NEMA Contactor Sizes 00–9 Explained

Selection steps + common use cases (with a simple size chart)

When someone says, “I need a NEMA Size 1 contactor,” they’re using one of the most practical rating systems in motor control. NEMA sizing is built to be forgiving—with reserve capacity intended to cover a wide range of real-world conditions without requiring detailed duty calculations every time. 

This post breaks down NEMA Sizes 00 through 9, shows a simple size chart, and gives you a step-by-step method to select the right size for new panels or replacements.

If you’re comparing standards overall, read: NEMA vs IEC Contactors – Selection Guide

---

Quick answer: how to pick a NEMA size

1. Identify the motor HP and voltage (and phase).
2. Choose the NEMA size from the HP-at-voltage chart below (full-voltage start, typical duty). 
3. Confirm the duty (normal vs plugging/jogging/reversing) because NEMA publishes different ratings for those harsher duties. 
4. Verify overload protection is appropriate for the controller and does not exceed the controller’s service-limit current guidance. 
5. Confirm coil voltage, enclosure/environment, accessories, and (if applicable) SCCR/short-circuit coordination.

---

What does “NEMA Size” mean?

NEMA contactors and starters are classified by standard frame sizes (00–9) with published tables for:

• Maximum continuous current
• Maximum motor horsepower at common voltages
• Additional limits such as locked-rotor current and service-limit current in the standard tables/documentation used by manufacturers 

The practical benefit: for typical across-the-line motor starting, you can often select a NEMA size quickly using HP and voltage—without deep duty modeling. 

---

NEMA Contactor Size Chart (00–9)

Use this as a fast starting point for typical, full-voltage, three-phase motor control applications. Always confirm final selection against the specific manufacturer’s tables for your exact motor and duty. 

Source basis commonly published for NEMA size tables: NEMA size current/HP groupings as compiled and widely reproduced from NEMA tables.

---

Common use cases by NEMA size (practical “what you’ll see in the field”)

These are typical patterns (not hard rules). Actual selection depends on motor HP/voltage, enclosure, duty, and coordination.

• Size 00–0: Small pumps/fans, fractional-to-small HP loads, small HVAC components, light conveyors
• Size 1: Small industrial motors, modest conveyors, small compressors, general-purpose machines
• Size 2: Medium pumps/fans, moderate conveyors, small material handling equipment
• Size 3: Heavier conveyors, process pumps, larger compressors, more frequent cycling environments
• Size 4: Large process loads, heavier inertia equipment, robust industrial service
• Size 5–6: Large motors commonly found in MCC lineups, large pumping/compressor applications, heavy industrial loads
• Size 7–9: Very large horsepower applications and high-current motor control where equipment is typically engineered as a complete assembly (often in MCCs or custom lineups)

---

The part many charts don’t tell you: duty matters (especially plugging/jogging)

If your application involves rapid reversing, plugging, or frequent jogging, you are no longer in “typical duty.” NEMA addresses this with separate ratings/tables for plugging and jogging duty.

One example of how “limited” that duty can be: manufacturer technical data describing NEMA plugging/jogging service references repeated interruption of stalled motor current and includes frequency limits (e.g., guidance tied to openings/closings per minute and per time window). 

Takeaway: For reversing/jogging applications, don’t rely on the simple HP chart alone—verify against the correct duty table.

---

Step-by-step selection guide (new design or replacement)

Step 1: Gather motor and control basics

• Motor HP, voltage, phase
• Motor nameplate FLA
• Starting method (across-the-line, wye-delta, part-winding, etc.)
• Duty profile: normal start/stop vs jogging/reversing/plugging
• Control coil voltage (24V, 120V, 230V, etc.)

Step 2: Pick the NEMA size from the chart

Use the chart above as the first pass for typical duty. 

Step 3: Verify duty category (normal vs plugging/jogging)

If your process includes frequent reversing, inching, plugging, or high-cycling, confirm the correct NEMA duty basis using the appropriate tables. 

Step 4: Verify overload selection against service-limit guidance

Beyond continuous current, NEMA documentation and manufacturer technical data define service-limit current as a maximum RMS current allowed for protracted periods, and note that overload device trip current should not exceed the controller’s service-limit current rating. 

Practical takeaway: Even if the contactor “fits” by size, overload selection still must be coordinated properly.

Step 5: Confirm environment and enclosure

Heat, dust, washdown, vibration, and ambient temperature can change what “works reliably.” NEMA contactors are often chosen because they’re designed for robust service and long life, but you still need the correct enclosure and installation approach. 

Step 6: Confirm accessories and interface details

• Aux contacts needed? (seal-in, status feedback, PLC I/O)
• Mechanical interlocks (reversing contactors)
• Space and mounting pattern
• Replacement coil availability (match coil voltage and frequency)

Step 7: Confirm short-circuit coordination/SCCR where required

In many real installations (especially panels/MCCs), selection must align with the assembly’s short-circuit rating and tested combinations. Manufacturer ecosystems often provide tested combination guidance for components. 

---

Replacing an existing NEMA contactor: fast checklist

If you’re replacing a failed contactor and want a “no surprises” swap:

1. Match NEMA size (00–9) first
2. Match poles (typically 3-pole for 3Ø motors)
3. Match coil voltage exactly
4. Confirm aux contact needs (NO/NC count and rating)
5. Confirm whether it’s part of a starter (contactor + overload) and match overload range/class
6. Confirm enclosure type and mounting constraints
7. If the system reverses/jogs frequently, verify it wasn’t actually a plugging/jogging duty case (don’t downgrade)

CTA: [Internal link: Shop NEMA Contactors]
Need help cross-referencing? [Internal link: Contact / Send us the existing part number + motor details]

---

FAQ

NEMA Contactor Sizes (00–9) FAQs

Quick answers to common NEMA sizing and selection questions.

Is there a direct “amp conversion” to NEMA size?

Not reliably. NEMA sizing is based on standardized tables including HP and current groupings, and selection can also depend on duty (especially plugging/jogging) and other limits in published data.

Why do NEMA contactors feel “bigger” than IEC contactors?

NEMA sizing is commonly described as having built-in reserve capacity so the same size can cover a wider range of applications without detailed application categories.

What’s “service-limit current” and why does it matter?

Service-limit current is defined in manufacturer technical data as the maximum RMS current allowed for protracted periods, and overload device trip current guidance is tied to that rating.

 

---

Trust and technical basis

Prepared by: Motor Controls Direct Technical Team

External references consulted:

• NEMA ICS 2 — Industrial Control and Systems: Controllers, Contactors, and Overload Relays Rated 600 Volts
• NEMA ICS 2 Errata/Addendum — updated tables for plugging/jogging duty and locked-rotor current considerations
• Rockwell Automation Technical Data — NEMA contactor/starter specs including service-limit current guidance and plugging/jogging service notes 
• Eaton Technical Information (Freedom NEMA) — design intent and life/performance notes for NEMA contactors and starters
• Commonly reproduced NEMA size tables used for quick-reference charts