To wire LEDs in series for hardwired home lighting, you must use a Constant Current (CC) LED driver. You wire the driver's positive output to the anode of the first LED module, daisy-chain a jumper wire from the cathode of each module to the anode of the next, and return the final cathode to the driver's negative terminal. This topology ensures identical current flows through every diode, eliminating the voltage-drop dimming that plagues long parallel runs and guaranteeing uniform brightness across your entire cove or architectural lighting layout.

While most off-the-shelf LED strip lights are designed for parallel wiring, true series wiring is the professional standard for high-end Constant Current (CC) COB modules and hardwired LED fixtures. Below is the exact procedure, sizing math, and termination sequence to do it safely and correctly.

The Decision Path: Do You Actually Need Series Wiring?

The most frequent error in DIY LED installation is confusing daisy-chaining (which is electrically parallel) with true series wiring. Before stripping any wire, use this decision matrix to confirm your topology and select the correct driver.

IF your LED hardware is... THEN wire it in... USING this driver type... Concrete Part Pick
12V or 24V flexible LED strip tape (Constant Voltage) Parallel (home runs or daisy-chained power injection) Constant Voltage (CV) Power Supply HitLights 24V 150W CV Driver
120V AC LED rope light (internal diodes) Parallel (plug-and-play) None (direct mains) N/A
Bare COB LED modules or hardwired CC fixtures (350mA / 700mA) Series Constant Current (CC) LED Driver Mean Well APC-35-350
The Concrete Pick: If you are installing architectural cove lighting using series-wired 350mA COB modules, buy the Mean Well APC-35-350. It is a 24W constant current driver that outputs exactly 350mA across a compliance voltage window of 12V to 48V DC, making it the benchmark for residential series LED loops.

Tools, Materials, and Sizing the Load

Wiring in series means the voltage adds up across each module, while the current remains constant. You must size your wire for the current, and your driver for the total forward voltage (Vf).

Tools & Materials List

  • LED Driver: Mean Well APC-35-350 (350mA output, 12-48V DC compliance range, 120V AC input).
  • LED Modules: 10x Series-Wired 24V/350mA COB LED modules (approx. 3.2Vf each at 350mA).
  • Wire (AC Mains): 14 AWG solid THHN (Black, White, Green) for the 120V branch circuit.
  • Wire (DC Loop): 18 AWG stranded THHN (Red and Black). 18 AWG is rated for up to 14A in chassis wiring; at 350mA (0.35A), it runs completely cold and easily fits into tight module solder pads.
  • Connectors: Wago 221-412 lever nuts (for AC splices), heat shrink tubing (for DC solder joints).
  • Tools: Klein 11055 wire strippers, Weller WLC100 soldering station, Fluke 115 True-RMS digital multimeter, non-contact voltage tester (NCVT).

The Compliance Voltage Calculation

A CC driver will only operate if the total forward voltage of your series loop falls within its "compliance window." The APC-35-350 has a window of 12V to 48V.

  • 10 modules × 3.2Vf = 32V total.
  • 32V falls perfectly inside the 12V-48V window. The driver will automatically adjust its output voltage to exactly 32V to maintain the 350mA current.
  • Warning: If you only wired 2 modules (6.4V total), the driver would fault or overvolt the LEDs because 6.4V is below the 12V minimum threshold.

Mains Safety and Preparation

LETHAL VOLTAGE WARNING: This procedure requires terminating 120V AC mains power. Before touching any wires, you must de-energize the circuit at the main breaker panel. Lock out or tag out the breaker if possible. Verify the circuit is dead using a tested NCVT, and then confirm 0V AC across the line and neutral conductors with a multimeter. Per NFPA 70 (NEC) Article 411 and local AHJ requirements, hardwired LED drivers installed in concealed spaces must be accessible and properly grounded. If you are not comfortable with mains termination, hire a licensed electrician.

Step-by-Step: Wiring the CC Driver and Series LEDs

Follow this exact termination sequence. Do not skip the grounding step, as LED drivers contain high-frequency switching components that require a clean earth ground to prevent EMI and shock hazards.

