Month: April 2019

What does “Saturated State” mean for Techs?

Like we often do in these tech tips, we will start with the common and more practical explanation of saturation and then move to the more technical and nerdy explanation later.

When we say “at saturation” or “saturated” in the HVAC/R trade we are generally referring to refrigerant that is in the process of changing from liquid to vapor (boiling) in the evaporator or vapor to liquid (condensing) in the condenser.

We generally look at a set of gauges or find the temperature on a PT (Pressure – Temperature) chart that matches a particular refrigerant and pressure and we call that the saturation temperature.

So when a tech connects gauges to the liquid line (high side) of a system and they look at the needle they will refer to the pressure in PSI and the temperature for the particular refrigerant as saturation temperature. On the gauge above the refrigerant in the system is R22 (green scale) they would say that the pressure is 200 PSI and the saturation temperature is 102°F.

To be even more specific, a tech might say that the condensing temperature of this system is 102°F because the saturated state is occurring during the process of condensing in this particular case.

From a practical standpoint in a refrigeration circuit when we say saturation we are referring to –

the pressure and temperature a refrigerant will be if both liquid and vapor are present at the same time and place

One of the most common cases where we will see refrigerant at saturation is inside systems that are off as well as inside a refrigerant tank. If you were to connect a gauge to tank (like this Testo 550 shown) the refrigerant pressure inside the tank will be equal to the pressure that correlates to the saturation temperature of the tank (I know that’s a mouth full but it’s really pretty simple).

In the case of the refrigerant shown above the room temperature is 71.9°F and the refrigerant is R-422D. All I had to do was connect the Testo 550 and select R422D and the saturation temperature (show above the psi on the right) is EXACTLY 71.9°F. In this case, we can say the saturation PRESSURE of R422D is 136.8 PSI at 71.9°F or that the saturation TEMPERATURE is 71.9°F at 136.8 PSI.

Either way, what are saying is that there is both liquid and vapor present inside the tank so it is at SATURATION or in the saturated state if you would rather. So as techs we see refrigerant at saturation pressure and temperature when the system is off, inside a tank and when it is in the midst of boiling in the evaporator or condensing in the condenser.

Now for the more in-depth explanation

I will warn you that this is a bit of a beating around bush explanation, but I’m writing the explanation I wish I had been given early on… so be patient young grasshopper.

The state or process that occurs when no more of something can be absorbed, combined with, or added.

So when something is “full” and can hold no more of something it is said to be saturated, like a sponge saturated with water, or air saturated with water vapor or a in this case, a liquid saturated with kinetic energy.

Many (including Wikipedia) will define saturation as the boiling point of a liquid. This definition is correct but can lead to a misunderstanding. Just because a liquid is at its boiling point doesn’t mean it is actively boiling. The refrigerant in an air conditioner is technically at the boiling point when the system is completely off. Refrigerant in a tank is at saturation (so long as it has some liquid in the tank) even though the refrigerant is static (nor flowing).

In nature, gasses (vapor) and liquids are free to move around and interact with one another with the predominant pressure being atmospheric pressure (14.7 psia at sea level).

You may have wondered why water exposed to the air will evaporate even though it has not reached the boiling temperature? This is because the temperature of a substance is the AVERAGE kinetic energy of the molecules in a substance not the specific kinetic energy of every single molecule. While there may not be enough energy for the entire substance to boil, there is enough energy in a few of the molecules to break free from the surface.

This is why when sweat evaporates off of your skin your skin cools. The highest energy molecules are leaving and taking themselves and their high energy ways with them!

Translation – Some molecules have more energy than others and are able to escape the liquid form out in nature and we call this evaporation. This evaporation can be measured but it happens below the boiling point and when a substance is uncontained it results in less liquid remaining.

Translation of the Translation – If you leave water out in a pan it will eventually disappear even when it isn’t boiling

Now if you put a liquid in a jar and screw the lid on, some of the molecules will escape the liquid bonds and fill the void in the jar until pretty soon the jar will be at equilibrium (static) pressure with an equal number of molecules condensing back into the liquid as those that are escaping. The more active the molecules in the jar the more pressure there will be in the jar. Since the definition of temperature is the average kinetic energy (energy of motion) of the molecules you can translate that as “The hotter the jar the higher the pressure” or “The higher the pressure the hotter the jar”.

Different liquids have a more or less tendency to escape the liquid form (evaporate), liquids that have a very high tendency to escape will evaporate more quickly and have a higher “vapor pressure” and are also said to be more “volatile”. Alchohol or gasoline are liquids that are more volatile and have a higher vapor pressure at atmospheric pressure than water and disappear quickly even when the ambient temperature is below their boiling point.

