load of RTA board Online
In later versions (I believe 5.0) the load can be read as OPC property.
Try creating a child object below any RTA object and choose "RTA Load" as object type. If no such type is listed, it is not available in your system version. If available, select the MB300 tab of the Control Connection and enter the local RTA's net and node numbers. Then try subscribe for live data.
Without OPC access you are left with manual use of ANPER.
Still, in newer system versions with OPC access to load, there are things you should check with RTA Board Config tool (ANPER Channel Load, clock synk, system messages, etc).
Load is just one of the most vital parameters - there are certainly more to check upon.