Siemens Tiastar MCC Overview
The Siemens Tiastar motor control center, designated as Series 89, has been in production since approximately 1990 and remains the current-production low-voltage MCC platform from Siemens. It replaced the earlier Siemens Model 85 and Model 95 lineups, incorporating modern safety features, improved modularity, and integration with Siemens industrial automation components. The Tiastar is manufactured at Siemens facilities in the United States and is widely installed across all major industrial sectors.
The Tiastar platform is rated for 480V and 600V three-phase service, with main bus ratings up to 4000A. Vertical bus ratings range from 600A to 2500A. The system is designed to UL 845 and NEMA ICS-18 standards, meeting all NEC Article 430 requirements for motor branch circuit protection and control.
While Siemens continues to manufacture the Tiastar, OEM replacement bucket lead times through Siemens distribution have historically been long (10-20 weeks), making aftermarket suppliers like MCC Depot a practical alternative for facilities that need faster turnaround.
Series 89 Designation and Identification
The Tiastar uses the Series 89 part numbering system for its plug-in units. When identifying a Tiastar bucket for replacement, key information includes:
- Series designation: Look for "89" in the catalog number on the bucket nameplate
- Nameplate location: Typically on the inside of the bucket door or on the side of the bucket enclosure
- MCC designation: The vertical section nameplate will read "TIASTAR" or "TIASTAR MCC"
- Vintage identification: Early Tiastar lineups (1990-2000) may show "Furnas" branding, as Siemens acquired Furnas Electric in 1988 and transitioned the product line
If you have a Siemens MCC but are unsure whether it is a Tiastar, Model 95, or Model 85, contact MCC Depot at 307-442-0382. Send photos of the bucket, nameplate, and stab assembly for positive identification.
Rotating Paddle Handle Mechanism
The Tiastar uses a rotating paddle handle to operate the internal disconnect switch. The paddle rotates approximately 90 degrees between ON and OFF positions, mechanically actuating the disconnect through an internal linkage. The handle is integrated with a door interlock that prevents the door from being opened when the disconnect is in the ON position.
The paddle handle design offers several advantages over older toggle and T-handle mechanisms:
- Positive visual indication of switch position (horizontal = OFF, vertical = ON in standard configuration)
- Ergonomic operation requiring less force than toggle handles
- Padlock capability for lockout/tagout (LOTO) compliance per OSHA 29 CFR 1910.147
- Durability suitable for frequent operation cycles
Despite its improved design, the paddle handle mechanism can develop issues after years of service. The most common failure is wear in the detent mechanism that holds the handle in the ON or OFF position. When the detent wears, the handle may not lock firmly, compromising the interlock function.
Stab Pattern Specifications
The Tiastar stab assembly connects the plug-in unit to the vertical bus bars in the MCC section. Key specifications include:
- Pattern type: Siemens proprietary horizontal stab pattern, specific to the Tiastar platform
- Voltage rating: 600V maximum
- Material: Silver-plated copper contacts
- Connection method: Spring-loaded stab fingers engage bus bars when bucket is fully inserted
- Vertical bus ratings: 600A, 800A, 1200A, 1600A, and 2500A
Tiastar stab patterns are not compatible with older Siemens Model 85 or Model 95 lineups. Each Siemens MCC generation uses a different stab geometry. MCC Depot builds replacement buckets with the correct stab assembly for the Tiastar platform, verified against your specific lineup configuration.
Siemens Component Integration
The Tiastar platform is designed to integrate with Siemens industrial component families:
- SIRIUS contactors and overload relays: The 3RT and 3RU series contactors and overloads are the standard components for Tiastar motor starter buckets. These provide motor protection up to NEMA Size 5 in various bucket heights.
- SENTRON breakers: Siemens SENTRON molded case circuit breakers (3VA series) are used in feeder bucket configurations, available in frame sizes from 100A to 1200A.
- SINAMICS drives: For VFD applications, Siemens SINAMICS variable frequency drives can be mounted in Tiastar buckets, providing integrated motor speed control within the MCC lineup.
- Communication modules: The Tiastar supports PROFIBUS, PROFINET, and Modbus communication options for integration with Siemens PLCs and SCADA systems.
MCC Depot builds Tiastar replacement buckets using genuine Siemens components where available. For applications where Siemens-branded components are not required, we offer OEM-equivalent alternatives from major manufacturers that meet the same electrical ratings and performance specifications.
SIMOVAC vs. Tiastar
Siemens manufactures two distinct MCC product lines that are sometimes confused:
- Tiastar: Low-voltage MCC rated for 480V/600V applications. This is the standard MCC for industrial facilities in North America. Tiastar buckets are what MCC Depot builds and supplies.
- SIMOVAC: Medium-voltage motor controller rated for 2300V to 7200V applications. SIMOVAC is a different product class entirely, used for large motors (typically 200HP+) in applications like pipeline pumps, mine hoists, and large industrial fans. SIMOVAC controllers are not interchangeable with Tiastar buckets.
Legacy ITE and Gould Compatibility
Siemens has a complex acquisition history that affects MCC compatibility. The lineage includes:
- ITE Imperial Corporation: Manufactured ITE MCCs through the 1970s-1980s
- Gould Inc.: Acquired ITE in 1976, continued manufacturing under the Gould/ITE brand
- Siemens: Acquired Gould's electrical division in 1988, also acquired Furnas Electric
Legacy ITE and Gould MCCs use different stab patterns than the Tiastar. If you have an ITE or Gould MCC, these require bucket configurations specific to those platforms. MCC Depot can build replacement buckets for these legacy Siemens-lineage MCCs, but they are distinct products from Tiastar buckets. Accurate identification is essential before ordering. For retrofit options that allow modern components in legacy ITE/Gould enclosures, see our retrofit services.
Common Failure Modes
Tiastar buckets can experience several failure modes over their service life:
- Paddle handle mechanism wear: The rotational detent and linkage components wear with repeated cycling, causing the handle to feel loose or fail to lock in position
- Stab contact wear: Spring tension decreases over insertion/removal cycles, creating high-resistance connections that overheat
- Contactor/overload failure: SIRIUS contactors and overloads have defined mechanical and electrical life ratings. Exceeding these limits results in contact welding, coil failure, or improper overload tripping
- Arc damage: Fault events cause internal damage to bus connections and wiring
- Environmental degradation: Chemical exposure, humidity, and temperature extremes accelerate corrosion and insulation breakdown