Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
For this project we are modeling a large office with VAV hydronic reheat with heat supplied by a conventional boiler, a condensing boiler, or an air to water heat pump. We intentionally used very low supply water temperature for the heat pump to achieve a high heat pump COP and therefore also a low delta T, based on conversations with Taylor Engineering about some of their recent designs. The conventional boiler uses a supply water temperature setpoint of 160F and delta T (LWT-EWT) of 40F. The condensing boiler uses a supply water temperature setpoint of 140F and delta T (LWT-EWT) of 30F. The heat pump uses a supply water temperature setpoint of 115F and delta T (LWT-EWT) of 13F. We had planned to use autosizing for the hydronic supply loop flow rate to account for the differences in water loop flow rate required. Is there a quick way to get the autosizing to work? Alternatively, we could multiply the water loop flow rate for the conventional boiler by the ratio of the delta T to estimate the new target water loop flow rate.
