GE IS230TNCIH4 In Stock | New Surplus Mark VIe TB Pack

Description

Product Introduction

The cabinet had 16 pressure transmitters, all loop-powered, and all needing a 24 VDC supply. The older design used a separate terminal block for power distribution—a mess of wires and terminal strips. The IS230TNCIH4 has a common loop power bus built right in: one 24 VDC input feeds all 16 channels, simplifying the wiring and reducing the point-to-point connections by 50%. Clean, organized, and less to go wrong.

GE’s IS230TNCIH4 is the termination assembly for the Mark VIe analog current input modules (like the PDOAH1A or PIOAH1A). It provides the physical interface between the 4-20 mA field instruments and the module—a 37-pin D-sub connector on one side and screw terminals on the other. Unlike the TCISH7C or TNAIH4C, the TNCIH4 has no per-channel burden resistors—the burden is provided by the I/O module internally. What it does have is a common loop power bus: a single pair of terminals supplies 24 VDC to all 16 channels, simplifying the wiring of loop-powered instruments. The H4 suffix indicates the specific terminal arrangement for common loop power distribution.

Key Technical Specifications

• Channel Count: 16 analog current inputs
• Input Type: 4-20 mA (loop-powered field instruments)
• Burden Resistor: None (provided by the I/O module)
• Loop Power: Common 24 VDC bus (single pair of terminals for all channels)
• Connector Type: 37-pin D-sub (female) for module connection
• Field Wiring: Screw terminals (0.5-2.5 mm² / 20-14 AWG)
• Loop Power Terminals: One “+” and one “–” terminal for 24 VDC supply
• Terminal Markings: Clearly labeled with channel numbers (1-16) and polarity (+/-)
• Mounting: DIN rail or panel mount
• Operating Temperature: –30 to +65 °C ambient

Quality Inspection Process (SOP Transparency)

This is what every IS230TNCIH4 goes through before it ships:

Incoming Verification: The OEM packing slip is matched against the shipping manifest. Visual inspection includes checking the GE holographic label, verifying the 37-pin D-sub connector is straight and has no bent pins, and examining the screw terminals for any signs of stripped threads or corrosion. We also verify the common loop power bus is intact—the “+” and “–” terminals must be connected to all 16 channels internally.

Live Functional Test: The TNCIH4 is installed in a test fixture with a Mark VIe analog input module (PDOAH1A). We connect a 24 VDC power supply to the common loop power terminals and verify that all 16 channels receive the 24 VDC supply.

We then connect a loop-powered simulator (a Fluke 789 ProcessMeter configured in loop power mode) to each channel in sequence, injecting 4.00 mA, 12.00 mA, and 20.00 mA. We verify the module reads the expected current value.

For the loop power distribution test, we measure the voltage at each channel’s field terminals—it must be the same as the common power supply voltage (24 VDC) minus the drop across the internal wiring (negligible, <0.1 V).

Electrical Parameters: A Fluke 1587 insulation tester measures isolation between the current inputs and the D-sub connector (the I/O module provides the isolation, but we verify the terminal block itself has no leakage). We look for >20 MΩ at 500 VDC. We also verify the continuity of the common loop power bus—resistance between the common terminal and each channel’s “+” terminal must be <0.1 Ω.

Mechanical Inspection: Each screw terminal is tested by tightening and loosening it five times to ensure the threads are not stripped. The D-sub connector’s mating surface is inspected for any burrs or damage. The mounting holes are checked for alignment and thread integrity.

Final QC & Packaging: The QC report lists the channel verification for all 16 channels, the loop power distribution test, the voltage measurements, and the isolation measurements. The terminal block goes into a new anti-static bag with a tamper-evident seal, then into a double-walled carton with foam inserts. A “QC Passed” label with the test date and technician’s ID goes on the outer box. All test data and photos are available on request.

Field Replacement Pitfalls

The TNCIH4 is a simple terminal block with a common loop power bus. Here’s my field-tested list.

Common Power Bus Short
The TNCIH4’s common loop power bus is internally connected—all 16 channels share the same 24 VDC supply. If one channel is shorted (say, a failed transmitter), the entire bus may drop voltage, causing all 16 channels to lose power. I had a plant where a single failed pressure transmitter shorted the common power bus; all 16 transmitters lost power, and the turbine tripped. The fix was replacing the failed transmitter and adding per-channel fusing (using an external fuse block). ❗ The common power bus is a single point of failure. If you need isolation, use the TCISH9 or TCISH9C with per-channel fuses. The TNCIH4 is for low-risk applications.

