What are the differences between Square D Model 5 and Model 6?

The main differences are the door handle (Model 5 uses a toggle, Model 6 uses a T-handle), the stab pattern (different geometry, not interchangeable), and production status (Model 5 is discontinued, Model 6 is current production from Schneider Electric). The Model 6 also supports higher bus ratings up to 4000A versus 2500A for the Model 5.

Can you mix Model 5 and Model 6 buckets in the same MCC lineup?

No. Model 5 and Model 6 buckets use different stab patterns and are not interchangeable. Each vertical section in an MCC lineup is built for a specific model. If you have a mixed facility with both Model 5 and Model 6 lineups, you need model-specific replacement buckets for each.

What is the standard lead time for a Model 6 replacement bucket from MCC Depot?

Standard lead time is 2-3 weeks for feeder buckets. Rush builds are available in 1-2 business days for emergency situations. Compare this to OEM lead times from Schneider Electric, which typically run 8-16 weeks. All MCC Depot orders include free ground shipping.

What arc flash considerations apply to Model 6 bucket replacement?

Per NFPA 70E Section 130.5, an arc flash hazard analysis should be performed before working on MCC equipment. Bucket insertion and removal should be performed with the vertical section bus de-energized whenever possible. When energized work is required, appropriate PPE must be worn per the arc flash hazard analysis. MCC Depot buckets are built with components rated to handle the available fault current at your installation.

What is the difference between breaker and fused disconnect options?

Breaker disconnects use a molded case circuit breaker as the main disconnect device, providing both overcurrent protection and switching capability with a resettable mechanism. Fused disconnects use a fusible switch with Class J or Class R fuses, which typically provide higher interrupting capacity and faster clearing times for short circuits. The choice depends on your facility standards, available fault current, and coordination study requirements.

Can Model 6 buckets accommodate VFD installations?

Yes. Model 6 buckets can be configured with variable frequency drives (VFDs) for motor speed control applications. VFD buckets typically require 24-inch or 36-inch bucket heights to accommodate the drive, line reactor, and associated wiring. MCC Depot can build VFD-ready buckets configured for your specific drive model and motor horsepower.

How do I verify vertical section compatibility before ordering?

Provide MCC Depot with the Model 6 serial number and nameplate data from your vertical section, including the bus rating and section number. Photos of the existing bucket stab assembly and the section slot are also helpful. Our engineering team will verify compatibility before production to ensure a correct fit. Call 307-442-0382 or email sales@mccdepot.com with your information.

Square D Model 6 MCC Bucket Guide | Specs & Replacement Options | MCC Depot

Square D Model 6 MCC Overview

The Square D Model 6 motor control center has been in production since approximately 1985 and remains the current-production MCC platform from Schneider Electric (which acquired Square D). It is the most widely installed MCC in North America, found in virtually every industrial sector from water treatment to petrochemical refining. The Model 6 improved upon the Model 5 with a more robust door handle mechanism, updated stab design, and modular construction that simplified bucket replacement.

Model 6 lineups are manufactured to NEMA and UL 845 standards, rated for 480V and 600V three-phase service. The vertical bus is available in ratings from 600A to 4000A, covering the full range of industrial motor control requirements under NEC Article 430. Main bus ratings extend to 4000A for large facility distribution.

Because the Model 6 is still in production, OEM buckets are available through Schneider Electric distribution. However, OEM pricing is typically 40-60% higher than aftermarket alternatives, and OEM lead times often extend to 8-16 weeks. MCC Depot builds Model 6 compatible buckets with significantly shorter lead times and competitive pricing.

Model 6 Variants: Class 8998 Type A and Class 8065 Type B

The Square D Model 6 platform includes two primary bucket classifications:

Class 8998 Type A: The standard plug-in bucket used for most feeder and motor starter applications. Type A buckets use the standard Model 6 stab pattern and are fully interchangeable within any Model 6 vertical section. These represent the vast majority of Model 6 installations.
Class 8065 Type B: A draw-out style unit designed for larger applications requiring easier maintenance access. Type B units use a cradle mechanism that allows the bucket to be partially withdrawn for inspection without full removal from the section. Type B units are typically used for higher amperage circuits (400A+) and applications where frequent maintenance is required.

