By:  Eric Shidell, HVAC Service Mentor

While technical aptitude and ability factor heavily in an HVAC technician’s success and rate of pay, that is not the end of the story.  In many ways, the number on your paycheck is directly related to the numbers on the bottom of your service tickets (also known as sales invoices).  The more you can sell, the more you can earn.

I understand that for many technicians, customer communication and sales seems hard.  Many of us feel more comfortable working with machines rather than people.  We feel at home with tools but maybe a little awkward with words.  Technicians may feel that they’re a better mechanic than a sales person.  Maybe you don’t want to feel “salesey”.   I know that I felt that way for many years

For most HVAC technicians, avoiding sales conversations is not an option.  You are both the technician and the sales person on every call.  Before you head for the unit, you need to have a preliminary conversation with your customer first.  You are there to solve a problem for another human being, not just to fix a machine.

This conversation should have you asking more questions than statements, and spending more time listening than talking.   You’ll find it’s the easiest thing in the world, because the customer is doing all the work for you and they are happy to do it!

They key to extending your service beyond the immediate problem and gaining a customer for life is TRUST!  Building and strengthening that trust must happen first.  After that, every sales process is much easier.  Without it, you will only collect the bare minimum and you may not get a second chance ever again.

People buy based on trust.  Your customer has enough trust to pick up the phone and call your company when there is a need.   That is just the start.  Once you are at the front door, you will either strengthen that trust in the mind of the customer or you will weaken it.  Strengthening that trust is the key to higher sales both now and in the long term.

One of the biggest things your customer wants from you is to know that you care about them and their problem and that you have their back in this situation.

People tend to trust people who demonstrate that they care about them.  This is your job.  Remember that you are not there to fix a machine.  You are there to solve a problem for another person.

You don’t have to get super touchey feeley, and you don’t have to be overly friendly.  All you have to do is ask one simple question.  This one question will open the door of trust to you and allow you to discover what the customer’s real concern is and take actions to remedy it.

Do not ask things like,” What seems to be the problem?”  Don’t ask “What can I do for you?”

Your customer does not know what the problem is, and they don’t know what you can do to help them.  Asking these questions just puts them on the spot and even makes them a little suspicious.  After all, isn’t that your job?

The beginning of the call is all about building trust and instilling confidence.

Here is the magic bullet question that opens the doors of trust and leads to the path of a high revenue tech:  “What did you experience that led you to call us today?”  Then stop talking and listen carefully for the answer.

People absolutely know what they have experienced.  Given the chance to express it, customers feel empowered.  When you indicate that you are interested in their experience of their problem and want to provide them a solution, the trust factor goes way up.  You will find that customers will often open up and tell you not only what they experienced, but also what that means to them and what it is that they are worried about in this situation.

Now, ask some follow up questions.  Here are a handful of examples that will help based on the situation.  “When did it happen?”  “How often does it happen?”  “Has this ever happened before?”  “When was the last time you had service on your system?”  “How did you like the way it was working before this happened?”

You may notice that these questions are all related to the customer’s experience of their problem and your ability to solve it.  It isn’t salesey at all, and it builds a solid foundation of trust.

If you listen carefully, you will also pick up clues that indicate what the nature of the breakdown is and where you should start looking for it.  This will save you time on your diagnosis.

This will give you the opportunity to do what you do best:  Be a great technician and apply all of your technical knowledge and skill toward helping that customer in the best possible way.  They will be happy to pay a premium for your ability to solve their problem , not to just fix their machine.  They will want to enroll for your service agreement and possibly go for that upgrade.  If not today, then next time.

And there will be a next time and you will be their first choice.  You will find that customers will be asking you to make sure to write down your name or give them your business card so they don’t forget you after you leave.  As they are signing their name on the bottom of your service contract, they will ask, ”Can I ask for you next time?”

When you review your completed service invoice, look at the description of work performed, the parts you used and the time it took.  Look at the amount collected and realize that you customer did not pay that amount for those parts or for that labor.  They paid for relief from their problem and for peace of mind.   That is your true service.

Always be in service.

By:  Eric Shidell, HVAC Service Mentor

A lot of HVAC service technicians learn early on that cleaning a flame sensor is a standard maintenance practice and that neglecting this basic task can lead to nuisance burner shutdowns and no heat calls.  Let’s look a little deeper into this situation and examine how and why flame failures occur and how to prevent them.

During a normal gas burner sequence of operations, the ignition device will activate, (spark or hot surface igniter) and gas will be released to the burner.  When the fuel / air mixture reaches the ignition source, flame will become established.

