DC cable is the smallest line item in a lighting fit-out and the one most likely to cost you a second site visit. Here is how to spec LSZH DC cable properly.
In a retail or hospitality fit-out budget, the DC power cable is close to invisible. Fixtures, millwork, and installation labor take up all the attention. The short cable that carries 12 or 24 volts from a power supply to a light strip is a rounding error on the quote.
It is also, with some regularity, the line item that sends a project manager back to the site.
Part of the problem is the word “commodity.” DC cable looks like commodity hardware, so it gets ordered the way commodity hardware gets ordered: by connector size and length, from whoever quotes fastest. Then the shelf lights at the far end of a 40-store rollout sit visibly dimmer than the ones near the power supply, or a landlord’s fire consultant asks a question about cable materials that nobody on the project can answer with a document.
Neither of those is an expensive problem to prevent. Both are expensive to fix after 40 stores are built.
Table of Contents
What LSZH actually promises, and what should you ask for?
LSZH stands for Low Smoke Zero Halogen. It describes a family of insulation and jacket compounds formulated without halogens—fluorine, chlorine, bromine, and iodine—so that if the cable is ever involved in a fire, it does not release the corrosive, acidic gases that halogenated PVC does. That matters most in enclosed spaces where people need to find an exit: shopping centres, hotel corridors, airport terminals, transit stations, hospitals. It is why building specifications in Europe and increasingly across Asia and the Middle East now call for halogen-free cable in occupied interior spaces as a default rather than an upgrade.
Here is the part worth knowing as a buyer: “LSZH” is a material description, not a certificate. It bundles two separate claims — low smoke emission, and zero halogen content — and each is verified by a different test standard. Halogen content is tested under EN 14582. Smoke density is tested under IEC 61034. Flame propagation is tested under IEC 60332.
A supplier can hold reports for one and not the others. When you ask “is this LSZH?”, the answer is almost always yes. When you ask “which standards do you hold test reports for, and were those reports issued on the finished cable or on the wire material?”, the answers get much more informative, and much more variable.
That second half of the question is the one most buyers skip. Most cable assembly factories buy their wire from a wire mill and do the moulding and assembly themselves. The test reports they hold are therefore usually material-level reports issued to the wire supplier. That is legitimate and normal. It is simply not the same thing as a finished-product certification, and any supplier who blurs the two is telling you something about how they will handle your other questions later.
Our own position at CITYLUX is the same as most of the industry, stated plainly: wire material is sourced from qualified suppliers and tested by CTI, the third-party laboratory, with halogen content verified to EN 14582, alongside RoHS, PFAS, POPs and PAHs screening. Moulding and assembly are done in-house at our own facility in Foshan. Reports are available on request. That is the level of specificity worth expecting from anyone you buy from.
Gauge and length: the two numbers that decide whether it works
The second failure mode has nothing to do with compliance and everything to do with physics.
Low-voltage DC has very little headroom. On a 12V system, losing even half a volt in the cable is a measurable brightness difference, and on a long shelf run that difference is visible to a customer standing in the aisle. Voltage drop scales with current, with length, and inversely with conductor cross-section — which is what the AWG number describes.
A worked example makes it concrete. A 20 AWG copper conductor has a resistance of roughly 32 ohms per kilometre at 20°C. Run 2 amps through 10 metres of it and the round-trip drop is about 0.64V. On a 24V system that is tolerable. On a 12V system it is more than five percent of your supply voltage, gone before the light ever sees it.
As a rough current-carrying reference for common gauges with 80°C-rated insulation: 24 AWG around 2.5A, 22 AWG around 3.5A, 20 AWG around 5A, 18 AWG around 7A, 16 AWG around 10A. Treat these as selection guidance from general wire standards rather than a performance guarantee — actual ratings depend on the specific wire specification, bundling, ambient temperature and how the cable is routed.
Two practical rules follow. First, specify gauge against your actual run length, not against the connector. Second, if you are using a splitter to feed several fixtures from one power supply, the input leg has to carry the sum of every branch current. Sizing the input the same as the branches is the single most common specification error we see on incoming drawings, and it is also the easiest to correct before tooling.
Where configuration saves you money
Most lighting jobs resolve into four cable configurations: a male plug cable for the fixture end, a female socket cable for the power supply end, a Y-splitter for feeding multiple runs from one supply, and an in-line T-splitter for tapping power along a trunk without breaking it. A DC Y-splitter cable with four or eight outputs frequently removes an entire power supply from the bill of materials, which is a larger saving than anything you will negotiate on the cable itself.
Connector standards are similarly boring and similarly important. DC5521 and DC5525 barrel connectors cover most indoor work; M12 or M15 threaded connectors are the answer for outdoor, refrigerated or wash-down environments. Standard DC power plug cable assemblies come in 0.5m, 1m, 1.5m and 2m, and custom lengths are worth requesting rather than coiling two metres of slack behind every fixture.
A short checklist
Before the purchase order goes out, get four things in writing: the test standards the supplier actually holds reports for and whether those reports cover material or finished product; the conductor gauge matched to your longest run rather than your shortest; the input gauge on any splitter sized for total load; and the minimum order quantity, because a supplier who can run a small first batch lets you validate on one store instead of forty.
None of this is difficult. It is a twenty-minute conversation that happens before the order rather than a site visit that happens after it.
