Hardness for Tankless water heater

[Technomystic]

What hardness is safe to use in a Navien tankless. Chicago water is 8 grains and a Rinnai needs to be descaled annually (quite a pain).
I am installing a softener in Indiana to treat well water with 14 grains hardness and 0.3 ppm iron.
I would like to set my softener to conserve salt but it would result in 2-3 grains hardness.
Would that clog my Navien with CaCl3?
It might be cheaper and easier to just set the salt consumption higher to get <1 grain output than to have to descale the Navien.
What is most efficient hardness please?
Thanks

 

[Reach4]

If you set your softener to use 5 or (preferably) 6 lb/cuft of salt, you should do better than your 2 grains of leakage. You would still be getting reasonable salt efficiency.

With the 6 lb/cuft it will make the water better than going leaner. 8 to 6 is the most popular range.