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CLS Mechanical Services Blog

Low-Cost HVAC PM: Preparing For the Heating Season Part I: Preventive Maintenance Strategies

It may seem a little odd to begin a blog post titled “Preparing for the Heating Season” by talking about air conditioning. Yet commercial buildings place constant demands on the systems that run them, and air conditioning is no exception. Equally notable, you can learn a lot by evaluating the performance and condition of your air conditioning unit or units at the conclusion of the cooling season – and then use that knowledge to make smart decisions moving forward.

Essentially, when the “panic,” or high-use air conditioning season is over, make sure a qualified technician performs a thorough inspection of each piece of HVAC equipment in your property or properties—and then provides you with a detailed report. This report will give you the necessary information to make informed budget decisions for next year. It also gives you time to prioritize repair and replacement in an orderly manner, thus reducing your start-up cost in the spring.

Because your air conditioning units are only partly loaded at the end of the cooling season, it is conceivable that you have lost capacity and aren’t aware that you have a problem. Performing preventive maintenance (PM) throughout the year – and particularly at the end of the cooling season – can red-flag real or potential problems and enable you to take appropriate action.

Types of Heating

  • Natural gas heating, the most common type
  • Electric resistance heating, when gas is not available or electric is not expensive
  • Oil heat, a common heating type in the Northeast U.S.
  • Propane heating, in cases where it can compete with natural gas, or in new construction when natural gas is expected later
  • Heat Pumps, particularly in the South

Preventive Maintenance

Rooftop blower belts tend to break in the winter when they are cold and less flexible. If a unit has been turned off for some time – perhaps on night setback – and then the motor is turned on, that motor will attempt go from 0 to 1,750 RPM instantly. This puts considerable torque on belts and the blower system. After the belt makes a few revolutions, it warms up as it goes around the pulleys. This usually is when cracked belts break.

Most PM programs include a belt replacement at least once per year. The belt’s condition should be checked and adjusted on each visit. You may have more than one stage of heating, and more than one compressor in cooling, but rooftop units (RTUs) have only one blower system. If that blower system will not operate, your RTU is non-operational, and it is highly likely that you will be unable to heat or cool your space. 

To reduce heating breakdowns, we at CLS Mechanical Services developed the following basic PM program. We recommend that you use refer to this as a guide, and employ the specific PM program provided by the manufacturer of your equipment, if available.    

Heating Start-Up Checklist for a Natural Gas RTU

  • Check gas pressure and piping for leaks, and support
  • Replace air filters
  • Inspect the blower and replace belt(s) once per year 
  • Inspect the condition of blower bearings and lubricate
  • Inspect the condition of the blower motor and lubricate
  • Brush-clean the heating elements and/or the heat exchanger
  • Test the operation of the heating system
  • Check the condition of the combustion blower
  • Check the pilot or ignition system
  • Check the heat exchanger
  • Check the thermostat and all operating controls
  • Tighten all electrical connections
  • Clean and check all grounded connections
  • Run through two complete heating cycles
  • Verify that the economizer dampers are set and operational

A Word About Economizers and “Free Cooling”

An economizer is an RTU accessory that allows you to vary the amount of outside or fresh air that you bring into the space you are controlling. In the spring and fall, there are many opportunities to use the outside air to cool a commercial space.

When economizers operate correctly, they provide several notable benefits:

  • “Free Cooling.” This really is a misnomer, but it does provide cooling at a much lower cost without mechanical refrigeration
  • An economizer flushes the VOC (volatile organic compounds) associated with new carpeting as well as merchandise in a retail store
  • An economizer provides fresh air with higher levels of oxygen. Casinos, for example, keep their gaming areas filled with fresh air
  • An economizer fills space with a positive air pressure and keeps odors from nearby areas (e.g., food courts and pet stores in malls) from infiltrating your space
  • With an economizer, you minimize the energy used to operate the compressor. You also save wear and tear on the compressor. It is much harder on a compressor to operate in the winter than in the summer. When the outside air temperature drops below 550 F, the compressor is stopped, and the commercial space is cooled with outside air

Conversely, an economizer that does not operate correctly poses several disadvantages:

  • High energy cost if the Outside Air (OA) dampers are open in the summer
  • High energy cost if the Outside Air (OA) dampers are open in the middle of winter, and it becomes necessary to run the heater in order to compensate for the improper damper setting
  • Lack of odor dilution, positive pressure, and oxygen depletion if the economizer is closed tightly

As the heating season looms, now is the time to take advantage of the economizer operation with all of the benefits. In the fall and beginning of winter, you may be heating at night and cooling in the day. Therefore, it’s wise to take advantage of the “free cooling” available with economizers.

In our next post on preparing for the heating season, we’ll use the checklist we provided above as a baseline for electric, oil, propane and heat pump heating sources and provide specific add-on tips for each one.

In the meantime, if you want to learn more about CLS Mechanical Services’ heating and cooling services, call us at 800-548-3542 or fill out the form below.

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