Home & Garden Columns

About the House; Checking Out Your Furnace for the Winter

By Matt Cantor
Friday September 01, 2006

This is a good time of year to take a look at our furnaces. One reason is that that’s true is that servicing can lead to repairs (or, Oh No, replacement) and this can take your furnace off line for some days and it’s better to face such an eventuality when it’s sunny and warm than when you really need the heat. Also, the best service folks (HVAC or Heating Ventilation & Air Conditioning technicians) are busy when the winter hits and everyone’s turned on their furnace for the first time only to discover something that’s gone awry. In fact, you’ll have your pick of the best HVAC folks if you get them at this time of year. 

But before we get to professional servicing, let’s see what you can do for yourself. I’ll start with common mid-efficiency forced air heating and then will devote just a little time to small gas heaters before we’re though. 

If you have central gas heat, which is what most of us, on the West Coast have for heat, you probably have a mid-efficiency furnace. This is large box, often found in the basement, garage or under the house. This unit usually has two metal doors on the front face and a set of visible burners somewhere near the middle of the unit. 

These units heat air which is fed to them through large ducts or tubes which are generally between 6 and 14 inches in diameter. One side usually has one very large duct which draws cooler air in from the house and the other end of the unit will have a trunk and branches that lead out to the various extremities of the house. The analogy of a circulatory system, like a bloodstream is apropos. 

If you have this sort of system, there are a number of things you can do yourself to help your forced air heating system to operate well. If you have the gumption to do so, I’d start by examining every part with the layman’s eye. Crawl or walk around so as to see every bit of the ducting that’s not buried in the walls. If a grill can be removed from the floor or wall with ease. Take it off and look inside. Check to make sure that the ducts or tubes aren’t loose from the fittings at either end. 

A good way to check is to turn the furnace on or run the fan-only setting. Some but not all furnaces are wired this way, although nearly all can be wired this way. A nice upgrade is to have your HVAC person upgrade the wiring to allow for the fan to be run without running the furnace. In this way, you’ll gain a secondary cooling and cleaning feature. 

The simple act of running air through the house provides some level of cooling, albeit minimal and the operation of the fan setting also carries air though your filter system, thus providing some cleaning of the air, and thereby the house. This is especially true for those who smoke or have animals. A really good filtration system, such as an electronic air cleaner can reduce the amount of cleaning you have to do inside, although this is not its intended function. 

When you run the fan or furnace, you’ll be inflating the system and it will be easier to see where air blows out of leaking ducts. Don’t be surprised if you crawl under your house and find a duct completely detached and heating the crawlspace (the mice really appreciate it! Be sure to look for the tiny beds and lawn furniture near the open duct). I see detached ducting and partially disconnected ducting all the time. 

Regulations now in force in our state now require most communities to repair any ducting with more than 15% leakage when any other servicing or work is being performed. It’s important that this be done by a professional since improper repairs can result in foreign substances being drawn into the living-space. Half of your furnace system is a vacuum cleaner and half is a blower. 

The vacuum cleaner half may have one or two large ducts running through the crawlspace (most do) and if detached or damaged in this space, can draw damp air, mold, fungus or other wondrous elements into the house. 

This can be happening now if the ducts are damaged, so it’s best to have a professional check for leaks. Nonetheless, many openings can be easily identified by an intrepid explorer with a bright flashlight and guts to examine all side of each duct.  

Next, look inside the registers or grills in the floors or walls or ceilings (most are in floors around here). Many grills simply slip out of the “boot” but some older ones have two or four screws. This is well worth the effort for the small change alone. Maybe you’ll find that missing earring or 53 cents. You will almost certainly find dirt and debris and this is your chance to vacuum out what you can readily see. 

The cold air intake (that’s the big one usually found somewhere near the middle of the house, often in a hallway or dining room floor) is often the main place that you’ll strike it big. You’ll find toys, Monopoly houses, more change and lots of dirt, dog hair and other splendid fortunes. Cleaning this out will help your air supply and the life of the furnace. 

Next it’s time to remove the doors to the furnace and vacuum there. Be careful with the vacuum in all these places, ducts are often quite fragile and it’s not too hard to rip through them with a bare vacuum wand. Don’t be too surprised if you find dead critters in the blower compartment of the furnace. If you note signs of corrosion in the furnace, it’s a very good idea to get it cleaned and examined. 

Make sure the blower (usually a squirrel-cage type fan) moves freely, be sure it’s turned off before you meddle. Older units have bushings along the axle that can be oiled (and should) but most modern ones do not. 

Some furnaces have anti-nitrous oxide rods that are mounted just above the burner (these burners are easily identified when the unit is running because the flames come right out of them just as in your gas oven) and these are often bent or burned through. If you see these pencil sized rods falling down on the burners or burned through, definitely call it to the attention of your HVAC guy or gal. 

Take a look at the flue which comes off your furnace (that’s the very hot pipe that comes off the furnace and heads toward the roof or chimney (usually about 4” in diameter) and make sure that nothing flammable is resting on or very near it. Double wall flues are better in this respect and are usually identified by a mark stamped upon them. They’re called B vents and look fatter than a single tube of metal that was more common 40 years ago. 

The last item we’ll tackle on the FAU (forced air unit) is the filter. If you have a common 1” disposable filter, change it now and often. 

These should be changed at least twice a year, although the cleanliness of the house atmosphere can make this vary quite a lot. A large dog may necessitate replacement 3 or 4 times a year. Filters are cheap and good ones are a bargain. I recommend the school of pleated filters that are usually electrostatically charged. Filtrete is one brand but many hardware stores carry a store brand for much less. 

The $8 filter is will worth it when you consider your lungs. These filters can capture very tiny harbingers of disease including mold spores, virus and pollen. They’re not perfect but they’re a big step above the common $2 filter. If you have a fiberglass mesh “reusable” filter, I’d suggest tossing it. They catch dust bunnies but not too much more. 

If you’re really interested in your health or have a household member who has allergies, consider installing a higher quality filter such as a media filter system (mid-priced upgrade), an electronic air-cleaner (higher priced upgrade-about $800) or a combination system. Some even have negative ion generator built into them designed to precipitate solid matter out of the indoor air. 

No matter what kind of gas heater you have, it’s a darned good idea to have an annual professional examination of the unit. It’s usually less than $200 and well worth it. 

As promised, here are a couple of words on gas wall and floor furnaces. While I’ve written more extensively on this in the past and won’t get deeply into these lower duty heater, I will say that cleaning of the accessible parts of any of these is wise and can reduce burned dander and other particulate in your home. 

If you have a furnace that doesn’t have a thermostat consider an upgrade. A furnace that can be left on full bore with no control related to temperature is unnecessarily dangerous and an upgrade isn’t ridiculously expensive (It’s just expensive). 

Make sure that nothing flammable is kept on or near the wall or floor furnace. I was once inspecting a rental unit with a small wall furnace mounted low on the wall. This was a direct-vent model and, while these are generally safer than most, the tenant had, in all her glorious hippyhood, chosen to burn lots of candles on top of this unit and the inside was coated with paraffin. 

We also had the de rigueur madras just above on the wall and various gods and goddesses arrayed beside said candles. As Harrod Blank’s license plate says “OMYGAWD.” Even Ganesha can’t help everyone. 



Got a question about home repairs and inspections? Send them to Matt Cantor, in care of East Bay Real Estate, at realestate@berkeleydailyplanet.com.