Gewiss GWD9121 MSX 125 MCCB 3P 20A Adjustable 36kA 690V

GWD9121 is a Gewiss MSX 125 moulded case circuit breaker, three poles, 20 A, with an electromechanical release that is adjustable on both thermal (0.63 – 0.8 – 1 x In) and magnetic (6 – 8 – 10 – 12 x In) settings. It is rated 690 V ac / 250 V dc, has a service breaking capacity of 36 kA at 400/415 V ac, and can be supplied fixed or plug-in.

A small-current MCCB with high breaking capacity

At 20 A the GWD9121 is the low-current end of the MSX 125 frame, used where a high fault level calls for a moulded case device but the load is small, for example a single motor or a sub-board feeder close to a transformer. Derived from the datasheet multipliers, the thermal trip can be set between 12.6 and 20 A and the magnetic trip between 120 and 240 A.

Breaking capacity is high for the frame size: Icu 50 kA at 220/240 V, 36 kA at 400/415 V, 25 kA at 440 V, 22 kA at 525 V and 6 kA at 690 V, with Ics equal to Icu at 220-690 V except 36 / 30 kA at 415 V.

Key features as printed in the datasheet

• 3P, 20 A, 690 V ac / 250 V dc, insulation voltage 800 V, Uimp 8 kV, overvoltage category IV.
• Adjustable thermal 0.63 – 0.8 – 1 x In; adjustable magnetic 6 – 8 – 10 – 12 x In.
• Fixed or plug-in execution; can be equipped with a motor operator.
• Compatible interlocks: lever and cable.
• Electrical life 30,000 cycles at 415 V; mechanical life 30,000 cycles.
• Total power loss 18 W; weight 1.1 kg; 90 x 155 x 68 mm.
• Operating temperature -5 to +65 C.

Technical specification

Electrical

Breaking capacity

Mechanical

Selection and ordering guide

Choose GWD9121 when you need a 20 A MCCB with adjustable magnetic setting and a high breaking capacity; its twelve-times-In upper magnetic setting helps avoid nuisance trips on motors with high inrush current, but verify with the motor data.

Other MSX 125 ratings use different order codes (the Gewiss list shows ratings from 20 A upward). The 160c frame (GWD9067 on this site) has fixed magnetic trip and lower Icu, so it is not a like-for-like replacement.

Installation and operation notes

The datasheet lists fixed and plug-in execution, front terminals, any mounting position and optional motor operator and interlocks (lever and cable). Order the accessory set that matches your execution.

Use cables and lugs suited to the front terminals; observe the -5 to +65 C operating range and the 18 W power loss when sizing enclosure ventilation.

Setting the trip: with In 20 A, thermal settings of 0.63, 0.8 and 1 x In correspond to 12.6, 16 and 20 A, and magnetic settings of 6, 8, 10 and 12 x In correspond to 120, 160, 200 and 240 A (derived values). For a motor with a full-load current of 12 A and a starting current of seven times that, a thermal setting near 12.6 A with a magnetic setting above the start peak would be the starting point; confirm with the motor datasheet and a coordination study.

Applications in Oman and the GCC

Typical uses are motor feeders and package-unit supplies on utility, water and HVAC projects, and as incoming devices on small panels close to transformers where the fault level is high.

For 690 V circuits the breaking capacity is 6 kA, so it is the voltage band where the device must be selected with care against the calculated short-circuit current.

Installation and selection notes

Because GWD9121 offers adjustable thermal and magnetic settings, record the chosen settings on the commissioning sheet. A thermal range of 12.6 to 20 A and a magnetic range of 120 to 240 A allow it to be matched to a motor or feeder. The breaker can be supplied fixed or plug-in, so confirm the version with the quotation, and check the fault level at the board against the 36 kA service breaking capacity at 400/415 V.

Information needed for a quotation

Send the code GWD9121, the quantity, the delivery location in Oman or the GCC and any accessories needed, such as auxiliary contacts or a plug-in base.

Documents and supply information

The manufacturer data sheet is attached to this page and should be read together with the project specification before a purchase is confirmed. Ratings, dimensions and protection classes are quoted as printed on that sheet. Lead time, stock position and certificates available with the shipment are confirmed in the quotation, and we supply to Oman and the wider GCC region for industrial, utility and building services projects.

Compatible accessories and related items

Related items: MSX 160c breaker GWD9067, other MSX 125 ratings, motor operators and interlock kits, and rotary isolators of the 70 RT HP family for local isolation.

Documents and quotation

Download the official Gewiss product data sheet for GWD9121 from this page. As an independent supplier based in Muscat, Seven Star LLC supplies Gewiss items on request: use the quote form with the quantity you need. Check every value in the document against your own specification before you order. Browse similar items in the category.