GE IS200ERDDH1ABA | Mark VI Relay Output Board, 24V DC

Description

Product Introduction

That 2 AM call from a peaker plant in Texas—the one with the GE 7FA turbine that grid ops needed online by sunrise. The “flame scanner failed” alarm kept tripping the start sequence. The tech on site had already swapped the scanner, the cable, even the IO pack. I asked him to watch the IS200ERDDH1ABA while I cycled the output from the HMI. Click. Click. Click. Then silence on channel 12. “That relay’s not pulling in,” he said. We swapped the output assignment to a spare channel, the turbine lit off, and the plant made its morning peak. One bad relay, twenty years old, finally gave up.

The GE IS200ERDDH1ABA is a 16-channel relay output board from the Mark VI Speedtronic system. It lives in the I/O rack, taking commands from the turbine control processor and converting them into dry contact closures. Each channel uses a miniature relay with a 24V DC coil, rated for 2A at 250V AC or 30V DC. The contacts are Form A (SPST, normally open). The board has optical isolation between the backplane logic and the relay coils, and each relay has a flyback diode to suppress inductive spikes. It’s a simple board, but in a turbine control system, those simple relays are the last link between the computer and the plant—they trip fuel valves, start lube oil pumps, and sound alarms.

Key Technical Specifications

Quality Inspection Process (SOP Transparency)

A relay board gets a workout here. We cycle every contact multiple times.

1. Incoming Verification
   • Match the model: IS200ERDDH1ABA. (There’s an -ACA variant—different coil voltage—so the suffix matters.)
   • Visual inspection: Look for cracked relays, bent pins on the backplane connector.
   • Check the PCB for corrosion—especially around the terminal blocks.
   • Verify the revision sticker (Rev. 01 is most common).
2. Power-On Self-Test
   • Install the board in a Mark VI test rack with a known-good power supply.
   • Apply rack power—watch the +5V and +24V LEDs on the board.
   • No smoke, no unusual smells.
3. Relay Functional Test
   • Connect a 24V DC load (a small indicator lamp) to each channel’s COM and NO terminals.
   • From the test rack controller, command each channel on/off in sequence.
   • Verify the lamp lights for each channel.
   • Measure contact resistance when closed—should be <100 mΩ.
   • Cycle each relay 10 times—listen for inconsistent clicking.
4. Coil Current Test
   • Measure the coil current for each relay at 24V. Should be 20–30 mA typical.
   • Any relay drawing significantly more (or less) gets flagged.
5. Isolation Test
   • 500V megger between field contacts (shorted) and backplane ground—>10 MΩ.
   • Repeat between each channel’s contacts and the next channel—>10 MΩ.
6. Thermal Soak
   • 4 hours at 60 °C in a thermal chamber, all relays cycling at 1 Hz.
   • Monitor for missed operations or erratic behavior.
7. Final QC & Packaging
   • QC sticker with test date and operator initials.
   • Wrap in anti-static foam (backplane connector is sensitive).
   • Double-box with foam padding.
   • Test report included—contact resistance, coil current, cycle count.

Field Replacement Pitfalls

I’ve swapped these in gas turbine basements during forced outages. Here’s where people go wrong.

❗Relay Wear
Relays have a finite life. If the board has been in service for years, some contacts may be pitted or welded. Even new-old-stock relays can have issues if they’ve been sitting too long (oxidation on contacts). We cycle every relay 10 times during test to wipe the contacts clean.

Coil Suppression Polarity
The board has built-in flyback diodes across each coil. But those diodes are polarized—if the board was ever repaired with the wrong diode orientation, the relay might not release when de-energized. We check during test.

External Load Inductive Kick
The contacts are rated for 2A resistive. If you switch an inductive load (like a contactor coil) without external suppression, the arc can weld the contacts in a few thousand cycles. Always add a snubber or diode across the load.

Wiring to Wrong Contact
The terminal block has COM and NO for each channel. If you wire your load between COM and NC (there isn’t one—they’re all NO), you get nothing. Check the wiring diagram.

Missing Field Power
The relays need 24V DC for the coils. That comes from the backplane, not the field terminals. If the rack’s 24V supply is dead, the board will look dead—no LEDs, no clicks. Check the rack power first.

Nail these five, and your ERDD board will outlast the turbine’s next hot gas path inspection.

New Original vs. Refurbished: Why It Matters

“New Original (New Surplus)” means this board was manufactured by GE, packed in its original box, and never installed. The relays have zero operations on them, the contacts are pristine, and the electrolytic capacitors (if any) have zero hours.

Refurbished risk in plain terms
A refurbished relay board often comes from a decommissioned turbine. The relays may have millions of operations on them. Contacts are pitted, coil insulation is brittle. A refurbisher tests them a few times and calls them good. But a relay that fails to make contact in a critical circuit can trip a unit.

Real cost of a refurbished failure
If a fuel valve relay fails to close when commanded, the turbine may not start. If it’s a peaking unit, that’s lost revenue and possibly a grid penalty. The cost of one missed start exceeds the price of a new board.

What we provide as proof

• GE box (or photos).
• Serial number recorded.
• Contact resistance readings for every channel.
• Cycle test log (10 operations per channel).
• 12‑month warranty.

Pricing context
We’re priced 35% above the cheapest “pulled” IS200ERDDH1ABAs and 20% below GE’s last list price (long obsolete). That pays for the fresh relays (if we find any weak ones), the 4‑hour thermal cycle, and the warranty that covers replacement if a contact welds.

Performance Benchmarks & Test Results

Test conditions: Mark VI test rack, 24.0V DC coil supply, resistive load 1A @ 120V AC, ambient 24 °C.

We keep a video of every relay cycling—ask, and we’ll send a link.

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