Getting the Most From a High Efficiency Furnace

 Lennox G71 MPP 95% Efficient Furnace

    

     If you've ever shopped around for a new or replacement furnace for your home, you know how confusing it can be. After all, how many times during your life do you replace your furnace? Once? Twice, maybe? Gone are the days of 50% efficient furnaces when half of the energy consumed by the furnace heated your home and the other half heated the great outdoors. Also gone are the days that you could replace your furnace for under $2,000.

     For today's technology, with furnaces reaching nearly 98% efficiency, replacing your furnace can cost upwards of $7,000. If you're spending that amount of money, shouldn't you make sure that you're getting the efficiency that you paid for? Of course. So here are some tips to ensure that your furnace investment does what you want it to.

A Lennox G61V high-efficient
furnace. Notice the two white
plastic pipes on the right
hand side of the furnace - the
intake and the exhaust.

 Tip#1

    Ensure that you get a 2-pipe system. By this I am referring to the vent pipes attached to the new furnace. One pipe is for the exhaust, the other is for air used by the furnace for the combustion process. With a two pipe system, the furnace draws cold, unheated air from the outside to burn with the gas then exhausts the waste products back outside through the second pipe. With a one pipe system, the air used by the furnace for combustion is drawn in from your home - that's air that you have already paid to heat.

     Remember, the efficiency rating of your furnace only refers to the efficiency of the internal operation of the furnace itself, and not to the overall efficiency of heating your home. You're wasting a lot of heat and money without having the second pipe. A 92% high-efficiency furnace with only one pipe can cost you nearly as much in energy costs as a mid-efficient furnace.

Tip #2

     Do not over-size your furnace. Bigger is not better. In fact, it can be worse when it comes to efficiency. If a furnace has excessive much heating capacity it can heat the home too quickly thereby never running long enough to reach its proper operating temperature. Think of this in terms of how your car operates before the engine is fully warmed up on a cold morning.

     Many times we have seen installers sell the highest profit furnace instead of the most suitable one. Here is a rough formula that you can use yourself. Every furnace has a rating plate on it stating the BTU input. If, for example, your furnace's rating is 80,000 BTU and has an efficiency of 50%, then the heat input into your home is 50% of the 80,000 BTU's, or 40,000 BTU's. If the new furnace you are considering is 95% efficient and has an input rating of 50,000 BTU's, then the 50,000 BTU input results in 47,500 BTU's of heat input into your home (50,000 x 0.95). That's comparable to the old, 80,000 BTU furnace.

     This is a rough guide only as it does not take into consideration other home upgrades such as new windows, added insulation or draft proofing having been done that will reduce your heat loss and lower the required furnace output.

     If you are being offered a furnace that does not have a BTU output calculation that is relatively close to the BTU output numbers of your current furnace, make sure that you get a logical answer as to why. Sometimes there are valid reasons for this and a qualified heating mechanic will be able to explain his reasoning.