The class method `+ (NSURLConnection*)connectionWithRequest:(NSURLRequest *)request delegate:(id)delegate;` "Creates and returns an initialized URL connection and begins to load the data for the URL request.", so calling `[self.connection start];` will fire off an additional request connection resulting in an error.

 `[self.connection start];` should only be used when using the instance method `- (id)initWithRequest:(NSURLRequest *)request delegate:(id)delegate;`