Author: BryanOrr

Bryan Orr is the CoFounder of Kalos Services Inc. a Multi-Discipline HVAC/R Contracting Company in Central Florida as well as the creator and founder of HVAC School podcast, YouTube and Website

Educators love lockout relays and we also love pretending you will still see them out in the field all the time. Sometimes I have to look myself in the mirror in the morning and sadly repeat “lockout relays are dead” several times before the reality sinks in.

before I get the emails… they aren’t COMPLETELY gone but the function of a lockout relay has largely been replaced by electronic controls.

We don’t love them because of their modern practicality, we love them because they help us understand something cool about electricity while we better understand schematics. The problem is, often the thing we learn from and about them is incorrect.

To paraphrase Ronald Reagan

It isn’t that we are ignorant about lockout relays, it’s just that so much of what we know about them isn’t so

In other words, lockout relays are the teenagers of the HVAC trade – We “just don’t understand them and what they are going through nowadays DAD!”

Enough of the misquoted and crappy metaphors… we have some more misunderstandings and crappy metaphors to debunk

The Legacy of “Path of least Resistance” 

Take a look at this very simple wiring diagram. Does the electricity ONLY follow the path of least resistance from left to right (L1 to N)?

Of course not… if it did only one of the loads shown compressor, condenser fan, evaporator fan motor or liquid line solenoid could work at once.

If this were true in real life your compressor would be the only one that would run on every air conditioning condensing unit you ever worked on, because the run winding on the compressor is the lowest resistance path on the unit.

What people could mean by saying “electricity takes the path of least resistance” is to say that more electrons move (higher current) on paths of lower resistance. This is a true statement and demonstrated clearly in ohms law. Because Volts = Amps x Resistance a path of lower resistance will result in higher amperage if the voltage remains the same.

The problem occurs when teachers use a lockout relay as PROOF that electricity takes the path of least resistance, and this, along with generally helping folks understand the lockout relay, is the reason for this article.

What a Lockout Relay Does

The purpose of the lockout relay is to keep the compressor off when there is a significant fault EVEN if the fault condition goes back to normal. For example, if a high-pressure switch opens the lockout relay can keep the system off even once that switch closes again.

Quite simply a lockout relay is an old-school way to keep a compressor or other critical component “locked out” so it doesn’t ruin itself slamming on and off when safeties open and close.

Take a look at the diagram above and find the LO contacts and Coil. The contacts are normally closed and under normal circumstances, the current will move through the LO contacts and allow the CC (compressor contactor coil) to energize bringing on the compressor and the CFM when the C contacts close.

It’s exactly how and why this strategy works that often leads to misinformation and misunderstanding.

Voltage Drop is Key

It’s no secret that I don’t like math and I don’t like showing math on tech tips because it causes instantaneous narcolepsy from most technicians. If you know how to calculate voltage drop in series circuits then this exercise will be simple and won’t require you to trust me at all.

NOTE: ALL THE NUMBERS SHOWN IN VOLTS AND OHMS ARE MADE INTO VERY ROUND NUMBERS FOR SIMPLICITY – THESE ARENT WHAT YOU WILL MEASURE IN REAL LIFE 

We aren’t used to working with series circuits so it’s easy to get confused but the easiest way to understand them is to remember that the voltage drop between any two points in a circuit is equal to the amount of resistance between those two points compared to the total circuit resistance.

Look at the hypothetical diagram above and you can see 24 volts total with a total circuit resistance of 20 ohms. Because each of the loads shown makes up 50% of the total resistance they also each have 50% of the total circuit voltage drop.

Easy enough right?

But now let’s say one of the loads has 9X as much resistance as the other – It would see a proportionally greater voltage drop across it than the other. This can be called voltage drop or it could be called applied voltage, either way, it is the voltage that a particular load is “seeing”.

In other words, in a series circuit, the greater the resistance a particular load has the greater the voltage that load will get in relation to the other loads in series with it.

The Incorrect Answer

Many people will explain the lockout relay circuit like this. When the relay and safety contacts are closed the path of least resistance is through the safeties and the contactor coil so the current takes that low resistance path. When any of the safety switches open the current is then FORCED to go through the lockout relay coil because it is the path of least resistance which then causes the lockout contacts to go open keeping the contactor coil locked out.

Why is this the incorrect answer?

Because electricity takes all paths where a sufficient potential difference is present not only the path of least resistance. The reason the lockout relay coil remains unenergized during normal operation is due to insufficient potential difference not the path of least resistance.