Some Liquids (like vacuum pump oil for example) have a very low tendency to evaporate and are said to have very low volatility and a low vapor pressure.

Liquids with low boiling temperatures (like most refrigerants) are very volatile and have a higher vapor pressure than liquids that remain a liquid at atmospheric pressure. We know that refrigerant does more than evaporate at atmospheric pressure and normal atmospheric temperature, it literally BOILS.

A liquid boils when the vapor pressure of the liquid matches the atmospheric pressure. At that point the liquid molecules begin to break free rapidly and if they are uncontained they will simply fly away like water vapor out of an open pot.

If the molecules are boiling and contained they will begin increasing the pressure as they boil until the temperature of the liquid no longer increases and it hits equilibrium between the vapor pressure of the liquid and the pressure inside the vessel (tank, pressure cooker etc..).

Once the vessel is allowed to reach a state of perfect equilibrium it may no longer be boiling but it can still be at the boiling point, that exact POINT of equilibrium between vapor pressure and temperature is the SATURATION POINT.

So long as the pressure remains constant on a boiling or static vapor/liquid mixed substance we can say that it is at saturation temperature because it remains at the same temperature until either

1. The pressure changes
2. The substance is fully boiled

But it is important to remember that it is the vapor pressure of a liquid substance being equal to the pressure around it that results in saturation and then boiling or in the opposite direction, condensing.

Also… Evaporators should be called boilerators but I’m doing being nerdy for now.

— Bryan

How to Reduce Indoor Humidity

Sometimes I beat around the bush too much in these tech tips, so let’s get right to the nitty-gritty! (as Nacho Libre would say)

Humidity inside a home should be maintained between 30% and 60% relative humidity.

I like to shoot for 50% in humid climates when possible (and by possible I mean financially feasible for the customer because anything is possible).

Causes of High Indoor Relative Humidity

• Low Heat Load / Short Equipment Run Time / System Oversizing
• High External Humidity Drivers / Humidity Entering the Home
• High Internal Humidity Drivers / Humidity Being Generated Inside the Home
• Poor or No Spot Ventilation in Kitchen’s and Bathrooms (or it Isn’t Being Run)
• High Evaporator Coil Temperature / High System SHR / High Evaporator Dew Point Temperature
• Insufficient Total Dehumidification Capacity
• Low Space Temperature
• Relying on the A/C alone to Dehumidify

This is the list of everything that causes high relative humidity in a home or building. Total humidity drops when you pull out more water than you put in and it increases when more moisture enters the space than you pull out.

Before we cover what to look for and how to fix it let’s first address some common fallacies that often crop up.

Truth = Lower Temperature Alone Means Higher Relative Humidity

The evaporator coil running below dew-point and water leaving the pan and going out the drain is what dehumidifies the space. This is called latent heat removal and it’s our friend when we are looking to drop the RH% in a space.

Sensible cooling is decreasing the space temperature and while this is a necessary part of comfort in most seasons, it is the enemy when it comes to dropping indoor RH%.

When air is cooled without being dehumidified the relative humidity in the space actually INCREASES because the lower the temperature the less water vapor the air can contain before turning into liquid water.

When we dehumidify with cooling equipment it is the water leaving the drain that matters (latent heat removal) not dropping the temperature of the space (sensible).

For dehumidification getting water out (latent heat removal) = good

dropping room temperature (sensible heat removal) = bad

Truth = Adding Insulation Will Decrease The Heat Load and Generally Increase the Relative Humidity

In order for an air conditioner to pull out humidity and drip it down the drain, it needs to run. In order for it to run it needs to be warm enough in the space for it to run.

When you add typical insulation in the ceiling, floors and walls you decrease the heat load without changing the humidity load. This will result in the RH% going up.

There are some insulation materials such as closed cell foam that will also act as an air & vapor barrier helping to block moisture from making it in. This can help reduce humidity but it is the air/vapor barrier portions that do it not the insulation.

Truth = Many Humidity Issues are Caused by Abnormally High Moisture Not the A/C

The air conditioner needs to be properly sized and selected with sensible and latent capacity that matches the building design. There are many cases where homes aren’t built or lived in exactly to design and cases where the weather doesn’t act like the models predict.

In Florida we have a lot of Hurricanes and tropical systems, In these cases we get tons of moisture, high winds that create big pressure differential across our homes and forces it in, low sensible temperatures so the A/C doesn’t run much and power outages that keep it from running for days in some cases.

