Do I need a new furnace?
I am a homeowner who is getting pretty confused as to how I should proceed with a heating problem. I will lay out the basic info first and build up to my questions.
House – split level 1,050 sq ft per floor. Well insulated. Single pane windows with storms on all. Frame Construction built in early 1970's. Located in Montana with minus 30 F not unusual. Natural gas, forced air heat. No air conditioning.
We have 15 supply ducts most are 6” but a couple are 5”. Plenty of return ducting.
We replaced the original furnace in 1999 with a 92% Fraser/Johnson that was recommended to us by a local contractor. We also purchased a 1” electrostatic filter at that time.
We washed and cleaned the filter faithfully every 3-4 weeks during the heating season but, over the years, it gradually began to provide reduced flow to the furnace. Of course we didn't realize this and never knew it was a problem until we had the furnace serviced because it was not working properly. The service person quickly diagnosed the reduced flow problem and since then we have used the 1” pleated filters.
A couple months ago we began to have new problems with the furnace. The service tech found that the high limit was bad and after replacment the system is working. However, the Tech told us that we have a number of problems that need to be addressed. This was confirmed by two other service persons, including the owner, of that firm as well as the owner of a second company.
The problems all stem from the fact that both the furnace and the installation were wrong for our house. The furnace they put in is 140,000 Btu which is apparently way too big for our house. In addition, the existing duct work that they connected to was inadequate for the amount of air (both supply and return) that the furnace needed to blow. They told us that the combination of the years of reduced return from the gradually clogging electrostatic filter, combined with the inadequate supply ducting have put a significant strain on the furnace and that it is in the process of prematurely developing serious problems.
They have recommended that we either do some work on the ducting to expand the flow to reduce that strain on the furnace. Or that we replace the furnace with a properly sized one (about 80,000 – 90,000 Btu) which would function properly with the existing ducting.
One more piece of info. We use a programmable thermostat to drop the temp to 60 at night. When the furnace was new it would take 30 minutes or less of run time to bring the house up to normal in the morning. It now takes at least 40 minutes to do the same thing.
1.Is there any way to tell how much life is left in the current furnace?
2.One of the Techs has told us that it is likely that we will crack the heat exchanger and we should be concerned about carbon monoxide. Is this a real possibility and should we be concerned?
We have secured two different bids for new furnaces, each from long established, reputable companies. The first company is recommending a LENNOX Elite 90 2-stage with a Lennox MERV 10 5” pleated filter
The other suggests an American Standard 80,000 92% efficient with a Honeywell F100 Envirocare air filter. However, They also offered that we should consider an upgrade to a variable speed American Standard.
1.Does anyone have an opinion on the different furnaces? I tend to trust the company with American Standard more but I need to know if this is a good product.
2.Should we consider the variable speed system?
We are really torn as to what to do here. If the old furnace is on the way out I hate to spend the money to have larger ducting put in that we will not need with a new properly sized furnace. However, if we are looking at years of useful life from the current furnace I hate to buy a new one.
Any thoughts comments or questions appreciated.
Can the existing FRASER furnace capacity be modified to 100,000 to 120,000 BTUh?
Originally Posted by apistobob
Can you replace the filter housing and use a 2" pleated filter? ( less resistance and a little more flow)
That just might easily get you another 5 years out of the existing furnace.
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It is very likely that the heat exchanger will crack if their is not enough airflow. Lack of airflow can cause the exchanger to reach a higher than designed temperature. That can be checked by sensing CO in the supply with a CO meter. As for a new furnace, American Standard is made by Trane which has the best reputation in the business.
There are a number of ways to determine what solution best suits your needs but unfortunately, there is no way to determine how much life is left in the unit. Typically, the average life of a warm air furnace is 12 to 15-years. Somewhere in that timeframe you usually start to lose parts, one at a time. That can get expensive, like putting new tires on a car with 400,000 miles on it. A typical furnace runs about 1,000 hour per year. If your automobile was driven for 1,000 hours at 30 miles an hour, it would accumulate 30,000 miles per year. Multiply that by 16 (2008 - 1992) and you find your existing furnace has 480,000 miles on it!! So even if you purchase the very best, most expensive system out there to replace what you've got, it's a bargain compared to a new car!
A crack in the heat exchanger is not a death threat. A large hole in a heat exchanger could be dangerous. I'd make certain I have multiple CO detectors in the home regardless of the age of the furnace.
A multi-stage, variable speed unit will deliver much greater comfort than a standard 1-stage unit. The variable speed blower is more energy efficient but the ducts MUST be sized to accommodate any variable speed product or you'll be driven from the home by noise. I'm attaching a document on how to select a good HVAC company. Good luck.
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As above, no way to reliably predict how much longer that furnace will last.
But now while its still working is the best time to get estimates, and look for Factory rebates.
You have some time to select a contractor.
I know it is easy for me to say but it sounds like you should cut your losses and replace it.
As for the Variable speed question. no doubt it is worth the money. actually if your current system was variable 2-stage then the oversiving would not be as big of an issue.
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this is super simple. One...and first and foremost......the furnace needs to be sized to properly heat your home. You don't need the details, but know this...undersized and it simply won't handle the load and oversized and it heats too quickly....we call it short cycling. A properly sized unit starts and runs for a while until set points are reached. Thereby heating the home correctly and getting it's effeciency.
If a contractor even suggested re-doing your (assumed) correctly sized ductwork to acomodate an oversized,older furnace.....then show him the door.
Both Lennox and American Sandard are reputable companies in the trade. As mentioned earlier...Trane is actually made by American Standard.
Anyway, you have the common problem of a bad first install,and are now paying the price. Sad to say, but true.
Myself, I am partial to the A.S. variable speed units. One of my favorites. You can't go wrong with either one of them if they are sized right and installed properly, and you'll be able to reap the benifits of the efficient, variable speed unit with a programable t-stat in the form of rebates. At least in my area....I shouldn't speak out of turn....but I know it sweatens the pot a bit and you'll also be much more comfortable with the right system !
Thanks all for the replies.
Does anyone know if American Standard offeres consumer rebates?
Currently, they don't have any posted on their website.
Talk to your contractor, he may know if any are coming soon.