Dual Stage vs Singe Stage Furnace?

Question

Hi, I plan changing my furnace. I have a 20 year old trane 40,000 BTU. I live in a condo, Approximate lot is 2516SF. 2 bathrooms, 2 bedrooms, kitchen, living room, dining room. My gas bill on the average is $130 in the winter per month in Jersey at average 74F. I assume the old one is Single Stage, works well, but I have to change the evaporator coil, so it would cost me less, to change both furnace and evaporator coil. I have 3 guys come out, and listen to what they want to propose. I plan getting an 80% AFUE, all recommend 80,000 BTU, that has 64000 BTU output, dont quite get, why all say I need 80000BTU, only one person said I need 60000BTU. Now I have to choose, single vs 2 stage furnace? I know lot of people told me its great in a house, the furnace runs longer at lower speeds etc. But I live in a condo, the difference between rooms is at max 3F which is the living/dining room since its big, compare to the other rooms, so if its 74 everywhere, the living room is 71F.

So the temperature difference is not an issue here. Some people told me Dual Stage is annoying, since the thing runs most of the time. I dont know if its true, false? What type should I get, and would a 2 stage make some difference in a condo size living home, as fas as expenses. Currently I spend around $120-$130 a month on the coldest month with 74F average heat? And whats better, Variable Speed Fan vs. Single Speed Fan? or whats the differences?

Answer 1

most effecient save the most money

Answer 2

Dual Stage Furnace

Answer 3

The dual stage has a 2 speed blower motor. When the temp is near the set point it comes on low speed and the higher speed is when there is a big difference between the room temp and the set point temp.
If your Trane 40K has done a good job for you then why do you want to go bigger? On the coldest day, you can tell how often the furnace cycles on and off and how well it holds the temp. If it has done a good job, then you can go up a little but you don't want to get too big. If so, it will cycle on and off much more. About the 2 speed, most of the time, mine will only kick in on low speed, so if you want to save some money then get the single speed.
Try lowering your temp setting, that will make a difference on the bill, too.

Interesting to know where in Jersey you are, that has 74 deg winters. I have relatives in Tom's River and it gets colder than that. Been to Cape May and yeah, it was colder than that too, and it was only Fall. lol

Answer 4

thats alot of question all at once- I'll try to give a few answers-

1. every furnace has two ratings, input and output so an older 85,000 furnace probably had an input of 80k and an output of 60k. So if the new furnace is rated at 64 output, it probably has an 80k input (80% efficient).
2. a single stage furnace has a two-stage gas valve, and its true that they typically run longer to keep more even temperatures and save energy by not having to turn on and off as much.
3. Finally- a variable speed fan adds itself to the mix, and it helps with efficiency by slowing down the air that blows through the heat exchanger allowing the air to pick up more Btus as it moves through the furnace.

A variable speed fan will reduce the overall sound level of the system since it will be runnign at slower speeds.

Unfortunately all these options raise the cost of the system. It really comes down to one thing- how long do you plan on living there. If you are only going to be there 1-2 years, get the cheap one because you'll never recover the up front cost in energy savings, and it really won't make a difference in the resale value of the condo.
If you are planning on staying there 5-10 years, then by all means- get the most efficient one you can afford, because you'll recover the money in monthly savings.

Answer 5

if it ain't broke - don't fix it