The HVAC/R Diagnosis Pyramid of Skill

WARNING: THIS ARTICLE CONTAINS GENERALIZATIONS. IT DOES NOT APPLY TO EVERYONE AND WE HAVE ALL PROBABLY BEEN ALL OF THESE AT ONE POINT OR ANOTHER. IF YOU FEEL PERSONALLY ATTACKED MAY I SUGGEST FINDING A SAFE SPACE AT A WEST COAST UNIVERSITY AND BORROWING A BINKY FROM A NEARBY TODDLER. ALSO… MY CAPS LOCK BUTTON IS STUCK.


It was my first few weeks out of tech school and I had already ridden with several guys. Some good, some not as good but today was the first time with this tech and something was already different. We were driving to our first call of the day and between dirty jokes and puffs on a cigarette.

“OK, let's guess what's wrong with this next one… they are all Lennox in this subdivision… so I'm betting…. a TXV”

That was my first exposure to the “Been there, seen that” tech, that relies on calibrated guesswork as a primary diagnosis tool. Along the way I've met many more of these and other types of techs in the “Diagnosis Pyramid” and so… I will share them with you now.

But first….

I confess I stole this pyramid idea from “Grahams Hierarchy of Disagreement” which is also one of my favorites… maybe I just like pyramids, my grandmother was an ancient alien so there's that.


The Hack

I literally just made a podcast where I said we should stop calling people hacks. So I guess I'm a hypocrite, but hack is much easier to say than “tradesperson of dubious skills, training or intellect” so hack will need to suffice here.

Many hacks think they know what they doing because they suffer from a heavy dose of Dunning-Krueger effect and are standing firmly on Mt. Stupid as shown here.

The good news is that many confident people start here and this is not a life sentence to stay stranded on Mt. stupid. I have done complete hack jobs in my career, thinking I had enough skill, knowledge and experience only to realize later that I was a bumbling goon. The hack has to travel through the valley of despair to reach the slope of enlightenment where they can become a real tech.

Strength = Ignorance is Bliss

Fatal Flaw = They Are Terrible at Working on HVAC/R 


White Shirt

Let's start by focusing on the good things about a white shirt:

  1. They smell nice
  2. They smile
  3. They have a firm handshake
  4. They rarely break systems because they don't use tools on them very often

Truth is that many good techs could learn a thing or three about positive communication and people skills from a white shirt, but that is where my positive comments end.

The trouble with white shirts advancing beyond that stage is they have no incentive to do so. They don't need to get dirty, they make lots of money and they look dang good doing it.

These are just salespeople and the more they learn technically, the more complicated it can be to sell systems so why bother?

Strength = Making Money & Looking good

Fatal Flaw = Greed 


Parts Changer 

There are two types of parts changers, the one who does it to make more money and the one who does it because he thinks that's what diagnosis is.

In flat rate environments that pay bid time or commission on parts there are techs who catch on quick that certain repairs are money makers so they look EXTRA HARD for those repairs on every job. It isn't to say they are purposefully looking to pad a ticket but they become fixated on certain things that bring in the most money to them.

The other parts changer is often an inexperienced or under-trained tech who throws a bunch of parts at a problem and honestly thinks that's how you fix problems.

I knew one tech that would replace the control wire and transformer every time he a low voltage fuse blowing that he couldn't figure out. He didn't do it because it benefitted him in any way, he just didn't know how to troubleshoot.

Strength = They Eventually Get The System Running (Mostly)

Fatal Flaw = It Costs a Lot and Often Requires Multiple Trips 


Been There Tech

The been there tech is common in all industries and is especially in techs who have done the job 10+ years. When you start out as a hack or a parts changer it's often easier to end up relying on what you've seen before than it is to go back to the start and really understand the fundamentals of how things work.

It can be a big ego hit for a been there tech to admit what they don't understand so they often form complex legends to explain why things happen the way they do.

Been there techs will often talk about “weird problems” and will concoct strange solutions to problems such as drilling holes places you are pretty sure they shouldn't or wiring this or that to that other thing or bypassing that one part because “it's not really needed”.

The been there tech should do more manual reading and less storytelling and they will find the myths and legends begin to look more like science.

