Wire Identification Reference
208–240V AC Supply — Line Side (Before Disconnect)
Hot 1 Ungrounded · Line
L1
208–240V AC
Hot 2 Ungrounded · Line
L2
208–240V AC
Safety Ground Protective Earth
PE
Ground
208–240V AC Supply — Load Side (After Disconnect)
Hot 1 Ungrounded · Load
T1
208–240V AC
Hot 2 Ungrounded · Load
T2
208–240V AC
Positive Bus +24VDC Supply
+24V
24V DC
Negative / Common Bus 0V Return
0V / COM
24V DC
Control Signal Switched +24V
24V-[suffix]
24V DC
Control Return Common / 0V
0V-[suffix]
24V DC
24VDC Relay Supply & Outputs
Relay Coil Supply
+24V
24V DC
Relay Coil Return
0V
24V DC
Relay Output (NO Contact) Switched signal out
201, 202…
24V DC
Relay Output Common
0V-[suffix]
24V DC
PLC Wiring — Keyence KV Nano · PNP Sourcing · Digital I/O
PLC DC Power +
+24V
24V DC
Digital Input Signal Label = PLC input address
000, 001…
24V DC
Digital Input COM Only +24V COM on PLC — no 0V common
24V-C0
24V DC
Digital Output Signal Label = PLC output address
500, 501…
24V DC
Digital Output COM +24V sourcing — no 0V common
24V-C1
24V DC
External Field Connections — Inputs & Dry Contact Outputs
External Input Signal NPN sensor or dry contact · Label = X address
X0, X1…
External
Dry Contact Output — Side A No panel voltage · External system supplies power
Y1-A, Y2-A…
External
Dry Contact Output — Side B No panel voltage · External system supplies power
Y1-B, Y2-B…
External
Quick Reference — Color Functions
Black
AC Hot 1 · L1 / T1
208–240V Line & Load
Red
AC Hot 2 · L2 / T2
+24VDC Power & Control
Blue
24VDC Negative · 0V
Common / Return
Orange
Relay Outputs
PLC Digital I/O Signals
White
External Field Wiring
X inputs · Y dry contact outputs
External voltage — unknown potential
Green / Yellow
Protective Earth (PE)
Safety Ground — All Circuits
Wire Label Convention — Suffix Key
24V Positive Supply Labels (Red wire)
24V-P
-P
PLC Supply
PLC 24V input
24V-H
-H
HMI Supply
HMI 24V input
24V-L
-L
Pilot Light / LED Supply
Panel indicator lamp
24V-C0
-C0
PLC Input COM (+24V sourcing)
Input COM +24V
24V-C1
-C1
PLC Output COM (+24V sourcing)
Output COM +24V
0V Return / Common Labels (Blue wire) — same suffix as matching supply
0V-P
-P
PLC Common Return
PLC 0V
0V-H
-H
HMI Common Return
HMI 0V
0V-L
-L
Pilot Light Common
Lamp 0V
PLC I/O Signal Labels (Orange wire) — label = PLC address
000 – 013
Input address
Digital Inputs
Wire 002 = I002
500 – 509
Output address
Digital Outputs
Wire 500 = Q500
External Field Wiring Labels (White wire) — external voltage, unknown potential
X0, X1…
Input label
External Input — NPN sensor or dry contact
Field signal
Y1-A, Y1-B
Relay · Side
Dry Contact Output — no panel voltage
External power
Wire Sizing & Overcurrent Protection
24VDC Control Wiring — Fixed Standard
All 24VDC control wiring uses 18 AWG / 1.0 mm² regardless of load. The 24VDC power supply output is protected by fuses — not breakers. Individual branch fuses should be sized to the device being protected, typically 1A – 4A per branch circuit.
Dedicated Overcurrent Protection Required
Each of the following must have its own dedicated breaker or fuse — they must never share overcurrent protection:
• VFD / Inverter — breaker type and rating must follow the VFD manufacturer's datasheet. Many VFDs require a D-curve breaker or fast-acting semiconductor fuse due to capacitive inrush. Using a non-specified breaker type may void warranty.
• Vibration Controller — dedicated breaker sized per controller nameplate rating.
• Switching Power Supply (24VDC) — dedicated breaker on the AC input side, sized per PSU rated input current.
