Automatically switches between two 120/240VAC power sources - shore power, generator, or inverter. Built-in 20-30 second delay for generator stabilization.
The PowerMax PMTS-50A Automatic Transfer Switch provides seamless, hands-free power management for RVs, off-grid systems, and backup power applications. This relay-based transfer switch automatically monitors two separate 120/240VAC power sources and intelligently switches between them to ensure continuous power to your appliances and systems.
When shore power or grid power is available, the PMTS-50A connects it directly to your RV's distribution panel. When you start your onboard generator or alternative power source, the transfer switch waits 20-30 seconds for voltage to stabilize, then automatically transfers electrical power to your appliances. When the generator stops or shore power returns, the switch immediately transfers back. This eliminates manual switching, prevents power interruptions, and protects sensitive electronics from unstable generator voltage during startup.
Intelligent relay system automatically selects available power source - no manual intervention required
Built-in 20-30 second delay allows generator voltage to stabilize before powering appliances
Handles full 50 amp 120/240VAC service - perfect for large RVs and off-grid installations
Certified for safety and electromagnetic compatibility - meets all regulatory requirements
Shore Power Priority: When plugged into shore power (campground hookup, grid power, or primary source), the PMTS-50A automatically connects that power to your RV's AC distribution panel. All your appliances receive stable shore power. Generator Startup: When you start your onboard generator (or switch to a secondary power source like an inverter), the transfer switch detects the voltage. It waits 20-30 seconds for the generator to stabilize and reach proper voltage/frequency before switching. Automatic Transfer: After the delay period, the relay-based switch smoothly transfers from shore power to generator power. Your appliances continue operating without interruption. Return to Shore Power: When the generator stops or shore power returns, the switch immediately transfers back to the primary power source. No delay is needed since shore power is already stable. Optional Bypass: The PMTS-50A includes a timer bypass switch that allows you to manually override the 20-30 second delay if needed for testing or emergency situations.
RVs & Motorhomes: Automatically switch between campground shore power and onboard generator. Perfect for 50-amp RV service - no manual switching required when moving between power sources. Off-Grid Homes: Seamlessly transfer between grid power (when available), solar inverter output, and backup generator. Ensures continuous power during grid outages or low solar production. Backup Power Systems: Automatically engage generator power during utility outages. Switch back to grid power when restored without manual intervention. Solar Systems with Generator Backup: Primary power from solar inverter, automatic transfer to generator when batteries are low or demand exceeds solar production. Mobile Command Centers: Switch between multiple power sources in emergency response vehicles, mobile offices, and field operations. Marine Applications: Transfer between shore power at the marina and onboard generator when cruising (Note: Use in dry, protected locations only).
Licensed Electrician Required - This is NOT a DIY Project • Professional Installation Mandatory: Transfer switches must be installed by a qualified, licensed electrician. Improper installation can cause electric shock, fire, or death. • Multiple Live Circuits: This device has TWO AC power inputs. BOTH inputs must be completely disconnected before any work is performed. • Location Restrictions: DO NOT install in compartments containing batteries or flammable materials (gasoline, propane). Unit produces arcs and sparks during switching. • Heat & Water Protection: DO NOT install near heat sources (water heaters, furnaces) or under refrigerators. NOT designed for wet locations - must be protected from water contact. • Ventilation Required: DO NOT mount in zero-clearance compartments. Overheating may result. Ensure adequate airflow. • Wire Specifications: All field wires must be rated for at least 105°C. Use appropriate gauge for 50-amp service (6 AWG minimum). • Never Drill Housing: DO NOT drill through metal housing. Use existing knockouts only - metal shavings can damage relay operation.
