Square D 999390 Molded Case Circuit Breaker
- 90A
- 3 Pole
- Bolt-On
Quantity
Square D 999390 - 90A 3 Pole Molded Case Circuit Breaker
Re-Certified
Quantity
Description
Serving commercial and industrial facilities, the Square D 999390 is a 3-pole, 90A molded case circuit breaker. It is part of the discontinued 999 frame family, providing an essential hardware solution for older networks. The breaker features a robust bolt-on mechanism tailored for Square D ML panelboards and motor control centers. By utilizing this Type ML-1 replacement, contractors can safely service existing enclosures.Specifications
| Brand | Square D |
|---|---|
| Part Number | 999390-R |
| Series | 999 |
| Amperage | 90A |
| Poles | 3 |
| Mounting Style | Bolt-On |
| Voltage | 600VAC |
| Phase | 3 |
| AIC Rating | 10kA @ 600VAC |
| Terminal Type | Lugs |
|---|---|
| For Use With | Square D ML Panelboards, Square D Motor Control Centers |
| Trip Technology | Thermal Magnetic |
|---|---|
| Trip Function Code | LI |
| Trip Function | Long-Time, Instantaneous |
| Trip Adjustability | Fixed Thermal, Fixed Magnetic |
| Standards | UL 489, CSA C22.2 No. 5 |
|---|---|
| Approval | UL, CSA |
| Temp Rating | 40°C |
| Construction Features | Obsolete |
Product FAQs
5 answersWhich panelboards are compatible with the 999390 circuit breaker?
This breaker is exclusively designed for use in legacy Square D ML panelboards and Square D motor control centers. It will not fit in modern QO, NF, or I-Line distribution panels.
How is the 999390 secured inside the enclosure?
This breaker utilizes a bolt-on mounting configuration. It bolts directly to the bus system of compatible ML panelboards, providing a secure mechanical and electrical connection.
What is the maximum fault current the 999390 can safely interrupt?
This breaker is rated to safely interrupt up to 10,000 amps (10kAIC) at 600VAC. Installing this in a system with a higher available fault current violates safety standards and can result in equipment failure.
How does the thermal-magnetic trip unit on this breaker operate?
The fixed thermal-magnetic (LI) trip unit provides two layers of protection. The thermal element responds to prolonged overloads with a long-time delay, while the magnetic element trips immediately during a severe short circuit.
Is the 999390 breaker part of a current Square D product line?
No, the 999 frame series is an obsolete, legacy product line. It is utilized as a direct Type ML-1 replacement to maintain existing older enclosures, allowing facilities to avoid a complete panelboard upgrade.
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