New gas furnace/AC recommendations?

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It's been a long time since I've seen a 1/4hp residential blower motor 1/3 seems to be pretty well standard for heating, with 1/2 HP being very common with A/C

It knows how fast it is turning and how much current it is drawing. The current draw is a direct function of the load on the motor, which decreases as the flow decreases

If you have a belt drive blower you will need to replace it with a direct drive blower, or cobble together some kind of mount and pulley setup.

That's all you do - the learning" is built in.

For more economy of operation. Turning the fan too fast can just draw more power, without moving any more air.

That's fine if you are not trying to enhance efficiency.

Moving less air does not provide fewer BTUs - it just makes the air hotter. Adjusting the amount of flame is what the motherboard you have been cuesing for the last week or two can do. Mine is a 2 stage burner, but there are "modulating" burners as well, that CAN control the amount of heat produced, according to the number of BTUs required (delta between current and desired temperatures)

You just don't (and won't - ever, by the looks of things) get it.
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The fun part is on an induced draft furnace with an in-shot burner set you can't reduce the gas flow without also slowing down the inducer motor so modulating furnaces and I assume your 2 stage have a small ECM for the inducer too that varies speed/flow to match the fuel flow.
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snipped-for-privacy@snyder.on.ca unnecessarily full-quoted:

You might be right.
The motor in my furnace is this:
Emerson SA55NXTE-4513 1/3 HP, 1725 RPM, 5.4 A
It's got a 5" pulley wheel on it, driving a fan with a 7" pulley wheel.

But the motor can't possibly know how many CFM of air is being moved with each turn of the fan rotor.

Actually, once you get the air in the house moving, you should also see a reduction in load. Also, I'm guessing that load will not increase linearly with air-speed or CFM.

If my existing motor is turning at 1725 RPM, and if I'm satisfied by the breeze generated by that RPM, then I sure as hell wouldn't want an ECM motor making it's own decisions about what RPM *it* wants to operate at.
The point of an ECM motor is that its supposed to be more efficient than a PSC motor at ALL rpm's. So if I drop in an ECM motor and wire it up for single-speed operation, I sure as hell would want that speed to be a constant 1725 RPM.

All you ECM-motor apologists are saying that ECM motors are *always* more efficient than PSC motors regardless what RPM they operate at. So now you're backtracking by saying that there's no savings when you replace a PSC motor with ECM if you force the ECM motor to operate at same, constant RPM that the PSC motor did.
What you're saying is that I'm supposed to allow the ECM motor to "learn" and to reduce it's RPM.
That's no different than if I were to replace my 1/3 hp motor with 1/4 hp and put a smaller pulley on the motor vs what I have now. I will use less electricity and the fan speed will be reduced.
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It doesn't have to - it's a relative thing - the motor adjusts itself by RPM and current to the most efficient point - at least that's what I gathered. If it runs too fast so the fan is "throttled" the current drops for the speed it is running at, so the motor can slow down 'till the current/rpm ratio ballances out.

You are right - partly. The inertia of the air is not much af a factor, what with air being compressible and all, so there is not much change in power required from "startup" to "air moving" - but the load is not necessarily linear with air-speed or air flow. The counterintuitive thing is the load DROPS when the back-pressure increases. (partly because the actual air movement drops and partly because of the way air behaves in a centrifugal blower (any fluid, actually - look at cavitation in a water pump)

And it would be if that is the right speed - but it MIGHT move just as much air at 1500, or 1375. It might actually move marginally MORE air at a lower speed, because the blower itself may be more efficient at a lower speed.

No, not saying that. It will be somewhat more efficent at the same speed, but may be considerably more efficient, while movong the same amount of air, at a lower speed.

And , depending on your furnace and setup, it may actually be more effective that way.(as well as more efficient)
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snipped-for-privacy@snyder.on.ca wrote:

Sure, the motor can know a lot about it's own current useage as a function of it's own RPM.
But it can't know anything about RPM and fan CFM - without getting feedback from air-flow / air-pressure sensors mounted in the ductwork.
ECM motors can't reduce their RPM to, say, 1600 RPM and magically give me the same CFM as my motor running at 1750 RPM - both given the same fan to turn in the same duct system.

Who says what the right speed is?

