Site Bite: Ruptured U-bends in a Frozen Water Coil

As winter rolls in, we often get calls about frozen water coils. This past week, we visited a New York City condo complex where the water had frozen inside a Dunham-Bush® unit, causing the u-bends to rupture. It's a problem that can lead to expensive repairs or even full coil replacements if not handled quickly.

The unit in question was a 2-row hot water coil and a 4-row chilled water coil, both using 5/8" copper tubing. Because of its location, it used 100% outside air. When the temperature dropped below freezing, the dampers should have closed to prevent cold air from entering. But in this case, the freeze stat wasn't working properly, so the dampers stayed open. That allowed the water inside the copper coils to freeze.

When water freezes, it expands by about 9%, which puts immense pressure on the tubes. In this instance, the pressure was too much for the u-bends, and they cracked under the stress. It’s a classic example of why freeze stats are so important — they act as a safety net against such damage.

To Repair or Replace? That is the Question.

In this case, we ended up replacing the entire coil, but that’s not always the best option. Sometimes, damaged u-bends can be repaired using brazing, a process where two metal parts are joined by melting a filler metal. Whether to repair or replace depends on several factors:

• Accessibility: If the damaged u-bends are on the back of the coil, it's easier to braze them than if they're on the front.
• Urgency: If the unit is critical to the building’s operation, brazing is often the faster and more cost-effective choice.
• Age of the coil: Older coils may not be worth repairing, especially if they’re nearing the end of their lifespan.

If you're dealing with a water coil or any other type of coil that’s been damaged, we can help. Email us for a quote today. We specialize in custom and OEM replacement coils for all makes and models, no matter how old or unique your system is.

Stay warm, and stay protected from the cold!