variable speed motors

[Zzz]

I did a repair on a carrier furnace the other day with both induced and curculation motors were dc's. The idf was shot and I ordered another. To my surprize I had one from a local supplier the next day at a suggested retail of $1068.00. THis furnace is just over the warranty period and the savings of fuel compared to the cost of repair came to mind. This was more than likley a $4500 furnace install (compared to a 80%er @ $1800) repair cost $1200 that's $120 a year for that one part. 15% of my gas bill is $333 a year, the cost of the low eff furnace difference is $2700 that's another $270 a year so $270 and $120 brings us to $390. per year. I am not saying the 80% er isn't going to brake down but chances are it will do ok if serviced regularly (which this high eff was )
Comparing the hi end stuff to the low end, I don't see a real savings at the end of the day, lets say a 15-20 year piriod. Now we must concider the blower motor is more than likley not far behind the idf, as they usually last 10 years or so, they also cost $900 compared to the split cap's @ $180.
I would appreciate some input from other teck's on this subject.

[Admin]

$1800 sounds low for a mid efficient variable speed furnace.  With a 80% vs 95% AFUE furnace you will save 10-15 cents for every dollar you spend on gas.  If you're comparing a mid efficiency non variable speed, then you would save at least 40% on the electrical consumption by going with a variable speed blower.

In my area we have about 2500 heating hours.  So a high efficiency furnace could save you up to $375 a year on gas.  There's usually government and utility rebates available for high efficiency furnaces.  It really depends on where you live and how many heating hours you have.  Most people around here go with high efficiency furnaces.

[Zzz]

I am back to diagnostics of variable speed motors again. In my area (Lower mainland BC) there was a major power spike and it took out all the ECM motors, that were running, in one area. I have diagnosed them by means of what the boards were telling me however, on a carrier 58mvp I was wrong thinking it was the board because, it told me both the idf and circulator motors were faulty. I normaly change the board if I don't bielive what it says, well this board retails for $530. I looked pretty stupid when I changed it without success. I have a tester for the blower motor but the idf's are a different story, there are to many different brands to have a tester for each one. I know you can test the blower with a 9v battery, but I don't know how to do that on the idf's.
Can anyone help me with this, I have been asking every source I can, and no one seems to be able to help.

[Admin]

I use the GE TecMate XL to help diagnose ECM motors.  I think you can buy one - Here

You can download a good ECM Service Guide - Here

[northerntech]

I would agree, ECM blower motors are nice but still to expensive plus the controls needed to run them, any customer I had who got a quote to replace one was shocked and we all know what that is like. I discovered a product called fan handler, I converted my furnace at home with this system and it blows ECM out of the water. You can visit their site online, I got the controller and the ball bearing PSC motor they sell. If you have clients with noisy blower complaints or temperature variations in the home Fan Handler is the way to go. Not to mention what it does for the A\C operation.

[Admin]

I just visited the webpage for FanHandler - Here

It seems like a cool alternative.

The rebates you get from the government and the OPA usually covers the cost difference to upgrade to a DC variable speed motor.  I usually end up selling the variable speed because of that.

[Zzz]

Today I brought that ecm IDF motor home since no one seems to be able to tell me how to diagnose it I will disect it on my bench and get back to you with the results. I am not a person who gives up easily. My only problem will be this IDF does not work so, diagnostics is going to include repair. I am sure there is something blown in the ecm part cuz the rest is just a  simple motor.
I will post the results.
Admin, thanx for the link it was very interesting.

[Zzz]

Don't make the same mistake I did the other day. I had a Lennox ECM motor on the shelf so I tried it in a Carrier. Althouhg the plugs fit the housing is the same size and they look identical, they use different pins on the 20 pin connector.
Most of what I know I learned from mistakes, if i share them others can learn in an easier way.

[Zzz]

