Beastie originally had a 30A AC circuit, which was pretty normal for the 80s. By today’s standards, that’s not great. 30A, single phase, can provide about 3.3kW of usable power. It’s a challenge to power 2 airco units at the same time with 30A. As a result, Beastie could run only 1 airco on shore power, and would need a generator to power the second airco. Above the kitchen, a selector switch would allow the owner to decide which appliance would get power (airco, microwave, oven, kitchen chef). We decided to completely overhaul the electrical system and install a 50A, 2 phase circuit, giving us a theoretical maximum of 11kW of usable power, more than three times what we had before.
This is the new circuit diagram:
Here are the key components of the system:
1. Smart Phase Selector
The Smart Phase Selector is a pretty cool device, especially when used in combination with a single phase inverter/charger like the Victron Multiplus. It ensures that no matter the source of your power (generator, 15A shore, 30A shore, or inverting only), your entire RV will have access to 110V (within the limits of the source of course). This means … no more sub panels, and no manual switches to select which appliances get power.
This is an excellent video describing how it works.
2. Victron Multiplus 3000/120
The Victron Multiplus 3000/120 is a hybrid inverter/charger that can handle 3kW of inverting, and includes a sophisticated battery charger with adaptive charge technology. It has a transfer switch built in that switches from shore power to inverting within 20ms, and takes over the supply of connected loads without interruption. Also, it has a power assist feature that enables you to provide up to 50A on a single phase, even when the power source is 15A or 30A. The Victron does this by using battery power to supplement shore/generator power.
More information about the inverter and its features see here.
3. Surge Protector
Shore power at campgrounds tends to be less stable than what we’re used to at home. As a result, it’s really important to protect sensitive electronic equipment against shore instabilities.
We installed a Progressive Industries 50A RV Surge Protector. It will protect our equipment against low and high voltages and will automatically shut down when voltage goes outside these boundaries. It also protects against frequency deviations and various other anomalies (open ground, polarity, lost/open neutral, etc.).
4. Transfer Switch
The heavy duty Esco 50A transfer switch will automatically switch power from shore to generator. It will transfer both hot and neutral legs simultaneously. The design of the transfer switch allows shore power to be run through the normally closed contacts of the relay. This means that whenever the shore cord is plugged in, power goes through the relay to the load panel. The relay doesn’t have to be energized. The switch is ‘generator priority’. This means that when the generator starts up, the transfer switch switches over to generator power and cuts off shore power. This happens within 30 seconds of generator start-up to allow the generator to stabilize its power output.
This is a different implementation from before. In the original Airstream one could run 1 airco off shore power (30A) and the second airco off the generator. With the transfer switch, shore power and generator power are mutually exclusive. This is generally not a big issue. When connected to a 30A shore, the system can sustain 2 aircos running at the same time thanks to (1) airco soft start, and (2) the ability of Victron to supplement power up to 50A by using the battery.
5. Breaker Panels
As mentioned before, we are not using sub panels. Instead we have 2 full breaker panels, one on each side of the MH. The bar, kitchen, and bathroom plugs are connected to GFCI breakers.
The decision on which circuit to connect to phase A or phase B is not really that critical anymore since the entire RV will get 110V regardless of whether source is 1 phase or 2 phases, thanks to the Smart Phase Selector. However, we tried to balance the load of the power-hungry appliances, so we can reasonably stay below 50A on each phase.
- Phase A: Living Room AC, Coffee Maker
- Phase B: Bedroom AC, Alde Heating, Oven
6. Wiring
We used 6 ga. wiring on all 50A circuits including the connection between the two breaker boxes, 12 ga. wiring on the 20A circuits and 14 ga. wiring on the 15A circuits.