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.