One of the very important safety features of modern gas burner ignition systems is known as “Flame Proving”.  This is a method whereby the ignition controller is able to recognize that the burner flame has been safely established.  This “knowledge” informs the controller that it is time to stop the ignition source and that it is safe to continue with the burner “run” operation.  In the event of a problem or failure to ignite, the flame proving system will shut down the flow of gas to the burner.

Problems that occur with the flame proving system can result in a nuisance shutdown of the burner system.  This results in a no heat situation.

A very common method of proving flame is called “flame rectification”.  A special metal rod is mounted in the path of the flame.  This is known as a “flame sensor” or “flame rod”.  Flame rods are found on nearly all induced draft burner systems and on many forced draft burners.

In a nutshell, the flame rectification system is an electrical process that causes a low level DC current to be conducted from the flame rod through the flame, and back to ground.  Technicians can measure this flame current by placing a meter that measures DC microamps in series with the flame rod.

The ignition controller is programmed to look for this DC current and make a “go – no – go” decision based on the strength of this current.  Normal flame current values for induced draft burner systems will vary between manufacturers and system styles.  A normal signal strength between 1microamp DC and 7 microamps DC is common.  If the flame current is too low, or not present, the ignition controller will stop the ignition operation and stop the flow of gas.  This prevents the possibility of explosion.

Two of the great strengths of this system is that is has very fast response (within microseconds) and it is impossible to bypass or defeat.  One of the weaknesses is that the amount of flame current is very low and can be diminished fairly easily.

Since the flame rod, the flame, and the metal parts of the burner and manifold are all part of a very low power electric circuit, they are subject to the same problems that all electric circuits are subject to.  As these components become dirty or rusty or corroded, the electrical path becomes corrupted and the flame current can be diminished even though the flame has been successfully established and everything is operating normally.

This results in a nuisance shutdown or lockout and a no heat situation.  In this condition, you will observe the burner go through its normal ignition sequence, ignite the flame, and then shut down within seconds.  Some burners will go into a retry mode and repeat the process a number of times.  Others will lock out until a power reset.  For the brief period that the flame is lit, you will be able to measure the flame signal and see that it is weak.

This shutdown is a normal response to a low flame signal.  The ignition controller is doing its job and working to keep things safe.

Flame rods don’t normally need to be replaced unless they are physically damaged or broken in some way.  To correct this condition, the flame rod needs to be cleaned as well as the burner tip.  The quality of flame should also be verified as a poor flame that is lazy or lifting off the burner will also interrupt the flame rectification circuit.  The same goes for the flame rod electrical connections and the ground connections.

Flame rods should be cleaned with a stiff steel wire brush or steel wool.  Never use sandpaper, plumber’s roll, or any other abrasive.  This will scratch the surface of the flame rod.  Once cleaned in this way, the contaminants will quickly fill in the scratches, causing the flame rod to foul again very quickly.  A scratched up flame rod should be considered damaged and it should be replaced.

The underlying cause of a fouled flame rod is actually contaminated combustion air.  Gas burning appliances that obtain all of their combustion air supply from indoors are more susceptible to nuisance flame failures than those installed in ventilated attics, crawlspaces, outdoors, or those that use outdoor air for combustion.

There are many chemical contaminants to indoor air. When these chemicals are burned in the flame they will leave a nearly invisible insulating coating on the flame sensor.  This is what leads to low flame signal.  Common culprits are:  Cleaning supplies, Laundry detergents and fabric softeners, Cat litter boxes, Pet food, Permanent wave solutions, Pool and spa chemicals, Fertilizers, and others.

The best long term solution to nuisance flame failures and dirty flame sensors is to find and remove contaminants from the combustion air supply.  It may be necessary to pipe in clean outside air for combustion into the appliance enclosure, or use a direct vent appliance that uses outside air for combustion.

Realize that while cleaning a flame rod is a pretty easy fix, there is often more to the story.  That represents a potential to turn your knowledge of the underlying cause of flame rod failures into a long term solution for your customer and more work for your company.

