Allen-Bradley 1734-EP24DC POINT I/O 24V DC Expansion Power Supply

Extending a POINT I/O node past the adapter limit

The Allen-Bradley 1734-EP24DC is the 24V DC expansion power supply for POINT I/O. It is installed within a node to regenerate the 5V DC POINTBus supply for the modules to its right, and it breaks the field power bus so that the modules to the right use a separate field supply.

This matters because an adapter supplies a fixed backplane current. The 1734-AENT adapter in the same family supplies 1.0 A and the installation sheet states that backplane current can be extended beyond that by adding 1734-EP24DC or 1734-EPAC supplies, allowing up to 63 modules in total. Add the current requirements of the modules and place an expansion supply before the limit is exceeded.

Technical specifications

Ratings and placement

The field power bus accepts 10 to 28.8V DC (24V DC nominal) with a maximum supply current of 10 A. Power consumption is 9.8 W at 28.8V DC and dissipation is 3.0 W. The isolation voltage is 50V continuous and tested at 2600V DC for 60 seconds.

The same device also provides a second use: when a node mixes different field voltages, the supply lets you separate one field power group from the next. Combine it with a 1734-FPD field power module if you need to split AC and DC field power on the same rail.

Wiring and installation

Use 22 to 14 AWG solid or stranded copper rated 75 °C or higher with insulation of at most 1.2 mm. The conductor category is 2 on the power ports. The unit mounts on the DIN rail as a normal POINT I/O device and is open-type equipment for indoor use inside an enclosure.

Do not insert or remove it while power is applied, because interrupting the backplane can cause unintended operation. Confirm the supply source and its protection against the 10 A field bus rating, and consult the same sheet for the temperature codes and the hazardous-location marks. The position of the supply in the node is decided by the running total of module currents counted from the adapter.

Planning a POINT I/O node with expansion supplies

Before ordering, build a simple table of the node: the adapter, every module in its physical order, the backplane current each one draws according to its installation instructions, and the field voltage each one needs. Add the backplane currents from the adapter outward and mark where the total approaches the adapter limit; that is where the 1734-EP24DC belongs. Group modules that share the same field voltage together, because the supply also starts a new field power group to its right. Leave some spare capacity in each segment so that modules can be added later without reorganising the whole rail, and keep the final layout drawing with the panel documents.

Sizing the 24V DC source

The expansion supply takes its power from an external 24V DC source, so that source must cover both the backplane load regenerated by the 1734-EP24DC and the field power drawn by the modules to its right. Choose a supply with a stable output inside the stated voltage range, add suitable overcurrent protection for the field power bus, and consider whether this segment should share a power supply with the adapter or use its own. Separating supplies can make fault-finding easier, but both should share a common reference arrangement consistent with the rest of the control panel design.

Commissioning and maintenance

After mounting and wiring with power isolated, check polarity and voltage at the terminals before energising. Once the node is powered, confirm in the controller software that every module to the right of the expansion supply is detected and communicating, and that field devices in the new power group receive the correct voltage. During routine inspections, look for loose terminals, discoloured wiring and dust on the rail, and check that the 24V DC supply voltage remains within range under full load. Remember that modules must not be inserted or removed with power applied, so plan any changes during a shutdown.

Control panels in Oman and GCC conditions

Because the 1734-EP24DC is open-style equipment, its operating environment is set by the enclosure it lives in. In the region, panels in field kiosks, pump stations and outdoor skids can become very hot during summer, so check the panel’s internal temperature against the ratings in the Rockwell documentation and allow for the heat dissipated by every module on the rail. Use enclosures with suitable dust sealing, keep filters on ventilated panels clean, and prevent condensation in humid coastal areas, where it can affect terminals and backplane connections over time.

Keeping the node documented

Mark the expansion supply position and its field power group on the panel drawing and on a label beside the rail. Technicians replacing a module later can then see at a glance which 24V DC source feeds which part of the node.

Documents and quotation

The sheet 1734-IN058 gives the full ratings. For a quotation, send the 1734-EP24DC reference, series, quantity and the module list of the node it will extend. Related items are shown in PLC & I/O Cards.