In The Box: • PMTS-50A Automatic Transfer Switch • Internal 12V DC Relay (Pre-installed) • Integrated Ground Terminal Bar • 5 Knockout Plugs (4 x 1", 1 x 2") • Installation Manual with Wiring Diagrams • Warranty Documentation NOT Included (Required for Installation): • AC Wiring (6 AWG minimum for 50A service) • Wire Connectors/Lugs • Mounting Hardware • Electrical Box or Enclosure (if needed) • Professional Electrician Installation Service
Compare the PMTS-50A with the 30-amp model to determine which transfer switch is right for your electrical system.
The PMTS-50A accepts two separate 120/240VAC power sources (Input 1 and Input 2) and provides a single 120/240VAC output. Common configurations include:
Important: Input 1 (shore power) always has priority. When Input 1 is present, the switch connects it to the output. When Input 1 fails or is disconnected, the switch waits 20-30 seconds for Input 2 (generator) to stabilize, then transfers power. When Input 1 returns, the switch immediately transfers back.
Location Selection: • Install as close as possible to shore power cord entrance and generator to minimize voltage drop • Choose dry, cool location away from heat sources (water heaters, furnaces, refrigerators) • Ensure adequate ventilation - do not install in zero-clearance compartments • Keep away from battery compartments and flammable material storage • Can be mounted in any position for flexible placement Wire Sizing & Connections: • Use minimum 6 AWG copper wire for all 50-amp connections (4 AWG recommended for long runs) • All field wiring must be rated for at least 105°C temperature • Terminals accept 6-14 AWG wire with ring terminals • Torque terminal connections to 13 inch-pounds • Torque ground bar connections to 35 inch-pounds • Use proper crimped ring terminals - do not use push-on connectors Grounding: • All grounds are connected internally within the transfer switch • Connect all equipment grounds to the integrated ground bar • Ensure proper grounding of both input power sources • Ground bar suitable for 6-14 AWG conductors Safety Compliance: • Rated for circuits capable of delivering up to 5000 RMS symmetrical amps • Maximum operating voltage: 240VAC • When L1 and L2 are connected in phase, generator-neutral capability increases to 70A • Install appropriate overcurrent protection (circuit breakers) on all inputs • Follow all local electrical codes and NEC requirements Testing: • With shore power connected, verify output voltage matches input • Start generator and verify 20-30 second transfer delay • Turn off generator and verify immediate return to shore power • Test timer bypass switch function if equipped • Verify all connections are tight and properly torqued
Product Documentation: Download PMTS-30A & PMTS-50A Installation Manual (PDF) Download PMTS Series Specification Sheet (PDF) Warranty Information: 2-Year Limited Manufacturer's Warranty Covers defects in materials and workmanship under normal use No forms required - call tech support for rapid replacement Replacement unit shipped within 24 hours of defect confirmation Return shipping label provided for defective unit Company Website: www.powermaxconverters.com PowerMax Converters 5107 Lena Road, Suite 108 Bradenton, FL 34211
A: The PMTS-30A is designed for 30-amp RV electrical systems that operate on single-phase 120VAC power only. It's ideal for smaller travel trailers and RVs with 30-amp shore power connections. The PMTS-50A handles 50-amp service with split-phase 120/240VAC - perfect for larger motorhomes, fifth wheels, and residential applications. The 50-amp model can handle much higher loads: two 120V legs plus neutral, allowing you to run multiple high-draw appliances simultaneously (dual air conditioners, electric water heater, microwave, etc.). The 50-amp version also has more knockout holes (5 vs 3) for easier wiring and weighs twice as much (6 lbs vs 3 lbs) due to heavier-duty internal components. Choose the 30-amp for smaller RVs with single AC units; choose 50-amp for large RVs, motorhomes, or homes with substantial power requirements.
A: The built-in time delay is a critical safety feature that protects your appliances and electronics. When a generator first starts, the voltage and frequency are unstable and can fluctuate wildly for 15-30 seconds until the engine reaches proper RPM and the alternator output stabilizes. Connecting appliances during this unstable period can cause: damage to sensitive electronics from voltage spikes, compressor damage in air conditioners and refrigerators from under-voltage, premature failure of motors and transformers from frequency variations, and tripped circuit breakers or blown fuses. The PMTS-50A monitors the generator output and waits for stable voltage before transferring power - ensuring your equipment only receives clean, consistent electricity. When returning to shore power (which is already stable), the switch transfers immediately with no delay. The optional timer bypass switch allows you to override this delay manually if needed for testing or emergency situations.
