Latest Discussions : HVAC

Jim from Ohio

06:38PM | 11/23/01
Member Since: 11/22/01
2 lifetime posts
The furnace in our home in SW Ohio has a cracked heat exchanger, requiring a replacement. We interviewed several contractors we consider to be reputable in order to determine the best alternative.

Many of the contractors have recommended a two-stage furnace (preferably with variable speed) to save energy on moderate-temperature days, as well as to reduce the temperature fluctuations in the house. What we don't understand is how temperature fluctuations in various regions of our two-story brick house can be reduced, as we will still have just one thermostat in a central location (first floor living room) which will control the activity.

Also, one reputable contractor recommended a single-stage furnace, stating that his experience is a two-stage furnace in a two-story house with our layout (pretty typical) doesn't work effectively. He offers a two-stage model (with the typical increased price tag), so he doesn't have the incentive to steer us to one stage because of a limited offering.

Could someone offer a simple explanation of the benefits of two vs. single stage furnaces? Is a two stage always more effective (in a two-story home)? Is a variable speed two stage always superior (neglecting the price differential)?

Need a quick response, as our current moderate temperatures are not expected to last. Thanks!

Jim from Ohio

05:27PM | 11/25/01
Member Since: 11/22/01
2 lifetime posts
Thanks for your feedback. It sounds like the two-stage, variable speed option is a favorable alternative.

This presents some additional concerns:
1) The manufacturer for our quote on the two-stage, variable speed furnace is Trane. I'm not an HVAC expert, but I believe Trane has a solid reputation. I'm wary, though, that their reputation is built on commercial business, not residential (I don't personally know of any people with Trane furnaces at home). Do you know if they have a substantial customer basis in the residential sector?

2)If we decide to pursue the other primary alternative (Carrier), their quote for a two-stage, variable speed furnace was substantially higher (over $900). How likely are they to negotiate and come down on price (ideally to match the other offer)?

Thanks for your input.


06:08AM | 10/07/10
Member Since: 10/06/10
1 lifetime posts
I am NOT a professional HVAC person at all, just a home owner. I too am in the process of purchasing a furnace and have done a lot of research. Two or Three Stage furnances are nice as far as comfort, but have nothing to do with efficiency. I personally am purchasing a single stage 95% efficiency furnace and have made sure I have adequate insulation in my attic, caulk windows, doors, etc. For me, it was a $1000 more for the two stage and I didn't think it was worth the extra money. As long as you get a high efficiency furnance with a good warranty, you should be fine. Nothing against two-stage furnances, I personally do not think the benefit is worth the extra cash.


09:11PM | 10/10/14
The video on the bottom of the page is "broken".


02:46PM | 08/04/16
I am looking for a good thermostat that will work e=with my 2 stage furnace which to choose can anyone help also reasonable price


09:43AM | 02/05/17
I live in Bracebridge Ontario Canada.
We are about to build a new home and our builder uses only the single stage furnace (he will get a 2 stage we just pay the extra). We have a 2 stage furnace in our home and like it but since it is only just over a year old have not given it enough time it see the cost savings of it.
Is it really worth the extra cost for the 2 stage.
Thanks for the info.


01:21PM | 07/31/18
I'm building a new one-story home in SE Iowa with a full walk-out basement. Main floor is just under 1400 sq ft. The basement has in-floor heat and I will use a wood stove upstairs when I can as I love wood heat. Given my additional heat sources would a one-stage furnace be a better choice than a two-stage for my main floor heating? Savings on purchase of a one-stage is less than $500, so although the cost is a factor, it's not a driving force in my decision.


12:48PM | 05/02/21
A single stage 3 ton furnace at rated 96% efficiency is just as efficient as a two stage 3 ton rated at 96% efficiency, by definition. They both waste 4% by definition, no more, no less. To claim otherwise about the furnace is false, correct?

Operating cost would be the same. Capital cost would be less for single stage.

To raise the indoor temperature from one set point to another, a specific amount of heat needs to be transferred. A single stage running 100% pushes out more heat for a shorter period of time, and, a two stage operating at say 80% pushes out less heat for a longer period of time. Once again, by definition of simple math. If the single stage used the same amount of time as a two stage then you would have a case, but it doesn’t so this claim is null.

Blowing at 80% compared to 100% should be no different in ECM noise for both so noise is really determined by air flow through ductwork. A 20% lower air flow won’t make that much difference on average, because the ductwork is design for 100% on the 2 stage anyway. The owner won’t know the difference unless the two different units were swapped inside his specific home and a decibel meter used to measure the difference so this claim is really disingenuous. If it was 50% or less then one could consider the claim.


12:54PM | 08/13/21
Actually a single stage is much more reliable and cheaper to repair.
The higher the "efficiency rating" the more the furnace relies on very expensive and easily damaged electronics so when components fail it will become very expensive.
Don't fall for these minuscule efficiency savings ploys.
Instead opt for the most basic model and it will not only cost you far less up front but down the road as well


11:31AM | 09/10/21
How did this situation turn out? And for Bob Vila, does your advice re: staging still hold for 2021? Thanks.

Post a reply as Anonymous

Photo must be in JPG, GIF or PNG format and less than 5MB.

Reply choose button


Post new button or Login button