A personal story about comfort, expectations, and the realities of domestic cooling.

Summer is well on its way, and a few things need attention. Booking a vacation and planning a gym regimen to work on your beach-ready bod are a couple that spring to mind. Perhaps more seriously, ensuring that the AC is fully functional is another key task for this time of year (with apologies to Southern Hemisphere readers).

One of the key differences between industrial cooling and air conditioning is that industrial systems are process dependent and required to run all year, usually on high load. Air-conditioning systems are seasonal, at least in temperate climates, and the load varies with the weather, building up from very low at about this time of year to peak in July or August and then tapering back down by October.

The term “mission critical” is sometimes applied to IT cooling in data centers. If the cooling is for a process, for example paint cooling on a car production line, is it mission-critical? In tropical and equatorial climates, where the seasons range from hot to very hot, is the “comfort air-conditioning” in a commercial building mission critical? I’d like to think so. Anything that could derail the smooth function of an operation, whether it is processing data, assembling components or keeping school pupils, hotel guests or office workers in good shape ought to be considered critical to the delivery of goals for an organization—the “mission.”

So why is it that at this time of year systems which have lain dormant all winter are brought online again with only a superficial glance at their operability? Is it assumed that, since it managed to survive to the end of the season it will be OK, or is it felt that the load will be light for the next few weeks so just get it running for now, and we will do the fine-tuning later? Either way it is probably an expensive mistake.

A few thing could go wrong. It’s possible that the system was already slowly leaking when it was shut down for the winter, or that a leaked developed during the off-season despite the plant not being in operation. Either way, the assumption that the plant is charged for optimum performance is weak. It’s also possible the system actually wasn’t performing well when it was turned off six months ago, but was overlooked because the load was light. Restarting in the same condition might not create a problem immediately, but if there is a sudden warm spell in mid-May or early June, there is a high probability that the system will fall short. Last month I mentioned that systems should be ensured to be safe, efficient and reliable (in that order), but sometimes not even one out of three is possible.

Outside of the refrigerant circuit there are also many things that can go wrong. Birds, wasps or even foxes nesting in air ducts can present a major issue, although it is fair to say if you’ve allowed them to get as far as the construction phase of their project you are already in trouble. It is better to be aware of this possibility through February and March, take preventative action and avoid the hassle completely.

Finally, a word about Legionella. Only about a third of outbreaks are associated with air-conditioning plants, but most occur when systems are restarted after the winter. Wet systems need to be chlorinated, but some outbreaks have been traced to air-cooled equipment, too—typically where rainwater had ponded near the condenser, perhaps due to a blocked drain, and the stagnant pool has blown through the fans and into the breeze without any control.

It is difficult to control what you don’t know about, but if you have read this far you can no longer claim ignorance as a defense.