For months afterward owners will complain of condensation, biological growth, high relative humidity etc… and everyone tries to “solve” the issue by messing with the air conditioning. These tropical weather events increase the amount of moisture in the home while at the same time impacting the ability of the equipment to remove the moisture.

My own house is another example of an extreme internal moisture condition. I have great insulation, good vapor and moisture barriers and excellent HVAC equipment (if I do say so myself).

However… I have 9 kids and we homeschool so they are home most of the day, we live in the country so we do tons of laundry (lot’s of dirt and mud) and we cook 3 meals a day at home …

Needless to say, our home has internal moisture loads that no model will be able to account for. This is why we added a whole-home dehumidifier to keep that humidity in check.

Final case study…

Many years ago I had a customer who always had high humidity in the main living area and the vents in the ceiling would sweat. I kept going back and messing with the equipment over and over and nothing I did seemed to help. I finally asked another tech and he laughed and said; “they have a pool don’t they?” I thought about it and sure enough, they did have a pool. “How did you know that?” I asked. He smiled and said “They are leaving the slider open when the kids play in the pool to keep an eye on things or they are in and out all time, that’s why the issue is always in that room”, I’ll be darned, he was right. You may be able to use a data logging humidity sensor to find these sorts of client caused intermittent issues.

What to Do About High Humidity

There are many approaches you can take on this depending on the types of tools you have at your disposal, as well as the severity and the budget and patience of your clients. I’m not going to give every possibility and test but here is what I would suggest for the average HVAC tech even if it makes my more hardcore building science friends cringe a bit.

1. Make sure you have a few good quality psychrometers/hygrometers. I use the Testo 605i as my go-to. Never trust a cheap tool with humidity measurement.
2. Ask the customer about how often they cook and note if they have a range hood that vents outdoors.
3. Ask the customer if they use bath vent fans when bathing and showering.
4. Look for roof leaks, proper grading around the home, ponding water etc…
5. Test the space humidity, temperature, and dewpoint at various locations around the home. Often you can find the source of an issue this way. keep in mind that the closer you get to the ceiling the dewpoint tends to increase due to that fact that water vapor is less dense than air.
6. Check the HVAC equipment in detail. When humidity is a challenge setting up the equipment for 350 CFM per ton is generally a good practice. Make sure it all wired properly if it is multi-stage or has dehumidification features. Confirm the system airflow, for newer equipment using the total system static and fan chart method is usually the easiest for a tech. I use the Testo 510 and 440dp for this.
7. Inspect the ductwork and seal any leaks. Leaking ducts cause pressure imbalance in the home and can either drive air in or out of the home.
8. Make sure there are no dryer vents, bath fans or kitchen ventilation leaking or discharging into attics or crawlspaces. Make sure the dryer vent is well-connected to the dryer.
9. Check and measure any incoming fresh through fresh air intakes, ERV’s or HRV’s. If it is too much it may be reduced but proper calculations and likely blower door testing will need to be done before reducing outdoor air.
10. Look for can lights, gaps around boots into the space, holes in walls between the attic and crawl space and the living space etc.. Sealing these can greatly reduce the moisture drivers.
11. Check seals, sweeps & weather stripping around doors and windows
12. Make an assessment if the equipment may be significantly oversized. If so then do a Manual J calculation to determine.
13. Discuss supplemental whole-home dehumidification with the customer, especially when the issue is a big priority for them.

The goals in inspecting the home and equipment is to make some of the following recommendations that can reduce indoor humidity when they are appropriate

• Run or Install Point Ventilation in the Kitchen and Baths to Remove Excess Moisture at the Source When in Use
• Alter Habits (like leaving doors open) That Lead to Moisture Issues
• Install New Weatherstripping and Door Sweeps
• Seal or Install Sealed Can Lights, Seal Around Boots and Seal Other Gaps Between Attic/Crawlspace and the Home or Walls
• Make HVAC System Settings Changes to Run Longer with a Colder Evaporator Coil (Reheat is an extreme example of this)
• Advise Properly Sizing Equipment or Installing Whole-Home Dehumidification Where Appropriate

Quick caution. It is possible to seal a building so tight that it can become unhealthy. Whenever sealing is in order it is best to do a before and after blower-door test on the space and decide if mechanical outdoor air needs to be brought in.

When this is the case I generally suggest a ventilating dehumidifier (and an ERC in some cases) in humid climates, otherwise, you can just make the situation worse.

