High efficiencey gas furnace-worth the investment?


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Old 11-22-10, 02:15 AM
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High efficiencey gas furnace-worth the investment?

I'll probably be replacing my 30 yr. old or so gas furnace in the near future. Is it worth it to spend the extra $1,000-$1500 or so for a 90% efficiency versus a model less efficient? I was talking to an HVAC tech the other day who is not a contractor & he told me that is in his opinion high efficient furnaces are not worth the trouble. He claims that parts are more expensive, they are more unreliable, they have to be serviced every year to run efficiently, that it can takes years to recoup the initial investment, etc. etc., you get the drift. My home is well insulated, I have all new energy star replacement windows, & I'm wondering if I should purchase an 80% efficiency model. I'm not sure if I can afford a high efficiency model anyway & anything I have installed has to be more efficient than the relic that I have now. My home is approx. 1200 sq. ft. What do you guys think?
 
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Old 11-22-10, 08:07 AM
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In my honest opinion, high efficiency furnaces will COST you more money to own and operate in the long run. The modest gas savings will be offset by annual preventative maintenance requirements, as well as high unplanned repair costs. My mother has a 15 year old Heil 90% condensing furnace, and she's had to have the heat exchanger replaced twice. Even though the heat exchanger is warranted by Heil, the labor is not. Even the mid-efficiency furnaces are not that reliable. I had a 80% York gas furnace installed in 1994. From then until 2006 (when I replaced it), I had to have the computer board, blower relay, flame sensor, hot surface ignitor, and the induced draft blower assembly replaced. The cost of this unplanned repair far outstripped the modest savings from my old 60% efficiency, standing pilot type furnace. With the newer furnaces, you are almost compelled to have a maintenance contract with the installer, which costs upwards of $150/year if you have central airconditioning along with the furnace.

Rarely does one winter go by that my 80% furnace doesn't have a complete failure leaving me without heat, which requires me to call a serviceman, invariabily on weekends or holidays. I was so frustrated that I replaced my furnace after 12 years, which is a far cry from the 30+ years you used to expect from a gas furnace. Like so many newer high-efficiency home appliances, high efficiency furnaces and air-conditioners are trouble prone and have useful lifetimes far shorter than their low-efficiency predecessors. I'd take a 1980-vintage standing pilot furnace and 8 SEER airconditioning unit anyday!
 
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Old 11-22-10, 08:24 AM
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Personally I'd favor a single stage 90% efficient furnace. Manufacturers have been making these for thirty plus years and have generally figured out how to do it.

I do agree that the higher efficiency multi input furnaces tend to have their problems, and I'd avoid those.


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Old 11-22-10, 02:31 PM
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The earlier models of condensing (90+% furnaces) did have lots of problems and especially with the secondary heat exchangers. These problems are mostly just a memory with the latest models.

As for multi-stage burners...they simply have multi-speed induced draft fans and gas valves that have different pressure stages that are electrically selected. My Lennox 80% with two-stage burner is now going into its fourth winter and it has only been professionally serviced once, because a free service one year after installation was part of the installation contract. The ONLY problem I have had is a plugging of one of the hose nipples for a pressure switch. It takes all of five minutes to clear the nipple which I have had to do maybe once a year.

IF you live in an area that has long cold winters the 90+% model will likely save some money but if you live in an area with generally mild winters (like I do) it might take ten years or more to recover the added cost of the 90+% model.
 
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Old 11-23-10, 09:42 AM
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You didn't say where you are from?

If you are in the mid to southern part of the state, then 80% will be fine.. On up north like I am, then 90% is the way to go since heating season are far longer. 80% are a rare thing to see here in Minnesota now days since code requires 90% in new homes.

As for break down, I hate to say this I'm just laughing at the comments that 90% tends to break down more than 80% furnace. The only extra parts on the 90% vs 80% is the secondary heat exchanger.

When I was in the service field, the service calls on them were about equal. They don't have to be serviced every year, and nothing "special" needs to be done.

As for two vs single stage, yes.. there are a few extra things there. but I see no reason for running away from them. I found them to give the best comfort on a cold winter day. Long run cycles allows the house have a more uniform temps though out the house. I have a few family members who owns a two stage, and they are pleased with them along with me.. My equipment is 6 years old, I would never go back to a single stage since I don't hear my 1st stage running.
 
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Old 11-23-10, 11:18 AM
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Excellent advice.
My 60%(at best) Homart(Sears) ceramic cost nothing but a high gas bill every month for 10 plus years......It just sits there and works........Far better than the Honda Accord or the Saab900.
The gas furnace just needs to be cleaned now and again, as does everything else...
Several years ago I lubricated the motor bearings...
BTW, I am suspicious of "service plans"...
Best to switch to coal, cheapest fuel, most expensive installation.......makes some sense.
 
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Old 11-23-10, 11:52 AM
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>



There are additional issues with condensing furnaces in my experience. Condensate leaks, corrosion, plugged drains, failing condensate pumps, frozen drain lines and such add to the problems that 80% furnaces do not have.
 
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Old 11-26-10, 05:16 AM
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Question

Hi

I was under the impression that high efficency furnaces needed to be serviced every year to rid them of rust on the exchanger tubes.
The rust insulates the exchange of heat and lowers efficency ..
or Are furnace manufacturers now building exchangers out of stainless high heat molybdenum metals ? ,

no wonder they cost a lot...

yup, thats why I ask
 
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Old 11-26-10, 05:48 AM
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Routine cleaning of the primary and secondary heat exchangers is not a part of annual maintenance on condensing furnaces.
 
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Old 11-29-10, 02:54 AM
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Thanx for all the responses. Some interesting information. I haven't gotten any estimates yet, & am still leaning towards an 80%. Of course, I can't make a final decision until I get some estimates. I'm on a budget as I just spent 6 grand on a new roof this spring. Can anyone give me a rough idea what it will run me for a furnace, assuming no major ductwork is involved in the install? Thanx again.
 
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Old 11-29-10, 07:16 AM
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Originally Posted by kpg7121
Thanx for all the responses. Some interesting information. I haven't gotten any estimates yet, & am still leaning towards an 80%. Of course, I can't make a final decision until I get some estimates. I'm on a budget as I just spent 6 grand on a new roof this spring. Can anyone give me a rough idea what it will run me for a furnace, assuming no major ductwork is involved in the install? Thanx again.
It's difficult to give you a good cost estimate, as labor charges very greatly, depending on what part of the country you're in. If you're planning on including new central A/C with the new furnace, don't be surprised if a new installation costs you as much as your new roof did. I spent a bit over $5,000 on an 80% furnace and 13 SEER A/C in 2006. No ductwork modifications were needed, except for the transition piece from the new furnace to the existing ductwork. This was for a 2.5 ton AC and 60,000 BTUH furnace.
 
 

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