Wiring Plan — Juliet Coffee Water System Control Panel
| Field | Detail |
|---|---|
| Document Number | RO-SPEC-001 / WIRE-001 |
| Revision | Rev A — initial issue |
| Anchored to | System overview §5 (controls), §6 (electrical); BOM Rev H |
| Scope | Internal wiring of the control enclosure: 240 VAC service in → branch breakers → VFDs / control bus → PLC, HMI, I/O, field devices. Field wiring stops at the panel terminal strip; piping, sensor placement, and motor mechanical install are covered in the system overview. |
⚠ All work shall be performed by a licensed electrician in accordance with NEC Article 430, NFPA 79, and UL 508A. This document is a build/wiring intent — it is not a substitute for the as-built panel schematic that the panel shop/electrician will produce and stamp.
1. Conventions
1.1 Wire colour code (UL 508A §66)
| Function | Insulation colour |
|---|---|
| Ungrounded AC line (240 VAC, 120 VAC) | Black (L1) / Red (L2) |
| Grounded AC neutral | White |
| AC control circuit ≤ 120 V derived inside panel | Red |
| DC control positive (+24 VDC) | Blue |
| DC control common (0 VDC) | Blue with white tracer |
| Equipment grounding conductor | Green or Green / Yellow |
| Foreign voltage — energised with main disconnect OFF | Orange (none expected in this build) |
1.2 Wire gauge & terminations
| Circuit class | Min gauge | Termination |
|---|---|---|
| 240 VAC branch to VFDs (CB-1) | 10 AWG THHN | DN-T12-A feed-through (24-12 AWG rated) |
| 240 VAC branch to VFDs (CB-2, CB-3) | 14 AWG THHN | DN-T12-A |
| 120 VAC control branch (CB-4) | 12 AWG THHN | DN-T12-A |
| VFD output to motor | VFDC-16-4B-1 (16 AWG, 4-cond, shielded XLPE/TPE) | Drive lugs at VFD; motor box at the load |
| 24 VDC field power | 16–18 AWG MTW | DN-T12-A |
| PLC discrete I/O field wiring | 18 AWG MTW | Field side: DN-T12-A. Module side: P2-RTB screw terminals. |
| PLC analog I/O (4–20 mA, 0–10 V, 0.5–4.5 V) | 18 AWG twisted-pair shielded (e.g. Belden 8761 or equivalent) — shield grounded at panel end only | DN-T12-A on field side; P2-RTB on module side |
| RTD (3-wire) | 22 AWG 3-conductor shielded | DN-T12-A; P2-RTB |
| RS-485 Modbus RTU | Q8302-1 (24 AWG, 1 twisted pair, shielded) — daisy-chain, 120 Ω terminations both ends | Drive RS-485 screw terminals; PLC RS-485 port |
| Equipment grounding | 12 AWG green (control), 10 AWG green (VFD) | DN-G10-10 grounding terminal blocks bonded to DIN rail and panel ground bus |
1.3 Tag conventions
- Terminal numbers follow the convention
<rail>-<block>— e.g.TB1-12is rail TB1, block 12. Each I/O point gets exactly one panel-side terminal block. - Wire labels are heat-shrink type, marked at both ends with the source-destination pair (e.g.
P101-VFD-101 U). - Device tags match the system overview (P-101, VFD-101, FT-101, SV-RECIRC, etc.).
