Incorrect autosizing of PTHP's heating coil

asked 2022-10-17 00:48:15 -0500

Keigo's avatar

updated 2022-10-19 02:00:51 -0500

I have doubts about sizing of PTHP(Packaged Terminal Heat Pump)'s heating coil and supplemental heating coil. I have ran several files which have PTHP, but let me explain with an ExampleFile: HVACTemplate-5ZonePTHP.idf and some revised files for easy validation.

  • Autosized heating coil capacity is exactly the same as the autosized cooling coil capacity, which suggests that the autosizing does not refer to zone heating load and the heating coil capacity is just set to the same as the cooling coils. Also, I tried changing Heating Sizing Factor in Sizing:Parameters, but the results remained the same.
  • Autosized supplemental heating coil capacity is not 0W even though the heating coil capacity is sufficient to meet the heating demand. In the first place, it is unclear how to size the supplemental heating coil capacity. Supplemental heating coil is located after heating coil, not in front of heating coil. Therefore, if the heating coil capacity is autosized, the heating coil capacity should be sufficient to meet the heating demand. Then, PTHP does not need supplemental heating. image description

Below is the coil sizing summary. All the relevant files are here (V9-6-0).

image description

Does anyone know where the detailed sizing description for heating coil and supplemental heating coil is in Engineering Reference? I may be just overlooking it, but I can't find it. I can't find the detailed description in Engineering Reference (but I may be just missing it)

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