Voltage Drop on Common Bus
The common loop power bus has a voltage drop due to the internal trace resistance. At 20 mA per channel, the total current on the bus is 320 mA (16 × 20 mA). The internal trace resistance is about 0.05 Ω, so the voltage drop is 16 mV—negligible. But if the common bus terminals are loose or corroded, the voltage drop can be significant (1-2 V). I had a plant where a corroded common bus terminal was dropping 1.5 V, causing the last transmitters in the chain to underperform. The fix was cleaning the terminal. ❗ Keep the common bus terminals clean and tight. Use a contact cleaner if you see any discoloration.

Wiring Polarity
4-20 mA loops are polarized—the positive and negative leads must be connected correctly. If you reverse the polarity, the instrument won’t power up (it’s reverse-polarity protected in most cases), and the module will read 0 mA. I saw a plant where all 16 loops were wired backwards—the readings were all 0 mA. The fix was reversing the wires on all 16 channels. ❗ Check the wiring polarity carefully. The terminal block is marked with “+” and “–” for each channel. Follow it.

Loop Power Voltage
The TNCIH4 distributes whatever voltage is applied to the common power terminals. If you apply 22 VDC instead of 24 VDC, the transmitters may not operate correctly—especially at high currents (20 mA). I had a plant with a 22 VDC loop supply and transmitters that required 18 V minimum. At 20 mA, the transmitters were operating at the edge of their supply voltage, and the readings were noisy. The fix was increasing the supply to 24 VDC. ❗ Measure your loop supply voltage at the common power terminals. It should be 24 VDC ±5%. If it’s low, increase it.

D-Sub Connector Pin Damage
The TNCIH4’s 37-pin D-sub connector is delicate. If a pin is bent, it can short to an adjacent pin, causing incorrect readings or damage. I’ve seen a plant where a bent pin caused a short between channel 1 and channel 2, making both channels read the same value. ❗ Inspect the D-sub connector pins for damage before you install the terminal block. Replace the block if any pins are bent.

Get these five right and you’ll cut rework time by 90%.

New Original vs. Refurbished: Why It Matters

The TNCIH4 is a simple passive terminal block. Refurbishment risk is low, but still present.

New Original (New Surplus) means this unit came from GE’s production line, sealed in an ESD-safe bag. It has never been wired. The screw terminals have fresh threads—no stripping, no galling. The D-sub connector has pristine pins. The internal copper traces have never been stressed by overcurrent. The serial number traces directly to GE’s production database.

Refurbished risk: The biggest issue with refurbished TNCIH4 blocks is the screw terminals. Stripped threads from overtightening are common—a refurbisher can re-tap the threads or replace the terminal block, but they often just leave it and hope the user doesn’t overtighten again. The second issue is the common bus trace. If a plant had a shorted transmitter that caused a sustained overcurrent on the common bus, the internal traces may have been damaged (heat discoloration). A refurbisher may not notice this. I’ve seen a refurbished TNCIH4 in a plant where the common bus trace had a hairline crack from overheating; the bus would intermittently lose connection, causing all 16 channels to drop to 0 mA. The plant spent two days chasing the problem before replacing the terminal block. The refurbished block cost 200; the new surplus unit was 300. The two days of troubleshooting cost $10,000.

Real cost: An intermittent loss of all 16 analog inputs can trip a turbine. The cost of a trip is tens of thousands of dollars. A new surplus terminal block is cheap insurance.

What we provide: We include a photo of the OEM packing slip with the GE part number and serial number. The anti-static bag is sealed with a tamper-evident label. The QC test report lists the channel verification, the loop power distribution test, and the isolation measurements. You get a 12-month warranty.

Pricing context: Our price sits 30-50% above refurbished alternatives but 20-40% below GE’s current factory list price.

Performance Benchmarks & Test Results

Measured during our QC test. Conditions: test fixture with a PDOAH1A analog input module, 24.0 VDC supply (Fluke 8845A), ambient 24 °C.

• Common Power Bus Voltage: Applied 24.00 VDC at the common power terminals. Measured 23.98 VDC at the field terminals of channel 16 (the furthest from the supply). Voltage drop: 20 mV. Negligible.
• Current Measurement Accuracy: At 4.00 mA injected, the module read 4.001 mA (error: +0.001 mA). At 12.00 mA: 11.999 mA (error: -0.001 mA). At 20.00 mA: 20.002 mA (error: +0.002 mA). All within ±0.05% of the module’s accuracy spec.
• Common Bus Continuity: Resistance between the common “+” terminal and each channel’s “+” terminal: average 0.03 Ω. Range: 0.02-0.05 Ω.
• Insulation Resistance (Terminals to D-sub): Measured 55 MΩ at 500 VDC—well above the 10 MΩ minimum.
• Insulation Resistance (Channel to Channel): Measured >100 MΩ at 500 VDC.
• Thread Integrity: All screw terminals were tested with 5 cycles of tightening/loosening. No stripped threads.
• MTBF (Published): GE’s datasheet lists 275,000 hours at 40 °C for the TNCIH4. Based on field data, expect 15-20 years of service under normal conditions.

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