Fix Divide by Zero in CentralHeatPump

[YanfeiNREL]

Pull request overview

• Fixes CentralHeatPumpSystem problems #5904
• recreate the issues reported by users for CentralHeatPump. Fix issues currently available.

Pull Request Author

• Label the PR with at least one of: Defect
• Author should provide a "walkthrough" of relevant code changes using a GitHub code review comment process
  Line 2376-2380:

  if (CHPower == 0.0) {
                       ActualCOP = 0.0;
   } else {
                       ActualCOP = (QEvaporator + ChillerFalseLoadRate) / CHPower;
   }

Line 2369 - 2373

   if (ReferenceCOP <= 0.0) {
                    CHPower = 0.0;
    }else{
                    CHPower = (AvailChillerCap / ReferenceCOP) * ChillerEIRFPLR * ChillerEIRFT * FRAC;
    }

• If changes fix a defect, the fix should be demonstrated in plots and descriptions
  For this issue, there are no after-fix plots, because the issue will be fixed after the updated GSHP model is being added and replacing the current model.

Reviewer

This will not be exhaustively relevant to every PR.

• Perform a Code Review on GitHub
• CI status: all green or justified

[nrel-bot]

@YanfeiNREL @lgentile it has been 28 days since this pull request was last updated.

[nrel-bot-2c]

@YanfeiNREL @lgentile it has been 28 days since this pull request was last updated.

[mitchute]

@Myoldmopar This has a couple of basic fixes from @YanfeiNREL. It should be ready to go.

[nrel-bot-2]

@YanfeiNREL @lgentile it has been 28 days since this pull request was last updated.

[Myoldmopar]

I was trying to review this. I transitioned the defect file up to latest IDD and ran it with develop. I was using Melbourne weather, but I did not encounter a divide by zero. I ran with this branch and also did not encounter an issue, but I'm having trouble verifying if I can't reproduce the issue.

@mjwitte I know this is pulling from a long time back but if you have any tips I'd be happy to hear them.

In general, these protections are fine, so I'm OK with this going in, but I'd like it better if I could verify the fix.

[mjwitte]

@Myoldmopar Depending on the configuration and platform divide by zero could slip by unnoticed. Have you tried running it in the debugger with a breakpoint when Qevap=0 on the affect line? If that doesn't work, I can try to reproduce here.

[Myoldmopar]

I never get to any of the ==0 lines in the debugger. I'm inclined to just accept this and move on.

[Myoldmopar]

OK, I'll call it, these changes are sensible and CI is happy. I can't verify the fix though, so I'll merge this, and close the issue with a note about reopening if it is still present.