New gas furnace/AC recommendations?

I don't know what you consider "cheapest, lowest efficiency", but I'm looking at quotes for a Rheem 120K BTU, 95% efficient furnace that meets the govt high efficiency standards for the tax credit. And it has a single speed PSC motor. Can also get the same furnace and AC system from Trane, for $800 more.

While I don't agree with Home Guy on everything, I do agree that in many cases the extra cost of models with an ECM blower aren't worth it. That's from two standpoints. First is that those models only save on the blower electricity. And then independent studies have shown that you get the 40% electricity savings if the duct work is ideal. If it's good, you get like 25%. If it's typical it's more like 15

-20%. And if it's poor ducting, you get 10% to -10%. So, for maybe a 15-20% savings, you have a significantly higher initial outlay, plus exposure to higher repair costs if the blower motor or it's added drive electronics fails.

I can see going with the variable ECM motor if you want to run the blower 24/7. Or if you highly value that it starts up quietly, can run at low speed longer to even out heat better with a two stage furnace on mild heating days. Or can run on slow speed with AC to dehumidify better. But none of those are that important to me.

Reply to
trader4
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I'm guessing that it's increasingly high targets for energy efficiency (combustion and electrical) set by gov't regulations is the reason why we're seeing the use of ECM blower motors in consumer HVAC equipment, just as we see the same when it comes to saftey equipment (air bags, ABS brakes, CAFE and emissions standards) in cars. Probably the same reason for electronic ignition vs standing pilot as well.

I can't believe that we'd see widespread use of ECM motors under true free-market-driven conditions (ie - with no gov't efficiency mandates or constraints).

Reply to
Home Guy

A lot of us don't live where they have 9 months of winter sports, and humidity control is a huge issue. Where I am, we run A/C from March 1st until November 1st with average summer temps of 90F with 75% to 85% RH you can *DO* what you want, you can be as ignorant as you want....thats your problem.

I do this for a living, and I *KNOW* first hand what the benefits of the new systems are, and how much my customers utility bills have dropped, as well as their comfort level increasing.

You can *TRY* to re-engineer a new furnace by taking out the electronics, ECM motor, and electronic ignition... Just remember that as soon as you screw with it, you have voided the warranty, as well as the UL ratings and if you burn your house down, your insurance company will deny the claim.

Maybe you should get a job in the engineering department with the equipment manufacturers.

Reply to
Steve

Steve, you can verify something for me because you do more of this work than I do. I've noticed a dramatic drop in price for the ECM motors over a period of time and I assume it's because millions of the things are being produced now, economies of scale. I'm seeing an ECM replacement for PSC motors offered like the Genteq EverGreen and I'm wondering if you've converted any air handlers for customers or have considered it?

TDD

Reply to
The Daring Dufas

I think that's still made by GE

At least tell us what the over-the-counter (cash and carry) price is for an ECM drop-in replacment 1/4 hp NEMA-48 1700 rpm PSC motor.

Reply to
Home Guy

The equipment I install, already has ECM motors in it. the stuff with ECM motors in it has a 10 year parts warranty, and the heat pumps have either a

5 year or 10 year unit replacement warranty.

I don't know why I would install an air handler with a PSC motor in it when there is only a small difference in price for the ECM, and the PSC only has a 5 year parts warranty, period.

Reply to
Steve

They are not interchangeable.

Reply to
Steve

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The Comfort Select FB motor is a brushless, direct current (BLDC), permanent magnet, electronically commutated motor (ECM). The motor is controlled by integrated electronics providing high efficiency, advanced motor protection, and has the same performance characteristics as a PSC motor. The Comfort Select~FB motor is designed as a direct replacement or retrofit product for a PSC motor.

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This brochure is confusing, because on the last page it lists 5 different HP sizes, while seeming to indicate the availability in only 2 HP sizes (1/2 and 1 hp) which is strange since I wouldn't think that a residential furnace would need anything larger than 1/3 hp.

The power consumption of the 1/2 hp unit (6.3 A at 115 V) seems excessive.

Example retail pricing:

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Upgrade your furnace or air handler to a high efficiency, variable speed blower motor without having to make complex changes to your system. The RESCUE EcoTech? motor drops into existing PSC (multi-speed) induction-blower applications, without making complex wiring modifications or changes to the system controls. Just connect the leads, and you?re done! No 24-volt signal leads or setup required ? it?s plug and play.

With the increased efficiency and available low circulation of this motor, you will be free to cycle air continuously without a significant increase in utility bills. Continuous fan operation supports improved filtration, helping to clear the air of dust and allergens ? all the while making your home more comfortable by working to reduce temperature variations throughout the home.