Measuring resistance: The difference between 0 and OL.
by:  Eric Shidell July 25, 2017
Measuring the electrical resistance (Ohms) of motors, compressors, and other electrical devices in HVAC systems may seem pretty straightforward at first. But when the measurements of 0 or OL come up, it becomes clear that there is quite a bit of confusion around this topic.
The answer to this one question holds the key to understanding resistance measurements…
Almost every thing has the property of electrical resistance.  This includes electrical devices such as motors, switches, wires, etc., and even the human body.  This property of resistance is measured in units called “Ohms” and can be measured with a standard Digital Multi Meter.
  The question to ask is,
“What does electrical resistance resist?”
The answer is “Electrical resistance resists the flow of electric current.”
Things that have a very high amount of electrical resistance (large number of Ohms) resist the flow of current almost completely.  These are known as insulators.  Substances like rubber, plastic, Glass, ceramic, and air are good insulators because they have a very high property of electrical resistance.
Things that have a very low amount of electrical resistance (small number of Ohms) such as Gold, Silver, Copper, Nickel, and even Steel provide very little resistance to the flow of electrical current.  These are known as conductors and they are used to build electric current carrying devices like wires.
The typical wire you are familiar with is actually a conductor (copper, low ohms) encased in an insulator (Plastic or rubber, high ohms).  This allows current to flow where it is wanted and prevents current from flowing where it is not wanted.
Electric Loads
Somewhere in between an insulator (Very High Ohms) and a conductor (Very Low Ohms) is an electric load.  Motors, Solenoids, Contactor Coils, Light Bulbs, and Heater Elements are examples of electric loads.  Electric loads are constructed with a carefully calibrated amount of electrical resistance.  When the proper amount of voltage is applied to this specific resistance, a certain amount of work will be performed, and a certain amount of electric current will flow.
When a motor experiences damage or malfunction, frequently the motor’s electrical resistance will deviate from what it’s normal value is.
This is where confusion often sets in.
“Ohming out a motor” is the process of measuring the electrical resistance of the motor windings and comparing that resistance to normal values.  One problem with this is that “Normal Values” will vary widely depending on what type of motor you are looking at and you usually do not have access to what the normal values are supposed to be for your particular motor.
Two measurements that often come up are 0 and OL.   Each of these measurements is very different from one another and they mean entirely different things.
A measurement of Zero, or very close to zero (less than .5 OHM) indicates a very low resistance to current flow.  Applying voltage to this low level of resistance will result in extremely high current flow.  In fact, the power supply will happily provide all the current it possibly can when there is  very little to resist it.  The result will usually be a blown fuse or breaker, or melted wires or something similar.
(Please note that very high power motors that normally draw high levels of current will naturally have windings with very low resistance.)
While you may not know exactly what the resistance of your particular motor should be, you do know that it should be more than zero!  A resistance measurement of less than .5 ohms usually indicates a short circuit in the motor winding.  A short circuit is literally an alternative path for current to flow that “shortcuts” the usual path and avoids all the normal resistance.
A measurement of OL is something else all together.
Most technicians these days use an auto ranging meter.  These meters automatically adjust themselves to the correct scale range depending on what they are measuring.  When your meter is adjusted to measure “OHMS or Ω”, and you don’t have your test leads connected to anything, your meter automatically adjusts itself to its highest scale of measurement and reads “OL”.
It is easy to think that you aren’t measuring anything at this point, and you are not measuring any OHMS.  In truth, you are.  Remember that Air is a very good insulator.  You are now measuring the resistance of the air between your two test leads and the resistance of that air is very high.
In fact, it is so high that it is more resistance than you meter is capable of measuring.  It is literally off the scale.  Your meter is experiencing so much electrical resistance that is literally OVERLOADED (OL)!
OL actually means that the meter is experiencing more Ohms than it can count.
The other thing you know about your motor is that under normal circumstances, it does flow some current, so it’s windings must have a normal amount of resistance that can actually be counted by your meter.  OL represents an open winding which usually means one of the fine wires that create the winding is actually broken.  No current can flow under this condition, and the motor cannot run.
When measuring between any motor terminal to Ground, or to the case of the motor, or to a refrigerant pipe of a compressor, you always want to see OL.  This means that there is no path for current to flow to ground.
If you see 0, or anything other than OL, there is some path for current to flow to ground.  That motor is experiencing a short to ground and must be replaced.
Many standard high quality DMMs measure resistance up to about 50 MegOhms.  (Meg is short for Million.)  To measure higher levels of resistance accurately, you will need a MegOhm meter. MegOhm meters (aka “megger”) are essentially Ohm Meters that have a much higher scale of measurement.  They are used to test the integrity of insulation.  No insulator is perfect, and as insulation begins to break down, it can start literally leaking small amounts of current to ground.  This is a useful test in very large horsepower electric motors and compressors.
There is a lot more to discover about measuring resistance, but for now, this should clear up any confusion between 0 and OL.
tldr:
0 means short, OL means open.

Summertime and the Living is Easy!

Summer time and the living is easy. Unless you’re an HVAC tech.

For many HVAC techs, summer is the busiest time of the year, and many companies bet the bank on a busy and productive summer season.

Without a doubt the busiest months should also be the most productive months. But with extreme conditions, high call volume, and long hours comes increased potential for errors. During this busy time, a call back or return trip caused by misdiagnosis is even more damaging than at other times of the year.

Here are some tips on how to make the best of the busy season and reduce or eliminate no charge calls.

