Why Does it Seem Like My Furnace Can’t Keep Up In Bitter Cold Weather?

When it comes to a heating and cooling system, many factors can lead to unsatisfactory performance.

From a failing component to the design of the system, there are many variables to consider. This is why proper diagnostic processes are so important. Today, we will look at one of the most common problems – a furnace that can’t keep up with the coldest winter days.

In central and northern New Jersey we are guided by the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) to design and install heating systems for a low outdoor or ambient temperature of O degrees Fahrenheit and still be able to provide 70 degrees indoors.

At the time this article was written, my home in Piscataway the temperature hit 5 degrees below zero. That’s probably the coldest I’ve ever seen it at my home in the 25+ years that I’ve lived there.

What does this mean to your heating system? In theory, a furnace with a capacity identical to the heat loss in your home would run continuously at 0 degrees to maintain 70 degrees indoors. For every degree the outdoor temperature fell below 0 degrees, the indoor temperature would also drop one degree.

However, seldom does the furnace capacity equal exactly the heat loss of your home. Furnaces are typically sized in 20,000 BTUH increments. For example, many furnace manufacturers sell furnaces that are 60,000, 80,000, 100,000, and 120,000 BTUH. If your home’s heat loss is 84,500 BTUH most manufacturers will recommend the smaller size furnace to ensure that it vents properly. An oversized furnace can have problems venting properly resulting in condensation in the flue which can damage your chimney and your home.

So, with a heat loss of 84,500 BTHU and furnace capacity of 80,000 BTUH the furnace in your home will be unable to provide 70 degrees indoors before the temperature drops below 0 degrees.

This is similar to what happens in the summer when the outdoor temperature exceeds the design standard of 92 degrees. The system wasn’t designed for temperatures above 92 degrees and the temperature inside your home starts to climb.

So if your furnace seems like it’s not keeping up when the temperature outside gets below a certain temperature, the system design could have something to do with it. Of course, any unusual behavior such as irregular noises or the system frequently turning off and on could indicate something more serious that warrants a furnace repair appointment. As always, feel free to give us a call and we’ll be sure to make sure everything is operating as it should be so you can rest easy.

Bobby Ring
President of Meyer & Depew


READ: 5 Tips for keeping your home warm this winter, and save you money.


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