This is a technical guide for understanding and interpreting the wiring diagram for a Century pool pump motor (formerly A.O. Smith). Since Century manufactures many models (UST, B2854, B2975, V-Green, etc.), this write-up covers the general wiring logic and the specific terminals you will encounter. ⚠️ CRITICAL SAFETY WARNING: Pool pumps involve high voltage (115V, 230V, or 400V), water, and rotating parts. Turn off the breaker and lockout/tagout the disconnect before touching any wires. If you are unsure about electrical work, hire a licensed electrician. Incorrect wiring can cause electrocution, fire, or pump damage.
Understanding the Century Pool Pump Wiring Diagram Century pool pump motors are dual-voltage (115V or 230V) and come with a wiring diagram printed on the motor nameplate or inside the junction box cover. The goal is to match your supply voltage to the motor’s configuration. 1. Key Components on the Diagram | Component | What It Looks Like on Diagram | |-----------|-------------------------------| | L1 | Incoming hot wire (Line 1) | | L2 | Incoming neutral (115V) or second hot (230V) | | Ground (Green) | Connects to motor bonding screw | | A, B, C, A1, etc. | Internal winding leads (often colored wires inside the motor) | | Dial/Toggle | High/low speed selector (if 2-speed model) | | Run Capacitor | Oval/cylinder component (usually 10–30 µF) | | Start Capacitor | Larger cylinder (if present; older single-phase) | 2. Reading the Diagram for Voltage Selection Century motors typically use a voltage change plate (a metal jumper or a rotary dial). There is no standard universal color code for the internal leads, so you must use the specific diagram for your model. Common terminal identification (based on actual Century diagrams):
L1 → Black wire from power supply L2 → White (115V) or Red (230V second leg) from supply P1 , P2 → Internal motor leads connected to power T1–T8 → Winding taps (T3 & T4 are often common)
Two common wiring patterns: For 115V operation (typical residential): century pool pump wiring diagram
Connect one hot leg to L1 Connect neutral to L2 Jumper/switch set to “115V” position If internal leads: T2 + T4 + T7 tied together; T3 + T8 + T5 tied together
For 230V operation (preferred for efficiency):
Connect hot L1 to L1 terminal Connect hot L2 (different phase) to L2 terminal Jumper/switch set to “230V” position Internal leads: T2 + T4 + T6 tied; T3 + T7 + T8 tied This is a technical guide for understanding and
3. Two-Speed Century Motors (e.g., B2854, B2975) Two-speed diagrams show a speed selector switch (often included with the pump or wired to an external timer).
High speed (HI): L1 to L1, L2 to L2 (full voltage across main winding) Low speed (LO): L1 to L1, L2 to low-speed tap (usually terminal “A” or “Yellow wire”) Common low-speed wire colors on Century: Yellow = low speed, Red = high speed, Black = common (but verify diagram)
Example from actual Century B2854 diagram: ⚠️ CRITICAL SAFETY WARNING: Pool pumps involve high
High speed: Black (common) + Red (high) to L1 & L2 Low speed: Black (common) + Yellow (low) to L1 & L2 (Requires an external SPDT switch)
4. Step-by-Step: How to Use Your Diagram