Dosing Pumps 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 dedicated CB-5 120 VAC metering pump branch, 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 (15 A 1P, L1 + N) ─► controls / brains
│ ├─► PLC PSU (P2-01AC)
│ ├─► HMI 24 V PSU (NDR-120-24)
│ └─► control auxiliaries
│
├──► CB-5 (15 A 1P, L1 + N) ─► metering pump power branch
│ ├─► MP-A relay / HOA switch ─► receptacle
│ ├─► MP-B relay / HOA switch ─► receptacle
│ └─► MP-C relay / HOA switch ─► receptacle
│
└──► CB-6 (15 A 1P, L1 + N) ─► UV GFCI receptacle / contactor
Per-Pump Switching
The three pumps share the CB-5 120 VAC branch. Each pump also gets an individual relay / selector-switch path on the hot leg so maintenance can disable or manually service one pump without dropping the whole controls branch.
Normal recipe dosing is still controlled through the DDC's external stop /
enable input using a Form-A dry contact on P2-08TRS #1 (Slot 2). In normal
AUTO operation, the pump electronics stay powered and the PLC decides when
each pump is allowed to dose.
| Pump | Mineral | PLC enable output | Power cutoff / service control | Receptacle | Voltage |
|---|---|---|---|---|---|
| MP-A | Magnesium sulfate (MgSO₄) | Slot 2 / Y3.NO | ZL-RLS4-24 relay + 22 mm HOA selector | NEMA 5-15R | 120 VAC |
| MP-B | Calcium chloride (CaCl₂) | Slot 2 / Y4.NO | ZL-RLS4-24 relay + 22 mm HOA selector | NEMA 5-15R | 120 VAC |
| MP-C | Sodium bicarbonate (NaHCO₃) | Slot 2 / Y5.NO | ZL-RLS4-24 relay + 22 mm HOA selector | NEMA 5-15R | 120 VAC |
The pump's onboard digital display sets dosing rate per the active HMI recipe.
The PLC relay opens/closes the external stop / enable contact. The added power
relay / selector-switch layer is for service isolation and manual operation, not
for normal recipe-rate control. 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-5 =
GMCBU-1C-15, 15 A 1P dedicated to metering pumps - Per-pump cutoff: relay / HOA selector switches only the 120 VAC hot leg to each pump. Neutral remains on the isolated neutral bus; ground remains bonded to the panel ground bus.
- Per-load fuse: optional. Use individual small fused terminal blocks if you want pump-by-pump fault isolation; otherwise the 15 A branch breaker and code-compliant 14 AWG receptacle wiring protect the pump branch.
- Ground: dedicated green per receptacle back to panel ground bus
Because CB-5 is now separate from CB-4 and CB-6, a metering-pump branch fault does not drop the PLC / HMI / UV. Per-pump fusing is a serviceability upgrade, not the thing protecting the brains.
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 | Applies when pump mains power is applied, not when the PLC dry-contact enable changes state |
| CB-5 branch budget headroom | comfortable | 3 × pumps ≪ 15 A |
Startup note: normal PLC dosing no longer creates repeated mains inrush. Inrush only happens when pump mains power is applied through CB-5, the relay / selector-switch path, or a manual service action. On first energising CB-5, power up the pumps one at a time or leave them unplugged until the branch is verified.
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
- CB-5 hot lands on the metering-pump relay / HOA switch common feed
- Each receptacle's hot pigtail lands downstream of its relay / HOA switch
- Each pump's external stop / enable input lands on its assigned relay dry contact
- 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-5 (15 A 1P) · individual hot-leg relay / HOA cutoff per pump Enabled by PLC P2-08TRS #1 dry contacts Y3 / Y4 / Y5 Normal PLC enable does not cycle pump mains power