How the Lockout relay works 

The lockout relay coil is a high resistance coil wired in series with the contactor coil but in parallel with the safety switches.

When the safety switches are closed the resistance through them is VERY small, in this example, I show a 0.1-ohm resistance through the safety circuit. Since the total circuit resistance is only 10 ohms the potential difference across the switches is only 0.24V – this is not enough to energize the lockout relay coil.

 

In this case, let’s imagine the high-pressure switch opens. Now the only path is through the lockout relay and the compressor contactor in series causing the total circuit resistance to go up to 100 ohms, this 10x increase will ALSO result in a 10X DECREASE in total circuit current (amperage).

Now 90 ohms of resistance are in the lockout relay coil and 9.9 ohms in the compressor contactor coil with 0.1 ohms occurring elsewhere in the wires.

Now the voltage drop across this hypothetical lockout relay coil is 21.6V  which is enough to energize the coil and open the normally closed lockout relay contacts. The compressor contactor coil now “sees” only 2.38V which is not enough to allow it to energize. The lockout relay contacts will remain open until the power is cycled to the lockout relay coil allowing the contacts to go back to the normally closed position. This could be accomplished by power cycling the equipment or adding a reset switch to the lockout coil circuit.

Conclusion

It is actually understandable why people say “Electricity takes the path of least resistance” because they see circuits like this one and that makes sense. I would just prefer a phrase like “Electricity takes all paths between points of potential difference with a current proportional to the potential difference and the resistance according to the units laid out in Ohms law…..”

I have no clue why my version hasn’t caught on 😉

— Bryan

 

 

 

Replacing a compressor is expensive, time-consuming, and physically taxing. If we are replacing a compressor I want us to be doggone sure we aren’t going to be dealing with the same thing again and this often includes a shiny new contactor and capacitor (on single-phase units).

We received a comment recently that called out the fact that we replaced a capacitor with a compressor even though it tested in range.

The commenter felt this was a slimy attempt to tack on more expense rather than a goodwill attempt to prevent future issues.

It is a fair question to ask, “What is appropriate to do when replacing a compressor?”

 

Why Replace the Capacitor?

For me, installing a new, properly sized capacitor with a new single phase motor or compressor is always cheap insurance. When I do this will always use higher quality, American-made capacitors just to give the customer the best chance at going quite sometime before another issue. In our market, run capacitors are among the most common failures we see due to the long run times, high temperatures, and high voltage transient events like surges. We have much better luck with higher quality capacitors so we use them as a standard operating procedure.

This also goes for hard start kits, I will always remove any old aftermarket hard starts and go back with a factory start capacitor and potential relay where it is called for by the application. Whenever I say something like this I get a lot of folks who love aftermarket hard starts who question it. My explanation is HERE.

If you are working on other motor types such as self-contained refrigeration with a current relay I would say the same, go ahead and replace it rather than run the risk of another issue.

Why Replace the Contactor? 

If a contactor is bright, shiny and brand new I’m probably not going to replace it. If it shows signs of wear it is a good practice to replace it with the compressor ESPECIALLY in three-phase units where single phasing can occur if one contact fails to connect.

This Tip from Emerson also confirms this policy as advised.

Anything Else? 

I recommend taking care of any contamination or burnout by using appropriate filter driers in both the liquid and suction lines and monitoring and/or replacing them depending on the application according to the recommendations by Emerson and Sporlan.

If the system contains an accumulator is advised to empty the old accumulator and measure the amount of oil it contains and its condition. I find it is often just easier to simply replace the accumulator rather than reinstalling especially if it has any signs of corrosion.

Take a close look at your pipework to make sure it is run properly without unnecessary oil traps, inverted traps at the coil where needed to prevent flooded starts, and good suction line insulation.

We also suggest using a virgin charge, cleaning the system condenser, evaporator, and condensate system, and making sure the proper airflow is present. It is also a good idea to make sure that all manufacturer-recommended accessories are installed especially if long lines are present. This could include things like a factory hard start, crankcase heater, pressure switches, or a liquid line solenoid.

Purge nitrogen, flow nitrogen while brazing, pull a proper vacuum, weigh in the charge and check everything… including suction temperature at the compressor and compressor discharge temperature to make sure it isn’t overheating.

All of this is in the service of the new compressor having a nice long life and the customer getting what they paid for… not as a way to drive up the invoice.

