Do you address a Chaplain as "Sir", respective rank, or by "Chaplain (last name)"?

A few people in my unit have been chastised for calling our Chaplain as "sir", instead of "Chaplain". They were told that as per the regulation (they don't say which one) a Chaplain is only to be addressed as "Chaplain". <BR><BR>I have looked through AR 600-25 and there is nothing in that regulation, except that you call an officer by either his/her rank and last name, or "Sir". I can't even find where it says that you are allowed to&nbsp;address him/her as "Chaplain". I know that it&nbsp;is&nbsp;done, but I can't find&nbsp;where it is okay by regulation. <BR><BR>Could someone please help me out with this? <BR><BR>Thank you in advance! &nbsp;