Also keep in mind that when you run a colder coil the equipment, ducts and vents will be more likely to condensate as they will also be colder. While a colder coil will decrease the space humidity it may not be an option if it results in excessive equipment, duct and vent sweating. This is situation dependent and often dictated by where the equipment and ducts are installed… attics are the WORST for this.

When condensation occurs you can either drop the dew point (humidity) of the air around it or increase the temperature of the surface that is sweating. Sometimes decreasing the dewpoint of the air is very hard (like ducts in an attic) so we are left with increasing the temperature of the duct with either more insulation or warmer air going through it.

Another thing worth mentioning is that varible speed blowers and multi-stage compression paired with humidity controls can help a lot with the coil temperature and run time side of the equation. Even then, they aren’t a silver bullet to fix all issues and if you over promise you may end up with a dissatisfied customer.

Once more… For lower humidity in a home, you want..

• Longer run times
• Colder evaporator coil
• Less moisture coming in from outside
• Less moisture being generated from outside
• Higher indoor temperatures
• Extra moisture removal with dehumidification when required
• Spot ventilate when cooking or bathing

— Bryan

Weighing Refrigerant In and Out

If you don’t use a scale every time you add or remove refrigerant I would suggest you begin doing so immediately if not sooner. Weighing in while charging is fairly obvious and is useful so you can keep track of what you are using and how much to charge a customer.

When you have a system that has just been repaired it is a good practice to weigh in the charge to factory specs plus or minus adjustments for the line-set if it is a split system. This is all pretty evident, but why would you weigh a charge out? There are many reasons but one good example is whenever you have a failed compressor, weighing out the charge can help indicate whether possible undercharge or overcharge may have contributed to the failure. With any significant failure on an older system, weighing out the refrigerant can indicate whether a leak is likely. When possible on major failures you could even weigh out the refrigerant at the time of diagnosis just to ensure that a leak or a compensatory overcharge may be at play.

Using refrigerant recovery as a means to find possible cause or even diagnose leaks on non-functional systems is next level diagnosis in my book. Use your scale.

Weigh out as a diagnostic aid and to ensure you don’t overfill your tank.

— Bryan

Cased Coil Misalignment

On occasion you will either find a furnace or be tasked with installing a furnace where the coil overlaps the edge of the furnace because the coil is wider. In the case of a Carrier CNPVP coil you need to ensure that you align the coil according to manufactures specs or you risk cutting off about 1/3 of the airflow.

The best case scenario is to use a coil that is a sizer match for the coil or to buy or make a  tapered metal transition between the furnace and the coil. The the case of the CNPVP the manufacturer allows the coil to be offset to the left.

In this video we illustrate replacing a leaking coil and reconfiguring it in the proper orientation.

— Bryan

The Impact of Adding or Removing Water From Air

Air conditioning was about humidity control from the very start. Willis Carrier’s very first air conditioning system was all about controlling humidity with the side effect that it also could reduce the sensible temperature. Theaters caught on that this new fangled contraption could lead to big Summer numbers when they installed it to keep patrons cool and the rest is history.

We often add water to the air (humidify) and remove water from the air (dehumidify) as part of our work but let’s take a different look at what happens when we do that, but first let’s all get on the same page with some terms. (Skip down past the terms if you already know them because that isn’t the point of the article)

Dry Bulb Air Temperature

When you measure with a typical thermometer you are measuring dry bulb temperature. It is a measurement of the average movement of the molecules in the air you are measuring with no consideration for the amount of water in it. We also call dry bulb temperature sensible temperature and changes in dry bulb, sensible heat change.

Latent Heat

When we change the state of matter by boiling, evaporating or condensing we cannot track the changes or movement of heat strictly with a thermometer. This heat the moves during a change of state is called latent heat.

Relative Humidity

The relative humidity is just a percentage that tells us how much water is evaporated in the air in relation to how much there could be at the same temperature. It’s like describing how full a glass is, it tells you how full or empty the glass is but by itself it doesn’t tell you how much energy or water is in the glass.

Wet Bulb Air Temperature

If you were to use an old school sling psychrometer you would simply wet a little sock around a bulb thermometer and sling it through the air. If the air humidity was less than 100% then the wet bulb temperature would be less than the dry bulb temperature. The difference between the wet bulb and dry bulb temperature is called “wet bulb depression” and is can be used to calculate relative humidity.

DewPoint

The temperature at which air becomes 100% saturated. Wet bulb, dry bulb and 100% relative humidity lines all intersect at the dewpoint. Dewpoint is the glass 100% full.

