This site is best viewed using Mozilla Firefox browser.

Environment

2007-11-01 10:18:00

Fall fracas…firing up the furnace

QUESTION: I’m getting ready to light my furnace. What should I be thinking about to keep from blowing myself up?

ANSWER: The changing of the season to fall…October each year is the month here in Kansas when we begin to think of those cold winter days when the leaves are off the trees, the grass probably won’t need another mowing until spring, and the sun goes down sometime around 5:30 in the afternoon here in the middle part of the country. It’s also the time when we begin to think about firing up that furnace that has been sitting idle all summer. Before we all had central heat and air conditioning, fall was the time of year when those folks who heated with pot bellied stoves ordered in their winter supply of coal or wood…laying in a good supply so that they didn’t have to worry about running out in the middle of a real cold spell. Later, lots of rural folks turned to heating with propane fuel, and had those tanks filled up in the fall. With most homes in urban and suburban neighborhoods now being on natural gas, and having furnaces that supply heat to the entire home, you might say we have things a little better than they did back in the "good old days". A good, well maintained central heating unit can have a normal lifespan of 35 or 40 years, and in the last couple of decades, those newer high efficiency furnaces can reduce your heating costs as much as $50 to $75 a month or more. The key words in this paragraph are "well maintained".

It’s really easy to just ignore your mechanical equipment in your home, because if it seems to be performing its job as you expect it to do, you don’t usually think about things like having it checked out by someone to head off potential problems…but that is one of the smartest and safest things you can do. Having those furnace burners and heat exchangers cleaned and checked will tell you if they’ve deteriorated any, and if you haven’t seen that deterioration first hand, it can be pretty surprising. Some furnace burners and heat exchangers, over a period of time, begin to flake off. The metal can begin to flake off in layers, and eventually, the burner will become blocked or rusted shut. Another problem that can happen with the heat exchanger is that it may develop stress cracks. Stress cracks in a heat exchanger form from the hundreds of times over the years that your furnace heats up and cools down. Any stage of this process can produce a dangerous situation for the occupants of that home, pursuant to last month’s column on carbon monoxide poisoning, or at the very least cost you additional money to heat your home. A professional heating and air conditioning technician can perform an examination and advise you as to the age and condition of your particular furnace.

Now, let’s talk about the pilot light.

Unless you have a newer furnace with an electronic or electric ignition system (in this case the furnace should light automatically), you probably have what is known as a standing pilot. That is a system where the pilot is always burning and is used to light the main burner. There are two basic systems used with standing pilots. The first is the thermocouple system that uses two dissimilar metals to provide electricity to hold open the pilot valve on the gas valve once you light the pilot burner. The main valve is operated by 24 volts from a transformer. The second system is called a Milli Volt system (there are very few of these systems still in operation on residential furnaces). The pilot heats a larger device that generates a bit more electricity, enough to operate the main valve. The theory is that if the pilot is not lit then the main burner won’t work. This system is used a lot on wall furnaces, free standing heaters, RV furnaces, and swimming pool heaters because they will work without utility power.

If you have a problem where the pilot won’t stay lit after you release the button or knob, the thermocouple may need to be replaced. If you replace the thermocouple and you still can’t get the flame to stay on, the pilot flame is probably weak or the thermocouple is not positioned properly in the pilot flame. A weak pilot flame may be the result of dirt, lint, or rust that has gotten into the pilot burner. If this seems to be the case, be sure and call a professional heating & air conditioning company to have this problem examined. Newer furnaces will have intermittent ignition systems that use an electronic control made by Honeywell, Robertshaw, Johnson controls, Fenwall, or White-Rodgers to light the furnace automatically and detect that it is lit. When one of these controls fails you have no choice but to call your heating and air conditioning company to have it replaced. The "Ole" standing pilot is reliable, but intermittent ignition systems offer both reliability and automatic lighting of your furnace. If you have any doubts at all about whether you are able to check your furnace out safely, call in a professional to do this...that’s the smartest and safest thing to do...More interesting information for you next month…