An RV transfer switch wiring diagram maps three distinct AC nodes—Shore/Generator Input, Inverter Input, and Main Panel Load—using internal relays to prevent backfeeding and safely manage your 120V or 120/240V AC system. The direct answer to reading these schematics is identifying the hot (L1/L2) switching path while recognizing that neutral and ground paths typically bypass the relay entirely on standard 30A units. Whether you are upgrading to a Go Power! TS-30 or an Iota Engineering ITS-50R, misinterpreting the schematic will result in a dead panel or a fried inverter.
Below, we break down the exact terminal mappings, trace the current path from source to load, and outline how to verify every connection with a multimeter before you energize the system.
Decoding the RV Transfer Switch Wiring Diagram (Symbols & Terminals)
Before stripping wire, you must understand the schematic symbols specific to RV automatic transfer switches (ATS). Unlike whole-home standby generators that switch both hot and neutral, most 30A RV ATS units only switch the hot leg.
- NO (Normally Open): The relay contact that remains disconnected when the coil is unpowered. In most RV ATS units, the Inverter input is wired through the NO contact.
- NC (Normally Closed): The relay contact that passes current when unpowered. Shore power is typically wired through the NC contact so the RV defaults to shore power without energizing the relay coil, preventing coil burnout during long campground stays.
- Hard-Bussed Bars: Represented by solid horizontal lines connecting input and output terminals. This indicates that Neutral (N) and Ground (G) do not pass through a relay; they are physically bolted to internal bus bars.
Terminal and Pin Mapping Table (Standard 30A 120V ATS)
The following table reflects the physical terminal layout of industry-standard 30A units like the Go Power! TS-30 and Iota ITS-30R. Always verify against your specific unit's silkscreen, as manufacturer revisions occur.
| Terminal Label | Physical Location | Wire Size & Color (US AC) | Function & Internal Path |
|---|---|---|---|
| SHORE L1 (or LINE) | Top Left Block | 10 AWG, Black | Shore Hot Input → NC Relay Contact |
| SHORE N | Top Left Block | 10 AWG, White | Shore Neutral → Hard-Bussed to LOAD N |
| SHORE G | Ground Bus | 10 AWG, Green/Bare | Shore Ground → Hard-Bussed to LOAD G |
| INV L1 | Bottom Left Block | 10 AWG, Black | Inverter Hot Output → NO Relay Contact |
| INV N | Bottom Left Block | 10 AWG, White | Inverter Neutral → Hard-Bussed to LOAD N |
| INV G | Ground Bus | 10 AWG, Green/Bare | Inverter Ground → Hard-Bussed to LOAD G |
| LOAD L1 | Top Right Block | 10 AWG, Black | Switched Hot Output → RV Main Breaker Panel |
| LOAD N | Top Right Block | 10 AWG, White | Common Neutral Output → RV Main Panel |
| LOAD G | Ground Bus | 10 AWG, Green/Bare | Common Ground Output → RV Main Panel |
Node-by-Node Trace: Source to Load Path
To truly understand the RV transfer switch wiring diagram, you must trace the current path under both power scenarios. We will assume a standard 30A 120V architecture where Shore Power is the default (NC) pass-through.
Path 1: Shore Power to Load (Default State)
- Source: 30A shore power cord delivers 120V AC to the RV's exterior inlet.
- Entry: 10 AWG THHN/stranded wire carries the hot (Black) from the inlet to the SHORE L1 terminal.
- Relay Logic: Because the internal relay coil is unpowered (or de-energized by default), the NC contact remains closed. Current flows directly from SHORE L1 through the NC contact to LOAD L1.
- Neutral/Ground Path: The White (Neutral) and Green (Ground) wires bypass the relay completely. They enter SHORE N/G and travel through the solid internal copper bus bars directly to LOAD N/G.
- Load: The 120V AC exits LOAD L1, N, and G, entering the main RV AC breaker panel, distributing power to the microwave, outlets, and AC unit.
Path 2: Inverter to Load (Switched State)
- Source: The onboard inverter-charger draws 12V DC from the battery bank and inverts it to 120V AC.
