Dear Everyone,
I got a comment for one of our project which in my opinion is not ccompatibe with ASHRAE. We do not have much time for the response, so I decided to ask about it here.
We modeled System Type 7 with some 3,9 and 10 if required. Main source of heat is Remote Hot Water from municipal grid.
"It is unclear how the hot-water design supply and return temperature difference (28 deg. C) has been determined for theBaseline model. If following Path 1. ASHRAE Standard 90.1-2010, Appendix G, the hot-water design supply and return temperature difference must be based on the actual hot-water loop conditions modeled in the Proposed model (which is 20 deg. C in this case)."
Appendix G states:
"G3.1.3.3
Hot-Water Supply Temperature (Systems 1, 5, and 7). Hot-water design supply temperature shall be modeled as 82°C and design return temperature as 54°C. " - because of that we modelled 28C.
I am confused now.
Tyler Thumma
7GroupLEEDuser Expert
67 thumbs up
March 4, 2021 - 3:34 pm
I believe this is based on an interpretation that G3.1.3.3 is applicable to an on-site Baseline boiler plant only, and not purchased hot water. Path 1 intends to keep the purchased energy cost-neutral in the Baseline and Proposed case (see the Definitions tab of the Minimum Energy Performance Calculator), hence the identical temperatures. It is also defined this way in the "Baseline Systems Helpful Notes" of the Water-Side HVAC tab of the Minimum Energy Performance Calculator.