Quote Originally Posted by frank View Post
Gents

Look carefully at the one way valves.

When in heating mode, (top sketch) the liquid exiting the condenser HE bypasses the outlet of the LH TEV, enters the filter drier and then the RH TEV. As it exits this TEV to feed into the evaporator HE, it also feeds back towards the LH TEV and creates a loop of liquid between the TEV's

It's similar when in cooling mode.

The machine feeds a Pre-heat coil/Pre-cooling coil on an AHU

I'm used to seeing the NRV's on a bypass across the TEV, not as shown here
look at heating mode

Just look at the TEV feed by the drier. It feeds the right evap. So far so good? What is the pressure at the heat exchanger inlet.?

But I hear you say "but it feed the inlet into the second valve as well". Yes it does, "sort of"
Now what is the pressure at the "outlet" of this second TEV?

So to get flow you in this direction the the pressure must be higher at the inlet of the TEV than that of the outlet!!!.