— Bryan

Fundamentally, three-phase, alternating current motors are about as simple as a motor gets. The power company produces three phases by spinning magnets and then on the other end we produce electromagnets that spin the motor according to the same 60 cycles per seconds frequency (60hz). All three-phases are 120-degrees out of phase from one another and work really well at turning a motor.

Let’s look at some of the things to consider about three-phase motors.

All the obvious things..

The motor needs to be a physical size that fits, it needs to be the correct voltage and it needs to be rated to do the job it is doing. You can’t put in a motor with a horsepower/wattage/current rating that is too small but you may… on occasion use one that is larger than the rating so long as it fits and the conductors/overloads etc… are appropriately sized.

Internal vs. External Overload

Many motors have internal overloads that will shut the motor off when it overheats. Others will require an external overload either at the motor or more commonly built into the “starter” which is essentially a contactor and an overload relay combined.

Motor Rotation

A three-phase motor can easily run the opposite or possibly the wrong direction by swapping any two phases entering the motor. This means that blower motors and scroll compressors can easily run the wrong direction if they are wired incorrectly. Also, keep in mind that if the blower is connected to a VFD and the compressor is not the blower could be running in the correct direction because the VFD can correct the phase rotation.

Always make sure that blowers and compressors are running the right direction before leaving them run.

3 Phase Voltage & Current Imbalance

Voltage imbalance is a motor killer. It causes poor motor performance and increased winding heat which leads to premature failure. In the case of HVAC blowers and compressors, this additional heat ends up in either the refrigerant or the air which must then be removed, further decreasing efficiency.

To test for three-phase imbalance always check from phase to phase not from phase to ground with the motor running. You simply check the voltage from each of the three phases to one another and find the average (add all three and divide by three). Then compare the reading that furthest from the average and find the % of deviation. For most of you I know that sounds like a giant pain so we made this easy calculator for you.

The US Department of Energy recommends that the voltage imbalance be no more than 1% while other industry sources say up to 4% is acceptable. In general, you will want to make SURE the imbalance is below 4% and work to rectify anything over 1%.

The same thing is true of the current. Because three-phase motors have windings with the same resistance they should also draw the same current while running. Any major variation should be investigated by double-checking the voltage imbalance and checking the resistance of each winding.

No Capacitors

3-phase motors don’t require run or start capacitors as having 3 phases solves all those issues. They may be part start or use other “soft” starting strategies and there may be capacitors used for power factor correction but neither of these are the same as the good old single-phase run capacitor… so that’s a plus.

There is a lot more to know but this is just an introduction on the basics I don’t want you to miss.

— Bryan

Let’s get through all of the jargon and try to get to the point as quickly as possible. All of these ratings are a calculation of how much energy you have to put into a system in order to get a BTU of heating or cooling out.

Simple…

But the problem is that cooling and heat pump equipment has a bunch of variables that impact the numbers so they are all a little different.

Here is a quick summary

EER (energy efficiency ratio) = BTUh of output ÷ Watts of Energy Input 

The nice thing with EER is you can measure it real-time if you know the watts being used and the BTU’s being produced. No conversions needed, no fancy math. Measured EER is an easy snapshot but rated EER is another matter as it is only based on RATED conditions. It doesn’t take into account seasonal temperature or runtime variations.

COP (coefficient of performance) = BTUh output ÷ BTUh of Energy Input 

In other words COP is the same as EER but you convert the input to BTUh from watts by multiplying watts by 3.413. Also easy with one more bit of math added in. The same issue in that it is snapshot of performance or based on only one set of operating conditions.

SEER (Seasonal Energy Efficiency Ratio) = BTUh output ÷ Watts of Energy Input / Averaged over an entire cooling season 

So SEER is just like EER but theoretically would be the average EER if you measured it all through the cooling season and then averaged it. The PROBLEM is that isn’t the same everywhere… so it is still based on a set of conditions that are meant to replicate an average.

HSPF (Heating seasonal performance factor) = BTUh output ÷ Watts of Energy Input / Averaged over an entire heating season 

This makes HSPF exactly like the SEER but the winter (heating season) version where the EER is calculated and then averaged out. The same challenge exists in that not all places have the same set of operating conditions.

The solution lies in understanding each efficiency measure as well as the requirements of the particular market you work in to provide your customers with the best possible products to serve their needs. If you live in a market with very high outdoor temps like Phoenix you want to look at the extended performance data on the equipment you see and find systems that continue t perform well at high temperatures.

If you are installing a heat pump in Maine the same is true but reverse it.

Ratings are great… being situationally aware is greater.

