UL 1310 and Class 2 Power Supplies: What B2B Buyers Actually Need to Verify

“We’re UL certified” is one of the least informative sentences in power supply sourcing. UL publishes hundreds of standards. A power supply can be legitimately listed to one of them and have nothing at all to do with Class 2. Buyers treat the sentence as a yes/no answer to a question they never actually asked.

This piece is about the specific question: is this unit a Class 2 power supply under UL 1310, and how do I verify that claim? It covers what the standard actually limits, why Class 2 matters commercially (it’s mostly about installation cost, not safety), how it differs from Class P and from CE marking, and the five checks to run on any certificate before you sign off.

One note up front: this is not a substitute for the standard, and I’m not going to link you to a pirated PDF. The standard is a copyrighted document sold by UL. I’ll point you to where to get it legitimately, and to what you can get free from us.

What UL 1310 covers, in plain terms

UL 1310 is the standard for Class 2 power units. It applies to the power supply itself — the thing that converts mains voltage down to a low-voltage output.

“Class 2” is a defined concept that exists because of a specific property: below certain power and voltage thresholds, a circuit is considered unlikely to start a fire or deliver a dangerous shock, and therefore doesn’t need the same level of protection as a normal mains circuit. Both a power limit and a voltage limit apply.

The commonly cited figures for Class 2 are a power limit in the region of 100 VA and a voltage limit in the region of 30 V RMS (about 42.4 V peak DC). Treat those as orientation, not specification — the authoritative values are in UL 1310 itself and in NEC Article 725, and the exact limits depend on which sub-category of Class 2 circuit you’re dealing with. If you’re writing a spec, cite the standard, not a blog post. This one included.

Two things follow from this that matter commercially:

A 24V supply can be Class 2. A 24V supply isn’t automatically Class 2. Output voltage alone doesn’t determine it. You need the power limit as well, and you need the unit to have been evaluated and listed as a Class 2 power unit specifically.

The listing is on the power supply, not the system. A Class 2 power supply feeding a circuit that then exceeds the limits doesn’t make the whole installation Class 2. The classification applies to the output circuit as designed and installed, which is why the inspector looks at the wiring, not just the box.

Why Class 2 changes your installation cost

This is the part buyers miss, and it’s usually worth more than the safety argument.

Under the NEC, Class 2 circuits are subject to less restrictive wiring rules than Class 1 circuits. The practical consequences, depending on the installation and the authority having jurisdiction:

• Conduit may not be required where it would be for a Class 1 circuit
• Separation requirements from other circuit classes are relaxed
• Cable types permitted for Class 2 work are broader and generally cheaper
• Junction and splicing rules are less onerous

On a large signage or architectural lighting installation, the labour and material difference between running Class 2 cable and running conduit is not a rounding error. It can be the single biggest line item in the electrical scope.

So the counter-intuitive point: Class 2’s real value to most buyers is installation cost, not safety. The safety benefit is real and it’s why the classification exists, but the money is in the wiring method. A procurement team that compares two 24V supplies on unit price alone, where one is Class 2 and one isn’t, is comparing the wrong numbers.

The reverse also matters. If you specify Class 2 because you want the cheaper wiring method, and the unit turns out not to be listed Class 2, you now have a conduit requirement you didn’t budget for and an inspection problem. This is exactly the failure the certificate checks below are designed to prevent.

Confirm all of this against the current edition of the NEC and with your local authority having jurisdiction. Requirements vary by jurisdiction and by installation type, and inspectors have discretion.

UL 1310 vs Class P vs CE: different rulebooks

These three get conflated constantly. They’re answering different questions.

Term	What it is	What it tells you
UL 1310 / Class 2	A standard for Class 2 power units	The output circuit stays within defined power and voltage limits, permitting relaxed wiring methods
Class P	A classification for LED drivers, under UL 8750	The driver has been evaluated for use outside a luminaire without additional protection
CE marking	A European conformity declaration, not a single standard	The manufacturer declares conformity with applicable EU directives — self-declared in many cases, unlike NRTL listing

Three distinctions worth internalising:

Class 2 and Class P are not alternatives to each other. They’re different standards addressing different questions. A unit can be one, the other, both, or neither. If someone tells you a driver is “Class P so it’s Class 2,” that’s a category error.

Class 2 is about the output circuit’s energy limits. Class P is about where the driver can be mounted. Different concern entirely.

CE is not equivalent to UL listing. This trips up buyers working across markets. CE marking is, for many product categories, a manufacturer’s self-declaration of conformity. UL listing (or ETL, CSA, TÜV) involves third-party testing and typically ongoing factory inspection. They are not interchangeable, and a supplier that presents CE as “the European UL” is either confused or being slippery.

If you need the deeper Class P comparison, we’ve covered it separately — see Class P vs Class 2 explained and the CE/RoHS verification process.

Five checks to run on a supplier’s certificate

None of these take more than a few minutes. All of them catch real problems.

1. Is there a certificate number, and does it resolve? A real listing has an identifier you can look up in the certifying body’s public directory. UL, Intertek (ETL), CSA and TÜV all maintain online directories. A PDF that looks like a certificate but has no number you can verify independently is a document, not a certification.

2. Which NRTL issued it? “NRTL” is a Nationally Recognized Testing Laboratory — OSHA-recognised in the US. UL is one; so are Intertek, CSA, TÜV SÜD/Rheinland and others. All are valid. What matters is that the body is actually recognised and that the mark on the product matches the body on the certificate. A certificate from an unrecognised body may not satisfy your inspector.

