FAQ
TL;DR: Connecting 3×24 V lamps in series needs 72 V; as one expert says, "you need a 72 V power supply." Wire + → lamp1 → lamp2 → lamp3 → −, and avoid L/N on 24 V DC. [Elektroda, kokapetyl, post #17178890]
Why it matters: DIYers and students wiring 24 V DC lamps can avoid damage, shorts, or dim lighting by following proven series/parallel rules.
Quick Facts
- Series voltage adds: three 24 V lamps require approx. 72 V DC from the supply. [Elektroda, kokapetyl, post #17178890]
- Only incandescent bulbs or simple LEDs (with resistors) should be series-wired; lamps with internal drivers should not. [Elektroda, jarek_lnx, post #17178904]
- At 24 V DC, label and wire as + and −, not L and N; observe LED polarity. [Elektroda, jarek_lnx, post #17178904]
- Mixed wiring (some parallel, some series) is not a pure series string and behaves differently. [Elektroda, kokapetyl, post #17178961]
- For series strings, keep bulb power ratings equal to avoid one staying dim or off. [Elektroda, kokapetyl, post #17178983]
How do I wire three 24 V lamps in series correctly?
Connect + from the supply to Lamp 1. Link Lamp 1’s other terminal to Lamp 2. Link Lamp 2 to Lamp 3. Connect Lamp 3 back to −. This is a true series path with no branches. Use + and −, not L and N, on 24 V DC. Verify LED polarity before powering. [Elektroda, jarek_lnx, post #17178904]
What supply voltage do I need for 3×24 V lamps in series?
Use a supply equal to the sum of lamp voltages. For 3×24 V, that is 72 V. Using 24 V will not drive a 3×24 V series string correctly. "You need a 72 V power supply." [Elektroda, kokapetyl, post #17178890]
Can I series-connect LED lamps, or only simple bulbs?
Series wiring is fine for incandescent bulbs and simple LEDs with resistors. Do not series-wire LED lamps that contain internal electronics or drivers. Such converters can exhibit negative dynamic resistance. Voltages will not share evenly, causing misoperation or damage. [Elektroda, jarek_lnx, post #17178904]
What do L and N mean at 24 V, and what should I use?
L and N are AC mains labels and do not apply to 24 V DC. Use + and − for DC wiring. Observe polarity in your diagram and on the device. Incorrect polarity can stop LEDs from lighting. [Elektroda, jarek_lnx, post #17178904]
How do I add one more lamp to an existing series string?
Insert the new lamp where a link currently exists between two lamps.
- Pick a wire segment between two series lamps.
- Remove that link and connect the new lamp in its place.
- Confirm the total lamp voltages equal the supply before powering.
This preserves a single series path. [Elektroda, kokapetyl, post #17178983]
My sketch shows two lamps in parallel and others in series—what is that?
That creates a mixed connection. The first two are in parallel, and the remaining ones are in series with that branch. It is not a pure series string. It will not behave like a single three-lamp series chain. Redraw if you need true series. [Elektroda, kokapetyl, post #17178961]
Do all bulbs in a series string need the same power rating?
Yes, keep power ratings the same in a series chain. Unequal ratings can cause uneven voltage drops and brightness. The higher-rated one may stay dim or not light at all. Match ratings to ensure proper operation. [Elektroda, kokapetyl, post #17178983]
How should I orient LEDs in series?
Match polarity on every LED in the chain. Anodes go toward +, cathodes toward −. A reversed LED will block current, and the string will not light. "Pay attention to the polarization of the LEDs!" Check markings before power-up. [Elektroda, jarek_lnx, post #17178904]
Can I power three 6 V bulbs from a 24 V supply in series?
Only if the total equals the supply. Three 6 V bulbs total 18 V, which does not match 24 V. Four 6 V bulbs would total 24 V. Adjust either lamp count or supply so the sums match. [Elektroda, kokapetyl, post #17178983]
Why did my first drawing short L and N?
Two of your “lamps” were actually direct links between supply lines. That created short circuits and left only one lamp effectively in circuit. Redraw as a single series chain without any bypass wires. [Elektroda, krzysiozak, post #17178883]
Can I run 3×24 V lamps from a 24 V supply by wiring in parallel?
Yes, if each lamp’s rated voltage equals the supply, use parallel wiring. At 24 V, connect all three lamps across the 24 V rails. Maintain correct polarity on DC systems. [Elektroda, kokapetyl, post #17178983]
What’s a simple series-wiring check before power-on?
Trace a single path from + through Lamp 1, then Lamp 2, then Lamp 3, to −. Ensure there are no branches or jumpers around any lamp. Use a multimeter’s continuity mode to verify the single path. [Elektroda, jarek_lnx, post #17178904]
