A few years ago we were involved with the same situation on a rather large school that had sizable addition. The FA contractor put in a separate system for the addition. AHJ refused it and in my view was absolutely correct. They had a number of NICET 4 guys and FP engineers look at it to see if the 2 systems could be made to act as one in order to make it code compliant. In the end all agreed it could not be done and they ended up removing the new system and extending the original system. They tried all kinds of interconnection schemes to make the 2 systems work as 1 but there were multiple operational issues that would not meet code.
Originally Posted by gadfly56