MTW Wire Ampacity Chart
Allowable ampacity for MTW / UL 1015 machine tool wire by AWG size in industrial control panels, per UL 508A Table 28.1 and NFPA 79. MTW is the 600V, 105°C PVC hook-up wire used for panel power and control wiring, machine tool wiring, and internal equipment wiring.
MTW Ampacity by Size (UL 508A Table 28.1, Copper Conductors)
| Size (AWG / kcmil) | Area (mm²) | Ampacity, 60°C Column* | Ampacity, 75°C Column* |
|---|---|---|---|
| 18 AWG | 0.82 | 7 A | 7 A |
| 16 AWG | 1.31 | 10 A | 10 A |
| 14 AWG | 2.1 | 15 A | 15 A |
| 12 AWG | 3.3 | 20 A | 20 A |
| 10 AWG | 5.3 | 30 A | 30 A |
| 8 AWG | 8.4 | 40 A | 50 A |
| 6 AWG | 13.3 | 55 A | 65 A |
| 4 AWG | 21.2 | 70 A | 85 A |
| 3 AWG | 26.7 | 85 A | 100 A |
| 2 AWG | 33.6 | 95 A | 115 A |
| 1 AWG | 42.4 | 110 A | 130 A |
| 1/0 AWG | 53.5 | — | 150 A |
| 2/0 AWG | 67.4 | — | 175 A |
| 3/0 AWG | 85.0 | — | 200 A |
| 4/0 AWG | 107.2 | — | 230 A |
*Ampacities per UL 508A (Standard for Industrial Control Panels) Table 28.1 for insulated copper conductors. UL 508A 29.6: use the wire temperature rating marked on the component or its instructions to pick the column; if none is marked, use the 60°C column for components rated 100 A or less and the 75°C column for components rated over 100 A. Sizes 1/0 and larger have no 60°C value in the table. This chart is for reference only; consult a licensed electrical engineer and the current edition of the standard for your specific panel.
Small-Gauge MTW for Control Circuits (NFPA 79 Table 12.5.1)
| Size (AWG) | Ampacity, 60°C | Ampacity, 75°C | Ampacity, 90°C |
|---|---|---|---|
| 24 AWG | 2 A | 2 A | 2 A |
| 22 AWG | 3 A | 3 A | 3 A |
| 20 AWG | 5 A | 5 A | 5 A |
| 18 AWG | 7 A | 7 A | 14 A |
| 16 AWG | 10 A | 10 A | 18 A |
Per NFPA 79 (Electrical Standard for Industrial Machinery) Table 12.5.1, copper conductors at 30°C ambient. Small-gauge conductors in control circuits must also be protected per NFPA 79 / UL 508A control-circuit rules (for example, 18 AWG and 16 AWG are limited to 7 A and 10 A overcurrent protection in most cases). Terminal ratings on the connected device govern in practice.
How to Size MTW Wire in a Control Panel
- Find the load current. For a motor branch circuit, use the full-load current from NEC Table 430.250 (not the nameplate) and apply the 125% factor required by NEC 430.22 / UL 508A.
- Check the terminal temperature rating. Look at the contactor, breaker, or terminal block marking. No marking means 60°C for devices rated 100 A or less, and 75°C above 100 A.
- Read down the matching column in the table above and pick the first size whose ampacity meets or exceeds the required current.
- Check overcurrent protection limits. NEC 240.4(D) caps protection at 15 A for 14 AWG, 20 A for 12 AWG, and 30 A for 10 AWG regardless of the ampacity column.
- Check voltage drop on long runs with our wire size and voltage drop calculator. Inside a panel this rarely matters, but it does for field wiring to remote motors and sensors.
What Is MTW Wire?
MTW stands for Machine Tool Wire. It is a 600V, flame-retardant PVC-insulated copper wire listed under UL 1063 for use in industrial control panels, machine tool wiring, and appliance wiring. Nearly all stocked MTW is dual-rated as UL 1015 appliance wiring material (105°C, 600V), and many constructions add UL 1032 (1000V, 90°C), UL 1230 (oil and moisture resistant), CSA TEW, and UL 1426 boat cable listings. The 105°C rating and oil-resistant PVC make it a workhorse for panel shops, OEMs, and plant-floor maintenance.
MTW is sold as solid or stranded tinned copper (our 80C series) and stranded bare copper (our 01D series), in 13 standard colors so AC, DC, neutral, ground, and foreign-voltage circuits can be color-coded per panel-shop practice. Full part numbers, stranding, diameters, and weights are on the MTW / UL 1015 product page and the MTW spec sheet (PDF).
Frequently Asked Questions
What is the ampacity of 14 AWG MTW wire?
15 amps in a UL 508A control panel, in both the 60°C and 75°C columns. NEC 240.4(D) also limits 14 AWG copper to 15 A overcurrent protection.
What is the ampacity of 16 AWG and 18 AWG MTW?
10 amps for 16 AWG and 7 amps for 18 AWG per UL 508A Table 28.1 and NFPA 79 Table 12.5.1.
Why isn't MTW rated at its 90°C or 105°C ampacity?
Because the terminals it lands on are usually rated 60°C or 75°C. UL 508A requires sizing to the terminal rating, so the wire's higher insulation rating gives you margin against heat, not extra amps.
Is MTW the same as THHN?
Not exactly. THHN is a building wire listed under UL 83 with a nylon jacket; MTW is a UL 1063 machine tool wire with thicker, more flexible PVC. Many wires are dual-listed THHN/MTW, but a wire marked only MTW is for equipment and panels, not building raceway. See our MTW panel wire guide for a full comparison.
Is MTW the same as UL 1015?
They are different listings that are almost always applied to the same wire. MTW is the UL 1063 machine-tool designation; UL 1015 is the UL 758 appliance-wiring style. Dual-rated MTW / UL 1015 wire satisfies both, which is why we list it as one product.