Ok, you need to step back and re-think this.
Within a normal range of operation, there is no way that I can turn a given fan at a slower speed and yet get more CFM being moved by that fan.
Again, you think that ECM motors can magically make a given fan move more (or even the same) CFM at a slower rotational speed than a PSC motor at the same speed. You're going to have to explain the physics behind such a phenomena.
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The right speed is the speed that 1) - moves the most air with the least power or 2) allows the most heat to be extracted from the heat exchanger by optimizing the air flow.
Moving more air does not necessarily translate to providing more heat.

Counterintuitive, yes - but if YOUR fan is turning too fast, turning it slower CAN provide the same or even higher air flow - and use less power to do it.

I didn't say that. If you could slow down the PSC motor you could have the same effect.. You could use a brushed DC motor and variable voltage to get the same effect - but ECM motors are less maintenance intensive, longer lived, and (can be)more efficient.
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snipped-for-privacy@snyder.on.ca wrote:

A drop-in replacement ECM motor that's replacing a single-speed PSC motor can't know how much air it's moving, because it doesn't know the size of the fan it's turning nor does it have duct-mounted sensors to tell it the CFM of air being pushed through the ducts.
A drop-in replacement ECM motor can't know anything about how much heat is being extracted by the heat exchanger, because it doesn't have temperature sensors telling it the input and output furnace air temperature.
A drop-in replacement ECM motor can "learn" it's energy-useage vs RPM curve is once it's been installed into a given home's furnace, but that doesn't mean that the most efficient RPM will be satisfactory for the comfort or desire of the home owner.

A drop-in replacement ECM motor will not be getting any feedback from any temperature sensors, so that point is moot.

You actually believe that a 1/3 HP motor running at 1750 rpm though a reduction pulley is going to be turning the furnace fan too fast - to the point that it's actually pushing *less* CFM through a "normal" home's duct system as compared to if it was turning slower?
I said given a normal range of operation - not given some ridiculously high RPM.

What effect?
If I slow down any motor, the fan will turn more slowly, and I will get less CFM.
You keep wanting to insist that in every case where there is a PSC motor, that it's almost certainly turning it's fan faster than it needs to, or faster than the home-owner wants.
Just because an ECM motor *can* run slower than a PSC motor doesn't mean that the resulting CFM is what the home-owner wants.

Tell me why an ECM motor is longer lived - given that we've really only had them in consumer furnaces for the past 10, 15 years max.
PSC motors don't have brushes, nor do they have sensitive electronics that are vulnerable to power surges and nearby lightning strikes, nor do they care much about pushing air though high-resistance ductwork.
What is it about the construction of a PSC motor can you point to as being more sensitive or less durable or more prone to failure vs an ECM motor?
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That is not NECESSARILY true.

I didn't say in EVERY case

And the homeowner is often too stupid to realise that what the FURNACE wants is more important than what he thinks he wants, in some instances.

Lets see. How long have electronically commutated motors been in common use elsewhere???? DC "muffin" fans have been in use in computer power supplies since before the IBM PC came on the market some 30 years ago. If the bearings don't seize up they run virtually forever.
And the ECM, or "Smart Motor" was first marketted for furnace use by general electric in 1969. That's FORTY TWO YEARS of history.

And nor are they anything approaching anyone's definition of efficient.

Because of lower efficiency they tend to run hotter.
Installed PSC motor efficiency is generally in the 12-45% range, which means a LOT of heat is produced. ECM motors generally run 65 to 72% efficiency as installed.. That means a LOT LESS HEAT. Add to this the FACT that a majority of the heat in a PSC motor is produced in the rotor, whech means a lot of heat is transferred out of the motor through the shaft and bearings. This reduces bearing life and stresses bearing lubrication.
I'm not saying PSC motors are failing at extremely high rates - but I have had them fail in signiificantly less than 20 years, and I reject yout hypotheses that ECM motors are either "puny", short lived, or intrinsically trouble prone.
I just saw a few weeks ago a ECM less tham 4 inches in diameter and less than 4 inches long that will put out 14 HP.
In the 20-200 HP range, Brushless DC motors (ecms) are actually less costly than brush DC motors or any other variable/controlable speed AC motors and are extensively used in industrial applications
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On 12/13/2010 10:32 PM, snipped-for-privacy@snyder.on.ca wrote:

ECM motors are being marketed to replace common evaporator fan motors in commercial refrigeration. Those refrigerated cases you see in the grocery store are getting ECM fan motors.
TDD
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snipped-for-privacy@snyder.on.ca wrote:

Unless you can show where someone has made some blower CFM measurements in a real house, then you have no real evidense to support that paradoxical statement.
And in any case, an ECM motor has no way to know how much CFM is being moved by the fan its running, especially as a drop-in replacement for a PSC motor.
And I bet that modern furnaces that come with ECM motors also don't know how much CFM they're actually pushing. They probably only know indirectly by monitoring return-air and output-air temperature difference. Do any of them have an integrated wind-speed sensor?