Don’t take shortcuts.

Getting through calls quickly is always a priority, but in busy times, the pressure can seem even higher. Even though call volume is high and the pressure is on, it’s no time to rush through any kind of job. Taking shortcuts only leads to two things: Callbacks and injuries. Don’t skip the steps that make a job thorough and don’t skimp on safety to save time.

Don’t Rush.

Trying to reduce call times by working faster frequently leads to either a mis-diagnosis which takes even more time to correct, or to identifying a symptom only to miss the underlying cause of a problem. In either case, revenue is lost and time is wasted. Remember, it is not your job just to clear the dispatch board. It is your job to maximize the opportunity on every call and to serve every customer in your highest capacity.

If you’ve ever watched a seasoned pro in the busy season, they don’t really look all that busy. Sometimes they look like they are working in slow motion without a concern in the world. This is because they have learned a special time saving technique which is…

Think before you act.

I’m fond of saying that the last thing you want to do on a service call is do something. All too often, we as hands – on mechanical people rush into grabbing some tools and taking something apart. The expert troubleshooter knows that even though it feels slow, stopping to think problems all the way through before reaching for the tool kit actually takes less time. This is why it sometimes looks like they’re working in slow motion. All the heavy lifting is taking place in the mind. The key to doing that is…

Implement a proven troubleshooting process.

Troubleshooting is not a physical activity, but it is a decision making process. In tech school, they teach you a lot of the physical activities involved in troubleshooting, but most of the techs I work with never learned a formal logical process of troubleshooting. The better and more organized your decision making process is, the faster and more accurate you will be. Unfortunately, too many of us make decisions unconsciously. If you have ever found yourself at your wits end with a problem you just can’t seem to figure out no matter what you do, this is usually the reason.

Please join me this Saturday, July 15, at 9AM MDT for a free 30 minute training on troubleshooting processes through Facebook Live. Attendance is totally free, but you must pre-register to attend.

This could be the best thing you can do while you’re eating breakfast. If you are working at that time, or otherwise busy, make sure you register anyway! The training will be recorded, and replays will be available to all registered participants. Plus, everyone registered will get a special FREE bonus at the end of the training!

Go to www.hvacservicementor.com/free-training/ to register!

Measure temperature the right way!

Most HVAC technicians have grown up being taught that when checking air conditioning systems, supply air temperature should be measured.  Naturally, this seems like a perfectly logical step.  Since an air conditioning system is meant to supply cold air, measuring supply air temp is a good idea.

But what supply air temp should be considered acceptable?  When I pose this question to my students during air conditioning advanced troubleshooting classes, I get a variety of answers!  The most common of which is 55 deg. F.  When I ask if 55 deg F is good, lots of heads start nodding, and at least one student will want to throw up a “yeah, but” and insist that because of the altitude, 50 degrees is really the number we want to look for.

So, I will say, “What if the temp is higher than 55?”

“Must be low on refrigerant” is a popular response.

“What if the temp is lower than 55?”

At this, some folks will shrug and say, “Colder is better than warmer any day”.

All of these statements reveal a long line of air conditioning myths that have been handed down from generation to generation.  Let’s look into these a little further:

First, let’s start with 55 degrees.  The “well known fact” that 55 degrees is the preferred supply air temperature comes to us from the commercial world.  For generations, large commercial air conditioning systems have been designed around a constant supply air temperature setpoint of 55 degrees.  Even today, many modern control systems will default to a supply air temperature setpoint of 55 degrees, and this is also the setpoint used to control compressor staging on variable capacity and variable air volume systems.  If the rest of the system was designed around a 55 degree supply air temp, this works great!

Compared to the whole of air conditioning, variable capacity and variable air volume systems are relatively uncommon.  Most air conditioning systems in operation today are fixed capacity constant volume types.  On these systems, 55 degree supply air doesn’t necessarily mean anything!

On these systems, the ∆T is the value we are interested in.  The symbol “∆”, or “Delta” means “Change in Value”.  When combined with the “T”, the meaning is “Change in Temperature”.  Another familiar term would be “Temperature Drop”.  These terms refer to the amount the air drops in temperature as it passes over the evaporator coil.

For example:  If the air entering the evaporator is 80 degrees, and the air leaving the evaporator is 60 degrees, the difference in temperature, or the ∆T, is 20 degrees.

Most HVAC techs will agree that 20 degrees is a good ∆T.  The best techs when asked what the ideal ∆T for air conditioning should be will say, “It depends”.  Here is why:

In every operating air conditioning system, there are two types of heat transfer taking place between the air stream and the refrigerant.  Latent heat transfer and sensible heat transfer.  Sensible heat transfer will be measured on a thermometer while latent heat transfer will not.  Latent heat transfer takes place when moisture held in the air condenses on the surface of the evaporator.