Air Enthalpy

A psychrometric chart displays the total amount of heat energy in the air between the dry air AND the evaporated water vapor in the air in heat per mass, in the USA that is usually BTUs per LB. Wet bulb temperature and enthalpy of air run VERY CLOSE to right along with one another so 63° wet bulb air will have an enthalpy of 28.3 btu/lb at typical conditions and often we use wet bulb as a proxy for enthalpy.

Absolute Humidity / Moisture

We can calculate the total moisture in the air in pounds or grains of moisture per pound of dry air. This is the TOTAL quantity of evaporated water in a pound of dry air by weight and shouldn’t be confused with relative humidity.

Here is the part I want to get to –

When we remove water from the air with an air conditioner or a typical dehumidifier we are cooling the air sensibly until it hits dewpoint. The evaporated water in the air will then begin to condense on the surface of the evaporator coil and will give up latent heat to the coil because the coil temperature is below the dewpoint temperature (at least most of the time on most systems).

When we dehumidify by cooling in an air conditioner we are dropping the enthalpy, temperature and absolute moisture of the air all at the same time and all of that combined heat is entering the coil.

In a dedicated dehumidifier we do the same thing but then run that air back over the condenser to add back enthalpy via sensible heat so the end result is less total moisture with higher air enthalpy to prevent overcooling.

What happens if we humidify or dehumidify the air by increasing or decreasing the total moisture WITHOUT adding or removing heat? This does (mostly) happen with evaporative (swamp) coolers and dessicant dehumidifiers.

When the humidity of air changes WITHOUT a change in enthalpy (total heat content, sensible + latent) the temperature of the air also changes, as a result, this is called an adiabatic process. Adiabatic simply means a change in temperature without a change in total energy/heat content within a system.

When you simply add or remove grains or pounds of water vapor to the air you would obviously change the enthalpy of the air UNLESS the temperature changed to compensate. This may sound like crazy science but we experience it every day.

The inside of your body is about 98.7°F but the outside of your skin is cooler than that, often more like 93°F.  Let’s say it’s 100°F in Phoenix and 40% relative humidity. We know that hot goes to cold so the heat from the air is headed into your skin and your body reacts by beginning to sweat.

What temperature is the sweat as it leaves your body? Well, it would need to be somewhere between 93°F – 98.7°F right?

So how can 93°F sweat cool you?

It cools you because as it evaporates into the air the water in your sweat takes energy to make that change, maintaining enthalpy (total heat) in the air around your skin but dropping in temperature.

If you were to measure the wet bulb or enthalpy change entering and leaving a swamp cooler (evaporative cooler) you would notice that it stays (mostly) constant but the temperature of the leaving air is still lower temperature.

Take a look at the two sets of air conditions shown above. If you were to use a dessicant dehumidifier that could decrease the total moisture content of 75°F air from 64.66 grains to 33.88 grains (per lb of dry air) without any exchange of energy (constant enthalpy) the temperature of the air leaving that dehumidifier would increase by 20°F to 95°F. This can and does occur in dessicant dehumidifiers every day.

Now…

Rarely do processes in real life abide by idealistic conditions plotted on a psychrometric chart. If the water is a different temperature than the surrounding air in a swamp cooler than there will be an enthalpy change, if the dessicant wheel is a different temperature than the air passing over it then there will be an enthalpy change.

The cool thing here is gaining a deeper understanding of the relationship between dry bulb temperature, enthalpy and total moisture content of air by understanding some of the edge cases many of us don’t experience as often.

Evaporation by itself leads to lower sensible air temperature

Condensation by itself leads to higher sensible air temperature

— Bryan

Unapologetically a Technician

For years I’ve worked with and around people who view work, problems and goals differently than I do. I’ve often told my wife that I have an issue managing and leading administrators, salespeople and other inside staff because I just don’t communicate in a way they seem to like.

It’s been 20 years in the trade now and almost 15 in business before I’ve come to a conclusion.

I prefer working with technicians

Before you call all the dispatchers, accountants and warehouse staff together with pitchforks and Molotov cocktails… hear me out

What is a Technician?

We aren’t going to reach for a dictionary to define what a technician is, we are going with the “Potter Stewart” method of “I know it when I see it” and I’m sure you do as well.

Now, there are many people with the title of “technician” on their LinkedIn account that don’t meet my smell test and there are many more who would never consider that title who are hard core technician in my book.

A Technician Wants to Understand

There is a big difference between knowing what to do and understanding. I was standing in line at the local fast food joint the other day and I was noticing all the teenagers moving around behind the counter, looking up at monitors,, hitting buttons, filling drinks and wrapping burgers.

