SIL 2 and Redundancy

Assuming FACP stands for Fire Alarm Control Panel.
Regardless, SIL2 does not necessarily mean redundancy.

Perhaps you can give further detail as a panel in isolation has no rating.
First of all, SIL 2 certified equipment means that the probability of failure on low demand (In other words, the safety function fails to do its job when called upon) is ≥〖10〗^(-3)<〖10〗^(-2) according to IEC 61508.
Based on that if you are having a Simplex FACP panel but certified with the above it can be a SIL2 otherwise it is not.
Generally redundancy (Dual and above) provides the hardware fault tolerance feature which helps to achieve SIL3 levels or even SIL4.
The highest achievable SIL with an non HFT system is SIL 2.