208–240V AC Main Supply — Fixed (Customer 20A Facility Breaker)
Main Incoming Supply L1, L2, PE to main disconnect
12 AWG4.0 mm²
L1 · L2 · PE
Max 20A
208–240V AC Load Side — Breaker to Device (C & D Curve)
6A
18 AWG1.0 mm²
Small AC loads · Indicators
C or D curve
10A
16 AWG1.5 mm²
Control transformers · Small PSU
C or D curve
15A
14 AWG2.5 mm²
AC loads to ~1.5kW · Small VFDs
C or D curve
20A
12 AWG4.0 mm²
Larger VFDs · Main supply
C or D curve
C CURVE vs D CURVE — WIRE SIZING NOTE
C-curve and D-curve breakers at the same amperage rating require the same minimum wire size — the wire is sized to the breaker's continuous current rating, not its trip curve. The curve only affects which breaker is appropriate for the load. However, if a VFD's inrush requires selecting a larger D-curve breaker (e.g. 15A D-curve instead of 10A C-curve), the wire must be upsized to match the larger breaker rating.
UL Wire Rating Requirement — All Circuits
All wiring must be copper only, rated for 600V minimum and 75°C minimum temperature resistance, per UL installation requirements. Do not downsize wire gauge when substituting higher-temperature-rated wire. For VFD installations in ambient temperatures above 50°C, 90°C rated wire is required.
VFD output wire (VFD → motor): Use the same wire gauge on the output side (U/T1, V/T2, W/T3) as the input side. The motor cable carries variable-frequency AC — do not reduce gauge based on motor nameplate current alone.
Application Examples — Delta MS300 Single-Phase 230V
Single-Phase VFD Input Current Warning
Single-phase VFD input current is 2.5–3× higher than the three-phase output current. This is due to capacitive rectification on the DC bus — the drive draws current in sharp peaks rather than a smooth sine wave. Always size the breaker and input wire to the VFD's rated input current from the datasheet, not the motor nameplate current. For 1.5kW and 2.2kW drives, verify the total panel load does not exceed the facility's 20A supply capacity.
0.37 kW0.5 HP
VFD1A6MS21ANSAA
A
16 AWG1.5 mm²
~1.8 A
6A · D-curve
3.33× input current @ 208V
0.75 kW1 HP
VFD2A8MS21ANSAA
A
14 AWG2.5 mm²
~3.1 A
10A · D-curve
3.23× input current @ 208V
1.1 kW1.5 HP
VFD4A8MS21ANSAA
B
12 AWG4 mm²
~5.3 A
16A · D-curve
3.02× input current @ 208V · larger wire reduces losses
1.5 kW2 HP
VFD7A5MS21ANSAA
C
8 AWG10 mm²
~8.3 A
16A · D-curve
1.93× input current @ 208V · verify total panel load on 20A supply
2.2 kW3 HP
VFD11AMS21ANSAA
C
8 AWG10 mm²
~12.2 A
16A · D-curve
1.31× input current @ 208V · verify total panel load on 20A supply
BREAKER SIZING RATIONALE & NEC NOTES
Panel breaker is capped at 16A to ensure coordination with the customer's 20A facility breaker — a breaker larger than 20A would never trip before the upstream one. Delta's Section 7-2 NFB table lists much larger values (up to 70A) based on UL 508 §45.8.4a worst-case inrush, but those ratings assume a dedicated supply sized to the drive. The MS300's internal soft-charge circuit limits power-on capacitor inrush in practice, making tighter sizing reliable. Ramp time (2–3 sec) reduces motor acceleration current but does not affect power-on capacitor inrush — breaker sizing is determined by the latter.
Input currents shown are calculated at 208V worst case (230V nameplate × 230/208 = +10.6%). All current calculations and wire sizing must use 208V as the design basis. NEC 430.122 requires VFD input conductors rated at 125% of VFD rated input current — not motor nameplate current. Wire sizes shown follow Delta Chapter 5 specifications which exceed the NEC 125% minimum. D-curve (high magnetic) breakers are recommended for VFD branch circuits to tolerate brief inrush peaks without nuisance tripping. All wire must be 600V / 75°C rated copper.
Compliance Notes
NFPA 79 SECTION 13 & UL 508A
This labeling system is a compliant extension of standard practice. NFPA 79 requires conductors to be identifiable at each end by color, alphanumeric marking, or both — no specific numbering format is mandated. Using PLC I/O addresses as wire labels is self-documenting and fully acceptable. Using descriptive suffixes on 24V/0V supply wires (e.g. 24V-H, 0V-P) provides circuit group identification at the bus terminal without pulling wire — an extension, not a violation.
Required on schematic title block:
A wire identification legend explaining the suffix convention and I/O address labeling method. This is what makes the system auditable by a UL field inspector.