— Bryan

 

 

Most of the content in this article is based on Alex Meaney’s contribution to the HVAC School podcast in the October 2nd, 2020 episode: “How to Get The Most From Online Education.”

 

Attending a class from your bedroom or home office sounds very convenient, right? That was probably what many Americans would have thought several months ago. Now, many of us shudder at the thought of learning remotely. With distractions and technical difficulties galore, many students and trainees have struggled with online education. Maybe you are one of those people, but fear not! Rock Star HVAC design educator Alex Meaney addresses the challenges of online education and offers advice for struggling students and educators alike. He has provided some crucial tips for overcoming the obstacles of distance learning and getting the most from your online education.

 

Take advantage of early reading

 

It’s a good idea for educators to provide educational materials before an online training session or class. If students or trainees have access to readings and videos ahead of time, they may enter the class or training session with a basic understanding of the concepts. Educators, it’s on you to set your students up for success.

 

Students, I’m afraid you aren’t out of the woods yet. It helps to go into a class feeling prepared. You may want to familiarize yourself with heat gain/loss equations before entering a psychrometrics class. That way, you will be ahead of the curve and won’t have to waste valuable time memorizing formulas.

 

Meaney also stresses the importance of learning vocabulary before attending a class. It helps to feel like you “speak the language” of the topic before attempting to grasp challenging new material. For example, you don’t want to look like you’ve seen a ghost when the educator says a word like enthalpy in a psychrometrics course. 

 

Look for opportunities to tutor difficult subjects

 

Meaney also gives a seemingly counterintuitive piece of advice for students: seek opportunities to tutor confusing subjects. Tutoring increases a student’s investment in the subject by making them accountable for your classmates’ successes. 

 

Some of you may enjoy the added pressure, and some may not. Regardless, you will obtain a more in-depth understanding of the material if you teach it to others. It also feels great to help a friend grasp a tricky topic. Who doesn’t want to be a good person and benefit from the experience?

 

Take a class with a friend

 

Taking a class with a friend is also a good strategy for getting the most from remote education. Studying with a buddy is useful for filling the gaps in learning. One person may better understand a topic than the other and vice versa. 

 

Manhattan Institute lists a few other benefits of friendship in education. Even in the virtual classroom, friends provide comfort and security. You may feel more comfortable asking questions or requesting clarification if you aren’t afraid of being judged by your classmates.

 

Friendship is also a source of support in the learning environment, even in nontraditional, remote settings. Students reinforce their learning when they tell their friends what they found exciting or challenging about a class.

 

Educators: show your faces

 

Educators can create a more engaging environment for their students by adding a video of themselves explaining the content in videos or PowerPoint slides. Although these learning formats do not compare to lectures in real-time, it’s nice to see a human face among diagrams and charts.

 

Work in a clean, distraction-free zone

 

This is a big one. Maintaining an organized workspace is a must for students and educators. For most people, this means limiting distractions and maintaining the cleanliness of the workspace. 

 

Putting away cell phones is a good start. Putting the cell phone away minimizes the temptation to look at text messages or social media during class. The last several times I checked, #HVAC wasn’t trending on Twitter anyway.

 

It also helps to remove irrelevant documents and materials from the workspace. Paying bills is essential, but nobody wants to think about that while they’re trying to learn a new skill. Even if you just need to shove them on the floor for a bit, it’s better than keeping them in front of you.

 

Closing background programs and internet tabs on the computer eliminates clutter on the screen. We know you enjoy listening to HVAC podcasts and checking out family photos on Facebook, but class time is not the time for that. The webpages will still exist when the lesson is over. 

 

Meaney also recommends taking notes with a writing utensil, not on a phone or tablet. Involving the hands in the learning process is an excellent way to engage the body while taking in new information, especially for those fidgety hands-on learners. (If writing is not required, try squeezing a stress ball while you learn!)

 

Ensure a stable internet connection

 

Anyone who shares an internet connection with other people may consider minding their bandwidth usage. This means ensuring that other people in the home or office don’t stream videos or play video games online.

 

Many people love watching The Mandalorian and playing Grand Theft Auto V online, but heavy bandwidth usage strains internet connection. A spotty internet connection can result in long download times, buffering, and disconnection from online lectures. 

 

It would be best to let roommates and family members know when it’s class time. That way, they can do their part to respect and support your remote learning process. Netflix, Disney+, and the PlayStation Network can wait.

