ᐅ Drain solar fluid for winter? Risk of frost damage?

Good day.
Our neighbor needs to repair the solar piping in the attic. It is leaking.
He now wants to drain the solar fluid and refill it in the spring.
The oil heating system is designed so that the solar system is not strictly necessary.
(It was installed later).

Question:
- Does he need to expect frost damage to the collectors if he drains the solar fluid and leaves the system inactive over the winter?
The pump, etc., will of course be turned off.
Or is it possible to do this as an exception?

Thank you very much.

What reason could there be for leaving it empty other than postponing the repair appointment? I wouldn’t want to leave it empty and unsealed over the winter. Without a detailed technical understanding of how filling behaves under oxygen in stagnant conditions, I would be concerned that drying out without a cleaning treatment could at least damage the pump.

Make sure to fill it correctly. Otherwise, you will end up with rust or condensation. Condensation can lead to frost damage if you are unlucky.