WHAT IS HAIL AND WHAT IS CONSIDERED DAMAGING SIZE HAIL?
Hail is destructive chunks of ice that falls from the sky causing over $1 billion annually in the US alone. Hail is a form of precipitation that occurs when updrafts in thunderstorms carry raindrops upward into extremely cold areas of the atmosphere where they freeze into balls of ice. Hail can damage HVAC Equipment including condenser coil and cooling tower fill, aircraft, homes, office buildings, cars, crops and more. Hailstones grow by colliding with supercooled water drops. Supercooled water will freeze on contact with ice crystals – The hail falls when the thunderstorm’s updraft can no longer support the weight of the ice or the updraft weakens. The stronger the updraft the larger the hailstone can grow and the more damage they can do. Hail stones generally fall at higher speeds as they grow in size, though complicating factors such as melting, friction with air, wind, and interaction with rain and other hail stones can slow their descent through Earth’s atmosphere. Severe weather warnings are issued for hail when the stones reach a damaging size, as it can cause serious damage to man-made structures and, most commonly, farmers’ crops. Although the diameter of hail varies, in the United States, the average observation of damaging hail is between Quarter Size (1 in) and golf ball-sized (1.75 in).
Top 10 Hail States & Regions
According to the Insurance Journal, the Top 10 States for Hail Damage Include: #1 Texas, #2 Illinois, #3 Colorado, #4 Missouri, #5 Nebraska, #6 South Carolina, #7 Pennsylvania, #8 Iowa, #9 South Dakota, #10 Kansas
Click on image below for closer view
This photo shows a dime, penny, nickel, quarter, small and large marbles and a golf-ball relative to the size of the Hail Master Mesh Openings.
Pea = 1/4 inch diameter (typically non-damaging to equipment and infrastructure)
Marble/mothball = 1/2 inch diameter
Dime/Penny = 3/4 inch diameter
Nickel = 7/8 inch
Quarter = 1 inch — (quarter size or larger is considered severe & damaging to equipment & infrastructure)
Ping-Pong Ball = 1 1/2 inch
Golf Ball = 1 3/4 inches
Tennis Ball = 2 1/2 inches
Baseball = 2 3/4 inches
Tea cup = 3 inches
Grapefruit = 4 inches
Protecting Your Condenser Coils and Mechanical Equipment
All roof mounted and ground mounted machinery and equipment is subject to hail damage. You should evaluate the critical nature of the equipment to your operations and the effects of damage to the equipment for your business. You should consider providing hail protection for this equipment based on the priority of importance to your operations. Equipment such as condenser coils, cooling towers, refrigeration units should be protected. The condenser coil is the heat rejection component of a chiller, rooftop unit and refrigeration unit – it is used to dissipate heat from a production process or from the inside of a building. Refrigerant gas is pumped from a compressor to a heat exchanger unit inside of the process equipment, or air movement system inside a building where it is then sent to the condenser unit located on the outside of the building where the fan pulls air through the coil / fins – as the air passes over the surface of the fins heat is rejected away from the coil and thus removes the heat from the process equipment or inside of the building – after the heat has been rejected, the refrigerant recycles through the compressor and the cycle repeats until the set temperature point is reached. To remove that heat with optimal efficiency, the condensing units typically feature a coil made of copper (which has high thermal conductivity) that is covered with many thin aluminum fins (to provide high surface area). In high efficiency equipment – the coils are commonly referred to as “Micro-channel coils” – where the number of fins on the coil could be double that of a standard efficiency coil in the same footprint. If you think about a coil as a filter, the high efficiency coil is like a high efficiency filter compared to a standard efficiency coil – that means high efficiency coils will have a tendency to foul out sooner between maintenance cycles vs. the standard efficiency equipment – furthermore, it micro-channel coils are impacted by hail, more damage will be done – The irony is that the very unit customers typically pay money for to achieve an energy savings, rarely actually capture the energy savings because the coil fouls out sooner between maintenance cycles which means it runs longer in a fouled condition between maintenance cycles and when they run in a moderately fouled to fouled condition, the very unit which has the capacity of delivering an energy savings actually becomes an “Energy Hog”.
The Key to actually capturing the energy savings one pays for in a high efficiency unit is to protect it in the first place – Protect it from airborne debris (cottonwood seed, pollen, bugs, leaves, etc.) and from hail. Keeping condenser coils clean and protected from hail damage is the single most important thing in proper care and preventative maintenance you can do to ensure you get the most out of your equipment.
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