For every pound or water that comes out of the condensate drain, 970 btu of heat is absorbed by the refrigerant in the evaporator.  These btus are the latent heat load on the evaporator.  The higher the relative humidity of the air, the greater the latent heat load on the evaporator.  The greater the latent heat load on the evaporator, there is less sensible heat transfer that can take place.  Therefore, the higher the relative humidity of the air entering the evaporator coil, the lower the sensible ∆T will be.

The following chart details the relative humidity and ∆T relationship:

Air Conditioning airflow chart
20% RH 26
25% RH 25
30% RH 25
35% RH 23
40% RH 22
45% RH 20
50% RH 19
55% RH 19
60% RH 18
65% RH 16
70% RH 15
*based on 400 cfm per ton of cooling
© 2014 Eric Shidell; HVAC Service Mentor

You will see that the “standard” ∆T of 20 degrees is only correct if the relative humidity of the air entering the evaporator is 45%.  As the RH changes to a higher value, the ∆T changes to a lower value.

The above chart is a great way to do a quick check on the condition of an operating air conditioning system.  First, measure the relative humidity of the air stream entering the evaporator coil using a digital psychrometer or similar device.  Next, accurately measure the temperature of the air entering the evaporator coil and the air leaving the evaporator coil.  Subtract the two to find the temperature difference or ∆T.

There are four major variables that contribute to the final ∆T in an operating air conditioning system.  They are:  Relative Humidity of the entering air, Refrigerant Charge, Air Flow Rate, and mechanical integrity of the system (compressor, metering device, coils, etc.)

In an operating system that is perfectly correct, the measured operating ∆T value should match the chart for the measured relative humidity within two degrees.  If the value does not match, something is wrong and further investigation is needed.

Cold Weather Air Conditioning Service

April, 2017
Eric Shidell; HVAC Service Mentor
If you are reading this in most parts of North America, you may be facing a string of cool, mild weather. This is definitely not air conditioning weather. For air conditioning service techs who need to be out doing service calls and planned maintenance visits, that is not good news. When there is cold conditions outside, and little to no demand for cooling inside, air conditioning systems just don’t perform worth a darn. It is very difficult to determine whether or not a system is performing adequately or has the correct amount of refrigerant in it under these conditions.
This causes a lot of technicians to stay home, watch cable, and worry about how they are going to make ends meet when there is no work to do. They also know that when the weather breaks, there is going to be hell to pay because the scheduled calls that got cancelled due to weather still need to get done somehow.
If you want to get out of the house and get your PM calls done even in poor weather conditions, here are some hot tips to make your life easier.
First, you need to have a dry outdoor coil. Even in a light rain, there is a good chance your outdoor coil is still dry. How do you know? If your liquid line temperature is lower than the outdoor air temperature, your coil is wet. For this reason, you want to make sure that washing the outdoor coil is the last thing you do on your PM visit in cold weather.
Manufacturer’s charging charts and slide charts will be accurate and helpful down to about 55 degrees outdoor temp. Below that, you need a little help.
First, when you are about to begin travelling to the job location, call ahead and ask your customer to adjust the thermostat to 80 degrees in Heat mode in order to cause the furnace to run and heat. This will allow some btus to start to accumulate in the house and give the air conditioning system something to do when it turns on. Many homeowners may express concern about that, but if you explain that it is helpful to give the AC something to work on, and that that will help your visit to be more accurate and productive, most people will happily do as you ask.
Next, do what you can to keep the heat running while you are there. If you can, perform your electrical inspection of the outdoor unit while the heat is on. Replace or clean the filter while the heat is on. Once it becomes time to turn the AC on and do the running tests including check refrigerant charge, switch off the heat and switch on the AC. Apply your refrigerant gauges and liquid and suction line temperature probes.
Let the unit run normally for about five minutes and allow the heat from the furnace to dissipate.
The next step is to simulate warm outdoor conditions. Find something you can use to restrict air through the outdoor coil. You can use spare pieces of cardboard, empty trash bags, sheets of plastic, or your jacket and a few convenient rocks.
You want to partially block air through the condenser in order to drive head pressure to a more normal level. Ideally, you want to achieve a consistent liquid saturation temperature of 100 degrees. For R-22 this is a head pressure of 200 psig. For R410a this is a head pressure of 320 psig. You will need to adjust your condenser blockade so that the unit runs and maintains that head pressure.  Let the unit run for about 10 minutes so that it reaches a stable operating condition.
Now, you can run your superheat and subcool and indoor temp drop like you normally would. For fixed metering devices, use 80 degrees for your outdoor temperature value when determining required superheat.
If there is an undercharge or overcharge situation, you will find it. You can be reasonably certain that if the unit is working well now, it will continue to do so in the heat of the summer. If it is having problems now, it will have problems later, too.  You can add adjust the refrigerant charge, find airflow problems, metering device problems, compressor problems just as if it was a nice, warm day.  You can also give the unit a clean bill of health if that is the case too!
Once you have finished all your checks, now you can wash the outdoor coil at the end.
This method is not exactly perfect. You may find there about 5% of the units that you just can’t make a definite conclusion about how they will perform in warm weather. Those are the ones you want to schedule a return visit to double check when it’s warm.
That’s a whole lot better than rescheduling all of them!
-Eric Shidell

