Russell:
The program does not differentiate at all with heated and unheated areas. That is one of the drawbacks of the DW method. You could in theory do an equivalent K-calc, like we used to do with in-rack systems.
Unless it really kills me on the calcs, I just typically treat the entire thing as it is in the freezing area. But, if you are in a really cold area, you will be looking at some large swings in pressure.
Also, don't forget to adjust your k-factor. HASS automatically adjusts the k-factor, but Hydratec does not do that. There was a paper by Ken Isman, PE that gave the formula for doing the k-factor adjustment for AF systems.
Give me a call if you have any more questions that I can clarify. I do A LOT of antifreeze systems each year. More than I care to, but that is what the customers want in some areas.
Travis Mack
MFP Design, LLC