Strength = They Often Have a Lot of Valuable Experiential Knowledge 

Fatal Flaw = What They Know Only Applies to What They've Actually Worked On. New Technology is Often Confounding. 


Average Tech 

The final four techs are all truly techs and they have more in common then they have that separate them. The majority of the techs you meet that can actually repair most problems on most machines are average techs.

An average tech generally knows how the system works, can use a gauge manifold and a meter and can figure out the location of a leak or a low voltage short.

Their focus is on diagnosing the primary problem, fixing it and getting out of there as quickly as possible. They don't do much with superheat or subcool though they know how to calculate it, they don't use a micron gauge though they know the “right” answer is 500 microns and they don't really care to learn much more.

Strength = They Can Consistently Make Stuff Blow Cold and Hot

Fatal Flaw = Callbacks are Pretty Common When “More Stuff Breaks”


Senior Tech 

A real senior tech has all the find and fix skills of an average tech but with extra insight as to the “why” behind a failure. Yes the TXV is restricted but WHY wasn't the factory drier replaced with a new one when that compressor was replaced 6 months ago?

A senior tech knows how a compressor works and what makes it fail, knows how to check combustion on a furnace and what is causing the rising CO and can spot a leaking flare fitting from a mile away.

The thing that keeps a senior tech from becoming a Supertech is the vision of more than one layer beyond the NOW cause to all of the contributing factors that are often outside of the equipment itself.

Issues like high a low humidity, sweating ducts, occupant discomfort, coils that keep leaking over and over, consistent compressor failures when all the readings look “fine”.

When issues start to spread outside of the equipment into the electrical system, indoor air, envelope, ducts and design a senior tech can find themselves frustrated.

Strength = Excellent Diagnosticians 

Fatal Flaw = Appliance Fixation 


Supertech

The term “Supertech” is often used as a pejorative to mean an experienced tech who thinks they know it all. These types of Supertech are often actually “been there” techs who like to talk on social media.

No, here I'm saying supertech as in a tech that can really fix just about anything with enough time alloted. They are nerdy enough to fill any knowledge gaps they may have about an issue before they call it good. They diagnose the entire structure and notice all of the contributing factors to problems. You can throw this sort of tech at almost any problem…. however…

They still are all about solving problems and can miss opportunities to optimize performance.

Strength = They Can Fix Anything 

Challenge = They Aren't Always That Profitable 


Unicorn Tech 

Ok… I'm stretching here, but let's face it… this whole thing is a bit of a stretch.

In order for a really good tech to also optimize profitability, they need to look outside of what is wrong in need of fixing and what can be improved for optimal

  • System longevity
  • Efficiency
  • Comfort
  • Indoor Health & Safety

Doing this really well is a heck of a lot more than just selling a UV light or PCO like many white shirts do, it's about really understanding how to tune a building and equipment to work better.

This is things like dropping the compression ratio on a rack by letting the head float a little lower, or recommending that can lights be replaced with sealed led trim to reduce attic infiltration.

There are many high-value solutions that HVAC/R techs can help to suggest and implement that lead to a profitable business and happy customers.

Strength = Living Happily Ever After 

Fatal Flaw = Too Much Money that They Must Build a Tower Like Scrooge McDuck to House (Ok, more like pride in their work and good nights sleep…. leave the gold tower to the white shirts) 

— Bryan

Milivolt Systems w/ Modern Thermostats

Jesse Grandbois is one of the techs who reads the tech tips wrote a few tips that he wanted to share on some gas furnace control basics. This tip is about how to use a fancy digital stat on a millivolt system

For those of you who don't know, a millivolt system uses a thermocouple / thermopile with a standing (constant) pilot flame to generate a tiny “millivolt” signal that is used to control the furnace rather than the 24v signal modern thermostats use.


