Motor Rotation

Many single phase motors can only turn in one direction. For example, pump motors and fan motors. Since the pumps and fans they operate only work in one direction, the motors that drive them re usually built for one direction.  This can pose a problem for service techs when replacing these motors. Often, service motors solve this problem by being reversible. However, OEM replacement motors are generally not reversible, so you must specify the correct motor rotation. To do this you need to understand the terminology that is used to describe motor direction.

There are only two possible rotations: clockwise and counter-clockwise. However, there are also two perspectives: looking at the shaft end of the motor or looking at the lead end (opposite the shaft end). A motor which turns clockwise looking at the shaft end is turning counter-clockwise when viewed from the lead end! The point is that just stating a direction is not good enough. You must also identify a perspective.

There are several names for the two possible perspectives. The most common are shaft end and lead end. The shaft end can also be called the output end, drives end, or pulley end. The lead end is sometimes referred to by placing “opposite” in front of whatever phrase is used to describe the shaft end; such as, “opposite drive end.”

Normally these descriptions are abbreviated, which tends to add to the confusion. Below is  list of some of the abbreviation used. The graphic above each group uses an arrow to show the rotation looking at the motor shaft.

CCWSE Counterclockwise shaft end
CCWOE Counterclockwise output end
CCWDE Counterclockwise drive end
CCWPE Counterclockwise pulley end
CWLE   Clockwise lead end


CWSE  Clockwise  shaft end
CWOE Clockwise output end
CWDE Clockwise drive end
CWPE Clockwise pulley end
CCWLE Counterclockwise lead end

Clockwise and Counter-Clockwise

Many folks have heard the phrase “righty tighty, lefty loosey.” This little limerick is a clever way of remembering which way traditional right-handed threads turn. However, it can be misleading. The right or left direction refers to the direction the top of the circle will turn. But the bottom of the circle turns in the opposite direction. So while the top is being turned to the right, the bottom is being turned to the left.

CLOCKWISE

COUNTER-CLOCKWISE

I really prefer the terms clockwise and counter-clockwise to describe rotational movement because you don’t have to be concerned if you’ re looking at the top of the circle or the bottom. You only have to remember which way a clock hand moves. Therein lies the problem. In today’s digital age, some people can’t tell you which way a clock hand moves because they rarely see one.

Every program should have an operating analog clock in the class room so students can learn the difference between clockwise and counterclockwise. Notice how the numbers on the clock face progress from the top to the right, creating clockwise motion. Logically, counter-clockwise motion is the opposite.

LEFT HAND THREAD ON ACETYLENE HOSE

This little saying also ignores the left handed threads, which are exactly backwards from right-hand threads. Although far less common, left hand threads are often found on connections for flammable gas, such as the regulators and hoses used for Acetylene on an oxy-acetylene torch. In that case it is “righty loose, lefty tighty.” Doesn’t have quite the same ring to it. Left hand threads on torches have a hash mark on them to indicate that they are left-hand threads. The acetylene and oxygen have opposite threads for a reason – to prevent mixing up the regulators and hoses. Mixing the gasses under pressure can create a combustible mixture.

Intelligent Controls Improve System Charging

"Charge View" by Johnson Controls

Units with intelligent boards that assist in system charging are available. Many VRF systems can assist technicians in charging the unit. They are so complex that some type of automated assistance is really necessary. With multiple heads and variable capacity compressors there is really no way to use system pressures to determine the correct charge. Computer assistance is available through installation and charging applications that run on laptop computers, to evacuation and charging modes built into the system controls.

Trane introduced split system units with “Charge-Assist” back in 2008 in their Xli line. These systems have pressure transducers and temperature thermistors which are used to operate the electronic expansion valves in the unit. The board can also use the input from these sensors to determine if the system charge is correct. An external  “Charge Assist” solenoid can be controlled by the board to allow the unit to charge itself. On these units, the technician only sees a blinking LED on the unit control board.