They all knew what to do to get me my food at Mickey D’s but put them in front of some raw ingredients in a home kitchen and do they UNDERSTAND cooking? No, of course they don’t.

If you handed them a hot-dog and they had never made one before they would look at you, blink and then ask some version of “how do I cook this?”. They will keep standing there until someone gives the answer and in their mind that is how cooking food works. Someone tells you what to do and then you do it the way you are told, this is how you cook and this is how having a job works in their world.

For the technicians out there, is that how you learned? is that how you solve problems? The idea that we would wait until someone tells us how to do everything before we do it is laughable. Technicians found how the why and how of how things work in order make sense of solving problems, even problems they have never encountered before.

This doesn’t mean a technician has all the answers, there are far too many questions for anyone to have all the answers, a technician just works on a problem until they understand the factors involved and can make a diagnosis and repair even if it’s imperfect.

Technicians Take Their Work Seriously

A true technician may be light hearted or severe, introverted or extroverted but they all take their work very seriously. When they put their name on something it means something and they never want it to be said of them that they were careless, lazy or sloppy in their work. In a technicians mind their work is nobody else’s responsibility and they want to get it right the first time.

A Technician Doesn’t Need to be Affirmed Continuously

I’ve noticed this new phenomenon where workers expect not only to be recognized for their achievements above and beyond the usual but to get verbal affirmation just for the regular execution of their job. It’s as if  every job task completed without a serious mistake is a huge accomplishment and requires commentary.

Technicians get satisfaction from a job well done, they pursue excellence for excellence own sake, not for the accolades of others ESPECIALLY when it’s given because its expected.

A Technician Goes Home When the Days Work is Done

Technicians don’t go home until their work is done. That doesn’t mean that they always work crazy hours but it does mean that they don’t start something that they aren’t going to see through to completion, even if that means handing it off to someone else.

I’ve had numerous interactions with staff who were getting behind in their core tasks because they “just don’t have enough time”. A technician doesn’t get behind for long because that just isn’t an option for them. There is another job to do and the only way to keep from drowning is to get better and more efficient at their work. If a technician is given far more than they can do then they talk to the dispatcher or manager to get help BEFORE they get stuck because just leaving it undone is off the table.

Technicians Fix Problems

Oh no! you have a problem that’s hard to figure out?

Technicians LIVE for the hard problems, the challenges they’ve never faced before, the once in lifetime issue.

Why?

Because to a technician work isn’t about showing up, doing the least possible work, staying comfortable and heading home a few minutes early if they can get away with it. Work is about fixing real problems, hard problems. Leaving everything you work on working better than when you started. Finding those hidden problems that everyone else missed and bringing harmony to discord.

To a technician every problem has a solution and if you aren’t working on the solution then WHY ARE YOU EVEN TALKING RIGHT NOW?

Technicians HATE Having Their Time Wasted

Standing around and shooting the breeze is OK every once and a while but to a technician it gets old real quick. A technician understands that the real work that pays the bills doesn’t get done by talking around the water cooler and the longer you put it off the tougher the day is going to be.

Technicians do not practice wasteful, non-sense processes without speaking up, even if it was their bosses idea or pet project. If a technician finds they are working at a place that wastes their time on useless reports that nobody ever looks at or double entry data procedures that has them writing more than they are working they will usually move on pretty quick.

Don’t ask a technician to train a slacker or suffer a fool in their work space, a technician would fire their own grandma if they slow them down and cause issues.

Technicians Don’t Need Emotional Support to Do Their Job

I’ve overheard people say that they “don’t feel supported” in their jobs on more occasion than once. If that means you aren’t being given the time and tools to deliver on what the company is requiring or promising than I guess I understand that. If it means you need someone to call and talk you through problems every-time you feel frustrated or that you need to talk to someone whenever a customer gets cranky then the technician in me says

Buck up Buttercup. It isn’t supposed to be easy and you won’t always “feel good” about every job or interaction.

A technician is an adult who doesn’t need someone to make them feel good about life in order to get the job done. So much of what people call “communication” is just empty talk designed to make people feel “heard” and that they could “Speak their piece”.

This doesn’t mean you need to be rude or nasty but what is with all this talking and meetings and talking about meetings!!

You know what makes a technician feel better? GETTING WORK DONE

Technicians Hate Failing But Accept That It’s Part of Growing

There are two common workplace responses to mistakes and failures when they come to light. The most common is to make excuses and place blame, the technician figures out what went wrong and learns ways to prevent it in the future to the extent it is preventable.