There's still a ton of millivolt furnaces out there and a lot of the owners want the new and fancy Wi-Fi thermostats. If you're not sure how to get the 24v out of a millivolt system, this tip is for you.
But first let's go over a couple basics.
You'll be using an isolation relay. It's just a SPST (Single Pole, Sngle Throw) NO (Normally Open) relay to separate the different voltages in a system.
Millivolt furnaces operate using a thermopile to power the system. A thermopile is simply multiple thermocouples. Some millivolt systems will also use a thermocouple for flame safety. Under load a thermopile should operate at no less than 190MV.
Please refer to the wiring diagram while reading the information below.
You're going to feed 120v to the transformer. This is what will be used to create the 24v for the thermostat.
Wire your hot side of the 24v transformer to R on the Wi-Fi thermostat.
Connect W on the thermostat to one side of the relay coil. On the other side of the coil you'll add C from the thermostat, and common wire of the transformer.
You're going to take the thermostat wires off your old millivolt thermostat and add them to the NO terminals on the relay.

On a call for heat the relay coil will be powered closing the SPST relay powering the millivolt system (NO terminals) for heat.

— Jesse

A Christmas Meltdown

There's a moral to this story though it is a bit more of a cautionary tale than most I write. While it doesn't rank with the story of three wise men or even Frank Capra's Christmas classic “It's a Wonderful Life”. You may find some common threads with both learning wisdom and remembering why throwing ourselves off a bridge isn't the best choice like George Bailey considered doing.


The year was 2007 or maybe 2008 and it was most certainly Christmas Eve.

We are close geographically and relationally to both my wife's family (The Claerbouts) and my family (The Orrs) and due to this we always spend Christmas eve with one side and Christmas Day with the other.

Luckily, while Florida Summers can drive an A/C tech insane, the winter and especially the holidays, tend to be quite slow. For me as a new business owner and one of the only techs at Kalos that meant that generally speaking, Christmas was a welcomed rest from a crazy year with seemingly endless hours.

As we were preparing the kids to head out to Leilani's parents my phone rings (My cell phone WAS the emergency line).

The caller was a notoriously…. challenging… customer with many vacation homes under management. I gritted my teeth, swore inside and answered as nicely as I could.

“Brrryyyyan” the customer exclaimed, he always had a way of stretchhhhing out my name in a way that exuded disappointment and condescension.

“We have guests arriving and the POOL IS COLD… You JUSSSSSTTTT serviced that pool heater last month and now it's NOT WORKING”

I need to step back a bit and clarify that we work on a LOT of pool heaters in the winter. Both gas and heat pump pool heating is used to keep pools over 80 degrees so that people from cold climates can vacation at Disney and swim in sauna-like temperatures even when it's 40 outside.

It's nice winter work for us… and I shouldn't complain… but ever since we started doing it the term “emergency” has come to include 57-year-old, very white grandmas from Buffalo who need to take a swim after their day at Disney World and GASP! the pool is 73 degrees! Somebody better dial 911!

On this particular Christmas eve, this particular pool heater happened to be on the very far side of town, on the other side of Disney over an hour away from where I live.

Good grief! said I as I hung up the phone, looking and sounding like Charlie Brown.

So I hopped in the van and drove to the offending pool heater.

When I hopped out of the van I found the very best thing an A/C tech can find when they are in a hurry.

So I call the customer, quote the capacitor to which they respond (as they always do) “Bryyyyyyannnn, you were Jusssstttt out there… that seems like a bit much don't you think'

Keep in mind, this customer is also British so every word carries the weight and gravitas of  Queen Elizabeth during a knighting ceremony.

Yes, that is the price

No, I didn't cause it

Yes, I can do it now

Yes, I will leave the pool heater on

I slap that sucker in, fire it up, check amps, grab the suction line it's cold, touch the discharge line, it's hot, check the pool timer, look at the pool valve positions … all is well as far as I'm gonna check today and I'm OUT OF THERE!

It is now approaching noon and I'm almost home and….

bzzzzt… bzzzzt… bzzzzzzzzzzzzt

Because I'm by myself with no wife and kids I curse out loud with all the words a Christian homeschooler can think of “Poppycock and Fiddlesticks” I exclaim…

“Brrrrrrryyyyannn, the pool is SHTILLLLLLL COLLLLDDD” shrieked Sean Connery's twin on the other end of the line in an agitated baritone.