Then put a number on it.

The home-owner is "often" too stupid ... in some instances. ?
That's a mixed message. You want to say that some arbitrarily large fraction of home-owners would (or are) choosing a fan-speed that too high (you'd have to show me how they have any real control over that, btw) then you back away by saying "in some instances".
You are showing a strange bias against homeowners that is affecting your ability to think rationally about this.

Yes, let's compare these other situations, where micro-power DC motors have been used:

So you think that these tiny, micro-power DC motors make for a good analogy when we're talking about the furnace fan motor market eh?

Tell me how many consumer furnaces were available in 1985 with ECM motors.
And you haven't told me anything to support your claim that ECM motors last longer.
Saying that the first ECM motor was made a hundred years ago, or that GE supposedly actually sold a furnace with an ECM motor in 1969 (which maybe they withdrew from the market a few years later ?) is not an answer to why ECM motors last longer (your claim).

Don't change the subject. We're talking about longevity, not efficiency.

Yes, they run hotter. They are also constantly cooled by the airflow generated by the fan.
Tell me which motor is more likely to survive constant use in a high-resistance duct system? Or survive a fan bearing that gets gummed-up over time? Or a filter that's not properly cared for? Or a power spike or brown-out on the AC grid?

That depends on how many PSC motors are multi-speed vs single speed.
And you can get high-efficienty PSC motors in the range of 62%, as claimed here:
http://www.nailor.com/pdf/ecm_1.pdf
And I suggest you also read this:
http://energyexperts.org/EnergySolutionsDatabase/ResourceDetail.aspx?id &13
Any furnace that has a shaded-pole variable-speed fan motor does have horrible efficiency, and perhaps some people here are confusing shaded-pole motors with PSC motors in these discussions about motor efficiency.
It's clear that when we're talking about 1/4 and 1/3 hp single-speed PSC motors, efficiencies up to 60 - 65% are obviously the norm, and bring us much closer to ECM motor efficiency than most people think possible.

It's clear that some furnace makers are using puny or wimpy ECM motors in their furnaces. But none of the HVAC regulars reading this will chime in and agree.
ECM motors have sophisticated electronics that PSC motors don't have. When-ever you include additional components into any system or device, you have more points of failure. You stubbornly refuse to believe that the electronics in an ECM motor represents an addition point-of-failure that PSC motors simply don't have.
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Ok homer, so when are you going to start you new job with the manufacturers and/or governing bodies to redesign and reclassify furnaces so that you can turn a multi billion dollar industry back in time 20 years??
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At least ONE. I'm done. You are too stupid to be teachable.
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On Dec 14, 12:44pm, snipped-for-privacy@snyder.on.ca wrote:

Excuse me, but I think the points Home Guy are raising are perfectly valid and you can't just dismiss them. You claimed that slowing down a fan motor may not lead to less airflow. I agree, thatis possible, IF the fan is turning so fast that it's no longer moving air, ie cavitation has occured. But that isn't the abnormal case we're discussing now, is it? We're talking about a normally operating home forced air funace or AC.
Also, HG raised a perfectly valid question of how a drop in replacement ECM motor could learn anything about air flow. It can't directly measure the CFM being moved. He asked a question I'd like to know the answer to, which is in new furnaces with ECM, do they have air flow sensors?
Also, to add to HG's case, I think all the hoopla about constantly circulating air 24/7 is a bunch of BS. Why? Let;s look at my house, which I'd say is typical. Furnace is in the basement, returns are uninsulated and some to upstairs even flow through outside walls. Those ducts have no insulation, because the wall cavity is used for the ducts and the insulation that the normal cavities would have is absent. Also, typical ducting is far from perfect, with leaks in botht the returns and supply commong.
So, now I'm to believe that running a blower 24/7 when it's 20F outside, drawing the air through the cold basement, the cold furnace that is not fired up, through ducts that are in outside wall, etc, is a smart thing? I don't care how much you think you save in an ECM motor. Even if the energy to run the blower is free, the rest of the above equation spells loss to me.
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On Tue, 14 Dec 2010 11:26:48 -0800 (PST), snipped-for-privacy@optonline.net wrote:

It is an all too common occurence when guys who do not understand what is happening try to "fix" their furnace.

