From a102deeff2d61870c3b7ba243b6022a21536027f Mon Sep 17 00:00:00 2001
From: Pranay Bhange <op.pranay.bhange@gmail.com>
Date: Fri, 23 Oct 2026 21:07:48 +0530
Subject: [PATCH] Fix ZoneHVACPackagedTerminalHeatPump writing a garbage DX
 Heating Coil Sizing Ratio

dXHeatingCoilSizingRatio() called OS_ASSERT then .get() on the optional
returned by getDouble(), which is undefined behavior when the field is
unset and has no IDD default (it's a \required-field with no \default).
In that case the model object silently returns whatever bytes happen to
sit in the optional's internal storage, which the ForwardTranslator then
writes straight into the IDF as a nonsensical value, causing EnergyPlus to
reject the file.

This field is normally always set by the constructor, so the unset case
only shows up on objects built outside the normal constructor path (eg: a
.clone() of a template that itself predates this field being set).

Mirror the existing self-healing pattern used by
supplyAirFanOperatingModeSchedule() just above it: log an error and fall
back to the documented default of 1.0 instead of reading uninitialized
memory.

Fixes #5635
---
 src/model/ZoneHVACPackagedTerminalHeatPump.cpp |  6 ++++++
 .../ZoneHVACPackagedTerminalHeatPump_GTest.cpp | 18 ++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/src/model/ZoneHVACPackagedTerminalHeatPump.cpp b/src/model/ZoneHVACPackagedTerminalHeatPump.cpp
index 40cda15284f..59bc6aaa74b 100644
--- a/src/model/ZoneHVACPackagedTerminalHeatPump.cpp
+++ b/src/model/ZoneHVACPackagedTerminalHeatPump.cpp
@@ -359,6 +359,12 @@ namespace model {
 
     double ZoneHVACPackagedTerminalHeatPump_Impl::dXHeatingCoilSizingRatio() const {
       boost::optional<double> value = getDouble(OS_ZoneHVAC_PackagedTerminalHeatPumpFields::DXHeatingCoilSizingRatio, true);
+      if (!value) {
+        // it is an error if we get here (eg: cloned from an object that had it unset), however we don't want to crash
+        LOG(Error, "Required DX Heating Coil Sizing Ratio not set, defaulting to 1.0");
+        const_cast<ZoneHVACPackagedTerminalHeatPump_Impl*>(this)->setDXHeatingCoilSizingRatio(1.0);  // NOLINT
+        value = getDouble(OS_ZoneHVAC_PackagedTerminalHeatPumpFields::DXHeatingCoilSizingRatio, true);
+      }
       OS_ASSERT(value);
       return value.get();
     }
diff --git a/src/model/test/ZoneHVACPackagedTerminalHeatPump_GTest.cpp b/src/model/test/ZoneHVACPackagedTerminalHeatPump_GTest.cpp
index 0b1dee273df..e5067e4d810 100644
--- a/src/model/test/ZoneHVACPackagedTerminalHeatPump_GTest.cpp
+++ b/src/model/test/ZoneHVACPackagedTerminalHeatPump_GTest.cpp
@@ -40,6 +40,7 @@
 #include "../BoilerHotWater.hpp"
 
 #include <utilities/idd/OS_Curve_Biquadratic_FieldEnums.hxx>
+#include <utilities/idd/OS_ZoneHVAC_PackagedTerminalHeatPump_FieldEnums.hxx>
 
 using namespace openstudio;
 
@@ -308,6 +309,23 @@ TEST_F(ModelFixture, ZoneHVACPackagedTerminalHeatPump_CoilSystemCoolingDXHeatExc
   model::ZoneHVACPackagedTerminalHeatPump pthp(m, availabilitySchedule, fan, heatingCoil, coolingCoil, supplementalHeatingCoil);
 }
 
+TEST_F(ModelFixture, ZoneHVACPackagedTerminalHeatPump_DXHeatingCoilSizingRatio_Unset) {
+  // Test for #5635 - cloning from an object that never had this required field set (eg: an
+  // older template) must not return whatever garbage memory the underlying getter finds
+  model::Model m;
+  model::CoilHeatingDXVariableSpeed heatingCoil(m);
+  model::CoilCoolingDXVariableSpeed coolingCoil(m);
+  model::ScheduleCompact availabilitySchedule(m);
+  model::FanConstantVolume fan(m, availabilitySchedule);
+  model::CoilHeatingElectric supplementalHeatingCoil(m, availabilitySchedule);
+
+  model::ZoneHVACPackagedTerminalHeatPump pthp(m, availabilitySchedule, fan, heatingCoil, coolingCoil, supplementalHeatingCoil);
+  EXPECT_EQ(1.0, pthp.dXHeatingCoilSizingRatio());
+
+  ASSERT_TRUE(pthp.setString(OS_ZoneHVAC_PackagedTerminalHeatPumpFields::DXHeatingCoilSizingRatio, ""));
+  EXPECT_EQ(1.0, pthp.dXHeatingCoilSizingRatio());
+}
+
 TEST_F(ModelFixture, ZoneHVACPackagedTerminalHeatPump_SupplyAirFanOpSch) {
   model::Model m;
   model::CoilHeatingDXVariableSpeed heatingCoil(m);