Johnson Controls (York, Coleman, Luxaire) are now offering units with built in pressure and temperature monitors and a screen to display system pressures, liquid line temperature, suction line temperature, superheat, and subcooling. The system will also tell you if it is correctly charged. It is like having a digital gauge set built into the unit. The main point is that you can check the unit charge without attaching any gauges or temperature probes. That means you will not lose any refrigerant while checking the charge.

These examples represent only the very high end systems from a few different manufacturers, but I believe it shows the direction the industry is headed. Systems will have sensors and intelligent controls monitoring system operation. I am sure that as the technology matures, its cost will come down, making this technology attractive to other manufacturers and in more main line units. Another driving force will be the desire to insure actual equipment performance and efficiency match the design. The most efficient system available installed incorrectly may perform worse than the lowest builder grade equipment available. Designing intelligent controls into a system is a way to improve system installation and service by taking guesswork out of charging. With systems employing these intelligent controls you really have no excuse for leaving the unit improperly charged.

Measure System Capacity and Efficiency

System tune-up time is here. Imagine if you could give your customers a report that shows the system capacity and efficiency before and after your system tune-up! There is a tool that can do that, the iManifold. It not only can measure system characteristics such as pressure, temperature, superheat, and subcooling; it can use the measurements to determine BTUs/hr capacity and system EER. To be sure, you need a few other measurements; namely, dry bulb and wet bulb in and out of the evaporator as well as system operating voltage and current. The iManifold with the correct accessories can measure the characteristics necessary to do system capacity and efficiency calculations and perform the calculations. It can also produce reports showing the details, including system capacity and efficiency. The report can be printed or e-mailed to the customer. The only “report” most customers get now after a traditional system tune-up is a bill. The iManifold and iConnect are the only tools I know of that can do this.

What accessories do you need? You also need two wireless temperature/humidity probes made to work with the iManifold and an electric meter that can communicate with the iManifold. The iManifold and the necessary accessories required to measure system capacity and efficiency are definitely more expensive than many other digital gauges. However, the iManifold does things other digital gauges cannot do.

To learn more about the iManifold chaeck out their web site imanifold.com

Don't Make the Problem Worse

There is a saying that if the only tool you have is a hammer, every problem looks like a nail. Many inexperienced techs make the mistake of trying to fix everything using the handful of procedures they are familiar with.

The most common “fix” applied to many systems is to add refrigerant. If a system is operating with low pressures or freezing up, many techs will add some refrigerant. Homeowners often actually ask for techs to add refrigerant, thinking that more refrigerant must mean colder air. However, adding refrigerant may not actually fix the problem. In fact, often it may make things worse.

For example, if a system has low airflow it will have low pressures, and often will freeze up. The reduced load will cause low superheat and refrigerant floodback. Adding refrigerant just makes the floodback worse, shortening the compressor life. An undercharged system would have a high superheat. You should always check the system airflow, superheat, and subcooling before adding refrigerant.

Another common example is a system with a refrigerant restriction, such as a plugged up filter drier. Again, both pressures will be low, and BOTH the superheat and subcooling will be high. This can look similar to an undercharge, except for the subcooling. An undercharged system will have a low subcooling. Adding refrigerant fills up the condenser, raising both the high side pressure and the already high subcooling. It may marginally improve the low side pressure and capacity. However, it forces the system to run at an excessive compression ratio and uses lots of power trying to force the refrigerant through the restriction. A far better solution is to remove the restriction.

Finally, a clogged or stuck expansion valve behaves like a refrigerant restriction. Failed expansion valves used to be quite rare. Unfortunately, they are pretty common today. Between the valves that were fouled up because of the compressor manufacturing problem and the valves that become clogged with black copper oxides, failed expansion valves have become all too common. The symptoms are identical to a refrigerant restriction: low pressures, high superheat, and normal to high subcooling. If someone has already tried to “fix” the problem by adding refrigerant, then the high side pressure may be high and the subcooling will be very high.

Please don’t make the problem worse. Before adding refrigerant to a system with low pressures, first check: airflow, superheat, and subcooling. A truly undercharged system will have adequate airflow, a high superheat, and a low subcooling. And if the system is undercharged, then maybe you should try to figure out why.

