How to Get Twenty Years Out of a Rooftop Unit

Most commercial rooftop units are scrapped between year ten and year fourteen. A reasonable manufacturer-rated lifespan is fifteen to twenty years. So where do those missing years go?

Across our forty largest preventive-maintenance accounts in Rutherford and Davidson counties, the answer is overwhelmingly the same: three small habits, repeated quarterly, add seven to nine years of usable life.

1. Coil cleaning, on a schedule, by hand

Condenser coils accumulate cottonwood, pollen, kitchen grease, and tire dust at a pace that surprises most owners. By the time airflow is visibly reduced, head pressure has been running 30–50 PSI above design for months — and the compressor is paying the bill.

We clean condenser coils twice a year and evaporator coils once. Hand-brush, low-pressure rinse, and a no-rinse alkaline coil cleaner where the build-up justifies it. No power-wash.

2. Belt tension and motor amperage, every visit

A belt that's too tight kills bearings. A belt that's too loose slips and overheats the motor. The middle is narrow, and it drifts with temperature, humidity, and age.

We log motor amperage at every PM visit and compare it to the nameplate. A 7% deviation gets a note. A 12% deviation gets a phone call. We've caught more failing motors with a clamp meter than with a stethoscope.

3. Drain pan and condensate line treatment

The most common cause of a service call we've seen — by a wide margin — is a clogged condensate line that floods the drain pan and trips a float switch. The unit calls for cooling, fails to provide it, and the tenant calls the property manager at 2:14 PM on a Friday.

A four-dollar tablet in the drain pan every visit, plus a nitrogen-flush of the condensate line annually, prevents nearly all of these calls. We've watched single sites go from twelve emergency visits a summer to one.

What it costs

For a typical 30,000 sq ft commercial building with four to six rooftop units, a quarterly PM program lands between $3,800 and $7,200 per year. The replacement cost of a single mid-size RTU is north of $14,000, and that's before the crane, the curb adapter, and the controls re-tie.

The math isn't subtle.

What to ask your current service provider

Ask for the last three PM reports. If they're a single page with a checkmark next to "filters changed," you're not getting maintenance. You're getting a filter change. Ask for motor amperage readings. Ask for photographs. Ask whether your drain pans were treated.

If you can't get those answers, you're paying for service that doesn't add years to your equipment. And it shows up later as a capital expense you didn't plan for.