1 Answer

If your actions are undertaken to isolate a valve connected within a system, it would be logical for whatever the ws valve was intended to control to be shut off...if it was cold, it's cold; if it was hot, it's hot.

Next thing to consider, is why you are isolating the valve. I say this, because if it is for repair or replacement, the valve should be isolated before and behind it's location in the system. This is to nullify the possibility that the system could backflow, or that it could be within a system where cross-connecting lines are possible. Many systems are created that way to create a redundancy in the system to overcome damage, or supply the system from multiple sources.