How Much Refrigerant Does it Take to Make the Fan Blow Harder?

My brother Richard sometimes finds himself helping younger technicians who are stumped and need the help of an experienced professional technician. However, they have to really need help because they know Richard is going to twist their tail a bit in the process.

One day a frustrated tech called and told Richard that he was working on a system with a low suction pressure that was frosting up. He further explained that his new digital gauges were telling him that the superheat was 0, so he added refrigerant. However, no matter how much refrigerant he added, the superheat would not increase.

Richard asked him, “how much refrigerant do you have to add to make the fan blow harder?” There was no response, so Richard asked again, “Tell me, I really don’t know. How much refrigerant does it take to make the fan blow harder?” Finally, the tech responds: “Your question makes no sense! There is no relationship between the amount of refrigerant in the system and how hard the fan blows.” Richard then replies “So why are you trying to fix an airflow problem by adding refrigerant?”

While it is true that an undercharge can cause an air conditioning system to frost, the most common cause of a frosting air conditioning coil is actually low airflow. Always look at airflow issues first when trying to remedy a frosting air conditioning system. Common airflow issues include a dirty air filter, a dirty evaporator coil (caused by dirty air filters), closed registers, and poor ductwork.

One tip-off is superheat.  A system with airflow issues will operate with a low superheat while an undercharged system will operate with a high superheat. Note that if the coil is frozen over it will need to be defrosted before any pressures or temperatures are checked. The ice covering the coil makes its own airflow restriction.

PHCC Scholarship Deadline May 1

Could you use another $1000 to help with your HVACR Education? The Plumbing, Heating and Cooling Contractors (PHCC) are handing out money! Specifically, PHCC has announced that the deadline to apply for a PHCC Scholarship is May 1st. The PHCC has 41 different awards totaling $87,500 to give to deserving students. Each awrd ranges from $1000 - $5000.

Eligibility Requirements For All Applicants

• A minimum cumulative grade point average of at least 2.0 for my previous academic work.
• A citizen of the United States or Canada.
• Have not previously won a scholarship from the Foundation. 

There are Scholarships for Apprentices, Technical School Students, and Students working towards a Bachelor's Degree

Apprentice Requirements

• You are or will be enrolled in an Apprentice Program
• You are or will be will be enrolled this year in a plumbing or HVACR apprentice program.
• You also work full-time for a licensed plumbing or HVACR contractor who is a member of the Plumbing-Heating Cooling Contractors—National Association (PHCC).
• Provide the PHCC Member Company Name, City & State:

Note: A max. of four employee scholarship applications per company will be accepted for consideration per year.

Community College and  Technical School Student Requirements

• You are or will be enrolled in a Community College, Trade or Technical School
• You are or will be enrolled this year in a full-time degree or certificate program at an accredited two-year community college, technical college or trade school.
• You are or will be enrolled in an approved major directly related to the plumbing-heating-cooling profession.
• Approved majors are: business management; construction management specializing in mechanical construction; HVACR installation, service or repair; mechanical CAD design; and plumbing installation, service or repair.*

Note: The PHCC of Massachusetts & PHCC of Texas Auxiliary scholarships have no restrictions on course of study.

Four Year College Student Requirements
You are or will be enrolled in a Four-Year College or University
You re or will be enrolled this year in a full-time undergraduate degree program at an accredited four-year college or university.
You  are or will be enrolled in or will be enrolling in an approved major directly related to the plumbing-heating-cooling profession.
Approved majors are: business management; construction management or science, specializing in mechanical construction; and mechanical engineering.*
Note: The PHCC of Massachusetts & PHCC of Texas Auxiliary scholarships have no restrictions on course of study.

Where to Apply

You can apply online here https://www.surveymonkey.com/r/PHCCScholarships
Or download and complete the pdf form found here
http://s3.amazonaws.com/rdcms-phcc/files/production/public/2011Foundation/PDFs/2017PHCCScholarshipApplicationForm.pdf