GE IS200TBTCH1CBB GE Mark VIe Thermocouple Terminal Module

Description

Product Model: GE IS200TBTCH1CBB
Product Brand: GE (General Electric)
Product Series: IS200 / Mark VI / TBTC (Thermocouple Terminal Boards)
Product Features:

• Accepts 24 thermocouple inputs (types E, J, K, S, T)
• Uses dual barrier-type terminal blocks for field wiring and shielding
• Compatible with both Mark VI / Mark VIe I/O systems (simplex/TMR)
• Built-in noise suppression, cold junction referencing, and support for long thermocouple cable runs

Applications & Industry Context

Thermocouples are the workhorses of temperature measurement in power plants, boilers, turbines, and heating systems. In gas or steam turbines, dozens of thermocouples monitor critical metal temperatures — bearing housings, exhaust housings, blade roots — providing real-time feedback to the control system. The GE IS200TBTCH1CBB sits right at that boundary: it gives you a solid, dependable interface from field thermocouple sensors into the control logic.

In many turbine control architectures (GE’s Speedtronic or later Mark VIe), you cannot simply run thermocouples into a generic analog board — the signals are small voltage differences, need cold-junction compensation, filtering, shielding, and often redundancy. The IS200TBTCH1CBB is designed to accept up to 24 TC inputs (E, J, K, S, T types) and shape them into signals that the I/O pack (or processor) can digest.

You’ll often see this board in control cubicles near turbines, in retrofit projects, or as spares in a hot spare rack. In plants converting from older control systems, it frequently replaces obsolete thermocouple interface cards. Its compatibility with both simplex and redundant (TMR) system architectures gives flexibility in modernization.

Because a bad thermocouple reading can mislead control logic (e.g. suggesting an overtemperature when there is none), having a robust terminal board like GE IS200TBTCH1CBB is not optional — it’s essential. In field audits, engineers often point to miswired thermocouple boards or degraded shielding as prime suspects behind spurious trips or alarms.

Product Role & System Fit

Functionally, GE IS200TBTCH1CBB is a thermocouple input terminal board (also called TBTC or TBTC-type). It bridges the physical thermocouple circuits to the digital side of the control system by implementing filtering, referencing, shielding, and connector routing.

The board feeds into a thermocouple processor in the control rack (for Mark VI it might be a VTCC, for Mark VIe a PTCC I/O pack) via DC-type connectors. Depending on whether the control architecture is simplex or TMR (triple modular redundancy), the board will support different connector configurations and wiring topologies.

Because GE IS200TBTCH1CBB handles up to 24 channels, it is appropriate for complex turbine systems, where multiple temperature points need monitoring. Each thermocouple signal enters one of two barrier-type terminal blocks, making field wiring modular, maintainable, and shielded.

In system fit, this board is not about control logic or actuation — it’s strictly a measurement interface board. But its reliability, integrity, and signal fidelity are foundational: everything in temperature-based control loops (fuel flow, turbine ramping, protection logic) depends on accurate data.

If your turbine control rack is already GE IS200 / Mark VI style, GE IS200TBTCH1CBB likely drops into the existing backplane footprint. That makes it friendly for upgrades or replacements. But follow care in revision matching and connector pinouts.

Technical Features & Benefits

One of the most useful features of GE IS200TBTCH1CBB is its support for multiple thermocouple types: E, J, K, S, and T can all be accommodated.  This ensures flexibility if your plant uses different types in different zones — you don’t need a bespoke board per type.

The board uses dual barrier-type terminal blocks, mounted on the front edge, to accept field wiring. These blocks are rugged, removable, and help keep wiring clean and service-friendly. Also, a left-side shield buss is usually connected to chassis ground to reduce electrical noise coupling.

Because thermocouple voltages are small (millivolt scale), noise suppression is critical. The board includes filters, often high-frequency suppression, to avoid aliasing or interference — especially in harsh electrical environments.

