---
title: "Class 2 DIN Rail Power Supplies: NEC/UL Selection Guide"
date: 2026-09-15T06:44:15Z
modified: 2026-10-13T00:33:06Z
permalink: "https://www.simplybuyglobal.com/industry-knowledge/class-2-power-supply-requirements/"
type: post
status: publish
excerpt: ""
wpid: 8720
categories:
  - Industry Knowledge
featured_image: "https://www.simplybuyglobal.com/wp-content/uploads/2026/10/class-2-din-rail-power-supplies-cover.webp"
featured_image_alt: Allen-Bradley, Siemens and MEAN WELL DIN rail power supplies.
timestamp: 2026-10-13T00:33:06Z
tags:
  - Industry Knowledge
---

## Quick answer

For a 24 V DC panel, the Class 2 power supply requirements come down to three things: an exact catalog number, its listing row, and one arithmetic check. The NEC caps a Class 2 circuit near 60 V DC and 100 VA of available power, and a supply below that ceiling is not automatically a Class 2 source. The line qualifies through a Class 2 listed supply or Class 2 approved protectors. Simply Buy supplies both routes as a multi-brand distributor and supply-chain integrator, not a manufacturer.

The page covers what the limit tests, the four things called “Class 2”, a six-family comparison of published listing wording, and the checks to complete before a BOM line is signed off. The recommendation is one step: pull the datasheet for the exact part number and read its safety-standards row.

One prerequisite controls the rest. A line reading “24V DC power supply, DIN rail” is a starting point, not a specification. The check happens at catalog-number level, on the manufacturer’s own document. A series name or a distributor spec table is not evidence: one family can ship two Class 2 power supply numbers and several standard ones.

## What Do Class 2 Power Supply Requirements Actually Limit on a 24 V DC DIN Rail Supply?

A DIN-rail power supply is a switch-mode supply. One platform can be sold as a general-purpose industrial power supply, as a Class 2 source, or as both, so two units can share a housing and differ only in the limiting circuit. For background, see [what a switch-mode power supply is](https://www.simplybuyglobal.com/wp-content/uploads/wp-mfa-exports/post/smps-what-is-a-switch-mode-power-supply-guide.md).

Class 2 power supply requirements reduce to a voltage ceiling, a power limit and one row of a datasheet. VA is volt-amperes, which on a DC output is volts times amps, so 100 VA caps the power the source may make available. Rockwell Automation’s white paper Designing NEC Class 2 Circuits characterises Article 725 of the US National Electrical Code, the part covering remote-control and signalling circuits, this way: a low-voltage DC circuit has a maximum voltage near the IEC 60950-1 limit of 42.4 V peak or 60 V DC, and a maximum power potential of 100 VA. Treat that as a manufacturer’s description, not a code quotation.

A supply rated at or below 100 VA is not automatically a Class 2 power supply, because UL applies specific tests when it certifies one. A [PLC panel power-supply selection guide](https://www.simplybuyglobal.com/wp-content/uploads/wp-mfa-exports/post/industrial-plc-power-supply-selection-guide.md) covers sizing, but Class 2 status is a separate question that starts on the datasheet.

A higher-current source fused down to 100 VA is not an acceptable Class 2 source; a fuse protects the wiring; it does not qualify the supply.

MEAN WELL’s NDR family shows why the wattage is not the deciding number. The [MEAN WELL NDR DIN-rail supply family](https://www.simplybuyglobal.com/product/mean-well-ndr-series-power-supply-3465/) runs NDR-75-24 at 24 V and 3.2 A, or 76.8 W, under the ceiling, and its datasheet names UL 508 and no Class 2 basis.

## Which “Class 2” Are You Being Asked For?

An NEC Class 2 circuit is the wiring between the load side of a Class 2 power source and the connected equipment. The circuit is Class 2 because its source is a Class 2 power supply, not because the load happens to be small.

A UL 1310 Class 2 power unit is a product listing. UL 1310 is the standard behind the Class 2 limits; the listing belongs to one specific Class 2 power supply and carries a file number a reviewer can look up. UL 508A, the standard for industrial control panels, routes a Class 2 power unit to UL 1310, which is why the listing row decides.

IEC Class II is about construction and shock protection: two layers of insulation, or reinforced insulation, with no earth terminal. XP Power sets out the [separation between Class 2 and Class II](https://www.xppower.com/resources/blog/difference-between-class-2-and-class-ii-power-supplies) as two different axes. Class II construction is not evidence that a unit is a Class 2 power supply, and a Class I supply can still be one.