Which someone has screwed around with

In most cases, if not all, no.

Not all basements are cold. A very large percentage of urban basements are heated, finished living space.

To you it might be. To me, and many others, it is not.
And I've checked the air temp from the heat outlets on the outside walls of my house - they are room temperature or better with the burner not firing
I've stood up for HG on many issues - but he'll never get it. The days of the model "T" are long gone - and the day of the standing pilot light, atnospheric burner, PSC fan gas furnace are pretty well gone too. Taking all the "advancements" off of today's equipment will not make it a) last longer b) work better c) cost less long term or d) run better.
He first argues for resizing the jet - which I agreed with him about, and adjusting the air dampers, which I also agreed with him on, then he starts talking about putting the gas valve "between settings" - referring to the 3 position gas valve as "variable", and adjusting the flame by adjusting the gas shutoff valve on the 1" iron pipe feeding the furnace. Sure he can reduce the flame that way - but it is sure not the right, or even an adviseable way to do it.
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On Tue, 14 Dec 2010 16:49:28 -0500, snipped-for-privacy@snyder.on.ca wrote:

We've beaten to death "modifying" furnaces to improve efficiency. It can be done with older furnaces because they just weren't designed with efficiency as a high priority. The priority was quick heat on demand. I wouldn't try modifying a modern "efficient" furnace. Correct sizing is what you want, so more heat goes through the heat exchanger and less up the stack.
Beyond that - and insulation - I've found the best way to reduce gas use is to not heat where it isn't needed. Working vents are important, as are just closing/opening doors. All depends on where the thermostat is, and that can be moved if it makes sense to your needs. I like the idea of zoned heat, though I have no experience with it. I just close or open vents and doors depending on what current needs are.
--Vic
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On Dec 14, 4:49pm, snipped-for-privacy@snyder.on.ca wrote:

But here's the problem. You claimed that slowing down a blower doesn't necessarily reduce the air flow. If you were taking about the pathological case where the blower can't move air because it's cavitating, they you should have pointed that out. Because if that's the case, there is a problem that needs to be fixed with the system that has nothing to do with an ECM vs conventional motor. To do otherwise is just to spread FUD.

Who said anyone was screwing around with anything? In the current discussion, all I saw was Home Guy asking some very relevant questions about ECM motors, including those installed in modern furnaces at the factory.

So then Home Guy's point remains valid. Apparently the motor can't know how much air is actually flowing. Sounds more and more like it's just a multi- speed motor that will be more efficient in most applications, ie those with typical or better ducting. In the typical install, that equates to using 20% less energy. Now, if we don't intend to run our blower 24/7, instead using it only when actually heating or cooling, how much will that amount to?
The question of course remains if cost is the only issue, with typical use, will you save enough in electricity to recover the cost? I'm looking at quotes where it's $1000 more for a 95%efficiency furnace with a two stage burner and variable speed ECM blower, compared to one without those features. Clearly all that cost isn't due to the blower but it comes with it, without choice. Combine that with the exposure to increased repair cost for the ECM and drive electronics and I'm not sure of the value proposition.
If you have issues other than saving energy that the variable speed drive will help with then it's another story. But for me, I don't see that extra value.

Around here, NJ/NYC area, I'd say the majority are not. My house isn't. And I see plenty of new construction where they have dual zone systems, putting one furnace in an unfinished basement, the other in the attic, which is even worse if you keep air moving 24/7.
Also, not one person that's hawking the wonders of variable speed blowers even mentions the above points. It's obvious I don't have a finished basement and not one contractor said a word about it. All of them are spouting mostly what we call marketing BS. Like the variable speed blower in a 5 ton AC is gonna use the same electricity as a 40W bulb. That the furnace which is still rated at 95% AFUE, just like the single stage, is now going to be way more efficient. Both of those are fiction. There's some truth that the furnace will be slightly more efficient when firing at 70%, but from physics and what I've been able to gather, it's a small percentage, a couple percent at best. And around here, it's gonna be firing at 70% in the Fall and Spring, when I use the smallest amount of energy anyway. So the gas usage difference is very slight.

You dismissed all the above on the basis that there are lots of finished basements, so the heat lost by constantly pumping hot air through cold basements, garages, attics etc isn't an issue. I say it is.

Explain to us how it's possible to send air through typical ducts in the outside walls of homes when it's 20 outside and not have them lose heat. Maybe you've re-written the laws of physics. Actually it sounds like you have, since you say the air coming out is room temp or better with the burner off. How is it possible to gain heat?