The pool is still cold? Yes…. of course, the pool is still cold. It will take DAYS for a full-sized pool to heat up to 80+ degrees with a heat pump heater… I know this, they know this… everyone who knows anything about pools knows this.

I explain this to my dear, sweet, favorite customer in a squeaky, pre-pubescent voice and reassure them that the pool will eventually heat up but that it will take half a millennium AS PER THE USUAL, not one hour, which is all it had been since I left.

“BRYYYYYANNNNNN!!!!” the customer howled with a voice between that of Lord Voldemort and a hungry werewolf, “It is one thing for you to continue to rip us off with all these failed capacitors but quite ANOTHER for you to make excuses for a pool heater that IS NOT FIXED, you must GO BACK.”

This is the moment that this article is about…. The moment of truth and choice that separates the wise leaders, managers and techs from the reactive.

I took a breath.

I paused.

I reflected.

And I told the customer

“I value your business, I'm as certain as I can be that the heater is working as expected and it will take at least 24 hrs if not several days for that pool to reach temperature, If it isn't warm in two days, give me a call… otherwise have a very merry Christmas.”

No…

That's what I should have done. What I did instead was to pull over my van too fast in preparation to turn around and hit an enormous piece of tire retread on the side of the road.

Just like ralphie, I shouted OHHH FUUUUUUDDDGEEEE on the phone.

Only I didn't say “Fudge.” I said THE word, the big one, the queen-mother of dirty words, the “F-dash-dash-dash” word!

The customer hung up on me and I was sitting on the side of the road with a big, black rubber road rash on my van and the metaphorical taste of soap in my mouth where the ghost of my mother past washed the dirty word out.

So I went back to the pool heater…

There was nothing wrong

I explained everything to the customer and apologized for freaking out.

It turned out fine

But the lesson of the story for us in the trade is that we need to be prepared for customers to be unrealistic, demanding and rude. It comes with the territory and who knows what they are going through that is contributing to their behavior.

All I needed to do was to be better emotionally prepared with what I am and am not willing to do, not with emotion, but as a clear business decision.

Many of our jobs in the field include being on-call and many customers will have a different definition of what's an emergency and what isn't. We are best off being friendly, clear and saying no sometimes in a polite, professional tone.

Merry Christmas and may your on-call be easy and your customers friendly

— Bryan

 

 

 

 

 

 

 

 

Ball Bearing vs. Sleeve Bearing Motors

One aspect of motor selection that can get overlooked is motor bearings and it can have big consequences.

Sleeve bearings are most common in residential and light commercial applications because they are less expensive and quieter. They don't have rolling “balls” but rather rely on a thin film of oil on metal sleeves.

Sleeve bearings work well when noise is a consideration and when the shaft load isn't high which is especially true in residential direct driven blower and condenser fan applications.

Ball bearings are the best choice when the motor is under greater shaft tension or when fan speed controllers are in place. This is common in larger commercial and industrial applications especially when the motor is driving a belt that pulls on the motor shaft.

If you accidentally use a sleeve bearing in a situation where there should be a ball bearing the motor will fail early,

If you use a ball bearing motor where there should be a sleeve bearing it may be bothersome from a noise standpoint.

— Bryan

An Electric Heat Mistake

I started working as a tech when I was 17 years old, fresh out of tech school. My first winter out on my own I went to a service call in an older part of Orlando, a part of town I had never worked on before. It was an especially cold winter that year, and the service call was for insufficient heat.

 

When I arrived, I found the system was a really old GE straight cool system. After testing the system, I found the system had a 10kw heater, but only 5kw was working. After a closer look, it was discovered that 5 KW of the heat was disconnected. This was no problem for me; wiring was always my specialty! I grabbed some #12 stranded and had that puppy heating in no time.

Problem…

#1 – It smoked like a chimney and set off every alarm in the house

#2 – Once I got the doors and windows open and the smell cleared out as best I could it got me thinking… How long has it been since that second 5kw was connected?

When I looked closer I saw that the feed wire going to the air handler was only #10… then it dawned on me.

The REASON they had one-half of the heat disconnected was because the breaker and wire size were only rated for 5kw. Why did they a 10kw you might ask? Likely it's what they had on the truck and they figured if they disconnected one-half it would be safe.

