The visits happen at most buildings. What is missing, almost everywhere, is what the visits left behind. A folder of contractor invoices proves that somebody attended; it does not say what state the unit was in, what was replaced, or whether the reading taken in March was better or worse than the one in December. Three kinds of record come out of preventive maintenance on HVAC equipment, they are worth different amounts, and sites reliably keep the least valuable one.
What was done: the weakest record and the most common
A visit date and a service description. It answers whether the interval was kept and nothing else. It is worth having, it is what an invoice already gives you, and treating it as the record is why so many buildings cannot answer any question about their own plant beyond confirming that somebody came.
What was found: the record that creates work
The belt that is wearing, the corrosion starting on a coil, the damper that is stiff. Findings are the output that justifies the visit, and they need a route into scheduled work or they evaporate. A finding recorded against the unit, with a date, is also what lets the next visit start from a position rather than from scratch.
What was measured: the record that predicts
Pressures, temperatures, currents, run hours. Individually they say little; across three visits they show direction. This is the record that gives a building any ability to see a problem developing, and it is the one most often reduced to a tick because pass or fail is quicker to write. Numbers cost seconds more and are worth an order of magnitude more. The practical test of any of these records is whether a person who was not there can answer a question from it a year later. If the answer requires ringing the contractor, the record is the contractor's rather than the building's, which is a position worth noticing before the contract changes hands.
Questions people ask about preventive maintenance hvac
How do we get numbers out of a contractor?
Ask for them in the scope, and give them somewhere to go. Most contractors take readings anyway; whether you receive them is usually a question of whether anybody asked.
Where should the records live?
Against the unit, not in a folder by month. Every question anybody asks later begins with the unit, and a chronological folder makes each of those questions a search.
How long should HVAC records be kept?
As long as the equipment is in service at minimum, because the trend is the value. Any retention requirement beyond that is a matter for your own adviser.