Multilin 369 Fail Safe vs Non Fail Safe 1

[multilinnoob]

Hello Everyone!

I am looking to upgrade my Multilin 269+ motor protection relay with the newer Multilin 369 relay. While analyzing the drawings, I observed that presently, the 269+ is wired up such that the normally closed contacts 30 and 31 feed the motor main contactor (M).

I am unsure if this is programmed to be a fail safe (FS) or a non fail safe (NFS), so I do not know what will happen on loss of control power. However, I do know that if there is an undervoltage condition, the relay will trip out.

I am not certain what I should assign as my relay trip contacts in 369. From the user manual, I understand that a FS contact changes state when power is lost to the relay, while a NFS contact does not.

So, how do I choose my trip relay contacts? NO or NC, which ones should be FS or NFS?

Also, if say I assign the NC trip contact as FS, then will it change state when powered up?

 

[LionelHutz]

A FS relay is powered-on when there are no trips. Then, it is powered-off if there is a trip or if the power fails. Your present relay uses a closed contact in the circuit. So, use FS and NO contact or use NFS and NC contact. The choice really depends on your particular application.