Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
If there is no heat exchanger, then I don't think it matters where this preheat coil is located in terms of energy usage. The load will be the same regardless. It will either be small flow rate with large delta T, if only outdoor air, or higher flow rate with smaller delta T in a mixed air configuration. In both configurations above (assuming that is no heat exchanger) the load on the coil is basically the same. If you are following the PNNL document above then it should be in the mixed air stream. In real life I would expect it to be in the OA stream, but, importantly, Appendix G systems aren't real life. I would place it in the space where it is with the system you are comparing it with. If you aren't comparing it with another system I would refer back to how much energy is it actually using? It will be pretty much the same in either configuration.