 

Set aside additional time to ask questions

 

Even with scheduled classes, students can benefit from managing their time. Students could consider reserving some time after a lesson to ask questions or do some independent learning. (For example, a student could set aside 2 ½ hours of their day for a 2-hour class.) If you don’t end up using the additional time, then it becomes free time. You can study some more, walk the dog, or take a nap. It’s your time. It is better to set aside more time than necessary than to plan poorly and need more time. 

 

Consider using the extra time to take advantage of the instructor’s availability. Ask questions! They love helping students understand their lectures. After all, they would not have chosen to teach if they did not enjoy helping others. There are plenty of jobs that pay better.

 

Don’t be tempted to skip material

 

It may be tempting to skip through sections of pre-recorded videos or speed up the playback, but it’s best to refrain from zipping through the first playthrough. Yes, the educator may talk slowly. Yes, you may already know what they’re talking about. That could change within seconds, and you don’t want to miss out on new information you’ll need later.

 

It’s okay to jump around and bypass some sections on subsequent playthroughs. You may choose to skip around the learning materials to focus on specific topics. Still, it would help to understand the terms and general subject before turning your attention to individual parts.

 

Take care of yourself

 

Not many people think about comfort in the learning environment, but it can significantly help the learning process. Exercising self-care is vital for getting the most from remote education. Hunger and thirst can ruin your mood and make it more difficult to concentrate. 

 

Bring a glass of water to class and have some snacks within reach. After all, eating or drinking during an online lecture is not as disruptive as eating in a classroom or auditorium.

 

Be aware of your microphone and webcam status

 

Students and educators can benefit everyone in the class by being mindful of their video and audio settings. 

 

Webcams are great because they can add a social component to distance learning. However, they can also disturb other students. Please wear appropriate clothing and monitor the activities of pets or other background distractions. Yes, everybody would love to see fido and tell him he’s a good boy. No, he is not helping anybody learn about the nuances of Manual J. . 

 

Students should ensure that they remain muted unless they have permission to speak. Even though we are strong proponents of staying comfortable in class, nobody wants to hear you crunch Doritos. Everyone’s online learning experience will improve if everyone makes an effort to be considerate and use technology appropriately.

 

Have faith that you will learn

 

The best thing students and educators can do to get the most from remote education is to remind themselves that we are all capable of learning. Distance learning is difficult for many people, and anyone who struggles with it is not alone. 

 

Getting the most from remote education primarily entails limiting distractions and temptations. Students can succeed with a healthy amount of educator guidance, discipline, and self-compassion.

 

The industry leaders are seeing positive trends and have faith in you, too. Dominick Guarino, chairman and CEO at National Comfort Institute, acknowledges that the HVAC industry is a little behind when it comes to online education. However, he and other industry leaders are optimistic about the progress contractors have made in distance learning over the past year. 

 

Educators can do the following things to maximize the effectiveness of their online classes:

 

  • Provide preliminary readings or vocabulary lists
  • Attach their face to the content to boost engagement
  • Make themselves available to answer questions
  • Be honest with what they do and do not know; follow up with students who ask difficult questions

 

Students can do the following things to get the most from their remote education:

 

  • Study materials and learn vocabulary ahead of time
  • Take a class with a friend
  • Seek opportunities to tutor difficult subjects
  • Set aside more time than the class itself
  • Ask questions!
  • Stay disciplined and committed to learning

 

Educators and students can benefit from:

 

  • Keeping a clean work environment
  • Minding bandwidth usage within their homes
  • Being aware of their microphone and camera usage

 

Remote education is efficient and cost-effective, but it presents a unique set of challenges for educators and students. 

 

To succeed in an online curriculum, students must hold themselves responsible for their learning. Taking responsibility includes limiting distractions within the workspace: putting away cell phones, closing unnecessary applications and tabs, and removing workspace clutter. 

 

Students should also challenge themselves and take advantage of opportunities to maximize their learning potential. These opportunities include tutoring other students, learning with a friend, asking questions, and setting aside additional time to learn the material. 

 

Students will learn to prepare themselves for class, manage their time, and take care of themselves in a challenging, unfamiliar educational environment. 

 

Educators can improve their students’ learning process by providing videos of themselves explaining the content, providing preliminary reading materials, and following up with students who ask complicated questions.

The biggest thing is to prepare and be intentional and learn how to learn in this brave new world we find ourselves in.

My goal in this tech tip is to help those who struggle to understand heat pumps to get their head around it as quickly as possible as well as understand some of the things a tech needs to know about them.

