m sleem]

If i'm going to size all branch conductors of the pumps except (hvac pumps circulation pump) to 140% of the pump name plates, am i correct? if yes, why always forum members use 125% rather than 140% in the most posts!

 

[david luchini]

If i'm going to size all branch conductors of the pumps except (hvac pumps circulation pump) to 140% of the pump name plates, am i correct? if yes, why always forum members use 125% rather than 140% in the most posts!

Motor branch circuit conductors are sized per 430.22, not 430.33.

 

[augie47]

Motor branch circuit conductors are sized per 430.22, not 430.33.

however, 430.33 for overload protection references you back to Table 430.22(E) which does size motor circuit conductors for "Other than continuous duty" motors.

 

[Smart $]

however, 430.33 for overload protection references you back to Table 430.22(E) which does size motor circuit conductors for "Other than continuous duty" motors.

I believe that's where m sleem's confusion originates. When forum members refer to 125%, it's in reference to minimum conductor sizing and quite possibly the largest motor in a load calculation. Has nothing to do with SC/GF or OL sizing.

 

[augie47]

To me the more basic question is at what point does one size the conductors per Table 430.22(E).

 

[Smart $]

To me the more basic question is at what point does one size the conductors per Table 430.22(E).

When the conditions of use match the Table's criteria... :blink:

I know that's stating the obvious... but what else can I say?

 

[augie47]

but more to m sleem's question..
430.22(E) lists "pumps" as a "classification of service for intermittent duty".. obviously all pumps are not "other than continuous duty"
What makes the determination as to a pump being an other than continuous duty operation ?
If I have a pump motor with a "CONT DUTY" nameplate... do I size my conductors at 125% or 140% ? What makes that pump "Intermittent duty" ? How many cycles per hour, ect. ?

 

[kwired]

but more to m sleem's question..
430.22(E) lists "pumps" as a "classification of service for intermittent duty".. obviously all pumps are not "other than continuous duty"
What makes the determination as to a pump being an other than continuous duty operation ?
If I have a pump motor with a "CONT DUTY" nameplate... do I size my conductors at 125% or 140% ? What makes that pump "Intermittent duty" ? How many cycles per hour, ect. ?

A motor nameplate that states "intermittent duty" and/or the duty cycle.

Most frequent place I have encountered them is in auto repair shops on hydraulic pumps of auto lift equipment. The motor only runs a few minutes at most to lift the vehicle, then sits idle for possibly hours before running again.

Specific loads that by nature of the use will typically have short duty cycles followed by periods of non use is where to look for them, they can save some $$$ on motor design compared to using one rated for continuous duty.

 

[Smart $]

but more to m sleem's question..
430.22(E) lists "pumps" as a "classification of service for intermittent duty".. obviously all pumps are not "other than continuous duty"
What makes the determination as to a pump being an other than continuous duty operation ?
If I have a pump motor with a "CONT DUTY" nameplate... do I size my conductors at 125% or 140% ? What makes that pump "Intermittent duty" ? How many cycles per hour, ect. ?

I see. Code provides no solid criteria to make a 'classification of service' determination. Perhaps it is in some NEMA standard...???

 

[augie47]

A motor nameplate that states "intermittent duty" and/or the duty cycle.

Most frequent place I have encountered them is in auto repair shops on hydraulic pumps of auto lift equipment. The motor only runs a few minutes at most to lift the vehicle, then sits idle for possibly hours before running again.

Specific loads that by nature of the use will typically have short duty cycles followed by periods of non use is where to look for them, they can save some $$$ on motor design compared to using one rated for continuous duty.

Understand all that..
BUT
In the '08 and '11 Code, there is a Table 430.22(E) which seems to indicate IF one has a continuous rated motor and it is used for intermittent or periodic duty the conductor should be rated at 140%....
The Code does not define those duty cycles so I find his question interesting........

 

[m sleem]

Understand all that..
BUT
In the '08 and '11 Code, there is a Table 430.22(E) which seems to indicate IF one has a continuous rated motor and it is used for intermittent or periodic duty the conductor should be rated at 140%....
The Code does not define those duty cycles so I find his question interesting........

IMO intermittent pumps e.g. (sump pump, pressure maintenance pump, booster pump, WAGD pump) shall have a conductor sized to 140% of name plate & the continuous pumps e.g. (hvac chilled water pump, hvac hot water pump, plumbing domestic circulation pump) shall have a conductor sized to 125% of name plate.

Originally Posted by kwired
Most frequent place I have encountered them is in auto repair shops on hydraulic pumps of auto lift equipment. The motor only runs a few minutes at most to lift the vehicle, then sits idle for possibly hours before running again.

Not really, the sump pump starts 6 times per hour & 5 minutes max per each start!

 

[david luchini]

IMO intermittent pumps e.g. (sump pump, pressure maintenance pump, booster pump, WAGD pump) shall have a conductor sized to 140% of name plate

Only if the pump uses a continuous duty motor. For an other than continuous duty motor, the conductors can be sized lower than the nameplate current based on the motor duty rating.

the continuous pumps e.g. (hvac chilled water pump, hvac hot water pump, plumbing domestic circulation pump) shall have a conductor sized to 125% of name plate.

The 125% for continuous duty is not based on the motor nameplate, but the currents in the tables 430.248-430.250.