Additional Validations
Using Helper Class Validations Only
If only validations from the helper class are required, use the Change Handlers getValidationRules() method to return the helper.getValidationRules(). This will enforce all the validations in the Helper class on the Change Handler.
Sample code:

public ValidationRule[] getValidationRules() { 
return helper.getValidationRules(); 
}
Using Helper and Change Handler Validations
Create an Array of ValidationRules in the getValidationRules() method of the Change Handler and pass this array to the helper.getValidationRules() method. The Helper class adds the rules passed to it to the standard set to provided validations.
Sample code:

public ValidationRule[] getValidationRules() {
return helper.getValidationRules(<Array of Validation Rules>);
}