Doing a remodel and installed a new split system. There is an existing split system twinned together (Heil). I need to install smoke detector in RA plenum in old units to bring up to code. No problem except they are not twinned together properly. I need to fix that problem before my detectors will work. I never twinned units before, but I know this was not done properly. Units do crazy things. detector is a Innovair dh100aacdclwp and want to insrall it using 24 volts.