The RESCUE EcoTech motor?s advanced design also features active airflow management, which allows the motor to compensate for static pressure changes to help maintain airflow. This means that as vents are closed or the filter becomes full, the motor will attempt to maintain the same airflow, helping to keep the system operating efficiently and the home comfortable.

Standard Features

  • Easy Installation - Drops into existing PSC (multi-speed) direct drive induction-blower applications without making wiring modifications or changes to the system controls.

  • Quiet, Efficient Circulation Speed - The advanced motor design provides a low, 600 rpm circulation speed, so you can cycle air continuously without the noise, draft or electricity cost of a PSC motor.

  • Money Saving Efficiency - Save money on your electric bill just by replacing the existing PSC blower motor in your furnace or air handler.

Product Specifications

Volts 115 VAC Blower Motor Horse Power 1/2 HP Rotational speed in revolutions per minute 1140 RPM Number of Blower Speeds 5 Motor Warranty 2 Years

Your Price: $323.99

Emerson EcoTech Estimated Electricity Savings:

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They estimate annual savings of either $38 (fan runs only during heating or cooling) or $106 (fan runs continuously). This is for the 1/3 hp model, based on 14 cents /kwh.

This place:

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Also lists the 1/2 hp Emerson 5530ET motor for $323.

The Emerson 5520ET is listed as 1/3 hp by some sellers and 1/4 hp by others. It's priced at about $300.

This is a brochure for the Fasco / Evergreen Motor:

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----------------- Fasco is proud to introduce the new Evergreen motor: the world?s first universal aftermarket Electronically Commutated Motor (ECM) specifically designed to save energy in residential heating and cooling applications. Like compact-fluorescent replacement bulbs now offer an energy-saving alternative to traditional incandescent lightbulbs, the new Evergreen motor is a new high-efficiency alternative for standard replacement motors. It uses proven ECM technology to save energy? and money?every time a residential HVAC system is in use.

On average, consumers can expect to save over 25% on annual motor operating costs ? or about $60 in annual heating and cooling operation based on 10¢/kWh. Even better, consumers can also expect to use up to

74% fewer watts with an Evergreen motor when they run their fans between heating and cooing cycles.

-----------------

So basically you're going to spend $300 and probably save $100 a year in electricity if you're lucky, and probably only if you can get an actual

1/4 or 1/3 hp unit - not a 1/2 hp one.
Reply to
Home Guy

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From looking at the information, I understand that the 1/2hp ECM motor is the replacement for 1/3 through 1/2hp PSC motors and the 1hp ECM is the replacement for the 3/4 through 1hp motors. The ECM motors are adaptable according to the literature and have the programming to learn how to operate much like an automotive engine control unit. It's very interesting what has been done with these new motors. It reminds me of the way switching power supplies have taken over the work once done by less efficient shunt regulated power supplies.

TDD

Reply to
The Daring Dufas

I'd say it's ignorant to assume everyone that's looking at a new HVAC system lives in the same climate that you do. I'm in coastal NJ and the existing 26 year old system handles the humidity just fine. If it's hot enough to be running frequently, no humidity problem. If it;s one of those few days where it's not hot enough to be running and it's getting humid inside, I lower the thermostat one degree and in 30-45 minutes, you can feel the humidity has decreased and it's comfortable. And that's with an inefficient system with a single speed blower.

My utility bills are gonna drop too when I swap out that 26 year old system and go to a high efficiency system with a PSC blower.

That part I agree with. But there is no need to take out an ECM motor. You just buy a high efficiency system that doesn't have one in it.

Reply to
trader4

Would you even use a 1/2 hp ECM motor for a home furnace? You certainly wouldn't save any money if you were replacing a 1/4 hp single-speed PSC motor with these 1/2 hp ECM units.

How exactly do they do that?

How does a motor know how much CFM the fan is moving?

Are there pressure or flow sensors mounted in the duct work for that?

How would you use one of those replacement motors when you have an ordinary single-speed PSC motor in a 25+ year old furnace?

Can you apply 115 vac directly to those motors to the appropriate set of wires to make them operate - to hell with this learning crap?

I don't get this learning crap anyways. What is an ECM motor supposed to learn? Don't you just want it to turn at a given RPM? Why all the fuss about finessing the CFM?

If the controller can make the unit start at low RPM and then speed up, that's great. Do it. Why worry about CFM? If the house isin't reaching the thermostat set-point fast enough, then speed up the motor, or turn up the burners.

To me, the feedback the motor controller should get is the difference between actual house temperature and the thermostat set-point temperature. The smaller that difference, the slower the motor needs to turn and the less BTU's the furnace needs to put out. What the actual CFM is is neither here nor there. If the occupants want to over-ride the motor RPM to get ambient circulation, then fine, given them the option for low and medium speed constant circulation mode based on motor RPM - not on some sort of "learning" crap.

