Plc Safety Integrity Level

Hi,
I came across with one project which requires my system to comply with certain SIL 3 standard. If I were to choose the componenets from PLC selection and instsrumentation used, is it necessary to have all componenets certified to SIL 3 or only for the PLC. Normally this type of requirement apply for hazardous area. Anyboday can clarify on this.

TQ

Gen-set

Hi,
I'm testing my HVAC system with using the gen-set with 100 A capacity. The load for gen-set is shared together with other utilitires like lighting etc. My HVAC system is using single phase and tap from the red phase. It seems the system is running steadily for few hours but suddenly the motor sounds abonarmal and further checking shows that the volatge drop to 155 V and cause the system malunction. I've checked the load distribution for gen-set and the result is as follow:

Without HVAC load:
Red - 21 A
Yellow - 7.8 A
Blue - 11.4 A

With HVAC load:
Red - 37 A
Yellow - 8.3 A
Blue - 12.0 A

The cable used from Gen-Set to DB is about 70 m and using $C X 18 mm sq. With the size and XLPE type cable used, I don't think cable is the problem causing the voltage drop but I see that there is unbalance current distribution among the phase. My question is either this unbalance current cause the voltage drop or any other factors contribute for the problem. I've also checked the motor and seems that the winhding (start, run) is fine. Anybody may have any idea.