When do we do a turnaround maintenance on HVAC system that works all year round?

It is done in pieces. Normally we have standby units which are maintained separately than systems. And if needed complete system it can be done in weekends or permission has to be taken for3 days or so.

In industry like pharmaceutical as we need definite temp. And relative humidity all the year so preventive and predictive maintenance is a must .

maintenance of the cooling portion should be done in the winter period and maintenance of the heating portion in the summer period

Thanks Rashad,