LPS, a limited power source, is a fourth limit set drawn from IEC/EN/UL 62368-1 rather than UL 1310. “Pass LPS” is a genuine safety statement, and it does not certify a Class 2 power supply.

Keep three things visibly apart: the “NEC Class 2” marking a catalogue prints, the UL 1310 Class 2 listing behind a file number, and “Pass LPS”. The same logic runs through switchgear, where [UL 489 and UL 1077](https://www.simplybuyglobal.com/wp-content/uploads/wp-mfa-exports/post/ul-489-vs-ul-1077.md) describe different breaker constructions and cannot be swapped by name.

One vendor knowledge base states that UL 1310 applies only to direct plug-in and cord-connected units and that its own DIN-rail supplies fall outside it. Siemens registers DIN-rail SITOP units to UL 1310 Class 2 under file E151273, and Phoenix Contact states “NEC Class 2 as per UL 1310” on DIN-rail UNO and STEP units, so UL 1310 is evidently applied to industrial DIN-rail Class 2 power supplies today.

Hero Product Highlight [ ![Siemens SITOP Power Supply](https://www.simplybuyglobal.com/wp-content/uploads/2025/10/1-14.jpg)

Siemens SITOP Power Supply

 **Manufacturer**: Siemens
 **Model**: SITOP Power Supply
 **Power Range**: 24W–480W
 **Supply Voltage**: 85–264V AC
 **Protection Rating**: IP20 

 View Product ](https://www.simplybuyglobal.com/product/siemens-sitop-power-supply/)## How Does the 100 VA Limit Work Across the Whole Output Range?

The ceiling has to hold at the top of the supply’s adjustable range, not at the nominal setpoint alone. Phoenix Contact’s white paper on NEC Class 2 circuits works the case: if a 24 V DC power supply’s specification allows its output to reach 28 V DC, the current has to be limited to 3.57 A at that threshold to hold 100 VA. A unit that holds 4 A at 24 V sits inside the limit at nominal and outside it at the top of its range, so that figure decides whether the Class 2 power supply claim survives the full range. It is a vendor-stated engineering requirement, not a code quotation.

![Comparison of 96 VA, 112 VA and 99.96 VA output calculations.](https://www.simplybuyglobal.com/wp-content/uploads/2026/10/class-2-100va-voltage-range-check-1200x675.webp)

## Can You Just Fuse a Bigger Supply Down to 100 VA?

No. Rockwell’s paper states that the NEC does not consider a higher-current source, fused to 100 VA, to be an acceptable Class 2 power source. A 24 V, 10 A unit with a 4 A fuse is still a 240 W source, and the fuse protects the conductor rather than turning the unit into a Class 2 power supply.

Phoenix Contact’s whitepaper describes using a standard, higher-amperage supply and protecting each branch with a Class 2 approved electronic circuit protector. An electronic circuit protector (ECP) is a solid-state device that interrupts a branch when current exceeds a set level. Used this way, Phoenix states, the protected branches qualify as Class 2 circuits, and the supply that feeds the panel does not need a Class 2 certification of its own; a standard industrial supply works with the limit set downstream.

The boundary is firm: in Phoenix Contact’s account, conventional fuses and circuit breakers cannot originate a Class 2 limited-power circuit. The reason is tripping behaviour: an ECP opens at roughly 20% over nominal current, while a thermal-magnetic breaker needs three to twenty times nominal to open, and a limited-power source may not deliver that current for long enough. That is why a standard branch protection device is the wrong tool for creating the limit.

Decide the architecture before you choose a model. The direct route means buying a listing. The ECP route means buying a larger standard SELV supply (safety extra-low voltage, isolated from earth) plus one approved protector per branch, and moving the documentation burden to the protector datasheet. A single low-wattage branch is simplest on a small Class 2 supply; a mixed 24 V DC bus documents more easily with the ECP route.

![Two Class 2 circuit paths using listed supplies or approved protectors.](https://www.simplybuyglobal.com/wp-content/uploads/2026/10/class-2-listed-supply-vs-approved-ecp-1200x675.webp)

## Which Class 2 DIN Rail Power Supplies Actually Qualify?

This Class 2 power supply comparison covers six families from four brands and is model-level: catalog numbers and listing wording come from the manufacturers’ own documents, not a distributor spec table. No source behind this article publishes a price, lead time or stock figure for these families, so the columns say what to ask for.



