Variable Speed?

15 years ago

Is a variable speed and two-stage furnace the same thing?

And how important is the difference between buying a variable speed vs. a single speed?

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Comments (8)

veesubotee
15 years ago
Variable speed refers to the blower. It has the ability to ramp up in speed to attempt to deliver the proper air flow. This is useful as your filter clogs, or to an extent, due to duct problems.

With proper controls (thermostat or a/c), it can cause the furnace (air handler) to slow down when dehumidification (in summer) is needed.

A two stage furnace has 2 fixed heat inputs. Fan speed may be by a variable unit or a multi-speed (descrete low or high) unit.

There are also single stage furnaces that are available with a variable speed blower.
jill1273
Original Author
15 years ago
Which is better for energy efficiency (ie;gas bill). Since
I'm putting more money out front, will I really
see a big savings, or will the single stage be sufficeint
I'm looking at a Lennox G61v Elite model. It offers
a Variable speed motor and 2 stage heating. The other
models we're considering is the Lennox G61, with 2 stage
heating but no variable speed, or the Lennox G51, with
one stage and no variable speed.. Which is worth the $$?
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tigerdunes
15 years ago
jill

what area of country do you live?

if this will be your home for 10 yrs or more, then go for the properly sized G61v two stg var speed furnace.

what do you get with the var speed?

quiet,better operating cost,improved room to room temp constancy, better dehumidification in AC mode, and improved air quality,overall comfort...

IMO
jill1273
Original Author
15 years ago
I live in NJ..Just moved in about 2 years ago, will probably
stay for at least another 8 years or so.
The quote for the G61V is around $8300, and $6700
for the G51..kind of a big difference??
ryanhughes
15 years ago
I think the G51 is a good basic furnace (I believe it has a low-speed constant fan option should you desire this, but I'm not 100% on that). The G61V would of course be better for comfort, but that is a big price difference that isn't justified in my opinion. I would get a couple more quotes.
bmrbabe
15 years ago
We are replacing our furnace and I have had estimates on four different furnaces, including the Lennox. If we go with Lennox it will be the G71P furnace. It has a variable capacity furnace AND a variable speed blower with a 95% AFUE.

A one stage furnace runs on DC which uses more energy, and it is either on or off. When heat is called for, it comes on at the same amount, whether it needs a little heat or a lot of heat. This means that in the fall and spring it will be cycling on and off more frequently, and will heat unevenly.

A two stage furnace runs on AC and has a lower heat setting, so that when less heat is called for it kicks on, and the hotter setting (which is the setting for a one stage furnace) comes on only when it is very cold.

A variable capacity furnace means that the increment of heat coming on can be very, very small, and adjusts to the amount of heat needed. Say on the two stage heater it is either 40% or 100%. If you only need 10% with a two stage, you get 40%. If you need 10% with a one stage, you get 100%. If you need 10% with a variable capacity furnace, you get 10%. Thus, you burn only the amount of gas required to bring the heat to a certain temperature.

I live in Minnesota, and we have weird temperature fluctuations in the spring and fall. Our fall temperature now is ranging from 60 during the day to 35 at night. In the winter we can have spells of -15 or lower, although it is considerably warmer now than it was 35 years ago. If you don't have such fluctuations in temperature, then a two stage furnace might suffice. Get different bids on the same furnace from different installers. With everything I have read, the consensus is that the installation is key. Work with a company that has experienced installers and get references, and check with the BBB as well.

Our installation price for the G71P is $4,350.00. This does not include a gas company rebate of $290, the Lennox rebate of $150, or the Electric rebate of $50. This is a 90,000 BTU furnace, and includes everything including sales tax and permit. With the installation of the furnace we can also get The Lennox filter ($290) and humidifier ($285). With our low winter temperatures, it gets very dry in the house. We will go with both of these "extras."

I guess it is less expensive to live in fly-over country!
tigerdunes
15 years ago
jill

shop around. BmrBabe's post is interesting and certainly the G71p Lennox furnace deserves consideration. That is a great price. One correction. Babe has her AC and DC current reversed in her post.

BTW, what are you doing about AC?

IMO
jill1273
Original Author
15 years ago
As for A/C..Lennox as well, a 14 seer, 2ton for a rancher+basement..

Variable Speed?

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Variable Speed?

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veesubotee

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