Replacing Condenser Fan Motors

Hot weather always brings on a lot of condenser fan motor replacements. Although it is not too difficult to change a condenser fan motor, it is still possible to do it incorrectly. Of course you need a motor that operates at the same voltage, phase, and frequency of the original motor and it should also be the same horsepower. However, I would like to mention a few items to check that I often find techs have overlooked. First, make sure the motor you plan to use is actually designed for a condensing fan motor. Specifically, is it sealed and is it designed for vertical shaft installation (assuming a typical vertical mount, induced draft condenser fan). Motors with air vents on the sides or top should not be used outside. Also, all motors are not rated for vertical shaft installation. Some motors are designed for horizontal shaft mount only because they do not have the necessary thrust bearing to take the downward force against the bearing when the fan pushes air up. Next, is the motor the correct RPM? Some condenser fan motors turn 1075 RPM while others turn around 850 RPM. They are not interchangeable. If you can’t read the label on the old motor, take it apart and look at the number of poles. A 6 pole motor will be a 1075 RPM motor and an 8 pole motor will be an 850 RPM motor. Does the new motor turn in the correct direction? If you cannot see the markings on the old motor, you can tell by looking at the fan blade. First, the cups of the blades should be facing up on an upflow blower. Next, the blade should turn in a direction that allows the lower part of the blade to hit the air first. If the blade turns clockwise looking down on it, this is called clockwise shaft end, or counter clockwise lead end because the lead end rotation is always opposite the shaft end. Some motors specify the rotation looking at the shaft while others specify looking at the opposite end where the leads come out. If you are using a general purpose replacement motor, such as a Rescue Motor, you can change the motor rotation if you need to. Some of these motors use different size capacitors for different horsepower ranges. Make sure the capacitor you are using fits the application. Most likely, the capacitor for the old motor will not be the correct size. Most sealed condenser fan motors have weep holes on the bottom that come plugged with plastic caps. You should remove these when installing the motor. The idea is to let condensation out. The motor will last longer if you open the bottom weep holes.   After installing the motor and fan, turn the unit on and then off again to see which way the blade is turning. If it is turning in the wrong direction, change the rotation leads on the motor. Changing the power leads will have no effect. Once you establish that the fan is turning in the correct direction, operate the unit and check the motor amp draw. If it operates close to  the manufacturer’s FLA specification for your particular application, you should be good to go.

Tools for Success

HVACR mechanics rely on their tools for survival. It is not possible to install, service, or troubleshoot HVACR systems without tools. Having the correct tools for the job and knowing how to use them can be the difference between success and failure. Teaching tool use is more critical now than ever before. I have noticed an increasing number of students who are quite intelligent, do well in class, show genuine interest in our field, but struggle to perform fairly basic operations with hand tools. One student confessed to me after he graduated that he had never held a wrench until he took Air Conditioning. What he didn’t know was that it was fairly obvious. The good news is that his innate intelligence and strong work ethic allowed him to overcome this and go on to be successful. He took a job as a helper for one of the best refrigeration mechanics in town, who also happens to be a patient man. You see, the mechanic had cancer, and his ability to perform the physical part of the job was declining. The student became the hands and arms for a gifted mechanic, and in the course of a summer the student became proficient at using tools. He has stayed with that company for five years. He loves his job and the people he works with. If you have bright eyed, eager students from the “virtual generation” show them how to hold a wrench, give them lots of shop work to practice their tool use, and be patient with them. They could end up working with the best mechanic in town.

High Flow Access Valves

I ran into something this week that I was not aware of ; a new design access valve that works like a Schrader valve with a pin to depress, but allows 5x the flow of a normal Schrader valve. They are called Coremax valves by a company named FasTest. You can’t take these cores out with a typical valve core tool. I assigned a student the task of removing a core from a Carrier packaged unit, and instead, they broke the valve. However, it was not their fault, you can’t remove these cores with a typical core tool. FasTest sells a tool that will do the trick – for $189. Alternately, you can recover the charge and take the core and the assembly that holds it out with two wrenches, which is what we did. 

Important Safety Note

Do NOT take the valve apart without first recovering the refrigerant - you will get a face full of refrigerant!

 

It is easy to tell these valves apart from regular Schrader valves if you look closely. First, the brass fitting holding the valve is larger than typical Schrader valves. Next, you can see that the top part can be removed from the bottom with a wrench Finally, the head on the pin that operates the valve is larger than the head on a traditional Schrader. The advantage of these is that they open to a full 1/4” hole just by depressing the pin – so you get faster recovery, evacuation, and charging. The disadvantage is that if you want to take the core out for even better flow or if you need to change a leaky valve core, you need their $189 valve core tool. I don’t know how many other manufacturers are using these, but I found out Carrier has been using them on packaged units since around 2006. Here is a link to a web site explaining how these valves work and showing pictures. Coremax Valves

Here is a link to a Carrier Service Bulletin that was posted on HVAC-Talk.com

So a word to the wise - if your valve core tool does not appear to fit - maybe it doesn't. You might have a Coremax valve instead of a Schrader valve.