- Entry: The inverter's AC Out hot wire connects to INV L1.
- Relay Logic: When the inverter is activated (and shore power is absent), the ATS internal logic or a dedicated sense wire energizes the relay coil. The NC contact opens (disconnecting Shore L1 to prevent backfeeding the campground pedestal), and the NO contact closes.
- Transfer: Current flows from INV L1 through the newly closed NO contact to LOAD L1.
- Polarity Note: The inverter's Neutral and Ground are tied to the same internal hard-bussed bars. Crucial safety note: If your inverter-charger has an internal neutral-to-ground bonding relay, the ATS diagram will not show this; it is handled inside the inverter chassis to comply with NFPA 70 (NEC) Article 551 regarding RV grounding.
Step-by-Step Verification with a Multimeter
Never assume the wiring matches the diagram. Previous owners or dealership technicians often make errors. Use a digital multimeter (DMM) to verify the physical installation against the schematic.
- Verify Dead Circuit: Set your DMM to AC Volts (V~). Measure between LOAD L1 and LOAD N. The reading must be exactly 0.0V. If you read voltage, stop and find the hidden power source.
- Ground Continuity Check: Set the DMM to Continuity (the diode/beep symbol). Place one probe on the SHORE G terminal and the other on LOAD G. You must hear a beep and read < 1 ohm. Repeat for INV G to LOAD G. If resistance is high, the internal ground bus bar screw is loose or corroded.
- Neutral Continuity Check: Measure SHORE N to LOAD N, and INV N to LOAD N. Both must read < 1 ohm. This confirms the hard-bussed neutral path is intact.
- Shore Relay Logic Check (De-energized): With the ATS unpowered, measure continuity from SHORE L1 to LOAD L1. It should beep (NC contact closed). Measure INV L1 to LOAD L1. It should read OL (Open Loop / infinite resistance), confirming the NO contact is open.
- Live Voltage Verification: Reconnect batteries and plug in shore power. Set DMM to AC Volts. Measure LOAD L1 to LOAD N. You should read between 114V and 126V. Unplug shore power, turn on the inverter, and measure LOAD L1 to LOAD N again. You should read ~120V (or ~115V if under heavy load), confirming the relay successfully threw to the NO contact.
RV Transfer Switch Wiring Diagram FAQ
Does an RV transfer switch wiring diagram switch the neutral wire?
In 95% of standard 30A (120V) RV applications, the answer is no. The neutral and ground wires are hard-bussed straight through the transfer switch from the input terminals to the load terminals. Only the hot leg (L1) passes through the internal relay. Switching the neutral is generally only seen in specialized 50A (120/240V) split-phase setups or specific high-end inverter-charger installations where neutral-ground bonding must be isolated depending on the power source.
How do I wire a 50A RV transfer switch diagram with two hot legs?
A 50A RV system (like those using the Iota ITS-50R) utilizes a 120/240V split-phase architecture. The wiring diagram will show two hot legs for every node: SHORE L1, SHORE L2, INV L1, INV L2, LOAD L1, and LOAD L2. You will need 6 AWG wire for the hot and neutral conductors, and 8 AWG or 6 AWG for ground (depending on the exact chassis ground path). The internal relay will be a DPDT (Double Pole, Double Throw) or dual-relay setup that simultaneously switches both L1 and L2 to prevent a 240V cross-phase short. Never wire a 50A RV plug into a 30A ATS; the wire gauges and pinouts (NEMA 14-50 vs TT-30) are incompatible and will cause a fire.
What do the "NO" and "NC" symbols mean on the transfer switch schematic?
These symbols represent the physical state of the relay contacts when the internal coil has zero power applied to it. "NC" means Normally Closed; current flows through this path by default. "NO" means Normally Open; current is blocked until the relay coil is energized, which pulls the contact closed. In RV diagrams, Shore power is usually routed through the NC contact so that plugging into a campground pedestal powers the RV immediately without requiring the ATS logic board to boot up and energize a coil.
