Bom dia Fernando, você pode utilizar classes que tratam as exceptions para você direcionando para páginas específicas. No código abaixo está um exemplo de como utilizar. No método handle da classe JsfExceptionHandler, caso seja uma ViewExpiredException, direcionar para /Principal.xhtml. Se for qualquer outra exception, direcionar para Erro.xhtml. Espero que estes exemplos te ajude. Att,

--- Classe JsfExceptionHandler ---
public class JsfExceptionHandler extends ExceptionHandlerWrapper {

    private ExceptionHandler wrapped;

    public JsfExceptionHandler(ExceptionHandler wrapped) {
        this.wrapped = wrapped;
    }

    @Override
    public ExceptionHandler getWrapped() {
        return this.wrapped;
    }

    @Override
    public void handle() throws FacesException {
        Iterator<ExceptionQueuedEvent> events = getUnhandledExceptionQueuedEvents().iterator();

        while (events.hasNext()) {
            ExceptionQueuedEvent event = events.next();
            ExceptionQueuedEventContext context = (ExceptionQueuedEventContext) event.getSource();

            Throwable exception = context.getException();

            boolean handled = false;

            try {
                if (exception instanceof ViewExpiredException) {
                    handled = true;
                    redirect("/Principal.xhtml");
                } else {
                    handled = true;
                    redirect("/Erro.xhtml");
                }
            } finally {
                if (handled) {
                    events.remove();
                }
            }
        }

        getWrapped().handle();
    }

    private void redirect(String page) {
        try {
            FacesContext facesContext = FacesContext.getCurrentInstance();
            ExternalContext externalContext = facesContext.getExternalContext();
            String contextPath = externalContext.getRequestContextPath();

            externalContext.redirect(contextPath + page);
            facesContext.responseComplete();
        } catch (IOException e) {
            throw new FacesException(e);
        }
    }
}

--- Classe JsfExceptionHandlerFactory ---
public class JsfExceptionHandlerFactory extends ExceptionHandlerFactory {

    private ExceptionHandlerFactory parent;

    public JsfExceptionHandlerFactory(ExceptionHandlerFactory parent) {
        this.parent = parent;
    }

    @Override
    public ExceptionHandler getExceptionHandler() {
        return new JsfExceptionHandler(parent.getExceptionHandler());
    }

}

--- Configuração do faces-config.xml
<faces-config xmlns="http://xmlns.jcp.org/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-facesconfig_2_2.xsd"
    version="2.2">

    <factory>
        <exception-handler-factory>com.exemplo.JsfExceptionHandlerFactory</exception-handler-factory>
    </factory>

</faces-config>