3. Does the model number match character for character? This is the check that catches the most problems, and it’s the one people skip. Certification applies to a specific model designation. If the certificate lists CPS-250-24 and you’re buying CPS-250-24-A, and that suffix isn’t also on the certificate, you do not have coverage for what you bought.

Suppliers rarely intend deception here — suffix changes happen through minor revisions and the certificate doesn’t always follow immediately. But from your inspector’s perspective, an unlisted model is an unlisted model. Ask for the certificate to explicitly cover the exact designation on your purchase order.

4. What’s the current status? Listings can be withdrawn, suspended, or allowed to lapse. Check the status in the directory, and check the date on any PDF you’ve been handed. A certificate from four years ago may not reflect the current listing.

5. Is there follow-up inspection? NRTL listing typically involves periodic factory inspection to confirm ongoing production matches what was tested. Ask whether the listing includes a follow-up service programme. A listing without follow-up is weaker evidence than one with it — it means the unit was tested once, not that it’s still being made to that standard.

When the certificate doesn’t match

The checks above turn up problems regularly. Here is what each one actually means and what to do about it.

The model number has a suffix that isn’t on the certificate. This is the most common finding and it is usually benign — minor revisions add suffixes faster than certificates get updated. But “usually benign” isn’t “covered.” Ask the supplier for one of two things: an updated certificate listing your exact designation, or a written statement of model equivalence on their letterhead referencing both numbers. Don’t accept a verbal assurance. If your inspector challenges it, the person who gave you the verbal assurance will not be standing next to you.

The certificate has expired or shows a lapsed status. Request the current listing. If the supplier can’t produce one, treat the product as uncertified for your purposes. A lapsed listing sometimes reflects nothing more than an administrative oversight, but you cannot rely on it until it’s corrected, and correction is fast when it’s genuine.

The issuing body isn’t an NRTL. The certificate may be entirely valid in its own market and still not satisfy your inspector. If the mark isn’t from a body recognised for your jurisdiction, you need either a listing from a recognised body or a field evaluation. Both cost money and time, so check this before ordering, not after.

You’ve been given a test report instead of a certificate. These are different documents and the distinction matters. A test report says a sample was tested and here’s what happened. A listing/certification says the product was evaluated against a standard and the manufacturer is authorised to apply the mark, usually with ongoing factory inspection. A test report is evidence. A listing is a compliance basis. Suppliers sometimes present one as the other, and on a small number of occasions that’s deliberate.

The certificate covers a different product family. More common than you’d expect when a supplier has a long catalogue. Verify the certificate applies to the family you’re buying, not just to the brand.

The general principle across all five: get it in writing, and get it before money moves. Certification problems discovered after delivery are your problem. The same problems discovered during quoting are the supplier’s problem, and they will solve them quickly at that stage.

Where to get the actual standard

To be direct about this: we’re not going to point you to a pirated copy of UL 1310, and you should be sceptical of anyone who does. Standards are copyrighted and sold by the standards bodies. A pirated PDF is also frequently out of date, which is worse than useless in a compliance context.

Legitimate routes:

• Direct from UL — standards can be purchased individually from UL’s catalogue
• Through your industry association — many have licensing arrangements or member access
• Via your certifying body — if you’re having a product evaluated, they can advise
• From your AHJ — the authority having jurisdiction can tell you which edition applies in your area

What you can get from us directly, at no cost, is the certification evidence for our own products — the actual listing certificates and test reports for the units you’re buying. Those are on the datasheets and certificates download page. If the specific certificate you need isn’t there, ask for it; that’s a normal request and we turn it around quickly.

And if you need a unit evaluated or certified to a standard we don’t currently cover, that’s an OEM/ODM conversation — certification scope is a real project lever with real cost and schedule implications, so raise it early rather than after the design is frozen.

FAQ

Does “UL certified” mean a power supply is Class 2? No. UL publishes many standards. Class 2 status specifically comes from evaluation to UL 1310. A unit can be listed to a different UL standard and not be Class 2 at all.

Is a 24V power supply automatically Class 2? No. Both voltage and power limits apply, and the unit must be evaluated and listed as a Class 2 power unit. Output voltage alone doesn’t determine it.

What’s the commercial benefit of Class 2? Mostly installation cost. Under NEC Article 725, Class 2 circuits generally have less restrictive wiring requirements than Class 1, which can remove conduit and reduce cable and labour cost significantly on large installations.

What’s the difference between Class 2 and Class P? Different standards and different questions. Class 2 (UL 1310) is about output circuit energy limits. Class P (UL 8750) is about whether an LED driver can be mounted outside a luminaire. A unit can be one, both, or neither.

How do I verify a certificate is real? Look up the certificate number in the issuing body’s public directory, confirm the NRTL is recognised, and check that the model number on the certificate matches your purchase order character for character.

Is CE marking the same as UL listing? No. CE is often a manufacturer’s self-declaration of conformity with EU directives. UL listing involves third-party testing and usually ongoing factory inspection. They are not interchangeable.

This article is general guidance, not a compliance certification or engineering specification. Confirm all limits, wiring methods and certificate requirements against the current editions of UL 1310 and the NEC, and with your authority having jurisdiction. Product-specific certification figures pending confirmation from our documentation.