Technology is making it possible for HVACR companies to ensure the most comfortable indoor environments possible. In our newest blog post, we dive into new technologies on the rooftop that help curb indoor humidity, make installations more effective, and can even monitor performance and usage logs by connecting to the internet.
When Carole King and Gerry Goffin wrote “Up On The Roof” in 1962 — recorded for hits by The Drifters and James Taylor, among others — they envisioned the roof as a sort of placid getaway. In HVAC, the world of rooftop equipment doesn’t quite resemble an oasis of calm up above the bustle, but that’s a good thing.
Some increasingly common capabilities and customer demands are trickling upward to the equipment in this area, while other progress continues in terms of rooftop unit (RTU) performance and better, cheaper maintenance. In at least one case, technology seems to be making a true leap in terms of what kind of equipment one might find (or install) up there.
A tour of rooftop trends begins with the natural pattern of technological advancements getting less expensive as they gain acceptance — which, in turn, leads to yet more acceptance.
Modulation is enjoying that phenomenon now, according to Eric Newburg, director of commercial product management, Commercial and Applied Ducted Systems, Johnson Controls Inc.
“Modulating gas heat, modulating compressors, and modulating hot gas reheat … the advancement of controls has made modulation more cost-effective,” he said.
Dedicated outdoor air systems (DOAS) have increased their usage in general and their name recognition over the last decade, but Chris Stocker, commercial rooftop product manager at Daikin Applied, sees one consequence.
“Most buildings’ largest humidity load comes from the ventilation air brought into the occupied space,” said Stocker. “With the rise in popularity of DOAS, rooftops are now the primary source of building dehumidification.”
Most equipment-related savings for owners tend to come as increases in performance efficiency. Newberg noted an exception that those minding the facility budgets will likely welcome all the same.
“There is growing desire for airflow systems on rooftop units to eliminate belts, to reduce the constant adjustment and replacement requirements,” Newberg said.
As a result, he sees direct-drive fan systems growing in popularity.
Another issue comes from more of a ripple effect following an earlier trend. As variable-frequency drives (VFDs) become more common in RTUs, that presence is shedding light on possible compatibility and sizing issues with power configurations serving the equipment, according to Newburg.
“VFDs are generally sized using balanced legs in a Y power configuration,” he said. “When delta power configurations are used, VFDs must be sized accordingly. When rooftop units are designed, it is based on balanced power.”
Thus, he concluded, delta power installation might lead to VFD failures.
CONTROLS AT THE GATEWAY
The mention above of controls as the key factor in extending the use of modulation was only the beginning. Stocker explained how inverter compressors in a modern RTU like his company’s Rebel® can keep the refrigeration circuit running in order to keep moisture from getting reintroduced into the space because a compressor has turned off with a wet coil.
“Advanced DOAS control in smart rooftops can aid further in dehumidification by independently controlling the evaporator, removing moisture down to a set dew point,” said Stocker.
“This further allows the use of free heating from the hot gas reheat coil to independently control the discharge to the desired dry bulb, resulting in a perfectly cooled space and optimum occupant comfort.”