  1. Terminate AC Mains to the Driver Input: Strip 1/2 inch of insulation from your 14 AWG THHN wires. Land the Black (Line) wire onto the driver's 'L' terminal screw and torque to 0.5 Nm. Land the White (Neutral) wire onto the 'N' terminal screw. Terminate the Green/Bare (Ground) wire to the green grounding screw on the driver's metal chassis or the metal junction box ground pigtail.
  2. Wire Driver DC Output to First LED: Strip 1/4 inch of your 18 AWG stranded wire. Solder or screw the Red (V+) wire from the driver's 'V+' terminal directly to the '+' (Anode) pad on LED Module 1.
  3. Create the Series Jumper (Daisy Chain): Cut a short length of Black 18 AWG wire. Solder one end to the '-' (Cathode) pad on LED Module 1, and the other end to the '+' (Anode) pad on LED Module 2. This forces the current to exit the first LED and enter the second.
  4. Repeat the Jumper Sequence: Continue using Black 18 AWG wire to connect the '-' (Cathode) of each module to the '+' (Anode) of the subsequent module until you reach the final LED in your run.
  5. Terminate the Final Return: Run a long Black (V-) 18 AWG wire from the '-' (Cathode) pad on the very last LED module all the way back to the driver's 'V-' terminal screw. This closes the series loop.
  6. Secure and Dress Wires: Use cable ties to secure the 18 AWG DC loop away from any sharp metal edges in the cove or junction box. Ensure no bare DC wire is touching the AC mains wires or the grounded metal box.

Verify and Test: Expected Meter Readings

Do not just flip the breaker and assume it works. Use your multimeter to verify the electrical parameters match the fundamental laws of series circuits.

  1. Test AC Input (Before connecting DC load): With the breaker ON and the DC output disconnected, set your meter to VAC. Probe the 'L' and 'N' terminals. Expected Reading: 114V to 126V AC. If you read 0V, check the breaker. If you read 240V, you have a split-phase wiring error.
  2. Test DC Open-Circuit Voltage: Set the meter to VDC. Probe the 'V+' and 'V-' terminals with no LEDs connected. Expected Reading: The meter will likely read the maximum compliance voltage (approx 48V DC) as the driver searches for a load. This is normal for CC drivers.
  3. Test Loaded DC Voltage: Turn off the breaker. Connect the DC loop. Turn the breaker back on. Probe the 'V+' and 'V-' terminals at the driver. Expected Reading: ~32V DC (the exact sum of your modules' forward voltage).
  4. Test DC Current (The Ultimate Proof): Turn off the breaker. Break the series loop at the final return wire. Set your multimeter to the mA (milliamp) setting and place the probes in series with the break (Red probe to the wire coming from the last LED cathode, Black probe to the driver V- terminal). Turn on the breaker. Expected Reading: 350mA (±5%). This confirms the driver is actively regulating current.

The Most Common Botch (and How to Fix It)

The Botch: Attempting to wire standard 12V Constant Voltage (CV) LED strip tape in series to "extend the run" without voltage drop.

The Symptom: You connect the positive of Strip 1 to the driver, and the negative of Strip 1 to the positive of Strip 2. When powered, the first strip glows dimly, pops a copper trace, or the thermal fuse blows, while the second strip remains completely dead.

The Physics: According to the U.S. Department of Energy Solid-State Lighting guidelines, CV strips contain internal resistors designed to drop a specific voltage at a fixed 12V input. When you wire two 12V strips in series, the combined forward voltage requirement becomes 24V. A 12V CV driver simply does not have the electrical "pressure" (voltage) to push current through a 24V requirement. The driver maxes out at 12V, the current starves, and the internal resistors overheat trying to compensate.

The Fix: If you are using CV LED tape, you must wire them in parallel. Run a home-run wire from the 12V driver to the input of Strip 1, and a separate home-run wire from the driver to the input of Strip 2. If you want to eliminate voltage drop on long CV runs, upgrade to 24V CV strips and inject power at both ends, or switch entirely to the Constant Current series-wired COB modules detailed in this guide.

Once your series loop passes the milliamp verification test and the cove is illuminated with uniform, flicker-free light, secure the junction box cover and schedule your final AHJ inspection if required by your local permit. True series wiring, when executed with a properly sized CC driver, will outlast parallel alternatives by years because every diode operates at the exact same thermal and electrical baseline.