I did an inspection correction a few years ago on a blower rated 120 volts and under 20 amps…according to the nameplate, but according to the inspector, if it’s 120 volts you go by the horsepower chart in the NEC, which required 30 amps. Is this procedure the same with all motors?
Pool Pump and Blowers 120 volt
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Dsg319
Senior Member
- Location
- West Virginia
- Occupation
- Wv Master “lectrician”
Motor OCPD is sized according to the HP rating of the name plate.
Unless it has specifications stating min/max OCPD from the manufacture.
Correct me if I’m wrong.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
HP determines the wire size per NEC Tables, it’s a conservative number to allow for motor replacement.
Branch ckt overcurrent protection determined by nameplate amps, typically is 150 to 250% depending if fuses or ckt breaker
OL size is per mfg instructions, often 115% of name plate
“The breaker protects the wire, the overload protects the motor”
Branch ckt overcurrent protection determined by nameplate amps, typically is 150 to 250% depending if fuses or ckt breaker
OL size is per mfg instructions, often 115% of name plate
“The breaker protects the wire, the overload protects the motor”
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Dsg319
Senior Member
- Location
- West Virginia
- Occupation
- Wv Master “lectrician”
Isn’t motor OCP sized per FLC in NEC based off of motor nameplate HP?
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
If there is a HP rating on the motor nameplate, you are required to use the NEC charts on FLC for the conductor sizing.
If there is NO HP RATING on the nameplate but it shows a kW (or Watts) rating, you can convert the watts to HP (there are 743 W/HP), then pick the conductor size based on the next closest HP up from that value. If the nameplate only shows the FLA, then you can size the conductors per the FLA.
The OCPD is always sized based on the motor nameplate FLA, as is the OL protection (if necessary).
If the machine provides values for MCA (Minimum Circuit Ampacity) and MOCP (Max Over Current Protection), then you use those values.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
What is the HP?
Is the motor thermally protected?
- Occupation
- Licensed Electrician
Circuits for motors are sized of the table values in part XIV of article 430 corresponding to the HP of the motor. FLC on the nameplate is used for sizing the overloads.
HP is 1 1/2. I’m not sure if it’s thermally protected
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
The nameplate will state if thermally protected. If so no overloads are needed
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
It might just say “Protected” or even just have a “TP” on the nameplate.
- Occupation
- Licensed Electrician
You always go by the chart for circuit sizing. You only use the nameplate to size thermal overloads if the motor requires them. Most 120V motors will have built in thermal protection.
So if I go by the chart, theoretically speaking it says 17 amps, and let’s say the chart says 27. I put a 30 amp breaker in with 10 gauge. What do you do if it’s not thermally protected? Does the chart say both amperage’s for thermal and non thermally protected motors? Sorry, I’m so confused. I appreciate everyone’s information
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
For a 120 V 1 1/2 HP motor my square d motor data calculator has 20 amps NEC FLC, minimum wire size 12 copper, TM breaker at 40 amps
For motors, the breaker is almost always larger than the wire, so the motor can start with out tripping the breaker
The only change for a TP motor is there are no overloads or thermals in the starter.
It’s thermally protected at 1.5 HP, max 12 amps and 120 volt. There’s a salt that needs to be plugged in as well. 20 amp and #12 because it’s thermally protected?
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
What is a salt?
You want this device on the same circuit?
You want this device on the same circuit?
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
If this is a garden variety pool spa blower the HP ratings are meaningless for NEC purposes and Article 430 has no relevance. The HP ratings for these things has no relation to NEMA HP ratings as used in Article 430. It is an appliance and you just go by the amperage on the nameplate or the manufacturers instructions.
This is not treated, for example, like a Roots blower that is driven with a standard NEMA motor.
This is not treated, for example, like a Roots blower that is driven with a standard NEMA motor.
It’s a salt system for a pool. They don’t require that much power
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