Do you know how old your rooftop units are? If they haven’t been replaced since flip-phones were in style, they might be running on borrowed time. With the median expected useful life being 15 years, you might find yourself in a situation of needing to purchase a rooftop unit this spring, and a lot has probably changed since the last time you spec’d one.
While regular preventive maintenance is incredibly important to extending the service life of a rooftop unit, there are many components that deteriorate and will eventually fail (like most major mechanical equipment). Fans, motors, compressors, valves, and dampers will wear out. Electronics and processors degrade. As a rooftop unit wears over its lifetime, its capacity to deliver heating, cooling, and ventilation degrades with it. It’s not uncommon for a unit’s cooling capacity to be 15% lower toward the end of its life than when it was new.
If you haven’t purchased a rooftop unit recently, you should know that controls, optimization, and energy efficiency are continually improving. And what may have been a premium upgrade years ago, or not even available, now often comes standard. Options you can reasonably expect include:
- Controls that are web-based and Wi-Fi connected, allowing you to monitor and change setpoints from anywhere.
- A dehumidification cycle to remove moisture without needing to cool, improving comfort and indoor air quality.
- Hail guards with cottonwood screens that protect condenser coils from being damaged or getting packed with cotton. They are attached by snaps and magnets and can easily be washed with a hose.
- A CO2 sensor to automatically draw in more (or less) outside air according to the actual need in the space. This saves equipment wear, reduces energy consumption, and improves indoor air quality.
- A powered exhaust fan can be added to control building pressure, especially while in economizer mode, to prevent over-pressurizing the building and hanging doors open.
With that said, purchasing a new rooftop unit isn’t a minor investment. For a new packaged rooftop, the installed cost is generally between $1,800 and $2,200 per ton. That would be in a situation where an identically sized unit would be swapped out and reconnected. If additional options and modifications are required to meet the current needs of the space, the cost goes up from there. With that in mind, here are three things a facility manager should take into account when buying a new rooftop unit:
- Lead time, especially if your new rooftop unit isn’t a standard package. Standard units are generally readily available in town and can be replaced on short notice. If not, it must be specially built to order, which can take 4 weeks or more. Advance planning becomes much more important when you have non-standard rooftop units.
- Compatibility with the replaced rooftop unit. Manufacturers are constantly updating and upgrading their lines of equipment. It is unlikely that a replacement rooftop unit will be identical — even if it is the same make and model. Make sure the power configuration, controls compatibility, ductwork, and gas connections all match so that the installation can be as smooth and inexpensive as possible.
- Have reasonable expectations of what you’ll get for your budget. In many respects you get what you pay for. There are dozens of manufacturers vying to produce the lowest-cost unit available to gain customers as the lowest bidder. That is accomplished by using less expensive parts and materials, thinner-gauge and lower-grade metals and plastics, simpler construction prone to leakage, fewer features, and options that make it harder to maintain, etc. While the marketplace will always create a place for the lowest cost possible, you should be aware that the lowest initial cost will often not be the lowest total cost of ownership over the life of the unit.
Don’t forget, a preventive maintenance plan is essential to keeping a rooftop unit running at its peak… even a newer unit. Yale Mechanical has been installing new HVAC systems since 1939. If you have any questions about what equipment is right for your building, we’d be happy to talk.