Aluminum Coils

Aluminum coils are here to stay. Not only have they been applied successfully for years by Trane in their spiney fin condenser coils, they have also been used for years as evaporator coils in refrigerators. Now several major air conditioning equipment manufacturers are viewing aluminum coils as a potential solution to the industry wide plague of formicary corrosion in copper tube aluminum fin evaporator coils. Trane and Goodman both now use all aluminum tube and fin coils in their indoor coils for air conditioning and heat pump systems. Nordyne uses all aluminum microchannel coils for their indoor coils, and Carrier is researching the use of microchannel indoor coils. In short, you really need to be prepared for aluminum coils regardless of how you feel about them. I confess to having a prejudice against aluminum coils. One of my issues is the difficulty of repairing aluminum coils. But truthfully, today’s copper tube and aluminum fin coils are not very repairable either. The copper is so thin that it is very difficult to braze. And brazing mico leaks from formicary corrosion is a losing proposition. You plug this tiny hole and leave 3 others. Or 3 more form a week after you leave. The biggest two service differences come in coil cleaning and system charging. Most manufacturers recommend only water to clean aluminum coils. The wrong chemicals can eat them up. As with any indoor coil cleaning, if you do use a chemical – make sure it is approved for use on indoor coils. Using an outdoor coil cleaner on an indoor coil can cause noxious fumes for quite a while. Some chemical companies do manufacture coil cleaners that are approved for use on indoor aluminum coils. One thing you might look for is NSF approval. A cleaner used on refrigeration equipment around food must be NSF approved. While not necessary for air conditioners, an NSF approval should mean that there would be no toxic fumes. For more information on cleaning aluminum coils look at these instructions from York, Nordyne, and SpeedClean.  

Reading Voltage Across Switches

Voltmeters read the difference in potential from one point to another. When a voltmeter indicates a reading of 120 volts, this means that one lead is 120 volts higher than the other lead. We often refer to this as voltage drop. I find that people often misinterpret voltage readings across switches. A switch is designed to either allow current flow, or stop it by opening the circuit. A voltage reading across a switch indicates that the switch is open (off). Let’s take a circuit with a light and a standard toggle switch controlling the light. With the switch off, you will read 0 volts at the light. If you read voltage across the light switch, you will read 120 volts with the switch off. The voltage is dropping across the switch. Now if you turn the switch on, the voltage reading across the switch will change to 0 volts. Checking the light, you now read 120 volts at the light. When current travels through a switch, there should be NO drop in voltage. When current travels through a load, there SHOULD be a voltage drop. A closed switch should have a resistance of close to 0 ohms, while a load should have a measurable resistance. Using Ohm’s law to calculate the expected voltage drop across a switch you would get 0 volts because 0 ohms times any amount of current would still be 0 volts. I have often seen students looking for the break in a circuit read voltage across a switch and declare that switch is OK because they got a reading. In fact, that switch is open because they got a reading. One point to keep in mind is that the voltage across all devices in the circuit should add up to the source voltage. If you are reading 120 volts across a switch in a circuit wit a source voltage of 120 volts, there is no voltage left for the load.

HFC Agreement

Recently on June 7, 2013, President Obama and Chinese President Xi Jinping met for talks in Rancho Mirage, California. One of the agreements to come out of the talks was an agreement for both countries to work together to reduce HFC production. The statement reads

"Regarding HFCs, the United States and China agreed to work together and with other countries through multilateral approaches that include using the expertise and institutions of the Montreal Protocol to phase down the production and consumption of HFCs, while continuing to include HFCs within the scope of UNFCCC and its Kyoto Protocol provisions for accounting and reporting of emissions."

Basically, the big news is that the two biggest producers and users of HFCs agreed with each other to work on reducing their use. Europe has already started their reduction of HFC use and their regulation of F-gasses. F-gasses are their catchy phrase for all fluorinated refrigerants. I believe the F part tells us what they think of them.  There is no need for immediate panic. Notice that the agreement basically says they believe that reducing HFC production and use is something good to do. There are not yet any targets, timetables, or details. However, it clearly lays out that HFC refrigerants will be with us for a far shorter period of time than the CFCs and HCFCs they replaced. You can read more details and background in this White House Press Realease.

Lights Out!

Last night my family and I were all engaged in our own individual electronic pursuits. All of us in close proximity, but worlds away in our own individual internet enabled abstraction. A thunderstorm cut off our power and our internet connection. So lacking the ability to communicate with our far flung internet friends, we were stuck in a room talking to with each other. So we talked about what was going on in our lives. What happened at church this past Sunday, what our friends were doing yesterday, details of the lives of people whose lives are intertwined with our own. Then my son got out his guitar and started singing. Nothing on you-tube compares to the joy of making music with your family. There are certainly better guitar players and singers on line, but they are not sitting in my living room. They don’t share my name and my blood. They don’t compare. I received an early father’s day gift when my connection to the outside world was severed. Preston Stanfield live in concert in my living room.

There is not an app for that.