2. Panel Layout
A NEMA 4 / UL 508A enclosure (sized for ≥ 25 % spare DIN rail per UL 508A §28) is partitioned into four horizontal zones, top-to-bottom:
┌───────────────────────────────────────────────────────────────────────────┐
│ ZONE A — Service & Branch Protection (top) │
│ Main disconnect (lockable) ─ L1/L2/N/G │
│ CB-1 (GMCBU-2C-20, 20 A 2P) → VFD-101 │
│ CB-2 (GMCBU-2C-15, 15 A 2P) → VFD-102 │
│ CB-3 (GMCBU-2C-15, 15 A 2P) → VFD-103 │
│ CB-4 (GMCBU-1C-20, 20 A 1P) → 120 VAC control bus │
├───────────────────────────────────────────────────────────────────────────┤
│ ZONE B — Drives │
│ LR2-21P0-1PH-A → VFD-101 (GS21-21P0) │
│ LR2-20P5-1PH → VFD-102 (GS21-20P5) │
│ LR2-20P5-1PH → VFD-103 (GS21-20P5) │
├───────────────────────────────────────────────────────────────────────────┤
│ ZONE C — PLC & Power │
│ P2-01AC ─ P2-11B base ─ P2-550 CPU │
│ Slot 1: P2-16ND3-1 (16-pt DC IN) │
│ Slot 2: P2-08TRS #1 (8-pt relay OUT) │
│ Slot 3: P2-08TRS #2 (8-pt relay OUT) │
│ Slot 4: P2-08AD-2 (8-ch analog IN) │
│ Slot 5: P2-06RTD (6-ch RTD IN) │
│ Slots 6–10: SPARE (reserved for future P2-08AD-2 expansion first) │
│ Mean Well NDR-120-24 (24 VDC field PSU) │
├───────────────────────────────────────────────────────────────────────────┤
│ ZONE D — Field Terminals (bottom) │
│ TB1: 240 VAC motor leads to drives (Zone B → motor) │
│ TB2: 120 VAC loads (UV, metering pumps) │
│ TB3: 24 VDC field distribution │
│ TB4: Discrete inputs │
│ TB5: Relay output loads │
│ TB6: Analog inputs (shielded TP) │
│ TB7: RTD │
│ TB8: RS-485 Modbus │
│ GND: DN-G10-10 grounding bar │
└───────────────────────────────────────────────────────────────────────────┘
DIN rail: all rails are 35 mm slotted plated steel — DN-R35S1 cut to length per zone. Each rail is bonded to the panel ground bus with a green 12 AWG jumper through a DN-G10-10 block. Each terminal-block group is bookended with DN-EB35MN end brackets and capped with a DN-EC1210MN end cover.
The HMI (CM5-T10W) is door-mounted (cutout per the C-more CM5 datasheet) and connects to the in-panel components by a service loop through a flexible cable carrier.
3. Power Distribution
3.1 Service entrance
- Supply: 240 VAC ± 10 %, 1-phase, 60 Hz, 3-wire + ground (split-phase L1 / L2 / N / G), nominal 30 A branch from the host facility breaker panel.
- Disconnect: lockable service-disconnect switch, panel-mounted at top; ahead of all internal breakers; visible from the panel face.
- Equipment grounding: dedicated green 10 AWG conductor from the host facility ground bar to the panel ground bus. The panel neutral and ground are bonded only at the host facility service entrance, never inside this panel.
3.2 Branch circuits (per system overview §6)
| Tag | Breaker (AutomationDirect) | Pole / Trip | Feeds | Wire (panel side) |
|---|---|---|---|---|
| CB-1 | GMCBU-2C-20 | 2P / 20 A | LR2-21P0-1PH-A → VFD-101 | 10 AWG black/red |
| CB-2 | GMCBU-2C-15 | 2P / 15 A | LR2-20P5-1PH → VFD-102 | 14 AWG black/red |
| CB-3 | GMCBU-2C-15 | 2P / 15 A | LR2-20P5-1PH → VFD-103 | 14 AWG black/red |
| CB-4 | GMCBU-1C-20 | 1P / 20 A | 120 VAC control bus (PLC PSU, HMI 24 V PSU, UV, 3 × metering pumps) | 12 AWG black + white N |
CB-4 is fed from L1 + N (120 V leg). The single-pole breaker interrupts L1 only; neutral is unbroken to its own DN-T12-A neutral block.
3.3 24 VDC field power — Mean Well NDR-120-24
- Input: 120 VAC from CB-4 bus, fused at 2 A on the line side (use a fused DN-T12-A or in-line midget fuse holder).
- Output: 24 VDC, 5 A continuous → DIN-rail distribution at TB3.
- A separate 2 A breaker / fused holder on the +24 V output protects downstream branches.
