Square D Model 6 vs Model 5: Key Differences Explained

Square D (now part of Schneider Electric) has manufactured some of the most widely installed MCCs in North America. The Model 5 and Model 6 are their two most common product lines, and understanding the differences between them is critical when ordering replacement buckets, parts, or planning upgrades.

History and Timeline

Model 5 was introduced in the late 1970s and produced through the mid-1990s. It was the workhorse MCC of its era and millions of units remain in service today. While no longer manufactured, Model 5 MCCs are everywhere in industrial facilities built during the 1980s and early 1990s.

Model 6 replaced the Model 5 starting in the mid-1990s and continues in production today as the current Square D MCC platform. It introduced significant design improvements including better accessibility, modular construction, and enhanced safety features.

Physical Design Differences

Section Construction

Model 5: Uses a bolted frame construction with individual bucket compartments separated by steel barriers. The sections are 20 inches wide, 90 inches tall, and 20 inches deep (standard). Back-to-back configurations are available but less common.

Model 6: Features a unitized welded frame design that is stronger and more rigid. Sections are the same 20 inches wide and 90 inches tall, but available in both 20-inch and 24-inch depths. The 24-inch depth provides significantly more wiring space and is standard for most configurations.

Bucket Compartment Access

Model 5: Buckets slide in from the front. The rear of the section has a bolted cover for access to the vertical bus and wiring. Rear access requires removing the entire rear panel.

Model 6: Also front-loading, but with improved rear accessibility. Individual rear covers for each bucket compartment allow access to specific units without disturbing adjacent wiring.

Door and Latch Design

Model 5: Uses a captive screw door latch. The door swings open to reveal the bucket interior. Door-mounted devices connect through flexible wire loops.

Model 6: Features a quick-release door latch with a single-point door release. The door design includes provisions for padlocking in the open or closed position. Door-mounted devices use a flexible conduit connection or plug-in connector.

Stab Connections

This is the most critical difference for bucket compatibility:

Model 5 Stabs: Use a spring-clip design with specific dimensions. The stab fingers grip the vertical bus from the sides. Stab assemblies are available in 100A and 300A ratings.

Model 6 Stabs: Use a different spring-loaded design with an improved contact mechanism. The stab geometry is not compatible with Model 5. Model 6 stab assemblies are available in 100A, 200A, 300A, and 400A ratings.

A Model 5 bucket will NOT fit in a Model 6 MCC, and vice versa. The stab connections are physically different and not interchangeable. This is the single most important distinction when ordering replacement buckets.

Bucket Sizes

Both models use the same standard bucket heights: 6", 12", 18", 24", 36", and 48". However, interior dimensions differ slightly due to the different frame constructions:

Model 5: Interior bucket space is slightly more constrained due to the frame design. Maximum component depth is limited by the 20-inch section depth.

Model 6: More interior space, especially in the 24-inch deep configuration. This additional space is valuable for VFD installations and complex control configurations.

Vertical Bus Ratings

Model 5: Standard vertical bus ratings of 300A. Higher ratings were available but less common.

Model 6: Standard vertical bus ratings of 300A or 600A, with 600A being more commonly specified in new installations.

Wiring Space

Model 5: Wiring enters from the top or bottom of each section through a common wire way. The wire way space is shared among all buckets in the section, which can become crowded in fully loaded sections.

Model 6: Each bucket has its own dedicated wiring entry point, and the wire way design provides more space per bucket. The 24-inch depth option further improves wiring accessibility.

Safety Features

Model 6 introduced several safety improvements over Model 5:

• Dead-front construction: All energized parts are behind barriers when the bucket door is open, reducing arc flash exposure
• Finger-safe bus: The vertical bus is enclosed in finger-safe covers
• Improved interlocking: Enhanced mechanical interlocks prevent bucket insertion or removal while the disconnect is in the ON position
• Arc-resistant options: Model 6 is available in arc-resistant configurations per IEEE C37.20.7

Model 5 has basic safety features but does not meet current arc flash mitigation standards without modification.

How to Identify Which Model You Have

Check the Nameplate

The MCC nameplate (usually on the main incoming section) will clearly state "Model 5" or "Model 6."

Look at the Door Latches

• Model 5: Captive quarter-turn screw
• Model 6: Quick-release handle with distinct styling

Examine the Stabs

If you can see the stab assembly on a removed bucket:

• Model 5: Simpler clip design
• Model 6: More robust spring-loaded fingers with a different profile

Check the Year

If the MCC was installed before 1995, it is almost certainly a Model 5. If installed after 2000, it is likely a Model 6. The transition period (1995-2000) could be either.

For detailed identification assistance, visit our bucket identification guide or see our complete Square D Model 5 guide and Square D Model 6 guide.

Replacement Bucket Options

For Model 5 MCCs

Since Model 5 is no longer in production, OEM replacement buckets have long lead times and high prices. Options include:

1. OEM (Schneider Electric): Available but expensive and slow (8-16 weeks typical)
2. Aftermarket manufacturers: Companies like MCC Depot build Model 5 compatible buckets with new components at competitive prices
3. Surplus/refurbished: Used buckets are available but condition varies widely

For Model 6 MCCs

Model 6 is current production, so more options exist:

1. OEM (Schneider Electric): Available through distribution (4-12 weeks)
2. Aftermarket manufacturers: Faster delivery and often lower cost
3. Direct from MCC Depot: We build Square D compatible buckets for both Model 5 and Model 6

Can You Upgrade Model 5 to Model 6?

Not practically. The section dimensions, bus configurations, and stab connections are different enough that you would essentially need to replace the entire MCC. In most cases, facilities continue operating their Model 5 MCCs with aftermarket replacement buckets until a full MCC replacement is justified.

Bottom Line

Model 5 and Model 6 are both excellent MCC platforms, but they are not interchangeable. When ordering replacement buckets, you must specify the correct model. Getting it wrong means the bucket won't fit.

MCC Depot builds replacement buckets for both Square D Model 5 and Model 6 MCCs. We match your existing stab configuration exactly.

Call 307-442-0382 or email sales@mccdepot.com with your MCC model and bucket requirements.