Category: Tech Tips

This is Part 4 series by Senior Refrigeration Tech (and prolific writer) Jeremy Smith. Pay attention to this one folks, I know rigging and safe lifting practices may be boring to some of you, but it could very well save your back or your life.


Disclaimer

This article is written by a technician representing his real-world experiences and his advice for best practices. You MUST understand the particular application, weight of materials and load strength of every item you use. From struts to pulleys, to anchors, ladders, ropes etc.. HVAC School is NOT giving OSHA approved safety advice. Refer to your managers, safety professionals and OSHA guidelines first and foremost. Apply any and all of these practices at your own risk with the knowledge that we are trying to help keep you from hurting (or killing) yourself.


Unistrut is your friend

The idea for a site built, customizable, gantry struck me about 4 or 5 years ago. I started by throwing a piece of unistrut over a pair of plastic folding sawhorses on the roof. The whole shebang collapsed and I had to muscle the compressor plus the weight of the strut onto the roof but I was convinced that the idea was sound. From that simple setup, I’ve experimented with using ladders, fall protection fences, and various supports I built out of unistrut. I’ve had varying degrees of success and have settled on a design that works and can be modified to suit the conditions on a job site.

Let’s start with a solid base. Looking at the “T” shaped part laying on the roof, make each piece 6’ long at a minimum and and bolt them together with a proper brace. From that solid base, install an upright and the angle bracket, again using proper fittings. The angle brace should be 2 to 4 feet long depending on the height of the upright and the height of the upright depends on what your job requirements are. I’ve used them from 30” high to one that was almost 15 feet high. Now, build a second upright, same as the first one. Remember that crossbar I said we had to just “accept” that is was there? Now it’s time to put it there for real. Using a couple 90° brackets, bolt your cross piece to the two uprights and check for level..

This may seem complicated to build and maybe it is, but a part of this is laying out the basis for some other stuff later. These pictures are from a lifting job I did. 2 15 ton Copeland scrolls up through a roof hatch that came out on a mezzanine, trolley over and lowered to the main roof level.

Note in the last picture, the chainfall is connected to a device extending out of the unistrut. That’s a trolley and it makes moving those loads once you get them up onto the roof very easy. Let’s go back to our block and Tackle example earlier. The crossbar is a piece of unistrut and, instead of connecting your pulley and rope to the bar directly, connect it to this trolley. It is now very easy to lift that load right through the roof hatch, trolley it to one side or the other and lower it onto a cart or a dolly for transport across the roof surface.

A really nice, slick setup based on this that I use very frequently is for loading and unloading these out of your truck. My van is outfitted with commercial steel shelving. If yours isn’t, you may want to just skip this part. So, cut a piece of unistrut to fit across the top of those shelves. You should really have to work to get it in and out. Once it’s wedged in there, it isn’t going anywhere. Now, take a longer piece and support it across the rungs of a ladder parked 4-5’ off the back bumper. Bolt that piece to the crossbar you just installed and, using a trolley and a ¼ ton hoist, you can easily move a compressor in and out of your truck.

 


Now for the cautionary stuff. Unistrut is awesome. It’s strong and relatively light, but there are limitations to its strength. Please, before you build anything I’m suggesting here, know exactly how much your load weighs and exactly how much every single piece of your lifting equipment will support. I suggest a 2:1 safety factor if at all possible, so if you’re lifting a 100-pound load, make sure that everything in your lifting system is capable of handling twice that weight. Strength information about unistrut in its various applications can be found HERE As you use this reference, pay attention to point load ratings and span figures. As span increases, point load decreases. You DO NOT want that strut failing under a load so keep your loads within the limits of your equipment. If you look closely at the crossbar I use, you’ll see that it is thicker than normal 1 ⅝” unistrut. That’s a 2 ⅛” piece and is much stronger. If you’re going to do heavier lifts, you really need a heavier crossbar like that. Be aware, the engineering specs and the catalog are very dry, boring reading but take the time to learn and know what your lifting gear will do before you have to really stress it and potentially injure yourself or someone else. Remember, the point of this is to lift and move things safely…

