Working on a 5 Ton Tranquility Horiz pkg unit, my discharge pressure is only about 200psi (should be around 300), suction pressure is also low(in heating mode)  my water and air delta t's  are quite low, I'm sure this all leads to a scaling problem (lack of heat transfer), I contacted the Michigan supplier for Climate master, and was informed  that I could use CLR, I contacted CLR directly and was informed I may not want  to use with cupronickle,  any recommendations?

I've seen previous recommendations around here to use nickle-safe ice machine cleaner.

CLR is a fairly weak lactic acid. I've also seen suggestions that other commonly-available weak acids like vinegar (acetic acid) or even muriatic acid can clean out scaling, but I've got no idea of what strength to use or what the issues are with copper vs curponickle coils.

I have always recommended ice machine cleaner to be on the safe side.

Yeah thanks , I was able to get my hands on some calgon nickle safe ice machine cleaner,( none of our local suppliers  stock it) and it worked just great... flushed it both ways, and it did take quite awhile, head pressure, delta t's all where they were at initial start up. Thanks again

Not a quick job depending on build up.
Using warm water helps too.