A: Yes, the PMTS-50A works excellently with solar inverter systems, but there's an important consideration about the transfer delay. You can configure it two ways: (1) Solar as Primary (Input 1): Connect your solar inverter output to Input 1 and generator to Input 2. The switch will use solar power whenever available and transfer to generator (with 20-30 second delay) when solar inverter shuts down due to low batteries or high demand. Returns immediately to solar when available. (2) Grid as Primary (Input 1): For grid-tied solar with backup, connect grid power to Input 1 and solar inverter to Input 2. Uses grid power normally, switches to solar backup (with delay) during outages. The 20-30 second delay can be a drawback for solar systems if you want instant battery backup. Many modern solar inverters have built-in transfer switches that are faster. However, the PMTS-50A is perfect for off-grid systems with generator backup where the delay is acceptable, or for adding a second level of transfer switching in complex multi-source power systems.
A: Many RVs with built-in generators do NOT include automatic transfer switches from the factory - you typically have to manually switch between shore power and generator using a selector switch or by unplugging shore power before starting the generator. An automatic transfer switch like the PMTS-50A eliminates this manual process and provides significant benefits: (1) Convenience: Start generator anytime without unplugging shore power - switch handles it automatically, (2) Safety: Never worry about backfeeding shore power to the generator or campground, (3) Protection: The 20-30 second delay protects appliances from unstable generator startup voltage, (4) Flexibility: Leave everything plugged in and running - power transitions seamlessly, (5) Emergency Use: If shore power fails unexpectedly, generator can be started and power restored automatically. Some newer high-end RVs include factory-installed automatic transfer switches, but most do not. Check your RV's electrical system - if you have a manual shore/generator selector switch, you'll benefit greatly from adding the PMTS-50A.
A: Professional installation by a licensed electrician is absolutely required - this is not a DIY project, even if you're comfortable with basic electrical work. Here's why: (1) Multiple Live Circuits: Transfer switches have TWO live AC inputs that must both be properly disconnected before any work - a dangerous configuration for untrained individuals, (2) High Current: 50-amp 240VAC systems carry lethal amounts of current - improper connections can cause fire or electrocution, (3) Code Compliance: Installation must meet NEC (National Electrical Code) and local codes - improper installation voids warranty and may violate insurance requirements, (4) Proper Grounding: Incorrect grounding can create shock hazards or cause equipment damage, (5) Wire Sizing: Using undersized wire causes overheating and fire risk - electricians know proper sizing for 50A circuits. A licensed electrician will have the tools, training, and knowledge to install the PMTS-50A safely, ensure all connections meet code, properly torque all terminals, and test the system for safe operation. Installation typically costs $300-600 in labor - a small price for safety and peace of mind.
A: The PMTS-50A always prioritizes Input 1 (typically shore power or grid power) over Input 2 (typically generator or inverter). When both inputs are live simultaneously, the transfer switch keeps the output connected to Input 1 and ignores Input 2. This is the desired behavior because: (1) Shore power is typically "free" (included in campground fees or utility bills) while generator power costs fuel, (2) Generators are noisy - you want to use them only when necessary, (3) Shore power is usually more stable and reliable than generator output, (4) Fuel conservation - no need to run generator when shore power is available. This priority system means you can leave your generator running and connect to shore power - the switch will automatically transfer to shore power, allowing you to turn off the generator. Or you can have a generator auto-start system that runs during power outages - when utility power returns, the switch automatically goes back to utility and the generator can shut down. The Input 1 priority ensures you always use the most economical and convenient power source available.