The basic idea of a heat pump is to use the compression refrigeration cycle to move heat in the opposite direction from what would be considered usual by making the coil that would usually be an evaporator into a condenser and the coil that would usually be a condenser into an evaporator.

This is generally done with a valve called a reversing valve or 4-way valve that connects to the suction and discharge line near the compressor and can redirect the flow from one coil to another as shown in the images above.

Pretty simple really…. but there are some things that can trip up techs who are used to cooling only systems.

Let’s look at some of the unique aspects of a heat pump one at a time.

Low Voltage O & B Terminals 

On a heat pump, the Y terminal isn’t really a “cooling” signal, it is now a circuit that energizes the compressor contactor in both heating and cooling. The shift from cool to heat is done by the reversing valve solenoid with the most common being a 24V call on the O terminal to designate cooling. Some systems use a 24V B call for heat instead of cool but this is far less common.

Reversing Valve Solenoid 

The reversing valve solenoid is an electromagnetic coil that mounts onto the reversing valve and is generally 24V on residential heat pumps. The solenoid does not actually shift the main valve, it only shifts a much smaller pilot valve that then uses system pressure to shift the valve. The solenoid should never be energized unless it is properly mounted on the valve or it can overheat and fail.

Two Metering Devices

Most heat pump systems will have two separate metering devices with one being outside for heat mode and one inside for cooling mode. This is due to the fact that the evaporator is inside in cool mode and outside in heat mode. In some cases, you may even find that the system has a TXV metering device inside and a piston outside. This can cause confusion for some techs because they may see the piston housing outside and just assume it is also a piston inside which can lead to charging issues.

Keep in mind that each of these metering devices must have a method of refrigerant bypass in the opposite mode by either an internal or external check valve. The goal is to have properly restricted flow in one direction and unrestricted flow in the other direction.

Bi-Flow Liquid Line Filter-Drier

In a heat pump, the liquid line is always the liquid line but the flow direction goes from outside / in during cooling mode and inside / out during heat mode. For this reason, we must use a bi-flow filter/drier on the liquid line that can filter the refrigerant in both directions.

 

High Head Pressure in Heat Mode

Because the indoor coil becomes the condenser in heat mode, low indoor airflow can cause really high head pressure, compressor overheating, and high-pressure switch trips. When you find abnormally high head pressure on a heat pump always look at indoor airflow (dirty filters, coils, blowers, duct issues etc…)

 

Defrost 

When outdoor temperatures get low enough the outdoor coil may become icebound and require a defrost. Different manufacturers use different control strategies but the common sequence is the system will switch into cooling mode, turn off the condensing fan and turn on aux. heat where applicable until the defrost is complete. Because of the sound of the valve switching and the steam leaving the coil this can cause nuisance service calls if the customer happens to observe a defrost.

You Need Compression For The Valve to Shift

The reversing valve solenoid relies on system pressure to force the valve back and forth. If the compressor isn’t running or has poor compression the valve can fail to shift or can fail to shift completely resulting in a possible misdiagnosis of the valve as the issue.

Suction Pressure Drops As Outdoor Temperature Drops

Because the evaporator is outside in heat mode the suction pressure and suction saturation will decrease as the outdoor ambient temperatures decrease. This will also increase the compression ratio the colder it gets, which reduces system capacity unless other strategies are employed to increase the capacity.

I have seen many techs overcharge a heat pump when ambient temperatures are low in an ill-advised attempt to increase the suction pressure which will only result in other issues.

Connect the Suction Gauge to the “Common” Suction Port

The large line we would normally refer to as the “suction” line becomes a vapor line, this is because it is high-pressure discharge rather than suction in the heating mode. In order to check suction pressure, you need to connect to the specially designed common suction port that connects to suction between the compressor and the reversing valve.

Obviously, this is just an introduction but don’t be afraid… Heat pumps are getting better and better and more technician friendly all the time. Start with reading the product info on the particular unit you are working on and go from there.

— Bryan

I hear the following phrase a lot

It’s the amperage that kills you not the voltage

While there is truth to the statement it is sort of like saying “it’s the size of the vehicle not the speed that kills you when it hits you”…

OK so that’s a pretty bad example, but hopefully, it gets the point across. BOTH of them are needed to cause injury or death and in the case of voltage and amperage the higher the voltage the higher the amperage.

This statement about amperage being the real danger as led to many people inaccurately believing it is the size of a panel or the gauge of wire that makes something more or less dangerous… which is 100% incorrect.

