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Optimal Installations in Any Season

Temperature variations can wreak havoc on equipment function and parts, requiring mechanical engineers and maintenance technicians to carefully consider how systems are selected and installed for optimal wear and use.

Keep these guidelines in mind if your project will face challenging conditions in the winter or summer.

Winter Weather

HVAC equipment and related piping are systems that can be sensitive to extreme seasonal weather. Ed Carlisle, P.E., vice president at R&W Engineering in Portland, Ore., notes that during winter, freeze protection is crucial on pipes or equipment exposed to outdoor temperatures. “To provide good indoor air quality, commercial buildings need to incorporate outside air even when it’s very cold,” Carlisle says. “Fortunately, there are a lot of ways to address the issue.”

Mixing outside air with the indoor air before it reaches HVAC equipment is one method to prevent equipment freezing. If you’re running outdoor air across heat coils, you can use a small heater to keep the coils operational or freeze-protect your coils by increasing the velocity of water through the coil. While some engineers use systems that shut off the intake unit during winter to eliminate cold air intake, that method compromises indoor air quality.

Engineers working with plumbing and piping in large, open-air structures should take special precautions to prepare their systems for extreme temperatures. In a parking garage, for example, it’s generally not feasible to heat the entire building to keep pipes from freezing. Placing heat trace (or heat tape) on all pipes exposed to freezing temperatures is the simplest way to protect them. If a significant amount of garage pipe is exposed to extreme weather, adding glycol to the system is another option, as long as the delivery isn’t used for domestic water.

“You have to know the application and what can be done with the different options,” Carlisle explains. “Once you’ve designed a system you know will work, it’s important to implement commissioning and staff training so everyone knows how to operate it most effectively.”

Solar hot water systems are another application where pipes can be exposed to seasonal variations in temperature. Solar hot water panels are particularly vulnerable to the weather in intermittent load conditions, says John Alger, P.E., manager of engineering and commercial projects at Green Cove Springs, Fla.–based Alternate Energy Technologies.

“Solar water heating works best if you have a continuous load, such as healthcare or institutional projects like prisons, so the system doesn’t sit dormant for an extended period of time,” Alger says.

Closed-loop solar hot water systems use heat exchangers to transfer heat from a fluid to the water, and using a glycol base for the heat transfer fluid prevents freezing. Another option is a drainback system, which allows water to drain out of the collectors and exposed piping for freeze protection.

Summer Solutions

While freezing temperatures can create winter challenges for plumbing systems, engineers must also prepare their projects for summer’s sweltering heat. On projects with solar hot water heating, drainback systems provide a year-round safeguard. During summer months, the drainback systems provide overheat protection if you turn the pumps off when the temperature soars.

On flat-roofed commercial projects, Alger says your collectors’ tilt-mount strategy should provide optimal performance and help prevent overheating. Ideally, the best tilt angle matches the degree of your latitude, but you can mitigate excessive heat gain by raising the tilt angle.

“You need a tilt-angle compromise for the time of year you want to use the heated water the most, but it’s important to recognize that higher-temperature water from a solar collector is not more efficient,” Alger asserts. “Shoot for 120- to 140-degree water, using a gas or electric water heater to bring the water up to the temperature you need. Also, smaller systems work more of the time to deliver heat, so the return on investment is better with a faster payback.” .

Whether you work in a climate with frosty winters or sweltering summers, ensuring the systems you install perform well in any month is essential to meeting your client’s expectations.