I can take the two stage complexity and the ECM out by simply choosing to not buy it and still get a 95% AFUE furnace. And as to repair cost, he has a valid issue. Are you going to claim that the replacement cost of the ECM motor or drive electronics is the same as a conventional motor? I've seen plenty of stories here over the years of people paying $800 to replace them. If a plain old motor goes, I can replace it for $100. Does that mean all the technology in today's furnaces isn't justified? No, but IMO you can't lump it all together. It's like buying a new car that has headlights that autmatically adjust and react to the cars pitch up or down at any given moment, to maintain them perfectly pointed evenly ahead. A nifty feature? Yes. But when that system goes out, it sure isn't gonna cost the same to fix as a conventional headlamp system.
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snipped-for-privacy@optonline.net wrote:

Mr. Snyder appears to have painted himself into a corner over the finer details of the operation of ECM motors and seems to just want to walk away from this conversation instead of admitting he's wrong or mis-informed.

There are several nation-wide HVAC retailers with websites listing prices for furnaces. I was looking at one a few days ago, and they listed various Goodman furnaces with various efficiences (from non-condensing to condensing, etc) and the price for the furnaces ranged from $750 to $1500 if I remember correctly.
Have a look at these retailers / wholesalers:
http://www.alpinehomeair.com/kitbuilder_new / http://www.thefurnaceoutlet.com http://www.gsistore.com / http://www.acwholesalers.com/Goodman_Gas_Furnaces_s/160.htm https://www.freemanliquidators.com/productcart/pc/HVAC-c2.htm http://www.ductworks.net/xcart/home.php?js=y http://www.theacoutlet.com/index.php
See if the furnaces you've been quoted on are carried on any of the above sites to get an idea of just how much your local contractor is over-charging you for the hardware.
I have a hunch that just like roofer's who over-charge you for the shingles, you'll pay a 50% premium for the hardware when you buy an entire package (furnace + installation) from a local contractor.
Your $1000 difference in the cost of a furnace with and without 95% / 2-stage / ECM is insane. Most 90+ furnaces seem to cost around $1000 judging by what I see on those sites.
See what your contractors say about just installing the furnace that you buy on-line. See if they balk and weazel their way out of doing that.

Your point about running the fan 24/7 is lost on a lot of people.
Your house loses heat through the walls, windows, and ceiling. Doesn't matter how much you insulate - the walls, windows, doors and ceiling are the containment envelope for the heat in your house. You're not going to loose heat through the wires or the plumbing.
And it's not just the basement walls (that's a red herring).
By running your fan 24/7, you're constantly forcing interior air to pass against the walls, ceiling, windows and doors, where the air will do it's best to either pick up heat (in the summer) or dump heat (in the winter) against those surfaces and tranfer heat to (or from) the outside. It's in the winter that this heat transfer is particularly of interested to us.
What you want is to achieve a still-air condition where there is no air motion inside your house. This condition will result in the least amount of heat being drawn off the interior objects (furnature, interior walls, floors, etc) and deposited against your exterior walls, windows, doors, etc. But with a forced-air system, you have no choice but to move air around and cause a breeze.
So while running a furnace 24/7 with the furnace dumping exactly as much heat into the house as the house is losing to the outside is (in theory) the most efficient way to operate, the very act of moving the air around inside your house is contributing to heat loss to the outside world. So it's probably the case that a furnace duty cycle less than 100% is more efficient at heating your house while conserving interior heat at the same time. I'm thinking more like 70% is probably where you want to be, and certainly to NOT run your fan at any time when your furnace is not on.
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Legitmate contractors will not install *ANY* equipment that the customer has purchased off the internet for 2 reasons.....
1) Manufacturers warranty is null and void for any and all equipment purchased off the internet.
2) Legitmate contractors cannot and will not assume *ANY* liability for said equipment.
I charge what I do, because thats what it takes to keep my companys doors open, and still make a small profit after all of the costs, expenses, salaries, and taxes are paid. Here's a hint..... "The bitter taste of a poor quality installation will linger far longer than the initial sweetness of a low price."
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On 12/14/2010 9:50 PM, Steve wrote:

The finest equipment in the world is worthless if installed improperly. I'm sure you've come across heartbreaking installations of expensive systems that some hack put in and you have to break the bad news to a very nice customer.
TDD
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wrote:

The especially bad (dangerous) ones, I take pics of and forward to the city code enforcement and/or county planners office, and the state fire marshal.
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