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Summer Thunderstorm Warnings: HVAC Preparedness

Published on: August 1, 2013

In the Southeastern states, HVAC preparedness should be part of a comprehensive plan to develop readiness before severe weather strikes, as well as recovery procedures after the storm has passed. The Southeast is uniquely positioned to be affected by a variety of severe weather. Damaging thunderstorms roam the landscape during spring and summer, frequently spinning off tornadoes. Ocean-spawned tropical storms and hurricanes may make landfall from the Caribbean or south Atlantic. Many low-lying areas are vulnerable to flooding, and in winter months crippling ice storms may occasionally strike.

Air conditioning and heating systems are susceptible to storm damage in several ways. HVAC preparedness takes into account physical damage from water, wind and impact, as well as harm from electrical sources. Because central air conditioning systems incorporate an outdoor component, this equipment is uniquely exposed to the effects of acute weather.

Electrical Matters

The 21st century home is particularly dependent on an uninterrupted supply of electricity. Today’s HVAC equipment frequently incorporates as much advanced electronic technology as any other home appliances, computers or entertainment systems. Effective HVAC preparedness against electrical issues caused by severe weather begins before a storm threatens.  

  • Whole-house surge suppression equipment can be installed at central locations such as the main electrical panel, and/or individual suppressors can be installed at locations such as the air handler and the outdoor compressor/condenser unit. Electrical surges resulting from storms can damage expensive equipment in a millisecond. These spikes in current may have a number of sources.
  • Lightning strikes can send voltage surges through home wiring, even though the home itself isn’t struck by a bolt of lightning. Nearby lightning conveyed through power lines can enter home circuits and damage equipment.
  • Non-power lines such as cable TV and telephone wires also can provide a path for lightning to enter home wiring. This fact warrants the use of individual suppressors at HVAC equipment to protect against surges that come in “through the back door” instead of through the main power panel.
  • Total power failures or partial brownouts may occur on the utility grid during a period of severe weather. When full power is re-established by the utility, damaging voltage spikes frequently occur in the first moments after restoration of service before generating equipment stabilizes.

Homeowners also play other roles in preventing storm-related electrical damage to cooling and heating equipment. At the minimum, when a storm threatens, sensible HVAC preparedness means turning off the air conditioner or furnace at the thermostat. Better yet, switch off the power to both indoor and outdoor units at the circuit breaker that controls those units. Many recently built homes feature dedicated emergency HVAC cut-off switches located in the furnace/air handler closet to cut off all power to the unit.

Does your system have a time delay? Many programmable thermostats incorporate time-delay technology, or it may be built into the system microprocessor. A time delay prevents the system from restarting after a momentary power failure until a certain time interval, usually five minutes, has elapsed. This allows sufficient time for power from the grid to stabilize after an outage and reduces the possibility of damaged HVAC equipment due to voltage spikes.

Consider a permanently installed standby generator to keep part or all of your home powered-up even if grid power is interrupted by a storm. These units are typically mounted behind or at the side of the house and often run off the home’s natural gas or propane supply, which is seldom affected by storm conditions. A standby generator constantly senses grid power and, in the event of an interruption, automatically starts and switches part or all of the home circuits over to generator power to keep systems such as HVAC equipment energized.

Water and Wind

Inundation of water from heavy rain or flooding can swamp the outdoor components of a central air conditioner. Wind-related impacts can also damage equipment outside the home. Effective HVAC preparedness strategies help reduce the extent of potential damage from water and wind:   

  • Make sure the outdoor A/C unit is securely anchored to its concrete pad and installed in a level attitude. Encroaching vegetation that could produce leaves and other debris that clogs vents should be cut back so clear drainage is ensured.
  • Consider a canvas cover that fits over the entire outdoor cabinet to keep out a deluge of rain. Make sure the cover is removed before restarting the system after the storm.
  • When a storm threatens, remove any loose objects such as patio furniture, children’s toys, barbecue grilles and the like from the vicinity of the outdoor A/C component. In high wind conditions, these can become flying missiles that damage the vulnerable condenser coil (not to mention creating a danger to human beings).
  • Hail guards can be installed to shield fragile fins on the outdoor condenser coil from damage by large hail. These are permanently installed over the coil vent opening and provide greater protection than the standard grille.
  • Storm water damage to HVAC equipment or ducts in the basement can be prevented by installation of a sump pump. These units are installed in a sump basin in the floor and automatically actuate when water in the basin reaches a preset level. Storm water is pumped up and out of the basement and discharged in the back yard.

Restoring Normal Operation

In information provided by local and federal authorities concerning HVAC preparedness, homeowners are usually advised not to be in a great hurry to restart HVAC equipment after a major storm. An inspection of the interior of the home, the basement or crawl space, heating roof vents and outdoor A/C components is usually advised before restoring power to the system. Here are some considerations that should take higher priority than the immediate restoration of interior comfort.

  • After a severe storm passes, ensure that the outdoor A/C or heat pump components are not underwater or internally swamped with water before restoring power to the unit. If water inundation is noted, leave the power off and call an HVAC contractor to check the condition of the equipment and, if necessary, service components so drying can take place.
  • Be aware that flying debris may have been blown into the outdoor coil or fan and prevent proper operation after restarting, as well.
  • Furnace vent pipes on the roof that exhaust combustion fumes may have been blown off or damaged so that fumes are not properly vented, causing dangerous carbon monoxide levels in the home. Proper inspection should precede restarting the furnace for the first time after a storm.
  • Severe storms may contaminate HVAC systems with water, bacteria or even sewage overflows that may accompany flooding. Heavy rain inundating crawl spaces or basements, or leaking into attics, can infiltrate ductwork and spawn bacterial or mold growth. When the system is restarted, air circulation may spread toxic contaminants throughout living spaces. If heating and cooling ductwork has been compromised by water infiltration during a storm, the services of an HVAC professional will be required to open and disinfect the ducts before use.
  • Change the air filter in the heating and cooling system immediately after a storm.

If damage to cooling or heating equipment prohibits restoration immediately after the storm, take steps to sustain healthy home comfort. In hot weather, open windows and utilize box fans and ceiling fans to sustain air circulation. In winter, if the furnace is inoperative after a storm, consider utilizing electric space heaters but follow manufacturer’s instructions for safe use.

As the premier resource for homeowners in Alabama, Florida, Georgia, Mississippi and South Carolina, AirConditioningSouthEast.com provides cooling and heating expertise for all seasons. Ask us about more ways to maintain HVAC preparedness and be ready when severe weather strikes.