Let’s take a quick look at OHM’s law –

Amps = Volts ÷ Ohms 

The resistance (ohms) of the human body depends on a lot of factors including things like the moisture content of the skin, what other objects the current path is traveling through, what path the current is taking through the body etc…

While the resistances vary based on these factors Ohms law still holds true that when you increase the voltage you ALSO increase the amperage.

Take a look at this chart from the CDC

Effects of Electrical Current* on the Body [3]
Current Reaction
1 milliamp Just a faint tingle.
5 milliamps Slight shock felt. Disturbing, but not painful. Most people can “let go.” However, strong involuntary movements can cause injuries.
6-25 milliamps (women)†
9-30 milliamps (men)
Painful shock. Muscular control is lost. This is the range where “freezing currents” start. It may not be possible to “let go.”
50-150 milliamps Extremely painful shock, respiratory arrest (breathing stops), severe muscle contractions. Flexor muscles may cause holding on; extensor muscles may cause intense pushing away. Death is possible.
1,000-4,300 milliamps (1-4.3 amps) Ventricular fibrillation (heart pumping action not rhythmic) occurs. Muscles contract; nerve damage occurs. Death is likely.
10,000 milliamps (10 amps) Cardiac arrest and severe burns occur. Death is probable.

*Effects are for voltages less than about 600 volts. Higher voltages also cause severe burns.
†Differences in muscle and fat content affect the severity of shock.

Let’s say that a particular shock is traveling through a 20 KOhm (20,000 ohm) path in your body

At 120V this would produce a 6mA shock

At 240V it would be 12mA

At 480V it would be 24mA

It becomes clear pretty quick that higher voltage does lead to more dangerous shocks as does the resistance of the path.

High Resistance and Low Voltage = Safer

Low Resistance and High Voltage = Danger

This is why working around live electrical should only be done with insulated tools, proper PPE and in dry conditions. These all serve to keep the resistance up to reduce the likelihood of a fatal shock. The higher the voltage the more diligent you need to be.

Some people may bring up high voltage shocks from a taser or static electricity as proof that “voltage doesn’t kill”.

In these cases, the power supply is either limited, intermittent or instantaneous. This means that while the voltage is high it is only high for a very short period. Unfortunately in our profession, those sorts of quick high voltage discharges aren’t the big danger we face, most of the electrical work we do is on systems that will happily fry us to a crisp before the power supply cuts out.

A circuit breaker or fuse will never protect us because we draw in the milliamp range when we are being shocked as almost all fuses or breakers don’t trip or blow until much higher levels are reached.

Be safe around high voltage and keep your resistance high.

— Bryan

 

 

 

As HVAC/R techs we don’t do a lot of soldering generally unless you are in a shop that has embraced Stay Brite® 8 from Harris.

There are several aluminum repair products on the market that also use an indirect soldering type technique so this is is a general and generic overview of some best practices. As always, follow the manufacturer’s instructions for best results.

 

Prep the Work Area

When soldering you will want to get everything as clean as possible before you start. You can begin with brushes or Emory cloth to get the big stuff off then go to alcohol and a lint-free cloth at the end to get off any residue or silica particles. Just make sure any alcohol is completely evaporated before using a torch.

Another nice trick for tight work on aluminum coils is using a wire wheel on a Dremel to get the area clean. I had luck with this when repairing a microchannel coil.

 

 

Use Lower Heat Than Brazing

Often soldering is best done with an air-acetylene or MAPP gas torch rather than a typical oxygen rig especially when you have room to work. If you are working a tight space you may opt for a small oxy/acet tip like the one shown above but be VERY careful. The flame may be small and therefore put out less BTUs than a larger flame but it will still be a much hotter temperature than air-acetylene or MAPP.

Work Indirectly 

When working with solders or lower temperature base metals like aluminum it is generally best to heat around the repair or joining area with your rather than right on it. The goal is to allow the heat to gently conduct into the area ESPECIALLY when working with the hotter oxygen flame. With brazing, we can almost put the heat directly on the rod as we work and for most of these products, this won’t work at all.

Watch the Flux

Flux not only acts to keep oxides away from the work area, but it also gives us a visual indication of when the work area is at the right temperature to apply solder. If we underheat the work area the solder won’t flow int the joint and if we overheat the work area we will burn the flux and the solder won’t flow into the joint.

Another note on flux is we only want to apply it to the male end when joining and we don’t want to overuse flux and contaminate the system. Many fluxes are corrosive so wipe it all off one the joint cools to prevent leaks.

