How to Identify and Replace Invensys Controls and GE Capacitors in Legacy Systems

While many operations are choosing to update their infrastructure to accommodate more advanced components and processes, some operators choose to keep their legacy systems intact. For decades, manufacturers like Invensys and GE supplied dependable control modules and capacitors that continue to operate in older HVAC units, control panels, and processing equipment today. Despite their reliable nature and longevity, these components are not immune to aging, prompting the need for thoughtful replacements.

This guide will help you with the basic approaches you should take when identifying and replacing legacy components, with a particular focus on Invensys controls and GE capacitors due their prevalence in older infrastructure. Regardless of the specific items you are seeking to replace or overhaul, you can apply this logic when approaching just about any system upgrade.

Step 1: Identifying Commom Legacy Components

The first step in approaching a legacy system revamp is accurately identifying the components currently installed. Without confirming the exact specifications, sourcing replacements or modern equivalents becomes inefficient and risky.

Recognizing Invensys Controls

Regularly found in building automation, boiler regulation, and industrial process systems, Invensys controls remain prevalent in:

• Temperature and pressure controllers
• Electro-mechanical thermostats
• Actuators and valve positioning mechanisms
• Time-delay relays and mechanical limit switches

When you are looking to replace them:

• Look for brand markings, including Robertshaw, Siebe, or Barber-Colman, all of which were associated with Invensys systems at one point
• Locate the product or model number, which is typically printed or engraved on the housing, and cross-reference with archived catalogs or manufacturer records
• Review wiring diagrams or labels on the device and compare them with known product documentation or technical specifications
• Note physical characteristics like housing dimensions, mounting configuration, terminal types, and enclosure style

Locating GE Capacitors

In legacy HVAC systems, control panels, and electrical enclosures, GE capacitors were widely used for functions like:

• Motor start and motor run support in compressors and fan systems
• Power factor correction in three-phase industrial equipment
• Filtering and voltage smoothing in power supply circuits

As you inspect a GE capacitor in the hopes of finding a replacement, pay attention to the following:

• Part numbers to help verify series and origin, as GE capacitors often begin with prefixes like 97F, 97L, or 97D
• Capacitance rating values printed in microfarads (µF), such as 35 µF, 80 µF, etc.
• Voltage rating, with common options including 370V, 440V, and 660V
• Shape, mounting style, and terminal configuration

Step 2: Determining the Need for Replacement

Just because a part still technically functions does not mean it is performing optimally, as wear, electrical stress, environmental exposure, and continued use all hinder performance over time. Aging components display different faults or inefficiencies depending on their function, but some generally applicable signs of degradation include:

• Inconsistent or drifting temperature regulation
• Sluggish or non-responsive operation
• Burnt terminals
• Cracked insulation or other aspects
• Corrosion

These symptoms are especially common in legacy Invensys controls, which were usually built with discrete analog circuitry and mechanical contacts.

Specific Indicators of Aging Capacitors

Capacitors, especially those used for motor start/run or power factor correction, tend to fail gradually, with symptoms including:

• Bulging or leaking enclosures, typically seen in oil-filled or electrolytic types
• Discolored or overheated terminals, which may indicate high current or poor ventilation
• Reduced capacitance
• Audible humming or buzzing caused by internal dielectric breakdown or instability

Even in the absence of these forms of damage, manufacturers often recommend replacing capacitors every 5 to 10 years, depending on conditions like ambient temperature, duty cycle, and voltage rating.

Step 3: Replacing Components Safely

Once a component has been correctly identified and deemed unfit, it is finally time to select a replacement that matches the original specifications while aligning with modern design standards and product availability.

Considerations for Replacing Invensys Controls

• Functional Match: The replacement must provide equivalent input/output logic, control range, and sensor or actuator compatibility.
• Mechanical Compatibility: Confirm that mounting hole patterns, enclosure dimensions, and terminal locations align with the existing setup to avoid having to make modifications.
• Environmental Ratings: The control should meet or exceed original IP or NEMA ratings and temperature tolerances, as well as exhibit needed resistance to dust or vibration.
• Updated Equivalents: If the original part is obsolete, Schneider Electric—which acquired Invensys—often offers successor models under new part numbers that maintain similar layout and function. Always review datasheets for technical alignment.

Choosing an Equivalent GE Capacitor

• Capacitance and Voltage Ratings: Always match the original capacitance (µF) precisely and choose a voltage rating that is equal to or higher than the original.
• Terminal Type and Mounting: Match the terminal configuration and mounting method to maintain a good fit and wiring integrity.
• Dielectric and Construction Type: Choose a capacitor with a similar or improved dielectric to ensure thermal stability.
• Safety Certifications: To guarantee both compliance and safe performance, select components that are UL, CSA, or IEC certified, especially in motor circuits or other high-load systems.

Strategically Approach System Upgrades with Industrial Parts Delivered

Legacy systems are valuable assets, but only when kept in proper working order. By correctly identifying components, recognizing signs of degradation or poor health, and selecting compatible replacements, operators can extend the life of their infrastructure without resorting to a full system replacement. This process requires attention to detail, accurate cross-referencing, and reliable sources for parts to guarantee continuity and safety.

To simplify this task, ASAP Semiconductor offers access to thousands of components from leading manufacturers like Invensys, GE, and more through Industrial Parts Delivered. Backed by a wide-reaching supply network, this website reduces the complexity of sourcing by enabling customers to meet all their operational requirements from a single location. Furthermore, with competitive pricing, efficient lead times, and dedicated service, you never have to compromise your needs when you shop here. Keeping all of this in mind, do not hesitate to kick off procurement on Industrial Parts Delivered at your convenience.