- Field load budget (estimate, per system overview §3 / §4):
| Load | Qty | Current draw (A) |
|---|---|---|
| Pressure transmitters PT-101…PT-104 | 4 | ~0.04 (ratiometric, < 10 mA each) |
| Conductivity sensors CT-101…CT-103 | 3 | ~0.10 (loop-powered 4–20 mA) |
| LT-102 level transmitter | 1 | ~0.025 |
| Flow meters FT-101…FT-103 (pulse, 5–24 V) | 3 | ~0.15 |
| Level switches LSH-101 / LSL-101 / FS-101 | 3 | ~0.01 |
| Solenoid valves SV-RECIRC / SV-ICE / SV-TREAT (24 VDC coils) | 3 | up to 1.5 (~0.5 each, holding) |
| Ball valve actuator (24 VDC, spring-return) | 1 | up to 0.5 (running), < 0.05 holding |
| HMI CM5-T10W | 1 | ~1.0 (per datasheet, 12–24 VDC input) |
| Subtotal (worst case all energised) | ≈ 3.4 A |
The NDR-120-24 (5 A) carries this with > 30 % headroom.
3.4 P2-01AC (PLC backplane PSU)
- Mounted at the left end of the P2-11B base (no slot consumed).
- Fed directly from the 120 VAC control bus through its own DN-T12-A pair (L1, N) and a green 12 AWG ground bonded to the panel ground bus.
- Powers the P2-550 CPU and all five I/O modules through the backplane. No external 24 VDC required for the discrete and relay modules. The P2-08AD-2 analog input module requires a separate 24 VDC supply — fed from the NDR-120-24 (see §6).
4. PLC Backplane — Slot Assignments
Reproduced from system overview §5.2, for cross-reference:
| Slot | Module | Field role |
|---|---|---|
| CPU | P2-550 | Main CPU |
| 1 | P2-16ND3-1 (16-pt 24 VDC IN) | Discrete inputs (level switches, flow pulse, VFD status, ice demand) |
| 2 | P2-08TRS (8-pt Form-C relay) | Loads bank 1 (ball valve, UV, 3× metering pumps, 3× VFD run/stop) |
| 3 | P2-08TRS (8-pt Form-C relay) | Loads bank 2 (SV-RECIRC, SV-ICE, SV-TREAT) |
| 4 | P2-08AD-2 (8-ch analog IN) | Pressures + conductivities + LT-102 |
| 5 | P2-06RTD | Temperature (TT-101) |
| 6–10 | spare | First reserved slot is a future second P2-08AD-2 (analog rail is full) |
Each populated module gets one P2-RTB 18-pin removable terminal block for field wiring. Stock four spares.
5. Discrete Input Wiring — P2-16ND3-1 (Slot 1)
Configured sinking (24 VDC source provided by panel; the field device sinks current to 0 V on closure). Terminal numbering follows the AutomationDirect P2-16ND3-1 RTB pinout: two isolated commons (C1, C2), eight inputs per common (X1–X8 on C1, X9–X16 on C2).
Both commons (C1, C2) are jumpered to the 0 VDC bus (DN-24J2Y push-in jumper across the common terminals on the field side). +24 VDC is delivered to each field device through a dedicated DN-T12-A; the device's dry contact closes to return that 24 V to the input pin.
| Input | Tag | Source device | Function | Wiring |
|---|---|---|---|---|
| X1 | LSH-101 | T-101 high-level float (N.O.) | Stop P-101 RO production at high tank | +24 V → switch → input pin |
| X2 | LSL-101 | T-101 low-level float (N.O.) | Stop P-102 to protect pump; alarm | +24 V → switch → input pin |
| X3 | FT-101 | Feed flow pulse | Recovery calc | Pulse output (5–24 VDC) → input |
| X4 | FT-102 | Permeate flow pulse | Recovery calc | Pulse output → input |
| X5 | FT-103 | Distribution flow pulse | POU monitoring | Pulse output → input |
| X6 | VFD-101 RUN/FLT | GS21-21P0 status (DO1 → MO/MCM) | Drive running OK | Drive sink → input |
| X7 | VFD-102 RUN/FLT | GS21-20P5 status | Drive running OK | Drive sink → input |
| X8 | VFD-103 RUN/FLT | GS21-20P5 status | Drive running OK | Drive sink → input |
| X9 | FS-101 | Ice machine demand switch | Triggers SV-ICE | +24 V → switch → input |
| X10–X16 | spare | — | — | — |
Note on T-102 level: the system overview specifies LT-102 (4–20 mA continuous transmitter on T-102) wired to the analog rail (P2-08AD-2 ch 8), not to discrete inputs.
