How Hail & Flood Might Damage Your HVAC Unit

How Hail & Flood Might Damage Your HVAC Unit

by Hammock's HVAC

When preparing for severe weather like a flood or hail, there are so many things to do that protecting your HVAC unit can often get left forgotten. But a severe weather-damaged HVAC unit can be an expensive problem to discover after a storm. Here are a few tips for preparing your unit for severe weather, as well as information on how events like hail, flooding, and lightning strike may damage your unit.
In all severe weather scenarios, you should turn off your HVAC unit and cut power to the unit and the thermostat to ensure it’s not trying to run while in a storm. Doing so could increase damage to your unit and also risk damaging the rest of your electrical system in your home.
It may also be a good idea to pre-cool your home before a severe storm hits, since you should have your unit off and could possibly lose your power during the storm. This will ensure that you stay cool throughout the storm. Close your blinds and curtains and keep windows and doors shut to keep the air in the house cooler.


Hail can dent or bend the thin metal slats that control air flow out of the unit. If air flow is restricted, the unit has to work harder to dispel heat from inside the system. Hail could also damage the condenser coils, the wiring, or the refrigerant tubing, which could be dangerous to your family and pets if it begins to leak. Very large pieces of hail can even dent or crack the fan blades located inside the unit, which will cause it to wobble or potentially shut down the whole system if the wobble is bad enough. Over time this will cause much more extensive damage if not repaired immediately.
To protect against this possibility, turn off the unit and protect it by covering it with plywood before the hailstorm arrives. Make sure to weight down the plywood with sandbags or very heavy stones to make sure it doesn’t go flying if winds pick up.


Flooding is a risk during hurricanes or extreme rain storms. A flood can cause extreme damage to the HVAC electrical components inside the unit, which will likely cause it to need to be completely replaced. Even a heavy downpour without flooding can cause damage to your unit if it is sustained long enough, but you are most at risk once flood waters reach a foot high.

To protect your HVAC from potential flood damage, try stacking sandbags around the unit like you would for a door or window on your home. Some sources recommend covering the unit with a tarp, although it won’t necessarily protect it from flooding. It could also be a breeding ground for mold and mildew in your unit if not removed immediately following a storm. If you live in a flood-prone area, you should consider having your HVAC unit installed on an elevated platform or even a second floor of your home. This will greatly reduce your risk of flood damage to your unit.

Lightning Strikes

During any storm, there is a risk of lightning strikes. Electrical surges from lightning strikes can cause serious electrical damage to your home and to your HVAC unit. This is why it’s so important to cut power to your unit before a storm.
For more information on lightning strikes or preparing your home for a storm, check out Trane’s recent blog “6 Ways to Prepare Your A/C for Storms“.

Assessing the HVAC Damage after a Flood

After the storm passes, your first priority should be to remove any debris surrounding your unit and try to clear any standing water in the area as best you can. You want your unit to dry out as quickly as possible. Check for physical damage to your unit, but if you had serious flooding (over a foot deep), get the unit checked by a professional before turning the power back on to the unit. Running a flood-damaged unit can cause issues to your entire system just like running it during a storm, so it’s best to get the green light from a licensed HVAC technician first.

Check out our other recent blogs