Can some of you a/c guys give me your opinion of this information?
TEMPERATURE CONTROLLED BLOWER MODULATION FOR AIR CONDITIONING HUMIDITY CONTROL.
The purpose of this article is to explain some of the common problems encountered with humidity control in modern high-speed air conditioning and how controlling blower speed from a temperature signal can eliminate these common problems as well as increase the comfort and livability of.a home.
FACTS AND RULES OF THUMB THAT YOU CAN TAKE TO THE BANK
1. If water stands in a drain pan, the pan is either poorly designed or improperly installed.
2. What is normally called "low load conditions" refers to load from temperature gain and is not necessarily the total load necessary for efficient operation and comfort.
3. Humidity can be a significant load that is not addressed.
4. Every 10% drop in relative humidity is the comfort equivalent of a 3° drop in temperature. I.e. drop the humidity by 10% and you can enjoy the same level of comfort at a three-degree higher thermostat setting. This saves energy.
5. Water adheres to the A/C coil better as the coil gets colder.
6. When the A/C compressor turns off and the blower's speed remains high, the coil gets warm very quickly and doesn't grip the water as tightly.
7. The faster that air moves over an A/C coil, the higher the coil's bypass factor, and the warmer the coil, and the warmer the delivered air temperature which results in the less adhesion the coil has to to water. Thus water sprays off the coil and into the ductwork.
8. A warm coil (either right after the compressor shuts off or under high air velocity) doesn't hold water tight enough to give it time to flow down the entire height of the coil to the drain pan before being blown from the coil by the high-speed air movement through the coil.
9. If (with the compressor running) the air velocity over the coil is less than 500 feet per minute: An A/C coil, under normal operating conditions, will hold water long enough for it to flow down the coil and into the drain pan.
10. The method of determining the air velocity (called face velocity) over the coil is to divide the CFM air delivery from the blower by the square foot face area of the coil. When velocities reach over 600 feet per minute, then you can be sure that water will strip from the coil and be blown down the ducts even if the coil is quite cold.
11. PHYSICAL CONSIDERATIONS THAT REQUIRE DISCUSSION.
a. The space between the coil plates or fins (Usually 14 fins per inch) is designed to allow air to move freely through the coil and still allow enough air to impact the coil to reduce the temperature of the air enough for effective cooling.
b. The thickness of the coil. Usually allows 3 or 4 rows of refrigerant tubing.
c. Water that is flowing down the coil takes up space. There is a condition where the amount of water in the coil can build up because it can't get down to the drain pan fast enough, this excess water takes up free space that was designed for air delivery and reduces the amount of free area for air to flow at an efficient (500 ft. per minute) velocity through the coil. It has the same effect as reducing the size of the coil. In this case, the air velocity through the remaining, or available, free area increases to over 600 feet per minute. At that point water is stripped from the coil.
12. Coil bypass factor is the percentage of air that goes through a coil without being affected by the coil. Cooling is done only to the air that actually touches the coil's fins.
13. Typical bypass factors for a three-row coil with 14 fins per inch are:
FACE VELOCITY IN FEET PER MINUTE
BYPASS FACTOR OR PERCENT OF AIR NOT COOLED BY THE COIL
COMMENT
600
23%
WATER SURFACE TENSION BROKEN RESULTING IN WATER SPRAYING DOWN THE DUCTWORK.
500
18%
500 FT PER MINUTE IS USUAL ENGINEERING DESIGN FOR MAXIMUM FACE VELOCITY
400
14%
300
11%
200
9%
VERY HIGH COIL EFFICIENCY
The delivered air temperature is the result of mixing very cold air cooled by the coil fins and the room temperature air that goes through the coil space without being cooled.
A COMMON ATTEMPT AT SOLVING THE HUMIDITY PROBLEM
Blower speed timed programs: i.e. run the fan for a number of minutes (maybe 7 minutes) on low (about ½ speed) During this time the coil is super cold and super efficient and collects large amounts of water. During certain high humidity conditions, the A/C coil loads up with water faster than it will drain. After the low speed segment has timed-out, the blower ramps to high speed. This does two things: First it warms the coil, which reduces the water's adhesion to the coil. Second, high velocity through the remaining free space breaks the surface tension of the water so the droplets break apart and they blow off the overloaded coil and down the ducts. This is why many contractors in high humidity areas do not use this feature.
ANOTHER COMMON ATTEMPT AT SOLVING THIS PROBLEM
In high humidity areas, it is also common to either run the fan on intermittent or turn off the fan for a period of time after the compressor shuts down in an attempt to give the coil time to drain. This is not a solution to the recognized problem of blowing water off the coil and re-evaporation. It is avoiding the problem rather than solving the problem. It also makes the home less comfortable, less quiet and the wide variety of indoor air quality products less efficient.
DRAIN PAN PROBLEMS
The common statement concerning coil drain pans is: "When you run the blower while the compressor is off, you'll re-evaporate the water standing in the drain pan." Somehow this statement has been used to the point that it has become folklore. The proper design and tilt of the drain pan is all that is required for it's proper function. First, the word drain in the name of the device should provide a clue to its function. Water should not be standing in a drain pan. Second, to evaporate a couple of ounces of water at temperatures we are dealing with is not instantaneous. Third, even if a few ounces of water were evaporated into the thousands of cubic feet of air that is inside a home, it would have about a zero consequence.
TEMPERATURE CONTROLLED BLOWER SPEED