6. Analog Input Wiring — P2-08AD-2 (Slot 4)
The B-P208AD2 supports both 0–10 VDC and 0–20 mA per channel, configurable in software per channel. The module requires external 24 VDC wired to its +24 V and 0 V terminals on the RTB — fed from the NDR-120-24 / TB3 bus.
All eight channels are populated. Shielded twisted pair from the field; shield drain wire grounded at the panel end only (DN-G10-10).
| Ch | Tag | Device | Range | Type | Wiring |
|---|---|---|---|---|---|
| 1 | PT-101 | Pressure — feed inlet | 0–300 psi | 0.5–4.5 VDC ratiometric | +V (loop +24 V), Sig → ch+, 0 V → ch− |
| 2 | PT-102 | Pressure — RO high-side | 0–300 psi | 0.5–4.5 VDC | as above |
| 3 | PT-103 | Pressure — permeate | 0–300 psi | 0.5–4.5 VDC | as above |
| 4 | PT-104 | Pressure — distribution header | 0–300 psi | 0.5–4.5 VDC | as above |
| 5 | CT-101 | Conductivity — feed (Hanna HI7635) | 0–3999 µS/cm | 4–20 mA | 2-wire loop powered (+24 V → tx +, tx − → ch+, ch− → 0 V) |
| 6 | CT-102 | Conductivity — permeate (Levtech HMCCS) | 0–1000 µS/cm | 4–20 mA | as above |
| 7 | CT-103 | Conductivity — T-102 inlet (Levtech HMCCS) | 0–1000 µS/cm | 4–20 mA | as above |
| 8 | LT-102 | Level — T-102 (continuous) | 4–20 mA = 0–100 % | 4–20 mA | as above |
The four 0.5–4.5 V pressure sensors are configured as 0–10 V channels in software; the four 4–20 mA loops are configured as current channels. Channel-by-channel mode selection avoids needing a different module.
7. RTD Input Wiring — P2-06RTD (Slot 5)
Temperature input only. The included P2-RTB takes 3- or 4-wire RTDs; this build uses 3-wire Pt100 or Pt1000 per the spec.
| Ch | Tag | Device | Wiring |
|---|---|---|---|
| 1 | TT-101 | Pt100 / Pt1000 — feed/permeate | EX+ (excitation), Sense, RTN — 3-wire, shield grounded at panel |
| 2–6 | spare | — | — |
8. Relay Output Wiring — P2-08TRS #1 (Slot 2)
The P2-08TRS provides 6 × Form A and 2 × Form C dry-contact outputs, each with isolated common, rated 4 A / point at 6–24 VDC or 6–120 VAC.
This module switches 120 VAC and 24 VDC loads. Use its dry-contact relays to make/break the hot leg of a separately fused load circuit — do not source power through the module common terminals.
| Output | Tag | Load | Voltage | Wiring |
|---|---|---|---|---|
| Y1 | BV-101 | Automated ball valve actuator | 24 VDC | +24 V → Y1.NO → actuator + ; actuator − → 0 V |
| Y2 | UV-101 | Pulsar PUV-200-20 contactor | 120 VAC | The Pulsar is plug-connected to a 120 VAC GFCI receptacle. Y2 switches the upstream contactor coil (120 VAC, < 0.1 A) that feeds that receptacle, so the PLC can de-energise UV power on hard-alarm. (Pulsar's own controller continues to manage lamp life and audible alarms while powered.) |
| Y3 | MP-A | Metering pump A — Mineral A (MgSO₄) | 120 VAC | Y3.NO switches L1 to the pump's plug receptacle |
| Y4 | MP-B | Metering pump B — Mineral B (CaCl₂) | 120 VAC | as above |
| Y5 | MP-C | Metering pump C — Mineral C (NaHCO₃) | 120 VAC | as above |
| Y6 | VFD-101 RUN | GS21-21P0 run command | 24 VDC dry | Y6.NO → drive MI1 ; drive DCM → 0 V (sink configuration). RUN is a maintained closure; drive is configured for 2-wire start. |
| Y7 | VFD-102 RUN | GS21-20P5 run command | 24 VDC dry | as above |
| Y8 | VFD-103 RUN | GS21-20P5 run command | 24 VDC dry | as above |
Per-load fusing: each 120 VAC output (Y2–Y5) is protected by its own 5 × 20 mm midget fuse on a DN-T12-A fuse block sized to the load (UV ≈ 1 A; metering pumps ≈ 0.25 A each), so a single load short does not trip the 20 A panel breaker.