| Family and catalog number | Output | Position against the 100 VA ceiling | Listing wording as published | Mounting | What to confirm on the datasheet |
| --- | --- | --- | --- | --- | --- |
| MEAN WELL NDR, NDR-75-24 through NDR-480-24 | 12/24/48 V DC; 76.8-480 W | Smallest member is 76.8 W, under the ceiling in W terms, and is still not a Class 2 power supply | “UL 508 (industrial control equipment) approved”; TUV BS EN/EN62368-1. No UL 1310, no Class 2 and no LPS wording in the datasheets reviewed | DIN rail TS-35/7.5 or 15 | Whether any model holds a UL 1310 listing; ask for the file number |
| MEAN WELL HDR: HDR-15-24, HDR-30-24, HDR-60-24, HDR-100-24, HDR-100-24N | 24 V DC; 15.2-100 W | HDR-100-24 is capped at 92 W and passes LPS; the -N variant runs to 100 W and is non-LPS | Current datasheets: “Isolation class II” and “Pass LPS (Limited power source)”; UL 62368-1, UL 508. An older short-form catalogue labelled these models “Class 2 power unit / Pass LPS”. No UL 1310 certificate was found for the series | DIN rail, plastic case, slim step shape | Which wording your dated revision carries, and whether a UL 1310 file number exists |
| Siemens SITOP PSU100C, 6EP1332-5BA20 | 24 V DC, 3.7 A, approx. 89 W | Under the ceiling | “NEC Class 2: Yes; according to UL1310, File E151273”; cULus-Listed UL 508 file E197259; cURus-Recognized UL 60950 | DIN rail EN 60715 35×7.5/15 | The article number on the quote is the Class 2 unit; larger PSU100C outputs are a separate case |
| Siemens SITOP PSU6200 single-phase under 75 W: 6EP3321-7SB00-0AX0, 6EP3331-7SB00-0AX0, 6EP3332-7SB00-0AX0 | 12-24 V DC; 1.3-2.5 A; under 75 W | Stated at the ceiling: output limited to 100 VA | “NEC Class 2 (acc. to UL 60950-1/UL 1310), file E151273”; cULus-Listed UL 508 file E197259 | DIN rail | That the unit is one of the sub-75 W single-phase article numbers |
| Allen-Bradley 1606-XLP: 1606-XLP95E, 1606-XLP90E-2 | 24 V, 3.9 A, 95 W; 24 V, 3.75 A, 90 W (two-phase 380-480 V AC) | Under the ceiling in W terms, but the published qualification basis found is not a UL 1310 Class 2 listing | Product Selection column reads “NEC Class 2”. The 1606-XLP CE Declaration of Conformity declares EN IEC 61010-2-201 with LVD, EMC, ATEX and RoHS, and carries no UL 1310 or UL 508 claim. 1606-XLP100E at 100 W is not marked Class 2 in the same table | DIN rail | What the Class 2 marking rests on, in writing, for your jurisdiction |
| Phoenix Contact UNO and STEP: UNO-PS/1AC/24DC/60W (order no. 2902992), STEP-PS/1AC/24DC/2.5 (order no. 2868651) | 24 V DC, 2.5 A, 60 W | Under the ceiling | “NEC Class 2 as per UL 1310”. UNO also lists a Class I Division 2 hazardous-location listing | DIN rail, screw connection | The rendered datasheet for the exact order number; the STEP wording came from a distributor mirror |

Send the BOM line as it stands, with the catalog number, quantity and destination region, and we will return the datasheet revision for that exact number, the listing row that applies, and the documents that will travel with the shipment. Our stated turnaround on a solution quote is 12 hours.

## What Should You Check Before the BOM Line Is Approved?

1\. Catalog number and current datasheet revision. Read the safety-standards row for the exact number being quoted, on the manufacturer’s own document, and note the revision date. A distributor product page is not the document, including our own.

2\. Listing wording and file number. Note which standard the row names and the file number behind it. Keep apart a “NEC Class 2” marking, a UL 1310 Class 2 listing, and “Pass LPS”. A row that says UL 508 tells you the unit is industrial control equipment, not that it is a Class 2 source.

3\. Operating-range arithmetic. Multiply the highest output voltage the datasheet allows by the current limit. If the product exceeds 100 VA there, the Class 2 basis does not hold even when it holds at nominal.

4\. Architecture decision. A Class 2 power supply used directly, or a standard supply with Class 2-approved protectors on each branch. On the second route, the protector datasheet is the document you will defend, so the protector has to be approved for Class 2 origination, not a plain electronic fuse.

5\. Wiring consequence. Rockwell’s paper frames the payoff of a genuine Class 2 circuit as design relief: conductors and devices intended for Class 2 circuits can be smaller because fire-initiation protection sits at the source. That relief applies only where the circuit actually qualifies, so the wiring method and the listing row must agree. In North American panels, the decision also depends on UL and NEMA motor-control products.