Lessons learned –

#1 – Never assume that a system was installed properly to begin with and keep an eye out for proper feed wire size.

#2 – Don't use improperly rated heat strips or other rated parts and simply make an “alteration”. When the next technician arrives he likely won't understand what you did. At best you confuse him, at worst you kill him.

— Bryan

Try and Stay Warm

Another quality tech tip from senior refrigeration and HVAC tech Jeremy Smith. Jeremy lives in Ohio so he knows a thing or three about the cold.


As HVAC/R techs, we're often called on to work in some of the worst weather conditions. With the cold weather, I thought it timely to share some tips and strategies that I use for staying warm in the cold weather, particularly for you guys in the south who think that 40°F Is ‘cold’.

Staying warm, particularly in very cold weather, isn't about having the thickest jacket or the most socks, it's more about picking the right layers to wear. Let's be honest, we're all tough enough to gut out an hour or so in the worst conditions imaginable with a hoodie and a beanie cap. But, when we're exerting that much mental effort just to endure being cold and miserable, we're not exerting that effort to work on solving the problem or making the repair, so staying comfortable is both to our benefit and to our employers benefit as we're more effective when we're not standing there shivering.

The first and foremost rule in staying warm is to stay DRY. Wet clothing, either from your own sweat or from rain or snow that melts into your gear doesn't insulate as well. Some fabrics, like wool, retain their insulation better, but if you get wet, you're going to have a long, cold day. Let's start with what's called a “base layer” the base layer isn't about insulation. It's about staying dry. Under Armour is a popular brand and their stuff is great, but I go in a different direction and use Merino Wool base layers. They can be cheaper than Under Armour and perform at least as well. These aren't Grandpa’s itchy wool long johns, they're very comfortable, warm and they help keep your skin dry which is really the secret to staying warm.

Next, you want insulation. Fleece is good here, so is a nice Under Armour hoodie or similar item. Even a nice, thick sweatshirt is enough to keep your body warm. A vest is also helpful because keeping your body core warm is more important than keeping your arms warm. I've also got fleece pants for when it gets really cold but I normally don't need them for work. Layer one or more on as needed for conditions. On top of all of this is your outer shell. This is the wind and water repellent layer. As HVAC/R mechanics, we need this layer to be abrasion-resistant as well. Something like a down ski jacket is probably the warmest thing you can find, but they won’t last very long around those sharp sheet metal edges.

A Carhartt coat and bib overalls are great and are the standard for tradesmen everywhere, but other brands like Walls and Dickies are just as warm and can be had for less money. Personally, I prefer a bib and coat set over a set of coveralls. That way, I can wear just what I need rather than having to either be cold or wear the whole, heavy setup and maybe overheat.

Another nice thing to have is a foam kneeling pad. Not just to cushion your knees from the roof but to keep snow from melting into your insulation and making you colder.

Now let's talk headgear. Sure, a beanie is great, but when you've got to be out there for hours, gotta keep the grey matter warm. My setup starts with a polypropylene fleece balaclava. They're great because they are so versatile. They're everything from a neck warmer to a full head, face and neck insulator. Every tech that works in cold weather needs one. When the wind really kicks up or the mercury really drops, though, that just isn't quite enough for all-day comfort out on that roof. Enter the “Mad Bomber” hat. Big, floppy rabbit fur ears wrap the sides of your face and buckle under your chin. Now, we're staying toasty. When the weather really gets nasty and the wind is howling, I'll pull the hood of my coat up then wrap a pair of inexpensive ski goggles over the whole mess. The hood keeps the wind off of the back of your neck and the ski goggles both protect your eyes from the harsh snow glare, cold winds and holds the whole thing together. Best of all, ski goggles don't fog up like regular sunglasses do.