It always cracks me up when something breaks and the customer acts totally stunned and says something like “That shouldn’t happen! This system is only _____ years old”as if someone must account for this horrible injustice.

Yes and war and sickness, crime and decay ALSO shouldn’t happen but they do every day, technicians realize this and embrace it as part of their calling to set things right rather than wallowing in blame and excuses.

If a technician is really stuck and need some expert advice then they MAY call another technician but only after they have read everything they can on the problem they are facing and took a solid shot at Google or any other online resources they have. They don’t call other technicians just because it’s “easier to call” and “I just wanted to talk”. If you want to talk to another tech when you are both on the way home to catch up on the events of the day then OK (we used to do this all the time in the days of radio dispatch), but technical questions are for specific technical answers not for chit chat.

My Epiphany

I realized that I am not going to stop preferring technicians.

So rather than trying to change that about myself, I’m going to work to fill my business with people who have a technicians mindset even if their job title isn’t one of a technician. The best dispatchers, receptionists, permit techs, parts counter staff, warehouse managers and installers I have known still have this “technician” mindset even though they may never work on a piece of HVAC equipment.

From now on I’m looking for dispatch technicians, sales technicians and warehouse sweeper technicians (you get the point). Sure a successful workplace takes all types of personalities and skill sets and if you are coming to work to get stuff done and broken stuff fixed then WELCOME. If you want a support group or new friends then may I suggest the Kiwanis club or Elks Lodge (that’s a thing right?).

— Bryan

CO2 Booster Systems (Codenamed CO2 is Interesting and Weird)

Illustration Courtesy of Emerson

CO2 is a pretty nice refrigerant.

It has zero ODP (Ozone depletion potential) and a GWP (global warming potential) of 1. CO2  has been used as a refrigerant almost from the very beginning of refrigerants and its been making a big comeback in market refrigeration (especially in colder climates).

CO2 (R744) is naturally better suited for lower temperature refrigeration applications because of its low temperature saturated state at atmospheric pressure (-109.3F). You will notice I said “saturated state” because CO2 does not “boil” at atmospheric pressure. At any pressure below 60 psig CO2 goes straight from solid (dry ice) right to a vapor, This is why 60 psig is known as the “triple point” or the point that could be either solid, liquid or vapor.

Now go to the top of the range with CO2, when you apply 1055 psig the saturation temperature is 87.8F but go up even 1 more degree and CO2 CANNOT be liquified, this is known as the critical point of the substance. Whenever a substance is forced beyond it’s critical point it becomes what is known as a supercritical fluid and has properties that are unique to this state but it is certainly not a liquid. You can see more in this natural refrigerants PT chart.

In a transcritical (trans means beyond or through so transcritical means “beyond critical”) booster refrigeration system the low temp portion of the system operates using it’s own compressors that “boost” the refrigerant from the low temp side and discharge into the suction of the medium temp side. The high stage compressors then pressurize the CO2 (R744) above its critical pressure / temperature.

What is traditionally called a condenser becomes a gas cooler and decreases the temperature (rejects heat from) of the discharge without actually condensing it into liquid. The cooled supercritical fluid goes through a pressure reducing valve, where some of it condenses into liquid and the rest remains as gas. Liquid and gas are separated in a flash tank (receiver). Pressure in this tank are usually controlled to around 450 to 500psig.

It’s super critical that you understand all of this…

See what I did there.

— Bryan

A job well done….. Almost

This tip is written by HVAC Applications and Technical Specialist Dakota Brown. Thanks Dakota!

As a technician it was always the same old story

Are you done yet?

There was always pressure from the office; either from the dispatcher, service manager or project manager to get the job done and get it done quickly.

When I became an estimator and project manager at the company I worked for I tried not to fall into the trap of pressuring the technicians (my former brothers-in-arms) to get the job done quickly by cutting corners but I’m sure I fell victim to that mentality a time or two.

Now that I work for a distributor and I am doing technical support including start-ups I can look at one of the biggest problems facing contractors more objectively. You all know what that problem is at this point or at least you should.

Call-Backs

We all talk about being thorough on service calls to prevent those dreaded call backs. But what about on installs? We all like to complain about [insert brand here] and how their equipment stinks but we all know that most issues with new equipment come from a bad install or worse yet, a bad start-up (GASP!)

“But I am always thorough on my start-ups!”

Bologna!

We’ve all gotten the call asking if we are done yet. Or, if we are coming home! We start to cut some corners to get packed up and neglect checking gas pressure (I’m sure it’s fine) or airflow (I hear the fan running) and pack up.

