One-stage versus 2-stage Carrier furnace


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Old 01-20-07, 08:31 PM
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One-stage versus 2-stage Carrier furnace

I live in an 1800 sq ft ranch built in 1972 in downstate NY. I am planning to replace the original furnace before it dies on a cold winter's night. I find that the current unit doesn't give great comfort: The room toasts-up nicely when the blower is on, but it cools down quickly, and then (naturally) we feel cold until the next hot flash.

I had a guy come out to give me a quote on a new furnace. He said he did not think I would need a 2-stage unit. He thought that the new one-stage units would give me more even heat than my current unit. The difference between the one stage and 2 stage is $800.

My main concern is comfort for my family, so I'd gladly paid the extra 8 if it means a noticable improvement in comfort. But if the difference between in comfort would be marginal, I'd just as well not spend the extra $$.

The current unit is a Tappan 112,000 BTU. My wife is home with the kids, but she's out a lot. When the house is empty, we turn the thermostat way down (60 degrees). Also, we turn it way down at overnight. Keep it to about 68 during the day when we're home.

Any opinions on the matter are appreciated.
 
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Old 01-20-07, 08:42 PM
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Oh yes, you will notice the COMFORT incresse with a two stage furnace.

I'd get another bid if this last guy said you didn't need it.

With a two stage furnace on a two stage t-stat will give you the best comfort. Make sure they do a Manual-J (Load Calc) on your home to get a correct sized furnace.

I used to have an old 115k furnace, and replaced it two years ago with a new 60k Trane two stage XV90 furnace with a two stage t-stat.

With the furnace running in 1st stage, it will run longer.. With the longer run time, the air has a chance to get "changed" out in the living space to even out with other parts of the home.. I have a 1700 sq ft split home, I run our heat at 68 when we are home, and 60 at night/gone. The room temps are -/+1 degrees from each other. NIce thing about the two stage is quietness.

Another things the furnace won't be "oversized" on mild winter/fall day when you just want to get the chill out.... So no host blast that you are feeling now on your current system.

I think it is worth the few extra bucks!
 
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Old 01-20-07, 09:09 PM
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Thanks. Any thoughts on a high efficiency unit (90+). He wants $500 more than the 2 stage. Worth the extra $$?
 
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Old 01-21-07, 06:03 AM
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Your saying it's going to be $1,300 more to go from a singe stage 80% to a 90% two stage furnace?

I'd get a few more bids.

90% will be worth it in northern states where our winters are longer and colder.

Are you planning on being in the home for a while?
 
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Old 01-21-07, 07:25 AM
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Honestly, I'm not sure if the high efficiency is one or 2 stage, but I will find out. I assume you are suggesting more bids because $1300 is a large premium for the H.E. Is that why?
 
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Old 01-22-07, 03:36 PM
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Well, I have 2-stage, and I honestly believe it is a gimmick. So what if it blows slow for a few minutes before it blows at regular speed? They'll tell you all about humidity control and such, but I honestly believe that the humidity/comfort issues are correct in theory, but if you did a blind test (like Pepsi and Coke), you will not be able to tell one from the other. That's just me, though.

As another example, they use the "On cold days, you will not get a blast of cold air when you turn on the heat because the unit waits to full heat before ramping up the blower, etc." Let's talk about that blast. Tell you what.... Google around and find the CFM (cubic feet per minute) a typical 6 inch and 8 inch duct will carry. You can calculate loosely here and there and figure that "cold blast" is a matter of seconds - like 5 to 8 seconds. It's nothing.

Anyway, I'm no pro. Just a handy person who installed 2 of these 2-stage systems. They work fine, so I'm happy. But there is no real noticeable comfort improvement. They are supposed to be quiet, but that seems only true when the low speed blower is going. At full speed, they are like any other. And they must all blow at full speed. That is how they are programmed. The low speed is only there for start-up and a few minutes after.

If you are loose with money and get buyer's remorse easily, get the 2-stage.
 

Last edited by Jeff Matthews; 01-22-07 at 03:51 PM.
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Old 01-22-07, 03:55 PM
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I don't recall right off hand since it been 2 years. I think I paid $2,000 for my furnace to be installed.

Jeff,

Sounds like your furnace is running off on a timer, so yeah it's worthless to have a 2-stage furnace that is not tied to a two stage t-stat.. When you pay for a nice two stage furnace you should get a matching T-stat.. Don't fall for the "Timer works just as well as a 2-stage t-stat" story.

Just for kicks I tried it for myself, I disable the 2 stage to a timer on mine for a few days, I noticed that the furnace cycled more often, and comfort went down. our bedrooms is over a tucked under garage, and noticed the bedroom and basement familyroom became 6 degrees cooler than the other rooms. Put it back onto two stage, bedrooms is 2 degrees cooler, and the family room is same is upstairs. With the t-stat controling the stages, the furnace runs longer in in low fire, with longer run, the air has a better chance to "exchange" in the room.
 
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Old 01-22-07, 04:11 PM
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Wink

I find that the current unit doesn't give great comfort: The room toasts-up nicely when the blower is on, but it cools down quickly, and then (naturally) we feel cold until the next hot flash.
Id say check the windows and the insulation you have in the home here first and see what you can do to hold the heat in first. Then get3 bids for the same job Make sure they run a heat loss on the home . That 112,000 btu in for 1800sq ft I think is high for even up where you are
 
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Old 01-22-07, 05:35 PM
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Thanks for the replies thus far.

Ed, the advice regarding windows/insulation makes sense. Window replacement is in the cards. Also, I know that the walls are under-insulated. When we bought the house, there was one wall in the "L" shaped living/dining room that had wood paneling, while the rest of the area had drywall. We decided to remove the paneling and put up drywall. When we pulled the paneling down, it revealed R-7 (2 1/2") fiberglass insulation. We supplemented the insulation on that wall, but I imagine the rest of the exterior facing walls are insulated the same way. Any suggestions on how to supplement the existing insulation without pulling down drywall?
 
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Old 01-22-07, 05:45 PM
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Wink

It would be to hard to blow cellulose in it with that 2 1/2" in there now. In the long run Id take the drywall off and do it right. With a R 13 if 2X wall
 
 

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