Temperature mapping is often executed every 12 months, but as confidence in the system grows then an argument can be made to extend the interval between repeating mapping. Certainly for new systems it should be repeated each 12 months, until a baseline is documented and then it can be increased to 2-5 years. When the mapping is repeated, summer and winter challenges must both be executed at times when the seasons are at their most extreme for your location.
That is unless there has been some event, which will demand repeating the temperature mapping immediately i.e. critical maintenance or significant change to the system.
- nothing has changed
- maintenance has been conducted without significant incident
- continuous monitoring does not show unusual trends or excursions
- calibration of the monitoring probe is satisfactory for that period
Then the temperature mapping interval can be argued to be extended to 3 years but no more than 5 years.
The change in temperature mapping interval should be documented in the Quality Management System, detailing the logic for the change. It would be good to use risk analysis vocabulary, in the documented discussion, to show the hazards of the system are under control and the probability of their occurrence in minimized.