Water remaining in equipment and pipework can be affected by low temperatures. The unit's permitted environment and winterising instructions matter.
What the observation means
An indoor-looking enclosure is not proof that every part of the discharge route is protected. Do not assume a running motor will prevent freezing.
A useful next step
Seek model-specific guidance before seasonal closure or use in a cold outbuilding. Do not pour boiling water into frozen equipment or apply an open flame. If freezing or damage is suspected, keep connected fixtures unused pending appropriate assessment.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.