Servicing Rooftop Units: Checklists to Success

by Dave Rothacker

When it comes to annual maintenance on rooftop units, it never hurts to review the essentials. Thorough maintenance ensures that your customer's equipment performs at its best and identifies replacement and repair needs.

It also allows your technicians to spend valuable time with the customer. In fact, every heating or cooling season service check should start and end with a customer-visit to uncover any performance-or comfort issues, as well as discuss-repair and upgrade options.

The following outlines the crucial steps for performing yearly heating and cooling inspections. Note that in addition to changing filters during these visits, they should be replaced two additional times per year ( although monthly or bi-monthly filter changes may be required, depending on the environment).

Cooling Season Service

  • Perform static air pressure check on equipment
  • Check condensate drain pan, clean if necessary
  • Check condensate trap and prime Visually check for refrigerant leaks
  • Check disconnect and fuses
  • Check electrical wiring
  • Check and tighten electrical connections
  • Inspect contactors for pitting
  • Check and test system safeties
  • Verify that the expansion valve bulb is in the proper location
  • Lubricate motors if applicable
  • Check voltage and amperage on compressor and all other motors
  • Check the temperature differential
  • (Delta T) across evaporator coil
  • Look at the difference between the return and supply air. If it's abnormal, attach gauges, check suction and head pressures, and obtain refrigerant pressures.
  • Check superheat and subcooling
  • Check and clean condenser coils. Straighten if necessary.
  • Check blower, clean if necessary
  • Check belt, replace if necessary
  • Check economizer for proper operation
  • Replace filters
  • Properly secure unit panels
  • Check thermostat operation

Once you've finished these steps, document and record all of the operating characteristics, and verify them against the manufacturer's specifications. Record the outside air temperature, as well.

Heating Season Service

  • Perform static air pressure check on equipment
  • Check gas pressure Inspect heat exchanger
  • Check and clean burners
  • Clean pilot assembly
  • Check ignition system
  • Check electrical wiring
  • Check and tighten electrical connections
  • Lubricate motors, if applicable
  • Check and test all system safeties
  • Perform combustion analysis
  • Check Delta T across heat exchanger
  • Check voltage and amperage on all motors
  • Check blower and belts
  • Check combustion motor assembly
  • Ensure proper draft operation
  • Check thermocouple operation
  • Replace filters
  • Properly secure unit panels
  • Check thermostat operation

Other Important Points
In addition to the aforementioned steps during a cooling or heating check-up, here are some critical, yet sometimes forgotten, points to remember:

  • Lock out breaker while on the roof. This prevents anyone from inadvertently turning the breaker on or off.
  • Dirt is a rooftop unit's biggest nemesis. Keeping the internal components clean prevents unnecessary breakdowns and energy use.
  • Use a megohmmeter to monitor the compressor's windings over a period of time
  • Abnormalities in system static pressure could indicate potential ductwork problems. Either include a ductwork inspection in the contract or perform it as an above-and-beyond service.
  • Verify that the unit's breaker is properly labeled on the panel
  • Identify where the main gas turn-off is located
  • When on the roof, you are the building owner's or facility director's eyes. Report any visual abnormalities such as roofing or electrical problems.
  • Take digital pictures and keep on file. The pictures can be used to help explain system deficiencies to the building owner.
  • Keep a service card with operation and maintenance documentation in a plastic, enclosed envelope on the unit. Documenting any service or maintenance performed provides a valuable history for the next technician who works on the unit.
  • Record model and serial numbers of the parts used. This helps tremendously when reordering parts.
  • Always make sure system is operating before you leave the jobsite. This means ascertaining that the breaker and disconnect are in the proper position.
  • Place company sticker with contact information on thermostat
  • Leave your business card with the building owner or manager.

Before You Leave
Before leaving the building, meet with the customer once more. This is a great opportunity to discuss upcoming equipment needs and suggest system upgrades such as:

  • System air balance
  • Demand ventilation/economizer
  • Digital/programmable thermostat
  • UV lights
  • Voltage protection controls
  • Higher MERV-rated filters
  • Low ambient controls
  • Evaporator pan treatment
  • Higher efficiency motors
  • Ducted return air
  • Proper duct insulation.

Finally, always keep in mind how the rooftop unit behaves as part of the whole system, which includes the ductwork, diffusers, thermostats. This holistic, bigpicture approach will ensure tenant comfort, equipment performance and energy efficiency, and the loyalty of your customer.

Dave Rothacker has more than 20 years of experience in HVAC service operations and management, and is an advisory board member for the National Comfort Institute and Service Roundtable. He can be reached at [email protected]

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