Single Stage, Two Stage, Modulating?

Single Stage, Two Stage, Modulating?

Single Stage, Two Stage, Modulating? What furnace is best for me?

These are questions Cross Heating are asked numerous times by clients and unfortunately some contractors have been misguiding people as they haven’t invested in any seminars, readings or upgrades since they got their license up to 30 years plus ago.

Natural Resources Canada (NRCan), Heating Refrigeration and Air Conditioning Institute (HRAI) and numerous manufactures have information to read that would give a customer in need of a furnace or air conditioner fact based results and recommendations.

At Cross Heating we attend many different seminars across North America about new technology and building science. We were also one of few contractors across Canada that were contracted by NRcan in 2018 to assist in the development of a sizing guideline for air source heat pumps. I hold an RASDT (Residential Air System Design Technician) and RHDT (Residential Hydronic Design Technician) certification as well that involves Heat Loss/Gain Calculation, Air System Design, Integrated Combo heat, Commissioning of new systems, Ventilation and Hydronic Radiant design.

A furnace that will provide the best heating effectiveness, lowest operating cost, longest life and most customer comfort can be selected by a Home Comfort Advisor or technician that is well informed with the NRcan “Master Planning & Decision Guide for Natural Gas Mechanical Systems” as well as HRAI CSA guidelines for F280-12 Load Calculations and Manufactures specifications.

A single stage furnace will meet the minimum requirement of heating your home. Typically they will have shorter run times but result in less comfort, higher operating cost and a shorter life as they start and stop numerous times during a heating cycle and operating in transitional state (least efficient) much of the time. The consistent heating and cooling of the heat exchanger and starting and stopping is why these units usually do not last as long and will have a shorter or less attractive warranty.

A two stage furnace can provide heat at two different levels. This way the furnace will operate longer and in the steady state (most efficient) more of the time. With a more consistent heat, comfort is improved for the occupants. Since the cycling time is longer, there are less starts and stops as well that prevents unnecessary ware on the equipment. Two stage furnaces are usually provided with a better warranty than a single stage as the operation is easier on the components.

A modulating furnace is the ultimate in comfort, efficiency and reliability. These furnaces will provide down to as little as 35% of the maximum heat capacity depending on the manufacturer. The run times are even longer than the two stage furnaces at a lower heat that is matched better to your homes heat loss on those cool fall or spring days and nights. Depending on the outside weather the modulating furnace can provide any amount of heat from the 35% to the 100% of capacity and all points in between. These furnaces will have the best warranty as they are capable of lasting the longest.

Other things to consider are filtration, controls and blower motors (Variable ECM vs. X13 ECM). Your comfort adviser should consider duct static, return air placement, duct leakage and end of line rooms to determine the best solution for you. Ultimately you will want about 3 different solutions with the pros and cons of each to make the best decision for yourself.