3,2,1…Contact!

Nearly all conventional split system air conditioner condensing units employ a contactor to energize the compressor and condenser fan motor.  A contactor is essentially a heavy duty relay.  When the indoor thermostat calls for cooling, it sends 24 VAC to the contactor coil.  When energized, the contactor coil creates a magnetic field which attracts the contact bar and draws the high voltage contacts together.

These contacts when closed, will complete the circuit for the compressor and condenser fan motor.  Contactor contact points carry the full amperage drawn by the motors.  As such, they must be designed to handle the load.  The larger the compressor and fan, the higher the amp rating of the contacts.

We don’t normally associate electrical components with mechanical wear.  Contactor contact points are a big exception to this.  Contact points are in fact wear items similar to the brake pads on your van.  They are meant to wear out and get used up.

Every time the contacts close or open, a small arc is created between them for a brief instant.  This arc is similar to a welding arc, and the results are similar as well.  A small amount of the metal contact material vaporizes and burns away.  Over time, more and more of the material is worn away, and the contact point begins to change shape.

Both mating surfaces of the contact points are convex, or rounded outwards.  Essentially, they are both shallow domes that come together on the round parts.  As they wear, the surfaces become flatter and flatter.  As the contact points flatten out, the arcing is augmented and the wear accelerates.

As contact points experience this normal wear and tear, a number of bad things become more and more likely to happen.

As the wear becomes pronounced, the contact point surfaces become pitted and rough.  Due to the flattening, it becomes more likely that the contact points may not draw together evenly.  Both of these conditions will create a high resistance path for current flow.  This can cause three potentially damaging conditions.

First, as the current flows through a high resistance path through the contact points, heat is generated.  This heat can build in the contact points and lead to a total meltdown of the contactor and a no cooling call.

Second, the additional resistance of the contact points can create a voltage drop across them.  In some cases, the compressor will receive voltage that is too low as a result.  This leads to additional heat in the compressor motor windings and to compressor failure.

Third, the contacts can become so worn that even though the contactor bar is down, there will still be  no current flow across the contacts, and the unit won’t run at all.

A fourth problem can also develop.  As the contact points flatten out and the arcing becomes more pronounced, the likelihood that they can weld together increases.  In a single phase unit, this can lead to the condensing unit running wild and either overcooling or freezing the coil.  If not detected soon enough, this can also lead to compressor failure.

In three phase units controlled with a two pole contactor, if one set of contacts welds shut but the other breaks at the end of the cycle, the compressor will experience a single phase condition and may be damaged.

In short, contactors should be replaced proactively whenever they become pitted, flattened, and worn.  This practice will prevent a no cooling call and a compressor failure.

I once had a chance encounter with a retired engineer from the Cutler Hammer company.  He had begun his career there in the mid ‘50s and stayed there until he retired, designing contactors and motor starters.  He gave me this bit of advice which I pass along to you :  He said that if you replace a contactor with one that is the next amp rating higher (As in replace a 30A contactor with a 40A contactor), the new contactor will have lifespan that is five times longer than the original.

I have used this advice to great success on water source heat pumps that seem to wear out contactors very quickly.  And now it is yours.

-EricShidell

The great debate

There is a great debate in the HVAC contracting and service world.  One side says that online training for technical people is the wave of the future.  The other says that distance learning for people who primarily work with their hands cannot be effective.

Recently, the ACHR News tackled this subject in the July 11 issue with an article written by Nicole Krawcke.  I was pleased to be quoted in the article and I’m glad to see that online training is becoming more recognized.     Click here to check out the full article.

I began to explore the idea of presenting training online when the demand for my live training grew to be intense.  I was teaching in 9 different locations across the state of Colorado and was getting a bit ragged.

I took a minute to think about what was going on and how strong the demand was for my training programs.

I asked the question:  What if instead of teaching the same class 9 different times in 9 different places, I could do the class for everyone at the same time through the internet?   I had received valuable training through the internet myself when I was involved in PV Solar.  It seemed possible.