No matter how cold it gets, I don't like insulated boots for work. If I'm working inside, my feet get wet and sweaty and uncomfortable then, if I have to go outside I'm already wet and, once you're wet you will get cold a lot faster. So, I stick with uninsulated boots for everyday wear and I carry 2 extra pairs of socks. A pair of polypropylene liner socks. These are the base layer for your feet. Not keeping you warm but keeping you dry. Over those, a pair of nice, thick wool socks. Lace your boots up over them and you'll be plenty warm but there is one more step to warm feet. Spend enough time out of the roof like this and one thing happens.. your boots get all snow-packed, then the snow melts and soaks through the boots and you wind up with wet, cold feet. The answer is a pair of overboots. Pull them on over your boots, buckle them up and now your feet stay dry and warm. One quick note on boots. OSHA requires safety toe boots, but that doesn't mean steel toes. The steel toes on those boots just stay cold, no matter that you do and it radiates what heat you've got in your toes and you suffer.

When boot shopping, buy safety toe boots with a composite toe. The plastic safety toe is still OSHA approved but it more comfortable to wear in the cold. One important thing is to avoid cotton. Cotton socks, cotton underclothing, etc absorbs moisture and doesn't provide any insulation value.

Unfortunately, I don't really have any all-day stay warm tricks for your hands. A pair of ragg wool gloves is about the best protection I've found. Usually, I wind up with my hands in and out of the gloves all day, balancing between keeping my fingers warm and and being able to do the job. Another nice thing to have on hand, so to speak, is a couple of packages of those disposable hand warmer packets. Unwrap one or two and throw it into your pocket. Cheap guy trick for those. If you're only out in the cold for an hour or so, seal that handwarmer up in a zip lock and press the air out. Since they're air-activated, removing the air stops the reaction. Open the bag back up, shake it up and it'll start warming back up again.

In practice, this is how I'll employ this layering system. Your situation may be different. I dress for work very much the same every day. Work pants and a T-shirt. As the weather cools, I'll add a sweatshirt and eventually, a vest. That's just for walking around. When the call drops that I have to go hang out on the roof, I find a place where I can change. Based on experience with in the cold, I'll select the right amount of layers to keep myself warm without overheating. Sweating can be as bad as shivering and will ultimately lead to shivering. I keep the heavy gear packed in a big duffle bag in reverse order of putting it on, so I can just pull a piece out, put it on and grab the next piece. Peel gear off in the same order and it packs away, ready for next time. If your gear gets wet, be sure to dry it before venturing back out into the cold.

Hypothermia and frostbite

Since we generally work alone, we really need to learn to self-monitor for these two conditions. Hypothermia is a serious, potentially life-threatening condition where the body core temperature drops below 95F and the body is no longer able to warm itself. Your brain and vital organs will stop working and you will go to sleep one last time. The first symptoms of this are violent and uncontrollable shivering. This is your body working your muscles vigorously in an effort to generate heat to keep itself warm. Further symptoms include slurred speech and disorientation. Don’t ignore these symptoms and if you find yourself in that condition of violent and uncontrollable shivering, get yourself somewhere that you can warm up and stay there until you are warm.

Frostbite is the formation of ice crystals in your body. This occurs when exposed skin, typically fingers, toes, ears and noses literally freezes. It is very painful and can result in the loss of flesh in the affected area. Symptoms include pain, itchiness and discoloration of the affected part which progresses to hardening as the flesh freezes deeper. Much like hypothermia, this is much better treated early than allowing it to progress. Stop and allow the area to warm slowly. DON’T RUB IT. This breaks up any ice that has formed and those ice crystals can cause more tissue damage. Cool water is the best way to warm a frostbitten area. One last caution or two to touch on.

A lot of guys like to drink coffee, tea or hot chocolate to warm up. While I love a good, hot cup of coffee, this isn’t always the best way to warm up. Caffeine is a vasoconstrictor meaning that it causes the small blood vessels in your hands, feet and elsewhere to constrict, limiting blood flow. That can increase your risk of conditions like frostbite because warm blood isn’t flowing to those areas. Also, we typically associate dehydration with summertime and sweating, but in cold conditions, this is also a concern because the air is so dry, we’re losing moisture with every breath plus we may be sweating and the wicking layers we wear are dissipating that moisture as they’re designed to and we don’t notice the sweat like we would in the summer. Stay hydrated.

