# Heat Troubleshooting
Editor: messages after Check Simulation, and the results of a Heat project · Python: td.HeatChargeSimulation
Each entry starts with what the editor shows. The messages come from the check that Check Simulation runs (see Run and Cost). In the error list, a message can start with the place of the error, for example grid_spec:.
# Not ready to run (why?)
Cause: The check found at least one error. The simulation cannot run until you fix it. An item with an error can show a red mark in the tree.
Fix: Click the text to read the errors. Fix each one, then click Check Simulation again.
# "grid_spec: Field required"
Cause: The project has no grid. A new Heat project starts without one, and Grid Specification shows a red mark.
Fix: In Setup › Configuration › Grid Specification, set Type to UniformUnstructuredGrid or DistanceUnstructuredGrid, and fill in the grid size.
Related: Uniform Unstructured Grid
# "Current 'HeatChargeSimulation' contains only Neumann-type boundary conditions. Steady-state solution is undefined in this case. …"
Cause: No boundary condition fixes a temperature or exchanges heat. A surface with no condition lets no heat through, so the temperature is not defined. This happens with no condition at all, or with HeatFluxBC only.
Fix: Add a TemperatureBC or a ConvectionBC, for example on the bottom edge of the domain.
Related: Boundary Conditions
# "List of structures for heat source is empty."
Cause: A Heat Source has no structure in Structures.
Fix: Open the source and pick at least one structure, or delete the source.
# "Structure '…' provided in a 'HeatSource' is not found among simulation structures."
Cause: The source names a structure that the project no longer has, for example after you renamed or deleted it.
Fix: Open the source and pick the structure again in Structures.
Related: Heat Source
# "No solid materials ('SolidSpec') are detected in heat simulation. Solution domain is empty."
Cause: No medium in the project has thermal properties. A structure without thermal properties is left out of the heat simulation.
Fix: Open each medium in Model › Mediums and set its Thermal Properties (Medium Type and Thermal conductivity).
Related: Material Thermal Response
# "Temperature monitor does not cross any solid materials ('heat_spec=SolidSpec(...)'). …"
Cause: The monitor covers only places where no medium has thermal properties. The temperature is recorded only inside solid materials.
Fix: Move or enlarge the monitor so that it crosses a structure whose medium has thermal properties.
# "Heat simulations require the definition of, at least, one 'TemperatureMonitor' but none have been defined."
Cause: The project has no temperature monitor, for example after you deleted domain_temp_monitor.
Fix: In Setup › Monitors, click +, then Temperature Monitor.
Related: Temperature Monitor
# "Input should be greater than 0"
Cause: A temperature is zero or negative, for example a value typed in °C. The editor uses kelvin.
Fix: Enter the temperature in kelvin: 25 °C is 298.15 K.
# The temperature rise is far too large or far too small
Cause: A value is in the wrong unit. The editor uses µm: Thermal conductivity in W/(µm·K) and the heat source Rate in W/µm³.
Fix: Convert the values: 1 W/(m·K) = 1e-6 W/(µm·K), and 1 W/m³ = 1e-18 W/µm³. For example, oxide at 1.4 W/(m·K) is 1.4e-6 W/(µm·K).
Related: FAQ: What are the units for a Heat simulation? (opens new window)