Contactor Wiring Guide

⚠️ Note: ECM pumps (electronically commutated motors <100W) have large input capacitors that cause a brief high charging peak (10–20A for microseconds) each time the relay closes. Over many cycles this capacitive inrush can micro-weld relay contacts. An RC snubber (100nF + 100Ω, X2-rated capacitor) across the relay contact suppresses turn-off transients/arcs, but it does not limit the closing inrush — it cannot prevent contact welding on capacitive loads. For ECM pumps use the contactor wiring below, or an inrush limiter (NTC) / a relay rated for capacitive loads.

The contactor solution below is intended for larger pumps (>300W) or inductive loads where running current exceeds 2A.

Overview

This document explains why the built-in relays of the NORVI AE01-R (and other standard relay modules) can fail when switching motor loads (pumps), and how to build a robust, long-term solution using external DIN-rail contactors.

Applies to: NORVI AE01-R (R0–R5) and external 5V relay modules (standard ESP32 builds).

Problem: Relay Contacts Weld Under Motor Load

The NORVI Relays

The NORVI AE01-R has 6 built-in electromechanical relays (SPST-NO, 5A/250V AC). These are rated for resistive loads — incandescent lamps, heating elements, or low-inrush electronics.

A pump is an inductive load (motor with coils):

In practice: A NORVI relay rated “5A” driving a 300–600W pump (1.3–2.6A running, 6.5–13A inrush peak) can develop welded contacts after a few hundred switching cycles. The relay coil still clicks audibly, but the NO contact stays closed — the pump runs continuously even with the controller showing OFF.

Field Report

In one field installation this failure occurred on two different relay outputs (R1, then R5) of the same NORVI AE01-R, both switching the same solar pump. The pump turned out to be a 6–28W ECM type (Lowara Artiga ECO AUTO+) — well within the relay rating, yet contacts welded. The cause is capacitive inrush from the ECM’s input capacitors (~10–20A peak for microseconds each switch-on). The identical R0 channel (pool pump, Speck BADU Magic II/6 450W asynchronous motor) showed no failure.

Solution: External DIN-Rail Contactor

A contactor is a heavy-duty relay built for motor loads. The NORVI relay switches only the contactor’s coil (a few mA at 24V DC) — the contactor’s main contacts handle the 230V AC load.

 NORVI Relay            Contactor (external)           Pump
 ┌──────────┐          ┌────────────────────┐      ┌────────┐
 │          │  24V DC  │  A1 (+)            │      │        │
 │ COM ─────┼──────────┤  (coil)            │      │        │
 │          │          │          A2 (-) ───┼── GND│        │
 │ NO  ─────┼──────┐   │                    │      │        │
 └──────────┘      │   │ 1 (L-input) ───────┤─── 2 │        │
                   │   └────────────────────┘      │  L-N  │
 24V DC (+) ───────┘                               └────────┘
 230V L (via contactor) ─────────────────────────────┘
 230V N ─────────────────────────────────────────────────┘
 GND ────────────────────────────────────────────────────┘

Benefits

Recommended Contactors

Finder 22 Series (recommended)

Compact DIN-rail contactors with built-in surge suppression.

Note: Finder 22 includes a built-in suppressor diode (varistor), but adding an external 1N4007 flyback diode across the coil is still recommended.

Eaton / Moeller DILM

Robust contactors, often more affordable.

Interface Relays (compact)

For maximum space saving:

Note: Interface relays are smaller than full-size contactors, but still significantly more robust than NORVI’s on-board relays. Adequate for pumps up to 600W.

Wiring Diagram

24V Control Circuit

 24V DC (+) ──┬── NORVI R0 COM ── NO ──┬── Contactor Pool A1 ── A2 ──┬── GND
              │                        │                            │
              ├── NORVI R2 COM ── NO ──┤── Contactor Solar A1 ── A2 ──┤
              │                        │                            │
              └───── NORVI 24V IN ─────┘                            │
                                                                    │
 GND ───────────────────────────────────────────────────────────────┘

Flyback diodes 1N4007 across each contactor coil:

• Cathode (banded end) to A1 (+)
• Anode to A2 (GND)

These diodes absorb the back-EMF spike when the contactor coil switches off. Without them, the voltage spike can damage the NORVI relay driver.

230V Power Circuit

230V L (Live) ─── RCD ─── MCB ──┬── Contactor Solar 1-2 ── Solar Pump L
                                 │
                                 └── Contactor Pool 1-2 ─── Pool Pump L

230V N (Neutral) ──────────────────────── Both Pump N

Always protect the 230V side with an RCD (30mA) and MCB (B10A or appropriate).

Bill of Materials (Both Pumps)

Installation Steps

1. Preparation

1. Disconnect power — turn off 230V breaker, disconnect 24V supply
2. Check DIN rail — contactors are 17.6mm (Finder 22) or 45mm (Eaton). Plan space next to the NORVI.
3. Prepare cables — 1.5mm² for 230V, 0.75mm² for 24V. Crimp ferrules.

2. Wiring

Step 1: 24V Control Circuit

1. 24V DC (+) to NORVI relay COM — bridge from NORVI 24V terminal to COM-R0 and COM-R2
2. NORVI relay NO to contactor A1 — R0-NO → Pool contactor A1, R2-NO → Solar contactor A1
3. Contactor A2 to GND — both A2 to GND bus
4. Flyback diode — 1N4007 across A1/A2 of each contactor (cathode to A1, anode to A2)

Step 2: 230V Power Circuit

1. 230V L from RCD/MCB — to contactor terminal 1 (both contactors paralleled)
2. Contactor terminal 2 — to respective pump L
3. 230V N — directly to pump N (not through contactor)
4. Earth (PE) — if pump has a housing, connect separately

Step 3: Verification

1. Continuity check — 24V side: ~100–400Ω between A1 and A2 (coil resistance). Diode test: measure in reverse direction
2. Short circuit check — 230V side: > 1MΩ between L and N
3. Isolation check — > 10MΩ between 24V and 230V circuits (galvanic isolation)

3. Functional Test

1. Apply 24V → controller boots
2. Controller shows pumps OFF → contactors must be open (no continuity between terminal 1 and 2)
3. Turn pumps ON (Web UI, MQTT, or OLED) → contactor must audibly click
4. Pump starts running → success

Troubleshooting

References

• SVG Wiring Diagram: Contactor Circuit
• NORVI AE01-R Configuration
• Hardware Guide
• Finder 22 Datasheet
• Eaton DILM Datasheet