Water leaking from pressure relief valve - need help

[drabina]

I have a gas furnace with an indirect water heater and 4 heating zones (plus hot water). Couple of days ago I woke up and the basement floor was wet which was due to the water leaking from the pressure relief valve. Since then I have replaced the pressure relief valve on the furnace, both expansion tanks (furnace one and potable water one) and also pressure regulator. Unfortunately, the water is still dripping from the furnace's pressure relief valve. A lot less than before but still a concern (1/5th of a bucket over night vs more than three buckets before the parts were replaced). I do not know what to check next. Any help would be appreciated.

 

[user 4883]

Do you have any working pressure guages on the system?
If so, do they indicate that the PRV and/or TXV should be lifting?
Are the replacement components of the correct rating for your system?

 

[drabina]

The replaced parts are specd for my system. The pressure control valve is even the same company. Expansion tanks have the same capacity.