Dosing Pump Power — Bench Reference
Scope: Quick printable reference for powering the three Grundfos DDC 6-10 mineral metering pumps (MP-A / MP-B / MP-C) on the bench layout and in the final panel install.
Sources: Wiring Plan §3, §8 · Metering Pumps §3, §5 Tier 0
Voltage
120 VAC, 60 Hz, single phase.
The DDC 6-10 is universal-input (100–240 VAC, 50/60 Hz), but on this skid it is fed from the 120 V control bus, not the 240 V leg. The 240 V split-phase service feeds only the three VFDs.
Power Path (single line)
Host facility 240 VAC / 30 A split-phase service
│
▼
Lockable main disconnect (panel top)
│
├──► CB-1 (20 A 2P) ─► VFD-101 (240 V)
├──► CB-2 (15 A 2P) ─► VFD-102 (240 V)
├──► CB-3 (15 A 2P) ─► VFD-103 (240 V)
│
└──► CB-4 (20 A 1P, L1 + N) ─► 120 VAC control bus
│
├─► PLC PSU (P2-01AC)
├─► HMI 24 V PSU (NDR-120-24)
├─► UV contactor
│
├─► Midget fuse ─► P2-08TRS Y3.NO ─► MP-A receptacle
├─► Midget fuse ─► P2-08TRS Y4.NO ─► MP-B receptacle
└─► Midget fuse ─► P2-08TRS Y5.NO ─► MP-C receptacle
Per-Pump Switching
Each pump's L1 (hot) leg is switched by a Form-A relay on P2-08TRS #1 (Slot 2). Neutral is unbroken back to TB2. PLC closes the relay when SV-TREAT opens (T-102 calling for fill).
| Pump | Mineral | PLC output | Receptacle | Voltage |
|---|---|---|---|---|
| MP-A | Magnesium sulfate (MgSO₄) | Slot 2 / Y3.NO | NEMA 5-15R | 120 VAC |
| MP-B | Calcium chloride (CaCl₂) | Slot 2 / Y4.NO | NEMA 5-15R | 120 VAC |
| MP-C | Sodium bicarbonate (NaHCO₃) | Slot 2 / Y5.NO | NEMA 5-15R | 120 VAC |
The pump's onboard digital display sets dosing rate per the active HMI recipe.
The relay just enables/disables the pump. Future upgrade path is 4–20 mA
proportional rate control from the PLC into the pump's AR analog input.
Per-Pump Protection
- Branch: CB-4 =
GMCBU-1C-20, 20 A 1P (shared with PLC PSU, HMI PSU, UV) - Per-load fuse: 5 × 20 mm midget fuse on a
DN-T12-Afuse block, 0.25 A per pump (UV gets ~1 A) - Ground: dedicated green per receptacle back to panel ground bus
A per-load fuse keeps a single pump short from tripping the 20 A branch breaker and dropping the PLC / HMI / UV with it.
Load Numbers
| Parameter | Value | Notes |
|---|---|---|
| Max power input (P1) per pump | 22 W | Grundfos catalog, Product 98586903 |
| Steady-state current per pump @ 120 V | ~0.18 A | 22 W ÷ 120 V |
| All three pumps, steady state | ~0.55 A | ~66 W total |
| Inrush current per pump | ~25 A for ~2 ms @ 230 V | Use Type C MCB equivalent; stagger PLC enables |
| CB-4 branch budget headroom | comfortable | UV ~1 A + PSUs + 3 × pumps ≪ 20 A |
Stagger note: the PLC ladder should not energise Y3 / Y4 / Y5 in the same scan. Add a small per-pump delay (e.g. 50–100 ms staggered) so the three ~25 A inrush spikes don't sum on the same branch.
Pump Cord Re-Termination
Factory cord on each procured DDC 6-10 (Made in France, EU production run) is 1.5 m with an EU plug. Two acceptable options:
- Re-terminate to NEMA 5-15P at the cord end and plug into the panel-fed receptacle. Simpler; preserves the strain relief.
- Hard-wire into the panel at TB2 with the factory cord cut to length. Cleaner install; loses the easy field swap.
Pick at panel build; document in the as-built.
Bench Layout Checklist (today)
- Three NEMA 5-15R receptacles laid out near where the three pumps will sit
- Each receptacle's hot pigtail lands on its own midget fuse → relay NO
- Neutrals bussed to TB2 neutral block
- Greens to panel ground bus via
DN-G10-10 - Cord plan decided per pump (re-terminate vs. hard-wire) — note on BOM
- Verify pumps are oriented so 1.5 m cord reaches without strain
- Label each receptacle MP-A / MP-B / MP-C to match the mineral jug
Quick Reference Card
Three Grundfos DDC 6-10 metering pumps 120 VAC · 22 W each · NEMA 5-15R receptacles Fed from CB-4 (20 A 1P) · individually fused at 0.25 A Switched by PLC P2-08TRS #1 outputs Y3 / Y4 / Y5 Stagger enables in ladder to spread inrush