York’s Affinity™ modulating furnace.

Most of us grew up with what seemed like a scary furnace that lived in the basement. It made creepy noises when it started up, and usually overheated the house before it finally shut off. And forget about energy efficiency; many furnaces manufactured before 1992 had AFUE ratings as low as 60 percent.

That has all changed. Over the last decade or so, manufacturers have incorporated numerous innovations into their furnace offerings in order to improve energy efficiency and comfort. Higher AFUEs and two-stage gas valves have ensured better energy efficiency, while variable-speed blowers have increased the level of comfort for occupants.

The latest innovation is the modulating gas furnace. Manufacturers say it maintains constant temperatures while delivering improved comfort, quieter operation, and reduced energy costs. All three of these items are extremely important for homeowners looking to invest in a premium furnace.


York - A Johnson Controls Company, introduced its Affinity™ modulating furnaces about two years ago. The furnace features a fully modulating gas valve that circulates airflow to closely match the amount of heat needed at any given time. Unlike traditional single- or two-stage furnaces that are staged at fixed input rates and often over- or undershoot the desired temperature setup, resulting in varying temperature swings, modulating furnaces adjust the gas input, inducer speed, and blower airflow.

“The furnace modulates in 1 percent increments from 35 to 100 percent,” said Mickey Smith, York brand manager, Johnson Controls-Unitary Products. “Comfort is drastically improved due to the modulation and is extremely quiet due to the ECM blower motors. The furnace is somewhat intelligent as it continues to narrow the operating band to eventually operate at the same rate heat is leaving the home. It may run longer, but it will run longer at a reduced rate, consuming less energy.”

Several built-in safety mechanisms offer increased customer satisfaction, noted Smith. “For example, if the homeowner is away for a period of time and the product senses there is a blocked flue or some other restriction, the product automatically reduces the level of operation to a safe operating level to continue conditioning the home. Many other technologies will automatically shut off.”

In addition to being energy efficient and quiet, the Affinity modulating gas furnace is also easy to install, maintain, and operate, said Smith. “There are no additional sensors, wires, or controls needed. In fact, it may operate using a traditional single-stage one-heat/one-cool thermostat.”

The sensors and controls automatically compensate for air supply and exhaust variations, wind gusts, and long vent runs. The modulating control employs multiple feedback loops to dynamically adjust the operation of the furnace and optimize the overall temperature control.

Affinity modulating furnaces, as well as modulating furnaces from sister brands Coleman Echelon™ and Luxaire Acclimate™, are available in both a constant-speed blower configuration and a variable-speed blower configuration, and are supported in all positions (upflow, downflow and horizontal). All models within the three modulating series meet the 95 percent-AFUE level required for the Energy Policy Act of 2005 (EPACT), so the units qualify for a $150 tax credit.

Carrier’s Infinity™ IdealComfort™.


Carrier also launched its own modulating gas unit. The Infinity™ IdealComfort™ modulating gas furnace can provide up to 3.5 times tighter temperature control than most standard furnaces, providing significant energy savings, the company said. In fact, Carrier estimates that consumers can save up to $345 a year in energy costs versus previous Carrier single-stage models.

“We utilized a throttling valve on the outlet side of a two-stage gas valve,” explained David Spaeth, product manager of heating products, Carrier. “The flow is regulated to 40-, 65-, and 100-percent rates to accomplish three stages of heat. Our patented technology then monitors the needs of the home as the unit cycles and adjusts its operation accordingly.”

With traditional furnaces, homeowners might notice a change in temperature just before their furnace turns on and just after the furnaces turns off. With this furnace, there is no noticeable change because it maintains the temperature within 0.3°F of the set point, the manufacturer said. The furnace remains on low speed for 83 percent of its operating time, automatically adjusting speeds to acquire the desired temperature.

The IdealComfort modulating furnace is also quiet. Carrier conducted sound tests against competitive units and this furnace outperformed each of them by a noticeable margin, said Spaeth. “In addition, they are as easy to install as the Infinity 96, requiring no special training or procedures to install,” he said. “There are also self-diagnostic tools in the control board that help troubleshoot the furnace.”

As you might expect, consumers will pay a premium for the modulating furnace technology compared to current premium heating technology. However, the value of the new furnaces outweighs the price and should help mitigate price objections. As Spaeth noted, “The energy cost savings, tighter temperature control, and quieter operation are a combination of features that no single competitive furnace can provide. When clearly shown the advantages this furnace has and the benefits it provides, I think consumers will be very comfortable with paying the difference.”

For more information, visit www.carrier.com and www.yorkupg.com.

Publication date:11/19/2007