I have 3 analog inputs from three different Multilin relays (3 hot oil pumps) that go into a SLS 1508. w/ 3oo3 voting. It is there to shutdown our heaters. Since the Multilin generates its own loop power, signal isolators are installed between the two since the 1508 uses its own loop power. In order to perform some maintenance on one of our Multlin relays, power was disconnected from the relay, thus we lost the 4-20ma output to the isolator. this should have been fine as we are configured for 3oo3 voting. It appears we experienced a blip of some sort and we experienced a general I/O failure that tripped our heaters offline. Everything seems to be configured properly.
We plan to run some test by bypassing this SIF next week to see if we can re-create the problem. Anyone have any ideas or has anyone experienced this issue? any help is appreciated.