9. Relay Output Wiring — P2-08TRS #2 (Slot 3)
| Output | Tag | Load | Voltage | Wiring |
|---|---|---|---|---|
| Y1 | SV-RECIRC | Solenoid — recirc to T-101 (N.O.) | 24 VDC coil | +24 V → Y1.NC → coil + ; coil − → 0 V (see below) |
| Y2 | SV-ICE | Solenoid — to ice machine (N.C.) | 24 VDC coil | +24 V → Y2.NO → coil + ; coil − → 0 V |
| Y3 | SV-TREAT | Solenoid — to mineral injection (N.C.) | 24 VDC coil | +24 V → Y3.NO → coil + ; coil − → 0 V |
| Y4–Y8 | spare | — | — | — |
SV-RECIRC fail-state nuance: the spec calls for SV-RECIRC to be normally open (energise to close, de-energise to recirc) so the recirc path is the safe default on power loss / PLC fault. There are two ways to wire this:
- Use a normally-closed solenoid (energise-to-open) plumbed in the bypass to demand leg. With this convention SV-RECIRC is replaced by a single energise-to-close valve in the recirc return, and the failure default is recirculation. Cleaner electrically.
- Use the table above with a normally-open solenoid wired through the relay's NC contact, so the coil is de-energised to keep the valve open and only energised to force it closed when SV-ICE or SV-TREAT opens. This matches the spec's "SV-RECIRC fail open" wording literally but consumes one relay continuously.
Build choice — to be confirmed at panel build with the procured solenoid model. The ladder logic supports either convention with a single coil-polarity flag.
Each 24 VDC solenoid coil has a flyback diode across the coil (cathode to +24 V) wired at the field terminal block to suppress the inductive kick when the relay opens.
10. VFD Power & Motor Wiring
10.1 Line-side (240 VAC input)
Each drive sees, in order:
CB-x (2P breaker) → LR2-xx-1PH (line reactor, input side) → Drive R/S terminals
| Drive | Breaker | Line reactor | Drive input current | Wire (line) |
|---|---|---|---|---|
| VFD-101 (GS21-21P0) | CB-1, 20 A 2P | LR2-21P0-1PH-A (1 HP, 11.6 A, 3 % Z) | 10.8 A CT / 11.3 A VT | 10 AWG |
| VFD-102 (GS21-20P5) | CB-2, 15 A 2P | LR2-20P5-1PH (½ HP, 6.2 A, 3 % Z) | 7.3 A CT / 8.3 A VT | 14 AWG |
| VFD-103 (GS21-20P5) | CB-3, 15 A 2P | LR2-20P5-1PH (½ HP, 6.2 A, 3 % Z) | 7.3 A CT / 8.3 A VT | 14 AWG |
The GS21 series in 1-phase mode uses two of three input phase terminals; per the GS20 manual, populate R(L1) and S(L2) and leave T(L3) open. Bond the drive chassis ground stud to the panel ground bus with green 10 AWG.
