confused about HVAC

last year

1. What is a 1-stage furnace or a 2-stage furnace or how ever many there are? Why would I want one over the other?

2. The furnace we have now seems very noisy. HVAC guy said trane is a noisy furnace, or maybe this particular trane is noisy. Is there such a thing as a less noisy furnace?

3. If the furnace and the AC are both old (12 years) and one dies, is it better to replace both? It seems the original owners never did any preventative maintenance on either of them.

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Comments (3)

sktn77a
last year
last modified: last year
Furnaces aren't noisy, installations are noisy! The most common cause of a noisy "furnace" is an undersized duct system (barring an obvious fault in the furnace).

A single stage furnace has one speed - full speed. A two stage furnace has two speeds - low (50% to 70% of full speed) and high (full speed). They operate on low most of the time. This improves comfort (noise, drafts, dehumidification in AC mode). If you can afford a two speed system, I'd go that route.

In the next 5-10 years, new furnaces and AC systems will be introduced. If you can keep your existing system going I'd try to tough it out. See if the furnace blower speed can be reduced to improve the noise performance. Maybe it can, maybe it can't.
juniperg92 thanked sktn77a
sktn77a
last year
Whatever you say, Ray.
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PRO
Charles Ross Homes
last year
Hi, Juniperg92,

1. A single-stage furnace has two operating modes: off and on. A two-stage furnace has three operating modes: off, low, and high. There are also modulating gas furnaces which have variable speed blowers and modulating gas valves. Modulating furnaces adjust to the required heating load in smaller increments. Two-stage and modulating-type furnaces enhance occupant comfort, and when operating at lower capacity, are quieter than single-stage equipment.

2. Furnace manufacturers will typically offer a range of different products with different performance attributes and prices. Trane's higher end furnaces will outperform their more basic units as will other manufacturers. I find HVAC replacement technicians tend to generalize based on their own limited set of repair experiences. If they characterize one particular manufacturer's products as "noisy" I'd suggest you ask to see the data comparing that manufacturer's equipment with others' of similar performance and price.

3. The average life expectancy of a heat pump or air conditioner is around 15 years. Furnaces typically last longer because they are both simpler and exercised less in all but the coldest climate zones. When your air conditioner reaches the end of its useful life expectancy, ask your replacement contractor to help you evaluate whether it makes sense to replace the furnace at the same time based on its condition, remaining life expectancy, and how its operating cost compares with that of a replacement.
juniperg92 thanked Charles Ross Homes