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Installing a Condensing Gas Furnace: What to Consider

Furnace shopping and installation don't have to be a major headache, but it does take time and attention to detail. “Measure twice – cut once”, you can apply this same wisdom when shopping for and installing the right furnace for the perfect in-home environment.  Measure your needs. If you live in Chicago, northwest Indiana or southwest Michigan, you should be looking for a condensing furnace with an annual fuel utilization efficiency of at least 90 percent. Condensing furnaces are highly efficient because they use a secondary heat exchanger that draws heat out of the exhaust gasses. The recaptured heat is then sent into your rooms. In noncondensing furnaces, this heat escapes up the flue. If you're planning on installing one of these furnaces, there are a few things to consider.  These high-efficiency furnaces have updated installation requirements that differ from older, mid-efficiency models.

Pick the Right Efficiency

The efficiency you need depends on how much you heat and how many years you plan to stay in your home.  A higher AFUE indicates greater efficiency. Although 90 percent AFUE is the lowest you're likely to find among condensing furnaces, their efficiency can go all the way up to 98.5 percent. Naturally, the higher the efficiency, the more expensive the furnace--but the faster you'll recoup your investment through reduced energy expenses.

Size matters

To find your home's heating load and required system size, your contractor should use the Air Conditioning Contractors of America's Manual “J”. Some contractors cut corners and “guestimate” the system size based on a home's square footage or the size of the old system. This can result in an oversized system and that’s money you just don’t need to spend. Oversizing also leads to uncomfortable temperature swings and frequent cycling thus wearing-out a system’s components and costing you more in repairs.

Location, Location, Location

Installation location is your next concern. Most condensing furnaces are sealed-combustion systems that use only outdoor air to burn fuel. These are more efficient and safer than atmospheric combustion models. Even so, properly locating your unit upon installation is necessary to ensure your furnace doesn't take in indoor air. Keep it away from the laundry area and anywhere else chemicals are used. Indoor air contains particles of household chemicals, such as cleaners and air fresheners, which quickly corrode a condensing furnace's components.

Let it Breath

Non-condensing furnaces release hot flue gasses and require a chimney made of brick, masonry or metal. A condensing furnace has cooler flue gasses and do not need a chimney. Their flue gasses can be vented through ABS or CPVC pipes. These vents are most commonly run through the building's side wall. The end should be at least 12-inches higher than expected snow levels. Extending the vent through the roof is another option but this is more common in new construction.

Most residential furnaces use a direct vent (two-pipe) system. One pipe provides fresh outdoor air for combustion, and the other carries away combustion exhaust gasses. When the furnace is installed in an un-conditioned area such as the basement, there may not be a need for a pipe to supply outdoor air.

Take Care with the Condensate Drain

Condensation is a bi-product of a condensing furnace's secondary heat exchanger as the flue gasses remove the heat.  This condensation contains particles which, if not properly drained, can cause damage to the furnace components or other metal. To drain correctly the furnace must be installed level or tilted slightly forward. If it's tilted back or to the side, condensate can build up and damage the furnace.

A special condensate drain is also required. This is usually a CPVC pipe or tube that empties into a floor drain. The drain must be installed carefully so it doesn't become kinked or blocked. For flexible tubing, adding a rigid PVC elbow where the tubing joins the furnace helps to prevent kinks. Be sure not to force the tube into the floor drain to allow for proper discharge.

Does your Contractor make the Cut? Choose Your Contractor Wisely.

Correct installation is essential if your furnace is to reach its maximum efficiency and run as reliably as possible. Work with experienced NATE-certified contractors whenever possible. Get in touch with one before you start furnace shopping, so you'll know what features to look for.

If you're considering investing in a new condensing furnace and want to ensure that it's installed correctly, contact a Comfort24-7.comdealer in the Chicago area. We also serve homeowners in northwest Indiana and southwest Michigan.

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