10.2 Motor-side (drive output → motor)
VFD output to motor uses Southwire VFDC-16-4B-1 (16 AWG, 4 conductors with green/yellow ground, shielded XLPE/TPE) cut to length:
| Drive | Motor | Run length | Cable |
|---|---|---|---|
| VFD-101 → P-101 (CRN1S-15) | RO feed pump | TBD on skid | VFDC-16-4B-1 |
| VFD-102 → P-102 (CRN1S-4) | Recirc/transfer pump | TBD on skid | VFDC-16-4B-1 |
| VFD-103 → P-103 (¾–½ HP class, TBD model) | Distribution pump | TBD on skid | VFDC-16-4B-1 |
Cable termination rules (apply to all three drive-to-motor runs):
- Conductors U / V / W terminate at the drive's
U(T1)/V(T2)/W(T3)lugs and at the motor'sT1/T2/T3(orU/V/W) leads. Phase rotation is verified with a phase-rotation meter on first start; reverse any two motor leads to correct. - The cable's green/yellow conductor terminates at the drive's
PEground stud and at the motor's grounding lug. - The braided shield is grounded at the drive end only with a 360° EMC gland; at the motor end the shield is cut back and insulated. (Single-end shielding avoids the ground loop that would otherwise inject high-frequency switching noise into the analog rail.)
- A lockable disconnect switch is installed within sight of each motor per NEC 430.102, on the motor side of the VFD cable (downstream of the drive). The disconnect is a non-fused door-handle motor switch sized for the motor FLA.
10.3 Drive control wiring
Each GS21's control terminal strip is wired:
| Drive terminal | To | Function |
|---|---|---|
MI1 | Slot 2 P2-08TRS Y6/Y7/Y8 (.NO contact) | Run command (sink mode, 2-wire start) |
DCM | Drive's own +24 V common | Sink-mode common |
MO1 (open-collector status) | Slot 1 P2-16ND3-1 X6/X7/X8 | Run/Fault status back to PLC |
MCM | 0 V on TB3 | Status common |
RJ45 (RS-485) | Modbus daisy chain (see §11) | Speed setpoint, monitoring |
Onboard analog speed pots are disabled in drive parameters; speed comes from the PLC over Modbus.
11. Communications
11.1 RS-485 Modbus RTU — PLC ↔ VFDs
Single daisy-chain bus, PLC P2-550 RS-485 port as Modbus master, three GS21 drives as slaves. Cable: Q8302-1 (single twisted pair, 24 AWG, shielded), cut to length.
[P2-550 RS-485] ─── [VFD-101] ─── [VFD-102] ─── [VFD-103]
| |
120 Ω 120 Ω
| |
shield ───────── (continuous shield, grounded at PLC end only) ─────
| Node | Modbus address | Settings |
|---|---|---|
| PLC P2-550 | master | 38 400 baud, 8N1, RTU |
| VFD-101 | 1 | 38 400 baud, 8N1, RTU |
| VFD-102 | 2 | 38 400 baud, 8N1, RTU |
| VFD-103 | 3 | 38 400 baud, 8N1, RTU |
- A 120 Ω termination resistor is fitted at the PLC end (across A/+ and B/−) and at VFD-103 (the bus end node). Drives in the middle (-101, -102) are not terminated.
- Q8302-1 has one twisted pair → use the pair for
A/B(D+/D−). The shield drain wire is the bus reference and is bonded to the panel ground bus at one point only (PLC end). - Polarity: AutomationDirect labels the P2-550 RS-485 terminals
D+(= A, non-inverting) andD−(= B, inverting). On the GS21, terminalsS+andS−correspond. Match D+ → S+ and D− → S− across all nodes. - Stub length from the bus to each drive is kept under 12 in.
11.2 Ethernet — PLC ↔ HMI
- CM5-T10W has dual Ethernet; P2-550 has dual Ethernet. Connection is a single Cat 5e/6 patch cable from one HMI Ethernet port to one PLC Ethernet port — no switch required for this point-to-point link.
- IP plan (factory default, change at commissioning):
| Device | IP | Subnet |
|---|---|---|
| P2-550 ETH1 | 192.168.10.10 | /24 |
| CM5-T10W ETH1 | 192.168.10.20 | /24 |
- The second Ethernet port on each device is reserved for a service laptop (programming / diagnostics) — left as default DHCP/auto.
11.3 USB / SD / serial
- Datalogging: an industrial-grade microSD card inserted in the P2-550 captures process variables per system overview §5.6.
- Programming: USB-microB on the P2-550 for Productivity Suite IDE; USB on the CM5 for CM5 Series Software v8.0. Both ports remain accessible without opening the panel (HMI USB is door-side; PLC USB requires opening the panel — acceptable for a maintenance-only port).
