Coming back to you with another exciting heat pump water heater (HPWH) question.

I've been testing an OpenStudio measure I wrote to add HPWHs on a few test buildings and am running into errors I haven't seen before. In particular, it is causing errors in this building that has 5 rooftop AC units and wanted to hear what you all thought.

Below are the error logs of the buildings before and after adding the HPWH. :

Lines in HPWH error file that are cause for concern:

   *************  ** Warning ** Enthalpy out of range (PsyTsatFnHPb)
   *************  **   ~~~   **   This error occurred 7144 total times;
   *************  **   ~~~   **   during Warmup 0 times;
   *************  **   ~~~   **   during Sizing 0 times.
   *************  **   ~~~   **   Max=-56493.273821 J/kg  Min=-11888262.758062 J/kg
   *************
   *************  ** Warning ** Temperature out of range [-100. to 200.] (PsyPsatFnTemp)
   *************  **   ~~~   **   This error occurred 728 total times;
   *************  **   ~~~   **   during Warmup 0 times;
   *************  **   ~~~   **   during Sizing 0 times.
   *************  **   ~~~   **   Max=-600.530182 C  Min=-11848.583984 C

Full error logs

• Baseline error log
• With HPWH error log

You'll see I get some very alarming temperature and enthalpy values. Any thoughts on what I should check or how to think through these types of errors? I'm stumped on why adding a HPWH would cause this.

I got E+ to report the inlet node temperatures for the cooling coil on the HVAC side as well as the inlet and outlet nodes for the SHW and not seeing anything near the ranges reported in the error files. All temperatures there seem reasonable.

TL;DR - Adding a HPWH caused strange errors with respect to temperature and enthalpy. Why would adding a HPWH cause such drastic temperature ranges? How would one check WHERE the temperatures reported in the error file come from?