You can't fix what you don't measure. That's why Rob Falke, president of National Comfort Institute (Sheffield Lake, Ohio), recently introduced SERâ„¢, a new field rating system for installed air conditioning and heating system efficiency.

SER, CSERâ„¢, and HSERâ„¢ are acronyms for system efficiency ratio, cooling system efficiency ratio, and heating system efficiency ratio. The tests depict the ratio of factory-rated equipment Btu to actual field-measured Btu, Falke said.

"These new diagnostic procedures enable the HVAC industry to present an easy-to-understand, quantified snapshot of system performance to their customers with less than one hour of field-testing," Falke explained. HSER is determined by measuring system-sensible Btu. CSER uses system-total Btu in the calculations.

"Heating and cooling SER ratings take the focus off the efficiency rating of a single component of the system - the equipment - and place the attention of the consumer where it belongs, on the system as a whole," Falke said.

"We [as an industry] tell our customers we are installing an 80-percent efficient system," he continued, "The equipment is an 80-percent efficient, 100,000-Btu furnace that's rated in the laboratory for 80,000-Btu output. When it's installed in the field, the system only delivers 40,000 Btu into the building. But we still call it an 80-percent efficient system."

The company's new rating method enables contractors to identify measured SER by measuring the delivered Btu (in this example, 40,000) and dividing it by the 80,000 rated Btu. This gives a SER rating of 50 percent.

"Without SER," Falke said, "we haven't been able to tell the whole truth. It's like a doctor telling a patient, ‘We have a cure for cancer ... but the success rate is only five percent.' Likewise, we once said, ‘We have a 90-percent-AFUE furnace' ... but we can now finish the sentence, ‘but your SER rating is only 50 percent.' After we renovate and balance the duct system, the SER should exceed 90 percent."

Falke said NCI has created, tested, and proven this system rating. "It includes all the necessary test forms and procedures to enable contractors to deliver this field-measured system efficiency ratio to their customers."

In this home, flex duct pressed between the furnace and structural framing was one of many installation errors.

Case In Point

He offered the following example: "Betty is a delightful, 79-year-old homeowner who displays wit and determination that exceeds most people half her age. Five years ago she had her retirement home built at the edge of the wetlands. Her comfort complaints have been dismissed by her general contractor, who assured her she had the best high-efficiency system money could buy. She has an 80-percent efficient, 60,000-Btu furnace.

"A pair of Performance-Based Contractorsâ„¢ arrived at her home recently and, in one hour, field measured the HSER of her system. A short interview was conducted about the home's comfort and the history of the system."

Equipment model numbers were recorded and some measurements were taken. Then came 10 minutes of "basic field engineering to estimate room-by-room airflows," Falke said.

The contractors took airflow readings using a recently calibrated commercial capture hood and airflow traverses. System static pressures that were recorded included total external static pressure, filter, coil, and fitting pressure drops.

A system inspection revealed:

  • An uninsulated return duct system, with flexible, uninsulated duct running 105 feet through a 42 degree F attic. Gaps were found in the connections.

  • A 180-degree transition 6 inches off the top of the slab coil.

  • Duct pressed between structural framing, reducing its capacity more than 50 percent.

    The readings included:

  • Supply airflow of 642 cfm (76 percent of required airflow).

  • Static pressure of 0.82 inch with a fan rated at 0.50 inch. "Nearly half the system pressure was due to the transition off the coil," Falke said.

  • A 24 degree rise over the system (average supply register temperature minus average return grille temperature).

  • A 12 degree temperature difference between rooms.

    Recounted Falke, "Betty made a fist and swung it through the air and said, ‘I knew I was right! This system hasn't worked since day one.'

    "Finally, we can provide our customers with a true picture of their systems' performance. We can move past the questionable practice of quoting equipment efficiency as system efficiency. This will enable us to focus on and sell systems that we design, fabricate, and install one at a time. We will move away from selling boxes that have become a fixed-price commodity and establish integrity as we discuss system efficiencies with those we serve."

    For more information, contact Falke at 800-633-7058 or

    Publication date: 06/28/2004