— Bryan

 

 

Let’s get something out of the way right off the top. Saying that we learn best “hands-on” is sorta like saying we prefer to breathe air…

WE ALL NEED TO APPLY THINGS TO LEARN THEM DEEPLY

David Sandler wrote the book “You can’t teach a kid to ride a bike in a seminar” and the same is certainly true for the trades.

But there is a distinction that needs to be made between “learning to ride a bike in a seminar” and “learning more about bikes in a seminar” or “learning about better riding technique in a seminar”  because these both could be valuable once you’ve already been riding a while.

This article is about HVAC training, but it’s also about things I’ve learned running a business, being homeschooled myself and home educating our kids as well as having a large family.

This is the perspective of one man so take it with a grain of salt.

I’m more of a hands-on learner

Inevitably when I teach a class, or give a seminar, or send an article or make a video or podcast or suggest that someone RTFM… there is someone who says some version of “I’m more of a hands-on learner”

Which… to be clear… is totally cool and should never be disregarded especially when learning an entirely new concept.

I went with my kids to the science museum the other day and the “Bernoulli table” with balls floating on high-velocity air streams created the “hands-on” and visual experience to illustrate Bernoulli’s principal.

It was a lot of fun and very interesting to see the balls suspended in the air, but imagine if I started to explain the principals of pressure and velocity and mass to the kids using words and they just look blankly and say “I’m more of a hands-on learner”.

Do you see the issue?

This is hands-on learning… it just isn’t ONLY hands-on learning.. almost nothing is ONLY hands-on learning if you want to understand what is going on.

Language needs to be used to explain the “why” behind something we can experience hands-on and if you refuse to listen or read the manual or plaque then you are left with experiences and observations that have no context or meaning.

To some degree, we are all hands-on learners but to really understand we would be well served to become, attentive readers and listeners as well.

You must be so patient 

It’s no secret that Leilani and I have 10 kids. When Leilani goes to the grocery store she gets three comments from people most often

  1. I don’t know how you do it
  2. You must be a saint
  3. You must have so much patience

We laugh because we ARE NOT naturally patient people AT ALL and we have no secret magical powers or heavenly bestowed holiness. People imagine that to have 10 kids and remain (mostly) sane you must have some special gift.

The truth is much more boring and mundane.

You don’t need a huge dose of natural patience, but you do need to work at being patient. You don’t need to be a saint but you do need to work to control your emotions when life gets crazy.

In the same way, you don’t need to be naturally gifted at listening or reading to learn, but it sure helps if you work at it

Obviously, some people are more academically gifted naturally than others and some people have learning challenges and disabilities. This isn’t to downplay that reality but I do think you would be better served to stop using it as an excuse.

Becoming a Visual Problem Solver

A visual problem solver is much like a hands-on learner in that they prefer to have a problem in front of them to find the solution rather than using words to describe it.

Some of the BEST problem solvers I’ve ever met weren’t big talkers, instead, they create images in their mind of a problem, structure or machine and work over the problem using the visual centers of their brain.

If you think about it, converting ideas and mental pictures to language is actually pretty inefficient if there is no reason to do so.

The challenge comes in when you need to communicate those ideas to another human.

If you start describing a problem to a visual problem solver they may request to take a look, or have a photo or screenshot sent to them, these are ways the visual problem solver has found to get around the challenge of translating things to language all the time.

They will often draw diagrams or ask you to draw diagrams and they may stare at them a bit as they build the visual model or “cartoon” in their head.

The visual problem solver doesn’t make excuses about how they prefer to learn. They don’t make it someone else’s fault that they aren’t getting a concept.

The visual problem solver finds workarounds to get things out of words and into their head where they work on it and ultimately SOLVE THE PROBLEM.

Take responsibility for the translation gap 

Good teachers find ways to meet their students where they are and teach to their learning style. The BEST teachers do the same and then ALSO teaches their students how to translate a world that doesn’t always cater to their learning style.

As a learner, it is our responsibility to take what we can from all sources and methods we can to learn how to problem-solve. I would argue that visual problem solvers actually have a HUGE advantage in our trade because by it’s very nature it is visual and hands-on.

It doesn’t change the fact that reading manuals is often the only way to get certain information and may continue to be a bit of a struggle. Where the person who always repeats that they are a “hands-on learner” may wait for someone to translate words on the page for them, the visual problem solver may build a cartoon in their head or doodle a diagram… whatever it takes to the solve the problem.

— Bryan

 

 

 

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