Question-and-Answer Resource for the Building Energy Modeling Community
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I've seen increases in energy use with ER in AHUs in models before. Usually, switching the "Supply Air Temperature Control" to "Yes" fixes the problem. I may be misunderstanding your problem, but here's what usually happens for me.
If your supply air temperature setpoint is 55°F, then on mild days (say about 45-50°F outside), the ER unit can get the air hotter than that (maybe about 58°F). Then, the cooling coil has to operate to meet the supply air temperature, then the heating coil may reheat in the VAV system
To check this, I would look at the temperature leaving the ERV, the OA temperature, the supply air temperature, and the heating/cooling provided. The temperature of the air leaving the ERV should be somewhere in between the OAT and the SAT (or equal to the SAT). If it "crosses over" the SAT, then the unit is cooling/heating when it shouldn't be. By controlling the ERV to the SAT, this crossover is avoided.
Hope this helps!
