Skip navigation

Chicago’s Choice Since 1961


24/7 Emergency Service

Chicago’s Choice Since 1961


Althoff Home Services Blog

2 Important Reasons Why Your HVAC Technician Measures Draft

One of the most important aspects of your furnace is how it drafts. When air drafts properly from your gas furnace or gas water heater, spent oxygen and carbon monoxide go up a chimney or chimney pipe where it is dispersed outside your home. As most are aware, too much carbon monoxide in an enclosed area can have tragic results. The importance of proper drafting of a furnace can not be overstated for both operating efficiency and monitoring safe conditions.

How do we know, however, that a gas furnace has the appropriate draft pressure and draft intensity to operate efficiently and safely? It can be done using a furnace diagnostic tool called a draft gauge. A modern draft gauge is a digital device that helps a technician conduct a draft test, measuring aspects like draft pressure, draft intensity, backdrafting, and the percentage of oxygen and carbon monoxide. A draft test is a critical part of any furnace maintenance or tune-up.

How Does a Draft Gauge Work?

A differential pressure draft gauge measures the difference in the pressures of the air flowing inside a chimney or ductwork and that of the air on the outside. A draft gauge will not tell our technician what the specific cause of the draft issue is, only that there is some issue causing a draft pressure problem. The technician will then rely on his training, experience, and knowledge to discover the source of the draft problem.

Common Causes of Poor Drafting in a Furnace

A variety of causes can create poor drafting for a furnace. These can include extremes in indoor and outdoor temperatures, blockage of the vent pipe, loss of a vent or chimney cap, high winds, and others. This can cause poor ventilation or backdrafting, causing harmful gasses to spill back into the home.

While a slow or diminished draft can cause safety issues, excessive drafts can create inefficiencies in your furnace. If too much air is delivered to the burner fan, it can result in air leaking into the heating plant. This reduces the amount of CO2 and creates an increased stack temperature. This, in turn, results in poor efficiency of the furnace.

Why a Draft Gauge is often Used with a Combustion Analyzer

A draft gauge is often used with combustion analyzer so a technician can better determine the extent of the poor drafting and see its effect on the air in a room. Depending on the readings of the combustion analyzer, it can direct the technician to check on potential issues with the heat exchanger. It can also be an indication there may be a gas pressure issue or a combustion air problem. A high carbon monoxide parts-per-million reading on a combustion analyzer could also mean that a furnace is recirculating flue products and re-burning them in the heat exchanger. We’ve created a brief video on how a draft gauge and combustion analyzer work together as terrific furnace diagnostic tools in helping direct us to the heart of many furnace issues promptly. This saves us time and you money.

Monitoring Safe Conditions

Many Chicago area homeowners will schedule a fall furnace check-up or tune-up to head off potential maintenance issues in the winter and to ensure their furnace is operating at peak efficiency. Another important aspect of an annual furnace check-up, however, is that it monitors the safety of you and your family. It determines the quality of the draft of your furnace, making sure it is operating without putting harmful gasses back into your home.

If you have yet to have a furnace maintenance check this fall, we invite you to contact the well-trained, well-equipped team at Althoff Industries.

Comments are closed.