Hager HHB250Z x250 3P 250 A 25 kA Thermal-Magnetic MCCB

A 250 A thermal-magnetic moulded case breaker for main and feeder circuits

The Hager HHB250Z belongs to the x250 range of moulded case circuit breakers. It is a three-pole, fixed, front-connected breaker rated 250 A with a thermal-magnetic trip unit (TM, listed by Hager as TM F/F). A toggle operates the contacts, and the ultimate breaking capacity at 400 V AC is 25 kA under IEC 60947-2.

With the F/F trip unit there are no dials to adjust, which keeps selection straightforward for incomers and feeders in distribution boards, motor control centres and small plant rooms where the load and cable are already defined.

Technical specifications

Rated current against temperature

The datasheet tabulates the current the breaker can carry at different ambient temperatures under IEC 60947: 263 A at 40 degrees C, 250 A at 50 degrees C, 243 A at 55 degrees C, 236.2 A at 60 degrees C and 222.2 A at 70 degrees C. At 30 degrees C the figure is 275.5 A. Plant rooms and outdoor enclosures in hot regions should be sized with the real internal air temperature in mind rather than the 250 A headline value.

Selection and installation notes

Confirm three things before ordering: the prospective short-circuit current at the installation point must not exceed 25 kA at 400 V; the cable must fit the terminal range of 35 to 185 mm2 rigid or 35 to 150 mm2 flexible; and the board must accept a fixed front-connected MCCB, because the device does not clip onto DIN rail. At 48 W dissipation at rated current, the heat load should be added to the enclosure thermal calculation.

If the load needs adjustable overload or short-time settings, or higher breaking capacity, look at the h3+ breaker family instead, such as the P160 and P250 frames.

How the Hager HHB250Z x250 MCCB protects a circuit

A thermal-magnetic moulded case breaker protects the circuit with two separate mechanisms. The thermal element is a bimetal strip that heats in proportion to the current and trips the breaker after a delay on a sustained overload, so cables and the load are protected from overheating. The magnetic element reacts to a short circuit with an almost instantaneous release. The F/F trip unit of the HHB250Z is fixed, so these thresholds are set at the factory for the 250 A rating and cannot be changed on site. The datasheet gives an opening response time of 10 ms and an ultimate breaking capacity of 25 kA at 400 V AC according to IEC 60947-2.

Applications for the HHB250Z

• Main incomers of small and medium distribution boards.
• Feeder protection for sub-distribution boards and large loads.
• Motor control centres and plant rooms with defined load and cable sizes.
• Commercial and industrial buildings that need a fixed-setting breaker at 250 A.

Selection checklist for the 250 A MCCB

• Prospective short-circuit current at the installation point, which must not exceed 25 kA at 400 V.
• Load current and cable ampacity, with the current-against-temperature table in mind: 275.5 A at 30 degrees C, 263 A at 40 degrees C and 222.2 A at 70 degrees C.
• Cable size: 35 to 185 mm2 rigid or 35 to 150 mm2 flexible conductors, with a tightening torque of 12 Nm.
• Mounting: the breaker is fixed and front-connected, and it does not mount on DIN rail.
• System voltage: rated operational voltage Ue of 220 to 415 V at 50 to 60 Hz.
• Enclosure heat: power dissipation of 48 W at rated current to be added to the thermal calculation.
• Need for adjustable trip settings, which would call for a different trip unit or breaker family.

Installation and maintenance notes

Isolate and lock out the supply before installing the breaker. Torque the terminals to 12 Nm, since loose terminations are a common reason for heating and nuisance trips. Check that the cable lugs suit the terminal range and that the breaker is installed in an enclosure with sufficient ventilation, as the ingress protection of the device itself is IP4X. After commissioning, test the toggle operation and record the settings in the board documentation. The datasheet lists electrical endurance of 1000 operations and mechanical endurance of 4000 operations, and the device is stated as RoHS conform and REACh-SVHC free.

Requesting a quotation for the Hager HHB250Z

Send the order code HHB250Z, the quantity, the board or project data and the delivery location. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.

HHB250Z electrical data at a glance

The breaker is rated for an operational voltage Ue of 220 to 415 V, an insulation voltage Ui of 800 V and an impulse withstand voltage Uimp of 8000 V at 50 to 60 Hz. Its product description is Moulded Case Circuit Breaker X250 3P 25kA 250A TM. Current-carrying capacity varies with temperature: 243 A at 55 degrees C and 236.2 A at 60 degrees C, which means a board in a hot plant room may need a larger breaker or better ventilation. Where selective coordination with downstream devices is needed, the manufacturer coordination tables should be consulted, and the breaker should be matched to the cable protection requirements of the local wiring regulations.

Documents and quotation

The attached Hager datasheet is the source of the values above. Send the order code, the system voltage, the fault level and the quantity with your enquiry. Related devices are in the circuit breakers category.