ABB AUX-C 2Q+2SY+1S51 250 V Auxiliary Contacts for XT2-XT4

The AUX-C 2Q+2SY+1S51 250Vac/dc, order code 1SDA066438R1, is a cabled auxiliary contact set for ABB SACE Tmax XT moulded-case circuit breakers in fixed or plug-in version. ABB’s product page names XT2 to XT4 as the breakers it fits. It reports two open/closed contacts (Q), two trip-signalling contacts (SY) and one trip-unit signalling contact (S51, written SA in some catalogue tables) at 250 V AC/DC. Breakers to carry it are listed under circuit breakers, for example the SACE Tmax XT range.

Technical specifications

What Q, SY and S51 signal

Q shows the position of the power contacts, open or closed. SY signals that the breaker opened because of a release, such as an overload or short-circuit trip, a shunt or undervoltage release or the test button. S51 indicates that a protection function of the electronic or thermomagnetic trip unit has tripped. The catalogue tabulates the contact changeover for each state: for example Q is at terminal 12 with the breaker open and 14 with it closed, SY moves from 96 to 98 on a trip, and S51 moves from 06 to 08 when the trip unit itself was the cause.

Compatibility to confirm before ordering

The ABB product page names XT2 to XT4 for fixed and plug-in breakers. In the catalogue combination table the 2Q 2SY 1S51 250 V AC/DC set is marked for XT2 and XT4 only, with XT1 and XT3 shown without an entry. Because the two sources differ on XT3, please confirm the breaker frame and version with Seven Star LLC before ordering, and use the breaker nameplate rather than the family name. The catalogue is dated 2010, so a later ABB revision may differ.

Ordering code and related sets

The type name breaks down as AUX-C for cabled auxiliary contact, then the contact mix, then the voltage. Other cabled sets in the same catalogue include 1Q+1SY 250 V AC, 3Q+1SY 250 V AC and 3Q+2SY 250 V AC, each with its own code. Please give the exact breaker type, fixed, plug-in or withdrawable version and the signals needed so that the correct set is quoted.

Choosing the contact mix for your panel

Start from the signals the control system or the building management system actually needs. If the PLC only needs to know whether the breaker is open or closed, a set with Q contacts alone may be enough. The 2Q+2SY+1S51 combination is chosen when operators must also tell the difference between a manual opening, a release operation and a protection trip, which matters on motor feeders, generator incomers and critical distribution where the reason for an outage drives the restart decision. Having two contacts of each Q and SY type means one can go to the local indication and one to remote monitoring without interposing relays.

• Check that the signalling voltage of the control circuit is within the 250 V AC/DC rating of the set.
• Confirm the breaker frame and whether it is fixed or plug-in, using the breaker nameplate.
• Make sure the space for the accessory is not already taken by another internal accessory such as a shunt or undervoltage release.
• Plan terminal block numbering in the drawing so that the catalogue terminal numbers are carried through to the panel wiring.

Fitting and testing

Switch off and isolate the breaker before opening its accessory compartment, then press the set into its seat as described in the ABB instructions and route the pre-wired cables out of the breaker without pinching them under the cover. Connect the cables to the terminal block, then test each function in turn: open and close the breaker to check the Q changeover, press the test button to operate SY, and, where test equipment for the trip unit is available, simulate a protection trip to confirm S51. Record the results in the panel test sheet so that the wiring is proven before handover.

Maintenance and troubleshooting

If a signal is missing on the SCADA or PLC, first check the state table in the catalogue to confirm which terminal should be made in that breaker position, then measure at the terminal block before suspecting the contact set. Loose ferrules, broken cores at the point where the cable leaves the breaker, and wrong terminal mapping are the most common causes. A set that signals SY but not S51 after a trip usually means the breaker was opened by a release or test button rather than by the trip unit, which is the intended behaviour. During planned shutdowns, check the cables for heat damage near busbars.

Notes for Oman and GCC switchboards

Low-voltage switchboards in the region often run warm, particularly in packaged substations and outdoor kiosks during summer. Keep the auxiliary cables tied away from hot conductors and busbars, and make sure the switchboard ventilation and cooling work as designed. Fine dust that enters the breaker compartment can affect small signalling contacts, so keep covers closed and doors gasketed. On coastal sites, humid and salty air can corrode terminal blocks and ferrules; sealed enclosures, panel heaters against condensation and periodic inspection of control wiring help maintain reliable signalling over the life of the board.

Documents and quotation

The linked ABB catalogue lists the accessory combinations, the changeover table and the ordering codes. Seven Star LLC is an independent supplier in Muscat; no price or stock is shown here.