Single Stage vs 2 Stage w/ variable speed Furnace

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Old 09-13-16, 04:27 PM
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Single Stage vs 2 Stage w/ variable speed Furnace

Hi. I am shopping for replacement of my 22+ year old furnace and AC. I got various quotes from local companies and quickly discarded high efficiency options - my house is small and so is my utility bill, it will take me 15 years to break even for a high efficiency unit. And I don't expect to stay more than ~5 -6 years in the house.

So I am choosing between a regular 80% 1-stage furnace and 80% 2-stage with variable speed. Both are by American Standard. The second option is 1200$ more expensive.

I am guessing the advantage of 2-stage is that the temperature in the house will be distributed more evenly. With current old unit it is very uneven. However, I am interested in your opinions and whether you think 2-stage with variable speed is worth extra 1200$. Would appreciate your advice. Thanks!
 

Last edited by sergojin; 09-13-16 at 05:03 PM.
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Old 09-13-16, 05:03 PM
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Have any of the companies suggested fixing the ductwork? That is more likely to fix an uneven house.
 
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Old 09-14-16, 06:13 AM
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No, nobody suggested to fix ductwork. I can make the temperetaure more even by closing vents downstairs and keep them open upstairs, but its still not perfect. I was hoping 2-stage with variable fan will make the situation better as the blower will be running constantly at low rpms. But I am not sure how effective this is and whether it is worth the money. The difference in price tags is pretty substancial.
 
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Old 09-16-16, 12:54 PM
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2-stage isn't normally about distributing more even air through house but about minimizing temperature swings and noise.

What happens when you change the thermostat fan settings from auto to constant on? If you get a furnaces with an ECM motor you won't draw much electricity so constant on could be a cheaper option. Standard motor is PSC for reference.

I assume they are quoting a 2 stage a/c compressor with this as well?
 
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Old 09-18-16, 06:25 PM
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No furnace on earth fan fix ductwork.

If you don't have enough supply upstairs or unbalanced loads you would have to fix that.

The full variable speed blower furnace can make balancing easier.

The variable speed motors automatically compensate for ductwork, meaning that when you close vent dampers they ramp up to maintain the same airflow.

With a regular blowers move less air when you close vents.

The 2-stage furnace actually moves less air on low than high so so distant rooms may get less flow.

The other advantage is energy savings -> you can keep the fan on all the time using as little power as a 100w light bulb. That can help compensate.

You can lock a 2-stage on high fire if you're buying it for the variable speed motor.

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With respect to efficiency, keep in mind that natural gas is dirt cheap now.

the price will have to go up and over 15 to 25 years the 90%+ furnace will have a lower total life cycle cost in any climate which gets real winters.

In canada we can't get mid efficiency furnaces any more, and even if you could it would be a terrible idea.

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When it comes to efficiency,
 
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