I began to poll my live class students.  I asked them if they would be interested in receiving the same instruction we did in class only over the internet.  After several hundred surveys filled out, the results came back with 70% yes, 30 % no.  I was encouraged to press on with the idea.

I began looking for an online teaching platform and was quickly led to the format that Harvard University uses for their distance learning programs.  If it is good enough for the ivy league, it’s good enough for me.

The first class on combustion analysis turned out to be a fantastic success.  The class was well attended by students from a very wide area spanning hundreds of miles including some remote rural areas that are typically underserved.  The feedback afterwards was outstanding, too.  Every attendee felt as though the experience was as good if not better than coming to class like usual.  Several students I have worked with since have reported that they were able to take the training right into the field the very next day and they have been using it every day ever since.

HVAC Service Mentor Online was born.  I quickly realized that the online format was not limited to just my home state of Colorado, but also the entire nation.  Also, I now could produce more in depth programs spanning several weeks.  The Boot Camp six week training format was created.  My first AC Boot Camp Online course debuted to a national audience and students enrolled from as far West as California, as far East as New York, as far North as Wyoming, and as far South as New Orleans.

The enthustiastic response from the students and their supervisors clinched it.  Online training programs have real lasting value and I have been providing online programs ever since.  Check out the feedback from one recent Masterclass participant:

“I think what you’re doing with these mini seminars is incredible and I think there needs to be more of it!  It’s one thing to take full time extensive training course but when one can hold a full time job and custom build a knowledge base specific to them; it proves to be an incredible resource.”

While I am committed to the online training format, I have not abandoned live training.  I still appear in Denver several times a month, and providing live private training sessions is a very important part of my work.

HVAC Service Mentor serves busy contractors and facility maintenance teams by boosting the technical capability and profitability of their field technicians with convenient and cost effective technical mentoring and training programs.  Online training programs work well for students who cannot be present in person for whatever the reason.  Click here to find out about my current online programs as well as live training sessions!

Let’s talk shop…

What if you could have access to the knowledge and experience of a true expert in the HVAC service trade?  Someone who has spent nearly two decades running calls, and working on every type of heating, cooling and hydronic system imaginable.  Someone who is the “end of the line” for HVAC service problems when no one else can figure out what is wrong.  Someone who knows what kinds of mistakes techs make that lead to callbacks and what to do about preventing them.

If you had the chance to sit and talk shop with an expert in the HVAC Service trade, what would you ask?  What could you learn?

I am Eric Shidell, the HVAC Service Mentor, and I am that kind of expert.  From 1997 to 2015, I was a top HVAC service technician running calls and getting things running when no one else could.  Not only that, but also mentoring and educating other technicians and molding them into experts in their own right.

A true HVAC nerd, I eat sleep and breathe HVAC systems.  I lived it for nearly twenty years.  In an attic on the hottest day of the year.  On the roof in the middle of a blizzard.   Covered in soot in the boiler room at 3AM.   I have learned the secrets of what it takes to be at the top of the service field.  I now spend all my time teaching these secrets to others, so they too may rise to the top.

As a leader in the service field, I am in a unique position to understand what it is that technicians need to know in order to be truly excellent.  I also know what it is that holds technicians back and prevents them from being truly excellent.  I call these things “knowledge gaps”.

Knowledge gaps are the parts of a technician’s training and knowledge base that are incomplete.  For example, most techs know “how” to replace an ignition control, but don’t actually understand what it is that determines whether or not the control is at fault (even if they think they do!)

The technicians I work with already have jobs in the trade.  They don’t need me to show them how to use wrenches, torches, or other tools.  They need help filling in their knowledge gaps so they are better able to decide where, when, why, and how much to use those tools.   Harnessing the communication power of the internet, I can share my considerable wealth of knowledge and experience with technicians from all over North America in a convenient easy to use format.

Some people prefer the in person experience.  For them, I still offer live training events around my home state of Colorado, and many private contractors invite me in to their shops to work with their service and install teams directly.  But I can’t be everywhere.  Offering internet based training programs allows me to help a much larger group of people in a much larger way.

You would be surprised how much you can learn from a veteran field tech through the internet.  My students are able to experience a dramatic shift in their understanding which allows them to be more productive, more profitable, and more accurate.

In the words of a recent internet student, “I think what you’re doing with these mini seminars is incredible and I think there needs to be more of it!  It’s one thing to take full time extensive training course but when one can hold a full time job and custom build a knowledge base specific to them; it proves to be an incredible resource.”