SOLVES THE PROBLEM
MORE FACTS THAT YOU CAN TAKE TO THE BANK
1. Blower speed can be controlled effectively and efficiently by changing the voltage to any high quality shaded pole or PSC blower motor. It has been done since the late 1950's or early 1960's.
2. When blower speeds are controlled through quality motors, the fan laws are in full effect.
a. When you reduce the speed of the blower by 50%, you reduce the CFM by 50%
b. When you reduce the speed of the blower by 50%, you reduce the static pressure to one fourth.
c. When you reduce the speed of the blower by 50%, you reduce the power required to one eighth of that required to run it at full speed. (i.e. You can run a good blower motor for eight hours at half speed for the same amount of money that it would take to run it full speed for one hour)
3. Typical speed/temperature relationships for blower speeds controlled by temperature. Using a typical, average designd for a three-ton system. (Using rounded numbers for simplicity)
a. 36,000 BTUH
b. 400 CFM per ton or 1,200 CFM at full speed
c. Minimum speed is set at about 35 or 40% of full speed or about 450 CFM at about 450 rpm blower speed when the delivered air temperature coming off the coil is above 68° F.
d. Maximum blower speed about 1070 RPM when the delivered air temperature coming off the coil is about 50° F.
e. The fan is set to run continuously.
f. For every degree of temperature reduction from 68° F delivered air the fan motor's speed increases about 34 RPM. Or for every 34th of a degree temperature drop, the fan speed increases one RPM. This is smooth and seamless.
TYPICAL AIR CONDITIONING CYCLE
USING TEMPERATURE CONTROLLED BLOWER SPEED MODULATION
1. Room temperature about 75°.
2. Indoor humidity high. (maybe over 70%)
3. Blower running continuous at about 450 RPM and delivering about 450 CFM.
4. Compressor comes on.
5. Air is moving over the coil slowly.
6. The bypass factor is about 10%, which means the coil is super efficient and very cold.
7. Because the coil is very cold and super efficient, it cuts into the latent load and begins rapidly collecting water.
8. Because the coil is so cold, the air coming across the coil also cools down rapidly and reduces the delivered air temperature.
9. Because the air temperature is reduced, the blower's speed is automatically and instantly increased.
10. Here are some interesting points: The coil has established its grip on the latent load and is collecting water to the coil's maximum design capability to capture water.
11. The compressor doesn't know the difference between latent and sensible loads. It only sees a load.
12. Because the coil is capturing water to it's maximum ability, the remaining capacity of the compressor is then devoted to the sensible load. The remaining compressor capacity may not be enough to drive delivered air temperature down to the 50° temperature required for full speed blower operation. The delivered air temperature might be 54° degrees and between 900 and 1,000 CFM. (That is why when Florida, gulf coast and contractors in other high humidity
areas first install temperature controlled blower modulating controls, they think that the blower is going too slow. However, when they look at their gauges, they see the unit is working its lungs out because it is concentrating on the latent load. A day or two later, the house has dried out. The delivered air temperature is colder and the blower is running faster.)
13. Compressor Shuts off:
14. The coil and delivered air begin to warm a little. The blower's speed immediately and smoothly drops to about 50% of the way between the highest speed that it achieved at its coldest point and the 450 CFM minimum speed. Lets say about 675 CFM.
15. 675 CFM isn't going to blow water off a 1,200 CFM coil. The coils is going to drain.
16. Interesting point #2: There is a good amount of cooling capacity in pressure equalization. The high-pressure liquid refrigerant moves into the evaporator and does some cooling. It usually takes about 5 to 10 minutes for the pressure in a system, with good valves, to equalize.
17. During this time, the blower's speed is smoothly dropping towards the minimum speed. The coil is cool, the coil is draining, and there is no re-evaporation.
SUMMATION
Temperature controlled blower speed:
1. Eliminates the problem of blowing water off A/C coils.
2. Results in maximum humidity removal by automatically adjusting for latent loads.
3. Allows comfortable and quiet continuous blower operation that permits all accessories attached to an HVAC system to operate at full-time at full efficiency.
4. Increases efficiency.

I am not trying to sell thi I want to buy one.

[northerntech]

 I have one running in my furnace at home right now, the comfort level and noise level are so much better. I cant wait until cooling season, the blower will run slower to remove a bunch of latent heat until the evap temp starts to drop. The result should be lower humdidty levels in the summer and greater comfort. So far the temperature difference between the main floor and basement is one half a degree celcius.

[northerntech]

 Sorry, I meant the fan handler product is in my furnace should have clarified that.

[Zzz]

ANy bad coments on the subject?
Everyone seeems to love em so far.
AM I right to assume (there's that word again) you need a ball bearing motor for these units?

[northerntech]

 You can use the control on any PSC motor, Fan handler claims that if the motor is of poor quality a grumbling noise may be heard. They sell a high quality Baldor motor wich happens to be a ball bearing motor, something I have never seen in residential grade PSC motors. So I thought why not give the motor a try as well, but nothing stops you from using it with the existing motor. Apparently their first control was designed for the old belt drive fan setup, that would be cool to see in operation.

[Zzz]

Northern
I think that would sell since some folks with belt drives don't want to give up the ole clunker that never let them down exept for the thermocouple they changed themself 8 years ago but, added a heat pump for efficience???not my thinking but try and change em ya know.