Reply to
Home Guy

I'd say it's ignorant to assume everyone that's looking at a new HVAC system lives in the same climate that you do. I'm in coastal NJ and the existing 26 year old system handles the humidity just fine. If it's hot enough to be running frequently, no humidity problem. If it;s one of those few days where it's not hot enough to be running and it's getting humid inside, I lower the thermostat one degree and in 30-45 minutes, you can feel the humidity has decreased and it's comfortable. And that's with an inefficient system with a single speed blower.

My utility bills are gonna drop too when I swap out that 26 year old system and go to a high efficiency system with a PSC blower.

--------------------------------------------- All of the high efficiency have ECM blower motors, the only ones that have PSC blower motors are the basic, low end, 13 SEER systems..... that would be the "spec house", and landlord specials.

That part I agree with. But there is no need to take out an ECM motor. You just buy a high efficiency system that doesn't have one in it.

You cannot get a "high" efficiency system without an ECM motor in it. Only the basic, entry level 13 SEER systems have PSC motors in them.

FWIW, the latest technologies in residential heating and cooling systems are using serial controlled, Variable Frequency inverter drives that literally vary the systems output from 40% to 115% of its rated capacity depending on demand. Even the compressor is variable speed..... This is where residential heating cooling systems are headed. Your not going to have a choice in refrigerants for air conditioning either.

These changes have been in the works for over 20 years.... I just gotta wonder why a select few are bitching about it now.

Reply to
Steve

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Switching power supplies are a replacement for many linear *series* (not shunt) regulators. Series regulators have the active device in series with the load. Shunt regulators have their regulating element in parallel (shunt) with the load.

Series Regulator (pass element) Shunt Regulator ____ | | ___ +-----+-| |-+-----+ +----+|_R_|-+--+------+ | |____| | | |/ | /+\ | .-. /+\ Zener - .-. (Vin) | | |Load (Vin) (Shunt) /A | |Load \-/ === | | \-/ | | | | GND '-' | | '-' | | | === | === | === GND | GND === GND === GND GND

(created by AACircuit v1.28.6 beta 04/19/05

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Reply to
krw

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I'm sorry, I should have written linear, I stand corrected. I've worked on enough of the darn things. It used to be everything had a linear regulator and heavy transformer but the power supplies were simple and reliable. The 78xx series regulators and LM317's make it so easy to put together a regulated supply for a project. I was working in TV shops back in the 70's when RCA, if I recall correctly, came out with a TV set that used the flyback transformer as a newfangled power supply for the whole set. The company rep had one of the new "all solid state" sets hooked to a variac transformer which he used to run the voltage up and down. We were all impressed by the fact that the set would show a clear but slightly shrunken picture when the power to the set was turned down to 80 volts AC. I knew then that things were know going to get very interesting in the field of consumer electronics. Most of the sets we were working on had hybrid circuitry using transistors and IC chips for low power and low voltage then tubes for the high voltage horizontal output stage. I remember when a horizontal output tube was under $5.00 and a horizontal output transistor was $25.00 or more. Gasoline was also

30 cents a gallon back then. Gosh darnit! I think I'm getting old. :-)

I just had a flashback to the good old Radio Shack 12 volt DC power supplies the company sold for powering up a car or CB radio out of a vehicle. The early units used a TO-3 power transistor and a zener diode as a voltage reference in the circuitry. The latter versions used the LM317 and 78xx series regulators. I get the same power now from a wall wort that feels so light for the power it will supply. Oh yea, some of those Radio Shack power supplies were unregulated. :-)

TDD

Reply to
The Daring Dufas

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.

Reply to
clare

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And the switch mode regulator can take the place of both. It is GENERALLY used in a series configuration because it is more efficient that way.

Reply to
clare

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Switching shunt regulators are exceedingly rare because the gain generally isn't worth the cost. Another topology almost always wins.

Reply to
krw

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I came across a ferroresonant transformer power supply in a piece of gear a friend had and he was mystified by the darn thing and why it wasn't working. I obtained a replacement oil filled capacitor from an electric motor rewind shop and got the equipment working again. He had worked with all manner of DC voltage regulators but had never seen an AC voltage regulator. I guess it helps to broaden your horizons in a search for knowledge. :-)

TDD

Reply to
The Daring Dufas

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They also are not often used anymore because it's cheaper to use a switcher of some sort. Iron is expensive. Silicon is cheap.

Reply to
krw

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I have a notion that the constant voltage transformer is a lot less susceptible to voltage spikes and lightening strikes than a switcher. I've installed a lot of them to protect phone systems power supplies. The things work well as AC line filters and isolators.

TDD

Reply to
The Daring Dufas

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