What should the water temperature be for average water heat pump for most efficiency

Biua

It should be called for by the person who designed your system.
Is this a well feed heat pump?
Is this a ground water feed heat pump?
What is the current water temp of the water?
Have you checked the heat pump to make sure it is working at maximum efficiency?
What is the discharge refrigerant temperature?
What is the return refrigerant temperature?
What is the discharge refrigerant pressure?
What is the return refrigerant pressure?
There is NO average water temp. It all needs to be calculated.
It would also be nice to know the following.
Whalen model and serial numbers for all units.
If you know the brand and model of pump being used.
What is the system velocity of water from heat pump to fan coil.
What is the temperature of the return air and the supply air (TD) total differential.

Take the easy way out?
Contact these people they built your system.

The Whalen Company
Post Office Box 1390
Easton, Maryland 21601
Tel: 410-822-9200