Hvac contractors and techs who service rooftop units may sometimes long for the good old days, when the condenser coils they had to clean were simple slabs. A new design is not quite as simple as those slabs, but in terms of size and efficiency, it’s better. And it is easy to clean.

The goal of the new design is to have coils cleaned more regularly. Make that easier to do without losing efficiency or increasing size, and you’ve got something.

Trane’s latest light commercial rooftop product line, Precedent, features a new condenser coil design that meets those requirements. The hybrid slab/multiple single-row coil is a solution to size, cleanability, and efficiency requirements.

According to Jim Wallin, marketing and sales team leader, “We were developing a brand new unit, so we started with a clean sheet.” The new coil design was on the customer and designer wish list — but how to simplify the coil design without increasing unit size?

Unit cost, limited space on rooftops, and the existing footprint of old (replacement) units also had to be considered.

COIL-CLEANING PROBLEMS

Condenser coils must be cleaned a minimum of once a year, depending on the environment. “If coils are not properly cleaned and maintained,” states Trane, “dirt and debris can build up, resulting in possible nuisance tripping and a reduction in capacity.” If the coils are difficult to clean, this raises the cost of maintenance and may discourage customers from getting their coils cleaned as often as they should.

According to Wallin, any unit with multiple, single-row formed coils presents cleaning problems. There also are gaps in between rows where layers of gunk can form, said Wallin. Cottonwood trees, for example, can create a big mess for these coils.

“In order to clean them, you have to remove the top of the unit” — potentially a two-person job — “pull the coil apart, and rake out the gunk.”

Pulling the coil apart and putting it back together creates its own potential problems. “There’s a 90-degree bend in coil,” Wallin explained. “When single-row coils are bent individually, the coil inside has a different radius than outside, and the fins don’t line up.” The coils won’t get the same kind of heat exchange as they were designed to achieve.

The problem with most slab condenser coils, Wallin said, is that they require a bigger footprint. “We wanted a small unit with the cleanability of slab coils.” This resulted in the design of the hybrid, multiple-row slab coil with a single-fin pack and multiple, single-row coils.

CONTRACTORS LIKE IT

The single-fin pack helps ensure that fins line up evenly in the slab coil, according to the manufacturer. At the bend of the coil, permanent spacers create a divergent gap in between the rows, making it easier for service technicians to remove dirt and debris.

And because the coil is slightly raised (3/8 in.) off the base pan by pads, the water and debris freely run out of the unit.

The new design simplifies maintenance, the company said. One service technician should be able to clean the coil without removing the top of the unit. The goal, said Wallin, was to get that service time down to 30 minutes.

“When we designed that unit, we used a team of customers for feedback,” said Wallin. “They all really liked the new coil design” because it cuts the manpower and time required to clean the coils.

The new coil design will eventually go into Trane packaged units up to 25 tons that currently have formed coils, said Wallin. The company also is planning a program to replace formed coils in existing units, he said. More information will be available through the manufacturer and its distributors in the future.

Publication date: 12/17/2001