MTL TP-AC420-N Industrial Transmitter Surge Protector
MTL TP-AC420-N AC Power & 4-20mA Surge Protector
Product Overview
The MTL TP-AC420-N is a high-performance surge protection device from Eaton's Crouse-Hinds MTL TP-AC series, specifically designed for AC-powered field-mounted process transmitters with 4-20mA signal loops. This unit provides comprehensive protection for both the AC power line and the 4-20mA signal line, safeguarding sensitive electronic process instrumentation against induced surges and transient overvoltages from field cabling.
The TP-AC420-N offers a level of protection that far exceeds the optional transient protection facilities available from transmitter manufacturers - achieved without any additional wiring modifications or costly additions. The unit is encased in a rugged ANSI 316 stainless steel housing with ½" NPT threads, designed to screw directly into spare conduit entries on process transmitters for easy, retrofittable installation.
Key Technical Specifications
| Parameter | Value |
|---|
| Model | TP-AC420-N |
| Manufacturer | Eaton MTL (Crouse-Hinds series) |
| Product Series | TP-AC |
| Protection Type | AC Power & 4-20mA Signal |
| Maximum Surge Current (8/20 µs) | 20kA peak |
| Leakage Current | <10µA at max. working voltage |
| Housing Material | ANSI 316 Stainless Steel |
| Thread Type | ½" NPT |
| Connection Type | Parallel (flying leads) |
| Loop Resistance Added | 0Ω (parallel connection) |
| Operating Temperature | -30°C to +70°C |
| Product Warranty | 10 years |
Features & Benefits
1. Comprehensive AC Power & Signal Protection
The TP-AC420-N protects both the AC power line (120V & 240V) and the 4-20mA signal line simultaneously, eliminating the need for separate protection devices and simplifying installation.
2. Superior Surge Handling Capacity
The TP protection network consists of high-power solid-state electronics combined with a gas-filled discharge tube (GDT) capable of diverting 20kA impulses (8/20 µs waveform). This robust design ensures reliable protection against lightning-induced surges and switching transients.
3. No Resistance Introduced into Loop
The parallel connection design means the TP-AC420-N adds zero resistance to the 4-20mA measurement loop. This is critical for maintaining signal integrity and ensuring accurate process measurements without calibration adjustments.
4. Ultra-Low Leakage Current
With leakage current of less than 10 µA at maximum working voltage, the device introduces negligible burden on the protected circuit, preserving normal operation while providing robust surge protection.
5. Rugged 316 Stainless Steel Construction
The entire unit is encased in ANSI 316 stainless steel, offering excellent corrosion resistance for harsh industrial environments, including offshore platforms, chemical plants, and wastewater treatment facilities.
6. Easy Retrofit Installation
Installation can be easily carried out retrospectively to existing installations. The unit screws into any unused ½" NPT conduit entry on the transmitter case, and flying leads are connected to the terminal block signal, power, and earth terminals. No additional wiring modifications or ground stakes are required.
7. Hazardous Area Approvals
The TP-AC420-N is FM Approved for use in hazardous locations:
| Classification | Rating |
|---|
| Explosion-proof | Class I, Division 1, Groups A-D |
| Non-incendive | Class I, Division 2, Groups A-D; Class I, Zone 2, Group IIC |
| Dust ignition proof | Class II, III, Division 1, Groups E-G |
| Temperature rating | Ta: -30°C to +70°C |
8. 10-Year Product Warranty
Backed by Eaton MTL's 10-year product warranty, ensuring long-term reliability and peace of mind.
Applications
The MTL TP-AC420-N is specifically designed for protecting AC-powered field-mounted process transmitters in the following applications:
| Application Area | Details |
|---|
| Oil & Gas | Wellhead monitoring, pipeline pressure transmitters |
| Chemical Processing | Reactor temperature and pressure measurement |
| Refineries | Flow, level, and pressure instrumentation |
| Power Generation | Boiler and turbine instrumentation |
| Water & Wastewater | Pump station and treatment plant sensors |
| Pharmaceutical | Critical process monitoring |
| Mining | Remote field instrumentation |
| HVAC | Large-scale building automation sensors |
Installation Guidelines
Simple 3-Step Installation
- Mount: Screw the TP-AC420-N into any unused ½" NPT conduit entry on the transmitter housing
- Connect: Connect the flying leads to the transmitter's terminal block:
- AC power leads to power terminals
- Signal leads to 4-20mA loop terminals
- Earth lead to transmitter casing ground
- Complete: No additional grounding or calibration required
Important Notes
• The device connects in parallel - no loop resistance added
• Earthing is achieved through the transmitter casing - no separate ground stake needed
• Suitable for retrofit installation on existing transmitters
• No signal attenuation or loop interruption during normal operation
Summary
The MTL TP-AC420-N Surge Protector delivers reliable, high-performance protection for AC-powered field-mounted process transmitters with 4-20mA signal loops. With its 20kA surge capacity, zero loop resistance, rugged 316 stainless steel housing, and hazardous area approvals, the TP-AC420-N is the ideal choice for engineers seeking to protect critical process instrumentation from costly surge damage.
Key Advantages
- Dual protection - AC power + 4-20mA signal in one device
- 20kA surge capacity - Handles the most severe transients
- Zero loop resistance - Parallel connection preserves signal accuracy
- Ultra-low leakage - <10µA at max. working voltage
- 316 stainless steel - Excellent corrosion resistance
- ½" NPT threads - Direct screw-in installation
- Hazardous area approved - FM certified for Class I, Division 1
- Easy retrofit - No wiring modifications required
- 10-year warranty - Long-term reliability assurance
Protect your critical process transmitters with MTL TP-AC420-N - engineered for reliability in harsh and hazardous areas.
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