The dining room is hot and the rooftop unit's down. Spring is when you prevent that call.

Ovens, fryers and dish machines put heat into the building from open to close. The hood pulls air out, and make-up air brings outside air in to replace it. In summer, that outside air is hot and wet.

The rooftop unit has to cool all of that, plus a full dining room. It runs longer and harder than the AC in an office of the same size.

1. Filters. Change them on schedule, often monthly in a restaurant. Grease in the air clogs them faster than in other buildings.
2. Thermostat. Check that it's set right, reads the right temperature and runs on its schedule. Keep the fan on auto unless your technician says otherwise.
3. Vents and returns. Make sure nothing is blocking them inside: no stacked chairs, boxes or decorations.
4. Water. Look for water stains on ceiling tiles under or near the unit. That can mean a clogged drain line.

A spring visit covers what the crew can't reach or shouldn't touch.

• Coils. The condenser coil outside and the evaporator coil inside collect dirt, grease and cottonwood. Dirty coils can't move heat.
• Belts and motors. A worn belt slips and squeals. A tired motor runs hot.
• Refrigerant. Low refrigerant means a leak, and the unit can't cool properly.
• Electrical parts. Capacitors and contactors wear out, and they tend to fail on the first hot day.
• Drain pan and line. A clogged drain overflows into the ceiling.
• Economizer. On units that have one, it should open and close as designed.

A kitchen that runs too hot wears on the crew and the equipment. Reach-ins near the line work harder. Cooks move slower.

If the kitchen is hot even with the AC running, the problem may be the balance between the hood and the make-up air. That's worth a look at the same visit.

Call in spring if the unit made noise, ran nonstop or left warm spots last summer. Call any time it blows warm air, freezes up, trips the breaker or drips water. Repairs in April are faster than repairs in July, when every technician in town is busy.