Cold junction compensation is another baked-in function. The board includes cold junction reference devices to reference all thermocouple readings relative to a known junction.

In terms of reach, the board supports thermocouple wiring runs up to roughly 300 m (984 ft) with acceptable two-way cable resistance (specified in sources as up to 450 Ω for the loop) — that’s often enough for field layouts in turbine halls.

A point often emphasized: the “1C” suffix in the model indicates a simplex (non-redundant) version with two DC-type connectors. In TMR systems you might see “1B” variants with more connectors (e.g. six) to accommodate triple paths.  When you see IS200TBTCH1CBB, it typically indicates the board is a “1C” (simplex) variant.

Because of this, in TMR systems you may need a different variant (TBTCH1B). Be careful not to mix up connectors or expect redundancy from a 1C board. Field engineers sometimes inadvertently install 1C in a TMR rack — that creates gaps in redundancy.

Another practical advantage: the terminal blocks are removable. So during maintenance or swap-outs you can pull the blocks independently of the board, reducing the chance of disturbing adjacent wiring.

From field experience, many users report that once this board is properly wired and shielded, it “just works” for years. Key failure modes tend to stem from wiring faults, corrosion, or connector fatigue — not the board itself.

Technical Specifications Table

Installation & Maintenance Insights

Proper installation of the IS200TBTCH1CBB is critical to reliable temperature monitoring. Begin by mounting it in a clean, temperature-controlled control rack, away from vibration, dust, or excessive heat. Although the board isn’t exposed to extreme ambient conditions, its signals are sensitive.

When wiring thermocouples to the terminal blocks, use twisted pairs, shielded cabling, and consistent polarity (positive and negative wires). The shielding should be grounded at one end (usually the board’s chassis side) to minimize ground loops and noise. The presence of a shield terminal strip on the left side of the block (connected to chassis) is typical.

Keep analog (thermocouple) runs physically separated from high-voltage or power cable bundles to avoid induced noise coupling. Where crossing is unavoidable, do so at right angles.

Before energizing, inspect wiring, check for continuity breaks or shorts, and ensure each thermocouple line is connected to the correct block and pin. Confirm that the cold junction sensors (provided onboard) are properly configured and referenced. Many I/O setups validate the CJ reading during initial startup.

During commissioning, test with calibrated thermocouple simulators or test rigs: apply known mV levels (within –8 to +45 mV), verify that the I/O processor reads correct temperatures, calibrate offsets if needed, and test alarm thresholds.

For maintenance, periodic tasks include checking connector retention, looking for corrosion or discoloration at terminal contacts, verifying proper torque on screws, and inspecting for cracked solder joints or component damage. The removable nature of the terminal blocks simplifies isolation for inspection without disturbing the board.

In some installations, especially older ones, shielding degradation or connector fatigue causes intermittent misreads. A common fix: reterminate shield ends, retorquing terminals, and recheck continuity.

It’s wise to keep a spare IS200TBTCH1CBB (or equivalent TBTC board) on hand, especially in plants with redundant racks. Swapping often takes minutes, so spare boards reduce downtime.

One caution: never mix a 1C (simplex) board in a TMR setup expecting full redundancy. That mismatch can lead to partial coverage or blind channels. Always match suffix variant (1C vs 1B) to system architecture.

Related Models

Here are several sibling or related thermocouple input / terminal boards in the GE / Mark VI / TBTC family (with brief differences):

• IS200TBTCH1CB — alternate suffix variant, possibly different artwork revision
• IS200TBTCH1B — TMR version (six connectors) rather than simplex 1C type
• IS200TBTCH1C — basic “1C” variant without extended suffix
• IS200TBTCH1CBA — variant with artwork revision A (slightly different configuration)
• IS200TBTCH1CBB — our focal model, with both functional and artwork suffixes B
• IS200TBTCH2CBB — version with extended channel or variant connector layout
• IS200TBTCH1CBC — variant for different I/O pack arrangement