Logix 5000 SCL Instruction Help

Working with a SCL instruction and need a little help. The logic is a Heat / Cool circuit controlled by a PID. The PID Zone_4.CVEU tag is coming into a SRTP block with a heat out being used but nothing attached to the cool out.

Connected to the PID Zone_4.CVEU tag before the SRTP is a SCL block and the out of the SCL block goes to the cooling valve. I really don't understand why it's done this way? Wouldn't the normal thing be to connect the cooling valve tag to the coolout of the SRTP?

On the SRTP the Max heat in is 100.0 and the minheatin is 50.0 and the maxcoolin is 0.0 and the mincoolin is 50.0

The weird thing on the SCL block to me is the inrawmax is 100.0 and the inrawmin is 0.0 but the inEUMax is 4000.0 and the InEUMin is 20000.00

This is going to the cooling valve and is a 4-20 ma output on the valve.

I would thing the inEUMax would be 20000.0 and the InEUMin would be 4000.0 or am I not understanding how these things work at all?

Sounds like some custom code to limit the cooling so it is always open a little but i maybe wrong of course

Hard to picture without a screenshot of the code, but I would imagine that the "reversed" output to the valve is to control the opening; 4mA would leave the valve wide open (inrawmax at 100%) and 20mA would close the valve (inrawmax at 0%).

From what I can tell the instruction help for the SCL instruction is it will take a floating point number in like 0-4095 and convert it to engineering units like 0-100 GPM.

It seems here they are trying to take the 0-100% output of the PID and send a vaule of -20456 which will produce 4ma on the 1756-OF8 and 28791 which will produce 20ma.