Quote Originally Posted by Krohnie84 View Post
The building was built in 1995, the original units were designed to defrost/heat with a regulated hot gas pressure of 70-75 psig. The expansion that took place in 2008 added units that are designed for 105 psig.
Usually, plan has outlet pressure regulator to keep certain constant(all year around) pressure in hot gas main. This is hot gas main. Evaporator has inlet pressure(or back pressure regulator) regulator to keep certain constant pressure inside the coil during defrosting. What do you have for new and old evaporators? What is the difference?