A service manager of an HVAC contracting firm who is a 22 year veteran himself, had this to say after completing a recent HVAC Service Mentor online course with his team:  “The knowledge presented by the HVAC mentor gives a basic technician not only the confidence to perform his work but actual understanding of the refrigeration process and all of its components. I would say with the knowledge presented, that it would save it technician a minimum of two years of experience and increase the ability for a technician and company to increase its profits while taking care of customers. It is phenomenal to have such a resource that is an experienced, qualified, working instructor.”

 

 

 

 

Why won’t it cool?

 

The other day, I was having a conversation with an experienced HVAC technician.  Let’s call him “Joe”.  Joe was telling me about a problem he was having on an air conditioning system that he had installed earlier in the year, explaining that everything was running, but the system would not maintain setpoint.

He told me that in the first part of the cooling season, the system ran great, but now that it was very hot, it wouldn’t keep up.  He had performed a load calculation before selecting the equipment and he was certain it was correct.  He even did it a second time when the customer called to complain.

“Is the coil clean?” I asked.

“Yup” Joe said.  “That’s the first thing I tried.  I put in a new filter, too, just to be sure.”

Before I had a chance to ask about any other details, Joe added “The Suction line is nice and cold, and it’s blowing cold air and everything.”

“What was your temperature drop?” I asked.

Joe responded with “I didn’t measure that” and then added that he felt cold air blowing from the supply registers.

“What do you think it could be?” Joe asked.

This conversation is typical, and is very similar to many other conversations I’ve had over the years with many technicians.

As HVAC techs, we are involved in the process of moving heat energy from one place to another.  Heat energy is a little hard to pin down.  I don’t know anyone who has held a handful of Btu.  You can’t put a bunch of Btu in a container and put it on the scale and weigh them.  You can’t pull out a tape measure and measure heat energy.

In fact, the transfer of heat energy from one place to another can’t really be measured directly.  The only thing we can do is measure the effect that heat energy has on something else as the heat is absorbed or rejected.  When a thing absorbs or rejects heat, either its temperature will change (sensible heat) or it will change phase (latent heat).

Test instruments are used so that you can visualize things you can’t see.  Things like electricity and heat energy.  When we’re talking about heat energy (which we usually are), we’re talking about measuring temperature.

By itself, a temperature measurement isn’t all that useful.  For example, it’s not very helpful to know that the supply air temperature is 60 degrees unless you also know that the return air temperature is 80 degrees.  That means something.  If the supply air temperature was 60 degrees when the return air temperature was 70 degrees, that would mean something very different.
Temperature measurements are comparative.  When we compare one temperature to another and calculate the difference between those temperatures, this is giving us an indication of the movement of heat energy into or out of the thing we are measuring.

I asked Joe to go back to the job and measure the return air temperature and the supply air temperature and report back.  The question he needed to answer was this: Is the unit operating properly and is undersized, or is the unit sized properly but having an operational problem.

“The weather report says we have a cold front coming through.  I don’t think we’re going to see the same temperatures we saw before.”  Joe said.

“That won’t make a difference.”  I told him.  “If you have a problem when it’s hot, you’ll have the same problem when it’s mild.”

Joe called back a couple days later.

“Supply air temp is 47 degrees!” Joe reported triumphantly!  “I knew it was blowing cold!”

“What about the return air temp?”  I asked.

“Looks like 74 degrees.”  Joe said.  “The thermostat was satisfied so I had to turn it down to get it to come on.”

“The difference between 74 and 47 is 27 degrees.” I said.  Under the conditions you had yesterday, you should be running a temperature difference between 20 and 22 degrees.  27 degrees is too much.  You may have an airflow problem.”

As air moves across the evaporator more slowly, it has more opportunity to fall in temperature.  Also, as air moves across the evaporator more slowly, fewer Btu are delivered to the evaporator and fewer Btu per hour get moved through the system.  Thus, you have nice cold supply air, but less refrigeration capacity.  This explains why it couldn’t keep up in the hotter weather.

“Calibrated hands” are not enough to measure temperature accurately.  Technicians must be using accurate calibrated digital thermometers, using proper measuring techniques, and comparing the results to calculated norms based on current operating conditions.

As I always say, “Btu and Temperature are not the same thing.”  Colder isn’t always better.

Joe went back in and looked for an airflow problem.  He called back a while later.

“I’m feeling a little silly.”  Joe said.  “I had the dip switches on the variable speed furnace set backwards.  As soon as I set them right, that fan took off and I started seeing a temperature difference of 22 degrees.”

“Don’t feel bad,” I said, “Everyone makes mistakes.”  It’s important to have a backup plan in order to catch your mistakes before you leave the job.  Check it, then correct it.

Word to the wise:  Failing to measure temperature appropriately is one of the main causes of missed diagnosis in air conditioning systems!