When ordering a replacement bucket, it is critical to specify which class and type your installation requires. The two types are not interchangeable within the same section slot.

T-Handle Door Mechanism

The Model 6 uses a T-handle mechanism to operate the internal disconnect switch. The T-handle rotates 90 degrees between the ON and OFF positions, actuating the disconnect through a mechanical linkage. The door interlock prevents the door from being opened when the disconnect is in the ON position, providing personnel protection per NFPA 70E requirements.

The Model 6 T-handle is significantly more durable than the toggle handle used on the Model 5. The T-handle design distributes operating force more evenly and uses a more robust pivot mechanism. However, after decades of operation, the T-handle mechanism can still wear and require replacement. Common issues include:

Handle detent spring fatigue, causing the handle to not lock firmly in the ON or OFF position
Interlock cam wear, allowing the door to be opened with the disconnect engaged
Linkage misalignment from mechanical impact or improper handling during bucket insertion

Stab Pattern and Bus Configuration

The Model 6 stab pattern uses a horizontal arrangement similar in concept to the Model 5 but with different dimensional specifications. Key specifications:

Pattern type: Three-phase horizontal stab, Model 6 specific
Voltage rating: 600V maximum
Material: Silver-plated copper stab fingers
Vertical bus ratings: 600A, 800A, 1200A, 1600A, 2500A, 3200A, and 4000A
Section width: 20 inches

Model 6 stab assemblies are not compatible with Model 5 bus bars. The stab finger geometry, spacing, and engagement depth differ between the two models. Always verify the MCC model designation before ordering replacement buckets.

Bucket Heights and Amperage Ratings

The Model 6 supports the same standard bucket heights as the Model 5:

6-inch: Pilot devices, control relays, small feeders to 30A
12-inch: Standard feeders 15A-100A, NEMA Size 0-1 starters
18-inch: Feeders to 250A, NEMA Size 2-3 starters
24-inch: Feeders to 400A, NEMA Size 4 starters
36-inch: Feeders to 800A, NEMA Size 5 starters, VFD installations

The Model 6 also supports combination buckets where multiple functions are combined in a single unit, such as a feeder/starter combination in a 24-inch or 36-inch bucket.

NEC Compliance and Arc Flash Considerations

Model 6 MCC installations must comply with NEC Article 430 for motor circuits and NEC Article 408 for switchboard and panelboard requirements where applicable. Key compliance points include:

NEC 430.97: Bus bars and connections must maintain manufacturer-specified torque values
NEC 430.98: Short-circuit current rating (SCCR) must be marked on the MCC and must meet or exceed the available fault current at the installation point
NFPA 70E Section 130.5: Arc flash hazard analysis must be performed for MCC equipment, with appropriate PPE categories posted

When replacing buckets, the SCCR of the replacement unit must equal or exceed the original. MCC Depot specifies components rated for 65kAIC standard, with higher ratings available on request.

Common Issues and Failure Modes

Even with the Model 6's improved design, components wear over time:

Contact wear: Stab contacts lose spring tension and develop surface oxidation, increasing resistance and generating heat at the bus connection
T-handle mechanism wear: The detent spring and cam assembly wear, compromising the interlock safety function
Door seal degradation: The gasket material around the bucket door hardens and cracks, allowing dust and moisture ingress that accelerates internal corrosion
Component obsolescence: Early Model 6 buckets may contain contactors, overload relays, or breakers that are no longer manufactured, requiring a retrofit with current-production equivalents

OEM vs. MCC Depot Pricing and Lead Time

Because the Model 6 is still in production, buyers have a choice between OEM and aftermarket replacement:

Schneider Electric OEM: Available through authorized distribution. Typical lead time is 8-16 weeks. Pricing is premium, often 40-60% above aftermarket equivalents.
MCC Depot aftermarket: Built with new, OEM-equivalent components in a UL 508 certified facility. Standard lead time is 2-3 weeks, with 1-2 day rush builds available. Configure and order online or call 307-442-0382 for a quote.

Both options produce a fully functional, code-compliant bucket. The primary advantages of aftermarket are faster delivery and lower cost, which are critical when a bucket failure causes unplanned downtime.

Square D Model 6 MCC Bucket Guide: Complete Technical Reference