6\. Documents. Ask for a certificate of conformity (COC), a certificate of origin (COO), the UL file number, and the datasheet revision the quotation was priced against, for the Class 2 power supply being quoted. Where a requirement is jurisdictional, ask for the declaration that covers your region, and keep a copy of the [datasheets and catalogues](https://www.simplybuyglobal.com/downloads/) you are quoting from.

## Does Cross-Brand Model Matching Change the Class 2 Answer?

Matching solves the sourcing problem, not the classification problem. A substitute is not a Class 2 power supply until its own datasheet says so, so the listing and arithmetic checks run again on the new catalog number.

Ask separately what is in stock and what is a factory order at the quantity you need, and for the lead time against that quantity, not the series; a series average says nothing about one line of Class 2 power supplies.

## How Do You Get Class 2 DIN Rail Power Supplies Supplied?

Genuine-product verification starts before the order: ask who inspected the units and what happens if one fails. Our stated position is a one-year warranty backed by factory quality control plus our own incoming inspection, with technical selection support and cross-brand model matching available before the order.

We supply Class 2 power supplies from MEAN WELL, Siemens, Allen-Bradley and Phoenix Contact. For Siemens, our [Siemens SITOP power supplies](https://www.simplybuyglobal.com/product/siemens-sitop-power-supply/) page is the distributor view; a Class 2 registration still has to be read on the article number, not the brand. Where a certificate has to satisfy a specific inspector, a regional declaration beats a generic pack, and our UL-listed industrial control products line is the one to raise for panels going into the United States or Canada.

Logistics follow the same rule: terms move, ratings do not. We hold inventory in warehouses in China, the United States and Europe (our warehousing network), ship by air, sea and express, and support DDP, delivered duty paid, as a standard trade term, with CIF, FOB and EXW also available. The trade term decides who carries freight, duty and risk; it does not change what the unit is listed to. Our published service figures are a 2-hour response rate, 100% on-time delivery, 99% customer satisfaction and a 98% resolution rate; ask for the current numbers for your lane.

Reach us on WhatsApp at +86 186 1636 9656, or [contact us](https://www.simplybuyglobal.com/contact/) by email at info@simplying.com, with the part numbers or the full BOM for the Class 2 power supplies you need, the destination country and the trade term. A usable quote returns six things: the exact catalog number and its datasheet revision; the listing row and UL file number; whether the quantity is stock or factory order, with the lead time for that quantity; the trade term and what it includes; the warranty and inspection documentation; and the COC and COO that travel with the shipment.

## FAQ

### 1. Is any 24 V supply of 100 W or less Class 2?

No. Rockwell’s paper states that a supply rated at or below 100 VA is not necessarily a Class 2 power supply, and that UL applies specific tests when certifying one. Wattage is a filter, not the answer.

### 2. Why is my supply marked “NEC Class 2” but not UL 1310?

The marking and the listing come from different vocabularies. Rockwell’s Product Selection table marks 1606-XLP95E and 1606-XLP90E-2 as “NEC Class 2”, while the CE Declaration of Conformity found for the [Bulletin 1606-XLP compact supplies](https://www.simplybuyglobal.com/product/allen-bradley-bulletin-1606-xlp-compact-power-supply/) cites EN IEC 61010-2-201, and no UL 1310 claim for them was found. Ask which document supports the Class 2 power supply marking in your jurisdiction.

### 3. Can I use a bigger supply with a fuse to create a Class 2 circuit?

Rockwell’s paper states that the NEC does not consider a higher-current source fused to 100 VA to be an acceptable Class 2 power source. The documented alternative is a standard supply with a Class 2-approved electronic circuit protector on each branch, so one larger unit can feed Class 2 power supplies on several branches.

### 4. Does Class II mean Class 2?

No. Class II is an insulation class, covering double or reinforced insulation without an earth terminal. Class 2 is a power and wiring limit. A double-insulated supply is not automatically a Class 2 source.

### 5. What if the exact model is obsolete?

Treat the replacement as a new catalog number, not a family member. The substitute still needs its own datasheet check: listing row, file number, and the arithmetic at its maximum output voltage. Cross-brand matching can find an equivalent quickly; see [how to source obsolete industrial automation parts](https://www.simplybuyglobal.com/wp-content/uploads/wp-mfa-exports/post/how-to-source-obsolete-industrial-automation-parts.md).

## What Is the Next Action on Class 2 Power Supply Requirements?

Class 2 power supply requirements are settled by a datasheet, not a family name. Pull the datasheet for the DIN rail power supply behind your current BOM, and if it names no Class 2 listing and no file number, change the catalog number or add a Class 2-approved protector on the branch before the line is approved.

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