Allen-Bradley 1734-IA4 POINT I/O 4-Point 120 V AC Input Module

Four 120 V AC inputs in a 12 mm POINT I/O module

The Allen-Bradley 1734-IA4 reads four 120 V AC inputs in one non-isolated sinking group. It is only 12.1 mm wide, which lets mains-voltage contacts such as starter feedback, pressure switches and selector switches be brought into a POINT I/O station beside DC and analog modules.

The 2-point sibling is the 1734-IA2, and the conformal-coated version is 1734-IA4K. All three are covered by one installation instruction, series C.

Technical specifications

Using AC inputs on a POINT I/O station

The module needs the 120 V AC supply brought to the terminal base as the sensing voltage, so the AC field wiring should be separated from the DC wiring with the right base. The long hardware delay of 20 ms plus the digital filter means AC inputs are suited to slow signals only. If the field device leaks current, the maximum off-state current of 2.7 mA at 43 V AC is the figure to compare against.

Ordering notes

The wiring base is ordered separately, and the keyswitch position of 8 must be set on the base. Check whether the existing station uses series C modules, and whether the four-input IA4 or the two-input IA2 is wanted. Terminal base choice (screw or spring) is covered in the installation instruction. The approvals printed in the document include UL listing for US and Canada (file E65584), Class I Division 2 Groups A to D (file E194810), CE marking to EN 61326-1, EN 61000-6-2 and EN 61000-6-4, and the module is open-style so it must be mounted inside an enclosure. Vibration is rated 5 g at 10 to 500 Hz, operating shock 30 g and non-operating shock 50 g.

Selection checks before specifying the 1734-IA4

The first check is the control voltage. The 1734-IA4 is built for a 120 V AC sensing supply, while many industrial panels use a different control voltage, so confirm what is actually present in the panel and at the field devices before choosing this module. If the field contacts are switched at a voltage outside the module’s on-state range, a different input module is needed rather than this one.

Next, list every signal that will land on the module and check that each one is a slow on/off contact. Because the module combines a hardware delay with a programmable digital filter, it is a good fit for motor-run feedback, limit and level switches, door contacts and selector positions, but not for pulse counting or anything that changes state faster than the filter allows. Confirm also that a single non-isolated group of four inputs is acceptable: all four inputs share the same AC supply, so signals that must come from separate circuits should go to separate modules.

Finally, check the field devices for leakage current. Two-wire proximity switches and contacts with RC suppression across them can pass a small current when open. Compare that leakage with the off-state current limit in the table; if it is higher, a loading resistor or a different sensor type may be needed to make the input switch off reliably.

Installation and wiring practice

Install the module on a compatible terminal base inside an enclosure, with the base keyswitch set to the position given in the table before the module is plugged in. Keep the 120 V AC field wiring physically separated from DC and analog signal wiring in the trunking, and label the AC terminals clearly so that maintenance staff know mains voltage is present on that part of the POINT I/O station. Fuse or protect the 120 V AC sensing supply according to the panel design and local wiring rules, and make sure the supply common is connected as shown in the installation instruction.

Commissioning the inputs

During commissioning, operate each field contact in turn and confirm that the correct bit changes state in the controller. Set the digital filter time in the module configuration to suit the slowest and noisiest signal on the module, then verify that genuine changes are still recognised quickly enough for the control logic. If an input does not drop out when the contact opens, measure the off-state voltage at the terminal base and look for leakage through suppression components or long parallel cable runs.

Panel environment in Oman and the GCC

Control panels in the Gulf can see high internal temperatures in summer, especially where enclosures stand outdoors or in unventilated plant rooms. Keep the panel interior within the operating temperature range listed above, using shading, ventilation or cooling as the site requires, and keep enclosures sealed against fine dust. In coastal or humid areas, condensation during cool nights can affect exposed electronics; where this is a concern, discuss the conformal-coated 1734-IA4K listed on this page as an alternative. Periodic maintenance should include checking terminal tightness, cleaning dust from the enclosure and confirming input states against the field devices.

Documents and quotation

The linked document is the manufacturer installation instruction for the POINT I/O 120 V AC input modules. For more POINT I/O items see PLC & I/O Cards. Send the catalog number and quantity to Seven Star LLC, an independent supplier in Muscat, to request a quotation.