Schneider Electric CAD50B7 TeSys D Relay 5NO 24V AC

CAD50B7: a relay with five normally open contacts for 24 V AC 50/60 Hz control circuits

If you are replacing or specifying a 24 V AC 50/60 Hz control relay with five normally open contacts, the CAD50B7 is the Schneider Electric TeSys Deca reference to look at. Its datasheet title reads: TeSys D control relay – 5 NO – up to 690 V – 24 V AC standard coil. Seven Star LLC supplies the CAD50B7 in Oman and the GCC as an independent supplier based in Muscat.

How the reference breaks down: CAD means a TeSys Deca control relay, 50 fixes the contacts at five normally open contacts, and B7 fixes the coil at 24 V AC 50/60 Hz. Because the other family members share the same housing, an error in the last two characters is the most common cause of a relay that arrives and does not suit the panel.

Technical data of the CAD50B7 at a glance

Field use of the CAD50B7 in the Gulf

Low-voltage AC coils are used where a control transformer separates the relay circuit from the mains. In the GCC they appear mostly in machine panels, HVAC and pump control cabinets built by international manufacturers, where a 24, 42 or 48 V winding supplies relays, pilot lamps and solenoid valves. Here the relay is a repeater and interlock element between a controller output and field loads or drives.

Panels in the region commonly see high ambient temperatures, so the transformer that feeds the coil, not only the relay, deserves attention. The datasheet allows operation up to 60 °C with derating to 70 °C, but an undersized transformer in a hot cabinet is the more likely source of unreliable pull-in than the relay itself.

For the CAD50B7, that means five normally open contacts from one 24 V AC 50/60 Hz command, sitting next to LC1D contactors of the same TeSys D family on the same rail.

Contact block of the CAD50B7

Choose it when a single initiating contact, for example a PLC output or a protection relay trip contact, has to be repeated on five independent circuits: alarm annunciation, a shutdown loop, a remote indication, an interlock to another panel and a counter or logger. If any of those circuits needs a contact that opens when the relay operates, the 3 NO + 2 NC member of the family is the right choice instead.

Contact data from the datasheet apply to all five poles: 10 A conventional thermal current at 60 °C, utilisation categories AC-15, AC-14 and DC-13, a rated operational voltage up to 690 V AC, and a minimum switching capability of 17 V and 5 mA, which makes the contacts suitable for low-level signals as well as for 24 V PLC inputs.

Coil data and timing of the CAD50B7

The coil is the one part that distinguishes the CAD50B7 from its siblings, so it deserves the closest reading.

A 24 V AC coil is fed from a small control transformer, a typical solution when the control circuit has to stay separated from the mains for safety. The datasheet gives 70 VA inrush and 8 VA hold-in at 50 Hz, which at 24 V means an inrush current of about 2.9 A and a hold current of about 0.33 A. The transformer must be sized for the inrush of every relay that can pull in together, not only for the sum of the hold-in currents.

With an operational window of 0.8 to 1.1 Uc at 50 Hz, the coil works from about 19.2 to 26.4 V, and from 20.4 V at 60 Hz, where the datasheet narrows the lower limit to 0.85 Uc. That makes the voltage regulation of the transformer important: a small, heavily loaded transformer can sag below the pull-in threshold when several relays operate together. The drop-out band of 0.3 to 0.6 Uc, about 7.2 to 14.4 V, is higher than on a DC coil, which helps the relay release cleanly.

The datasheet gives operating times of 12 to 22 ms coil energisation and NO closing, 4 to 12 ms coil de-energisation and NO opening. The 50/60 Hz AC coil responds quickly, with closing times of 12 to 22 ms.

Installing and keeping the CAD50B7 in service

Fit the relay in an enclosure with the front face reachable for inspection: the datasheet quotes IP2X at the front face, which protects against finger contact but not against dust. The weight of 0.58 kg is modest, so the relay is held securely by its rail clip, but plate mounting is preferable on machines with strong vibration. The datasheet lists vibration resistance of 2 Gn open and 4 Gn closed (5 to 300 Hz) and shock resistance of 10 Gn open and 15 Gn closed for 11 ms.

For spares planning, the CAD50B7 is a good candidate for a stocked spare because it is physically identical to its siblings and the coil is the only part that differs. Mark the coil voltage clearly on the terminal block door or on the panel diagram, test it after any control-supply change, and keep a record of the coil code. The datasheet gives an 18-month warranty from the manufacturer, which applies to the product as supplied by its own channel.

Family table including the CAD50B7

The CAD50B7 is one member of a family of TeSys D control relays that share the housing, the contact data and the mounting. Only the coil voltage and type change from one reference to the next, together with the contact arrangement: the CAD32 series is 3 NO + 2 NC and the CAD50 series is 5 NO. The table lists the CAD50 references we are asked for most.

If the supply is not in the table, ask us; the CAD32 series has the other contact arrangement. AC-coil versions are 84 mm deep and DC-coil versions 93 mm, which matters in a shallow enclosure.

What to confirm before you buy the CAD50B7

• Coil: 24 V AC 50/60 Hz, confirmed from the supply drawing or the nameplate of the relay being replaced.
• Contacts: five normally open contacts, matched to the interlock and signalling circuits.
• Supply sizing: about 2.92 A at pull-in and 333 mA held in (derived from the datasheet power).
• Window: operates within 19.2 to 26.4 V at 50 Hz (0.8 to 1.1 Uc), from 20.4 V at 60 Hz and releases at 7.2 to 14.4 V (0.3 to 0.6 Uc).
• Contact load of the CAD50B7: 10 A thermal, AC-15, AC-14 or DC-13 duties; use a contactor for motor-power loads.
• Space: 77 mm high, 45 mm wide and 84 mm deep.
• Environment: operation up to 60 °C, up to 70 °C with derating; storage -60 to 80 °C.
• Type: AC and DC coils of the same voltage are different references; do not mix them.

Quotation details we need for the CAD50B7

• Delivery location in Oman or the GCC and the date required
• Panel or machine the relay must fit, and whether it is a spare, a replacement or a new installation
• The load or circuit each contact will switch (voltage, current, signal level)
• The coil voltage and type seen on the supply drawing or on the old relay nameplate
• Full reference CAD50B7 and the quantity

Documents and quotation

A datasheet for this product is attached on this page. It lists the electrical, mechanical and environmental data summarised above, and it is worth reading beside the panel drawing before you order.

Send us the part number, quantity and application and we will confirm availability and a quotation. Seven Star LLC is an independent supplier in Muscat and is not affiliated with the manufacturer.