Interior view of a Transfer Switch
Automatic Transfer Switch
Current coaches
with a
generator will also
have a transfer switch installed
in the cord
compartment. An automatic transfer switch converts two inputs and connects them to
a
single common output.
The
shore power cord is connected to one of the inputs,
while
the generator is connected
to the transfer switch's second input.
Automatic transfer switches
are logic-controlled to convert under a given set of
conditions. The transfer switches used in RVs are typically
generator priority
switches
which
connect to shore power under normal use. As soon as the transfer switch
detects
the presence of 120 Volt power on the generator input lines, it will switch over
to the
generator's inputs and drop the connection to shore power.
Transfer switches are designed so that only one input can be connected at a time in
order to prevent any back feeding of electrical power. In addition, RV transfer switches
generally have a built-in delay allowing the generator to warm up and speed up
before
actually switching the load.
This
prevents
stalling or stumbling while the engine is still
cold and not producing full power.
Main Service Panel Breaker Box
The main service panel or
120 Volt
breaker box
is typically located
inside a bathroom, bedroom, or front overhead
cabinet
depending on the coach model and floor plan. The breaker box contains the main 50 Amp (or 30 Amp if
equipped)
breaker and the individual breakers protecting each circuit from overload conditions. Any unit equipped with
two air
conditioners or more must have 50 Amp service. The task of the breaker is to “trip” if the current exceeds the
amperage
rating on the breaker to prevent damage to the wiring of the circuit.
The breakers are resettable by simply flipping the breaker to the 'off' position, and then back to the 'on' position once the
overload condition is removed.
All 120 Volt
circuit breakers are located in the main service panel unless the coach
is
equipped with an inverter/charger. These units are also equipped with a subpanel.
Breakers positioned next to each other are on different poles in a 50 Amp panel. If only part of the electrical
circuits are working, you may have a poor connection at shore power. In this instance, power is most likely
only being provided to one pole or leg.
Subpanel
The subpanel is a smaller 120 Volt
breaker box containing
the breakers for the circuits which the inverter is wired to
power.
It is typically
located near the main breaker box unless the coach is equipped with an Energy Management
System (EMS).
In this case, the subpanel is often located within the EMS panel.
The subpanel is installed to limit the
AC
power use to specific circuits
when the electricity is supplied by the inverter.
Some inverters may be used to power
a
specific circuit.
In this case, a subpanel is not used.
50 Amp Energy Management System (EMS)
The 50 Amp Precision Circuits
Energy Management
System is currently offered
as standard
equipment on all Canyon
Star, Ventana, and Dutch Star coaches.
Its function is to provide power management
for certain
120 Volt
loads and as a
system of energy management to minimize the overloading and tripping of circuit breakers.
The EMS contains
a main
distribution panel with a self-contained control module and a remote display panel, which is typically located in the dash
overhead electrical control cabinet.
The EMS control module automatically senses the available power being supplied to the coach.
The module determines
whether it is connected to a 50 Amp (240 Volt)
or the
generator.
On
120 Volt service, it is unable to determine if the
source is providing
30, 20 or 15 Amp shore power.
Depending on available power, it
can control up to seven loads.
The
EMS controls air conditioner loads using low-voltage switching and other 120 Volt, heavy-load appliances, such as block
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