- The CM5's RS-232 / RS-485 serial ports are unused in this build; left for future expansion.
12. HMI Wiring (CM5-T10W)
| Connection | Wire | To |
|---|---|---|
| 24 VDC + | 16 AWG blue | TB3 / NDR-120-24 +24 V (own fused branch, 1 A) |
| 24 VDC − (0 V) | 16 AWG blue/white | TB3 / NDR-120-24 0 V |
| Chassis ground | 12 AWG green | Panel ground bus via DN-G10-10 |
| Ethernet | Cat 5e/6 | P2-550 ETH1 |
The HMI is door-mounted; the four-wire bundle (24 V, 0 V, ground, Ethernet) routes through a flexible cable carrier to allow the door to swing without cable strain.
13. Grounding Scheme
A single panel ground bus (DIN-rail-mounted DN-G10-10 grounding terminal blocks bonded to the rail, with the rail bonded to the enclosure backplate) is the reference for all equipment grounding inside the panel.
Host facility ground ─── 10 AWG green ─── Panel ground bus
│
├── Enclosure backplate (bonded)
├── DIN rails (each rail bonded)
├── Door (bonded via braided strap)
├── Drive PE studs (3×, 10 AWG green)
├── PLC PSU (P2-01AC) ground
├── 24 VDC PSU (NDR-120-24) ground
├── HMI chassis (12 AWG green)
├── Analog cable shields (drain wire)
├── Modbus cable shield (drain wire)
└── VFD output cable shields (drive end)
0 VDC reference: the negative output of the NDR-120-24 is bonded to the panel ground bus at the PSU. All field-side 0 V returns are referenced to this single point — this gives the 4–20 mA loops and the discrete-input commons a single, clean ground reference.
14. Build Sequence (recommended)
- Mount enclosure, backplate, and DIN rails (cut from
DN-R35S1). Bond each rail to the panel ground bus. - Install P2-01AC and P2-11B base; clip in P2-550 and the five I/O modules in the assigned slots; install P2-RTBs.
- Install the three drives and three line reactors in Zone B; route line-side wiring through the breakers in Zone A.
- Install the NDR-120-24 PSU and bring 24 VDC + / − to TB3.
- Populate Zone D terminal strips (TB1 through TB8) with
DN-T12-Ablocks bookended byDN-EB35MNbrackets, capped withDN-EC1210MN. UseDN-24J2Ypush-in jumpers to bridge commons within input groups. - Wire the PLC backplane to its field terminals per §5–§9.
- Wire drive-to-PLC control (run, status) per §10.3, then bring up the Modbus daisy chain per §11.1.
- Wire HMI per §12; bring up Ethernet per §11.2.
- Cold checkout: continuity-check every wire to terminal map before applying power; megger the VFD output runs.
- First power-up: energise CB-4 only (controls); verify PLC and HMI come up; then individually energise CB-1, CB-2, CB-3 and verify each drive boots and reports on Modbus before connecting motors.
- Connect motors one at a time and bump-test for rotation (correct phase rotation with a phase-rotation meter, then jog at 5 Hz from the PLC).
15. Open Items
- P-103 model and FLA: distribution pump not yet procured; final wire size to motor may need to drop from 16 AWG if the procured motor's FLA exceeds the VFDC-16-4B-1 ampacity at run length. Confirm at procurement.
- SV-RECIRC fail-state convention (§9): pick energise-to-close-with-N.O.-solenoid vs. plumbing inversion at panel build.
- UV contactor sourcing: identify a 120 VAC contactor with a 24 VDC or 120 VAC coil and a > 1 A AC-1 rating for the Y2 switching of the Pulsar PUV-200-20.
- Ground-fault protection on CB-4: the spec calls for the UV unit to be on a 120 VAC GFCI receptacle (per Pulsar manual); confirm whether the host-facility branch ahead of this panel already provides GFCI, or whether a GFCI-protected DIN-rail receptacle needs to be added inside the panel.
- Field cable lengths (motor runs, sensor runs, Modbus run): record final pull lengths during install and update this document with the as-built values.