75% of the service calls I get on new equipment come from bad start-ups. Even when a contractor does the best install possible they can blow it right at the end with a bad start-up.

That is why I say “almost.”

I liken it to a race. Nothing drives me nuts while watching a race or any other sporting event more than seeing someone pull up at the last-minute, right before the finish line.

Run through the finish, don’t pull up at the end.

Time and time again I see a good install go bad. So, let’s talk about a few key points.

• Check your voltages on a 208/230 volt unit. Most RTUs and splits that are dual voltage have multiple taps on the low voltage transformer and if you don’t have the incoming voltage tapped right you won’t get proper outgoing voltage.
• Make sure your trap has a large enough drop to prevent condensate being sucked back through and inspect the drainage while it’s running.
• Check phasing, seriously. It is simple enough to do beforehand with a phase rotation meter and keep in mind that VFD’s can correct phasing so just because your condenser fans or blower run the right direction that doesn’t mean the phase direction is correct in there is a VFD driving the motors.
• If your unit has a smart control board (I’m looking at you York) make sure you configure the board to reflect what you just installed.
• Check your economizer in all modes.
• Airflow, airflow, airflow. This is the biggest one, really. I mainly work with York these days and they have what is called a dry coil pressure drop in their manuals. Using some ports built into the unit and a manometer with some metal tubing you can get the static pressure drop across the coil. This allows you to estimate airflow moving through the unit. This is so simple and a lot of people don’t do it. I understand this is just a starting point but we don’t live in a perfect world and not everyone has an in duct anemometer.
• Owner training!!!!! Teach the end user how to use their new equipment, educate them on maintenance requirements, tell them something!

A lot of issues can be solved by reading the install manual and filling out the start-up sheet that comes with the equipment. If you don’t have one with the equipment, make one.

We could go on and on with start-ups and proper start-up practices and maybe we will but for now lets all try to remember that rushing off of the job to get to the next one will catch up with you and your reputation.

— Dakota Brown

Properly Deburring (Reaming)

Deburring copper tubing (often called reaming) is the practice of running a blade around the inside of tubing after you cut it to remove the burr edge from the inside.

It’s an important practice and should be performed whenever practical to reduce turbulence inside the lines that can be caused by the burr…. HOWEVER

YOU MUST MAKE SURE THE SHAVINGS DON’T FALL INTO THE LINE

Whenever possible point the open end downward while you run the blade around the inner edge and then tap the line to ensure that the shavings fall out of the line rather than in. In some situations during repairs it may make sense to purge nitrogen out the line you are deburring especially in repair situations like replacing a compressor where making the lines point downward may be impossible.

If you are given the choice where you must choose between deburring and possibly dropping shavings into the system I would rather you didn’t deburr.

In the case of making flare connections deburring is critical. For a flared tube it is also critical that you don’t over ream the tube and thin out the copper edge otherwise it will be prone to cracking.

In summary…

Deburring is important, but keeping shavings out of the system is even more important.

— Bryan

32° Saturation (Evap Temperature)

Evaporator temperatures below 32° are common and acceptable in refrigeration, that’s why there is a defrost sequence.

In a heat pump running in heat mode,, it’s the same, freezing is a part of the process and defrost is necessary.

In comfort cooling… we can’t allow the evaporator to get below 32°… or it will freeze.

I can’t tell you how many times I look back and technician notes and can see in plain black and white that the system will freeze.

And that is not OK…

Freezing causes flood back, no cooling, water damage and biological growth.

We cannot leave a system that is just going to freeze.

The image above is of the Danfoss refrigerant slider app and it shows that when suction pressure drops below 102 PSIG on an R410a system…. the coil hits 32° and will start to freeze.

This means that we need to setup equipment so that it will not freeze during normal operating conditions.

A typical residential A/C system should be setup so that the return temp can get all the way down to 68° and still be just above freezing.

Let’s say it’s 78° in a house on an R410a system and your suction pressure is 108 PSIG (like shown)

Your suction saturation (coil temperature) is 35°, and so the coil won’t freeze.

However…

The coil temperature will drop approximately 1° for every degree the return temperature drops. So if the customer sets it down to 74° the saturation will now be 31° and the coil will freeze.

Pretty basic stuff but very important if you don’t want to leave a problem for your customers.

There are many things that can cause this (low airflow, restrictions, low refrigerant) but step #1 is having the wherewithal to catch it.

Keep in mind that this is only once the system has run long enough to stabilize. Don’t start making changes until the system has run at least 10 minutes and leveled off.

— Bryan

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