— Jeremy

Shopping list
Sportown Men's Merino Wool Lightweight Long Sleeve Crew Base Layer Top,XXL 

Minus33 100% Merino Wool Base Layer 706 MidWeight Bottoms Black XL
Balaclava Fleece Hood – Windproof Face Ski Mask – Ultimate Thermal Retention & Moisture Wicking with Performance Soft Fleece Construction, Black, One Size

Mad Bomber Supplex Hat with Grey Fur, Black, Medium

RefrigiWear Insulated Wool Gloves Green Large

Fox River Outdoor Wick Dry Alturas Ultra-Lightweight Liner Socks, Medium, White

Wigwam Men's 40 Below Heavyweight Boot Socks, Grey Twist, X-Large

Ski Goggles for Youth Age 8-16 ¨C UV400 Protection and Anti-Fog ¨C Double Grey Spherical Lens for Sunny and Cloudy Days (Black)

How (and Why) to Flow Nitrogen While Brazing

When I started in the trade the idea of flowing nitrogen while brazing was nothing more than a punchline of a joke. Like pulling a vacuum with a micron gauge or proper recovery it was a wink and nod proposition rather than a real practice. I've had to unlearn many bad habits since those early days and the practice of flowing nitrogen while brazing is one that I still hear being mocked as “overkill” by old-timers. It isn't hard, it isn't overkill and it makes a BIG difference. If you will just keep reading instead of rolling your eyes I will tell you the reasons why. What Flowing Nitrogen Accomplishes Copper and oxygen react to create “cupric oxide” or copper oxide in the same way that iron and oxygen react to create rust. When we heat copper over about 500° this begins to occur rapidly with more copper oxide scale building up the more heat and oxygen there is. We see this occur all the time on the OUTSIDE of the copper where oxygen is prevalent in the air and this can also occur inside the copper if there is air inside the system rather than dry nitrogen. This is made worse the hotter the joint and the longer the copper is left open while working. When we prevent air from entering the lines in the first place by keeping them sealed as much as possible and THEN flow nitrogen while brazing we can prevent copper oxide from forming. This keeps line filter/driers, screens, compressor oil and valves (ever heard bad TXV?) free from contamination and prevents many issues not to mention that it ALSO helps speed up the evacuation process. Why Old Timers Say it Doesn't Matter Many techs who have done it a long time haven't flowed nitrogen EVER and have gotten away with it because of mineral oil. Older CFC and HCFC refrigerants used mineral oil rather than POE/PVE or PAG oils that we see today which have higher solvent properties that “scrub” the oxide from the walls and deposit it into driers and screens. Techs in the Grocery industry know that when a system is converted from Mineral or AB oil over to POE that it is very common for this cupric scale to clog screens pretty quickly after the changeover. The point being that mineral oil was forgiving on small amounts of cupric oxide on the walls of the tubing, POE isn't. The Process Keeping copper oxide out of the system is really quite easy with a common-sense approach in place starting with just pulling the nitrogen tank and flow regulator off of the truck along with the torches FIRST THING. There are several great flow regulators on the market, a few built right into the regulator and some that you attach on the outlet of the regulator. Keep in mind that you need to FLOW nitrogen not PRESSURIZE with nitrogen while brazing otherwise you never get the joints to hold.

  1. REMOVE CORES – When you set up you first need to remove your cores in the inlet and outlet of the brazing path so that you can get full flow with minimum backpressure.
  2. PURGE OUT AIR – Purge nitrogen at fairly high pressure in the direction of the refrigerant flow to help “chase” the air out of the circuit and fill with nitrogen.
  3. FLOW WITH 2 – 5 SCFH – Flow with a VERY LOW flow of 2 – 5 Standard Cubic Feet per Hour of flow which is just a whisper out the end.
  4. DON'T FREAK OUT – The very last joint can be tough on small systems. It's OK if you shut off the flow or reduce down to next to nothing for that last joint. Don't make being “perfect” the enemy of getting started flowing nitrogen while brazing. Don't overthink it and stop making excuses for not doing it.

If you follow this process and then pressure test with nitrogen prior to evacuation it will go much more smoothly and all in all can save you time in the process. Nitrogen is cheaper than callbacks and early component failure. Use it.

— Bryan  

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