Originally posted by BaldLoonie The CDX isn't that noisy of a furnace. It is a builder grade but still... I'd guess it is oversized or underducted. Make sure whatever dealer looks at replacing it takes this into consideration. A variable speed could make it worse with air noise since the ECM will push harder to move the air.
Well, to be fair, I haven't actually heard the unit in the attic. He installed the same unit in the basement and I'm basing my opinion on that. And, true, the one in the basement is a huge improvement in noise over the 40 yr old Lennox it's replacing. But in the attic I'll be trying to write at my desk maybe 4 ft from the furnace so if there are significantly quiter units, it might be worth the effort - which I guess begs the question, Are there significantly quiter units? Also, what is the ECM and why would this make it noisier? I ask because the Carrier guy said the variable speed feature is what made it quiter, since it operates at low speed off a DC charge about 90% of the time.
Originally posted by BaldLoonie The Freedom 90 2 stage variable speed is also a very quiet furnace when you stand beside it. Ours is a downflow in the 2nd floor. Right in front of it you barely hear it. Below it on the first floor above the salesmens' desks, you get a good hum of air noise.
If you were to rate the CDX, the Freedom 90, and the Infinity 96 in terms of noise, how do you think they'd stack up against one another?
Also, do you think sound batting in the floor joists beneath the furnace/ducts would help with the air noise?
If quiet is your goal by locking in low you will never here furn but when furn. shifts to hi you will definitly here it and if duct is a bit small the curtains will be flapping in the wind nobody said anything about being cheap if you want cheap don't call carrier dealer they have nothing cheap. "It is unwise to pay yoo much, but it's worse to pay to little. When you pay too much,youlose a little money-that is all. When you pay to little,sometimes you lose everything,because the thing you bought is incapable of doing the thing it was bought it to do. The common law of business balance prohibits paying a little and getting a lot- it can't be done. If you deal with the lowest bidder,it is well to add something for the risk you run, and if you do that you will have enough to pay for something better.
That's just it. I did choose the installer first. He was the only installer I met w/who seemed to understand what I was trying to do and who came up w/a plan for doing it. He was also recommended by the GC, who's opinion I trusted. He told me he was installing Amer. Standard furnaces, which I knew to be top of the line. Of course, the devil is in the details and I failed to find out exactly which AS furnace he planned to use. Didn't even know there was a "buillder's grade." I just trusted him.
Originally posted by BaldLoonie
A variable speed could make it worse with air noise since the ECM will push harder to move the air.
Can anyone explain this comment? Just don't know what an ECM is and why this would be noisier when these units are supposed to be "whisper quiet." Thanks.
Let's see, BaldLoonie's posts usually strike me as knowledgeable, so it might be worth trying to figure this one out. In context, BL was talking about a system known to have undersized ducts. With undersized ducts and a fixed speed (PSC) blower, chances are you are getting less than the design airflow (unless the installer took the trouble to select higher fan speed to get the right flow). So the system with a PSC blower might be quiet (and wrong) in that case. An ECM blower will sense the airflow and ramp up until it is actually giving you the correct flow. So, that could make it louder, but it's the sweet sound of correctness.
Makes sense. Still wish I knew what "ECM" meant - anybody know of an online HVAC glossary?
Electronically Commutated Motor. The 'commutator' in a motor is whatever does the job of feeding power to the magnetic coils in the right timing to keep pulling the shaft around in rotation. In the ECM, which is a GE product you can read about on geindustrial.com, a chunk of electronics mounted on the end of the motor does that job. This is the motor you'll find in any of the residential variable speed furnaces or air handlers being sold (but beware, even though it's the same motor, you can't swap it between makes and models of furnace; it has to be programmed with the airflow calibration of a specific blower wheel and furnace, which is done by the furnace mfr, so you can only replace the ECM in a given furnace with the replacement supplied by that manufacturer, unless you have facilities to program it yourself and the right manufacturer data).