Replies

1. 
   paul42 | Aug 31, 2006 11:50pm | #1

   I think that a two stage furnace can be more comfortable than a single stage - most of the time you will only need the lower 'speed' setting. 

   However, the best that it will do is 90% efficient at turning natural gas into hot air in your house.  I'm sure there will be some minor differences, but a two stage furnace doesn't improve it's efficiency on the low speed setting.

1. 
   DanH | Sep 01, 2006 12:06am | #3

   The two-stage is a lot quieter, if it stays on low. Of course then you get used to that and you're unnerved if it comes on high, even though high may be quieter than your old furnace.

   If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison

1. 
   kayaker | Sep 01, 2006 12:59am | #4

   but over the corse of a winter which will cost less to run the two stage or the normal funace?

1. 
   DanH | Sep 01, 2006 01:03am | #5

   I suspect that depends more on other details about the furnace.
   If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison

2. 
   DanH | Sep 01, 2006 12:03am | #2

   I am amazed at how much electricity a variable-speed DC motor appears to save over a standard 2-speed AC. Something to consider if you tend to run the fan to circulate air when the heat or AC isn't on.

   If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
3. 
   rjw | Sep 01, 2006 01:10am | #6

   Jim Davis, an expert on combustion analysis, says the 2 stage burners are very inefficient on the low setting

   The variable speed blowers are said to provide energy savings in their elec use.

   ---

   Fighting Ignorance since 1967

   It's taking way longer than we thought

1. 
   kayaker | Sep 01, 2006 01:21am | #7

   so less efficent on low for burning fuel and more efficient just for the electric fan.  sounds like I should keep the extra 600$ in my pocket and use a normal 90% that most people are familar with and use to.

4. 
   danski0224 | Sep 01, 2006 02:06am | #8

   A two stage furnace will not save you any significant amount of money.

   It is designed for longer run times on low demand heating days for improved comfort (more air circulation).

   A variable speed furnace will save you money in heating and cooling season on your electric bill.

   A properly sized furnace will save you money.

   If you go two stage to save money on gas, you will be disappointed.

   Spend the money on more insulation/caulk/etc.

5. 
   ClaysWorld | Sep 01, 2006 03:33am | #9

   I vote for upgrade for a couple of reasons. If you can look at VS 95%+. Sound,comfort, efficiency and the tax credit. And More of the same if you are doing AC also.

6. 
   Tim | Sep 01, 2006 03:30pm | #10

   First, there are multi-speed, two stage 90+% furnaces and then there are variable speed, two stage 90+% furnaces. The variable speed unit will save some electricity, depending on use. I operate mine with constant fan year-round. The VS unit ramps from "ventilation speed" to low fire speed, to high fire speed and to cooling speed, if in a system with cooling. The multispeed unit starts the fan at one speed for low fire, a second speed for high fire and a third speed for cooling. If you have the fan switch in the "on" vs "auto" setting it will run at either low fire speed if the thermostat is set for heating or the highest speed if the thermostat is et for cooling. The main reason for going two stage is comfort and consistency. A properly sized unit will be able to heat your home under the worst case conditions. The fact is that those conditions occur less than 1% of the time. So the two stage furncae will run most of the time on low fire, which as one pointed out, is less efficienct from a combustion standpoint, but not by a significant amount. In other words your 94% AFUE furnace will not operate at 85% on low fire, maybe 90 or 91%. I don't have good numbers on that. OTOH, the variable speed furnace is very quite and provides a more consistent temperature control. The two stage unit will not save gas. The VS unit will save electricity, possibly. From a comfort standpoint, I highly recommend the VS two stage.

1. 
   kayaker | Sep 02, 2006 12:28am | #11

   Thanks guys for all of the help and insight!

1. 
   DougU | Sep 04, 2006 02:18am | #12

   What brand are you putting in?

   I'm in the market for a new furnace and I'm trying to get a good idea on what brand to buy.

   Doug

1. 
   rjw | Sep 04, 2006 05:22am | #13

   >>trying to get a good idea on what brand to buy.Accepted wisdom is that it is more important to pick a good heating contractor.

   Fighting Ignorance since 1967

   It's taking way longer than we thought

1. 
   DougU | Sep 04, 2006 05:27am | #14

   I'm installing this myself so there will be no heating contractor.

   When I add the air conditioning there will be a contractor but that wont be until next summer.

   Doug

2. 
   kayaker | Sep 05, 2006 01:47am | #15

   Doug,  I was given a bid with a Bryant 93% gas funace.  And I understand that this is a very good brand.

1. 
   DanH | Sep 05, 2006 05:10am | #16

   We're happy with our Carrier dual stage, variable speed unit so far. Have only had it since late last winter, though, so have no long-term experience.
   If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison

2. 
   Stuart | Sep 05, 2006 05:14am | #17

   I just had a 93% Bryant furnace and central A/C installed a week ago.  Interestingly, when the furnace tech started it up and tested it out he determined it was actually running at 94% efficiency.

3. 
   kayaker | Sep 05, 2006 11:11pm | #18

   I think I am going to go with the same funace

4. 
   jrnbj | Sep 07, 2006 06:14am | #19

   man, he saw you coming ;-)