— Jeremy
Shopping list
Genuine Unistrut P2950-EG 4 Wheel Trolley Assembly for use with P1000, P1001, P5000, P5001, P5500, P5501 and All 1-5/8″ or Taller Strut Channel

Genuine Unistrut P1325-EG 4 Hole 90 Degree Angle Connector Bracket for All 1-5/8″ Strut Channel

Genuine Unistrut P1031-EG 4 Hole “T” Shaped Connector Bracket for All 1-5/8″ Strut Channel

45° inside brackets for unistrut

A good leak detector is a big investment and one of the more important tools a tech has on the truck. I’ve had the same leak detector for years and I’ve replaced everything on it from sensors to pumps to the probe.. and no, the one shown above isn’t mine.

One thing that I have learned is that with leak detectors care, maintenance and testing is a huge part of finding leaks the first time and will also save you a lot of money. This little tutorial covers the Bacharach H10 series but many of the tips apply to most detectors.

Keep it Clean and Dry

Leak detectors don’t like moisture and dirt. Make sure to keep the rubber tip and filter on the end to help prevent creating a seal that pulls in moisture and keep the detector off the floor and out of the dirt. If you ever DO get your detector wet, shut it off quickly, pull out the batteries (if it has them) and put them in a degassing chamber and pull a vacuum on it. This will dehydrate the detector and can often save it.

Store it in a Safe Place

Leak detectors have sensitive pumps and sensors in them that can be damaged if they are handled roughly. Also, keep from kinking the hoses or probes as this can cause leaks in the tube that will impact your reading as well as restrict flow to the sensor.

Confirm Flow

The H10 series of leak detectors has a red ball flow indicator in the probe. The first thing I do when I start the detector and allow it to warm up is to check the flow through the probe by pointing it down and seeing is the red ball floats.

Check your Sensor

Make sure your sensor is properly connected and on the H10 you can physically feel the heat from the sensor guard door when the unit is running.

Adjust the Sensor

On the H10 you can use the adjustment on the bottom to increase the current through the sensor as it ages to maintain performance. Make sure to adjust it back to the starting point when you install a new sensor to extend the life of the sensor.

Use a Reference Leak

I see many techs attempt to use a bit of refrigerant out of a tank to test their leak detector. With most detectors having a published leak detection accuracy of 0.10 oz per/yr this is a really rough way to test a detector. The best way is to use a tiny calibrated leak or a leak reference bottle like the one shown above to ensure that your detector is going to find small leaks as well as large ones.

If you treat your detector well and confirm the operation of it every time you use it, you should get great results and a long life.

— Bryan

 

This is Part 3 series by Senior Refrigeration Tech (and prolific writer) Jeremy Smith. Pay attention to this one folks, I know rigging and safe lifting practices may be boring to some of you, but it could very well save your back or your life.


Disclaimer

This article is written by a technician representing his real-world experiences and his advice for best practices. You MUST understand the particular application, weight of materials and load strength of every item you use. From struts, to pulleys, to anchors, ladders, ropes etc.. HVAC School is NOT giving OSHA approved safety advice. Refer to your managers, safety professionals and OSHA guidelines first and foremost. Apply any and all of these practices at your own risk with the knowledge that we are trying to help keep you from hurting (or killing) yourself.


Complex block and Tackle systems

Now that we have a basic understanding of how to handle ropes, tie knots and rig a basic pulley system, we’re ready to dive into more complicated systems. I reserve these for buildings that have a roof hatch so that I can setup a gantry over the hatch. I haven’t yet figured out a system to extend a beam over the edge of a building, but I’m working on it. I’ll go into the basics of how I build and what I build in the next section. For now, let’s just accept as a given that we have a solid beam installed over the hatch opening to connect ropes
and pulleys to.

For jobs like this, I keep a double pulley on the truck. Threading or ‘reeving’ these takes more time and is more complicated but the reduction in effort is worth it. Start by fixing your single pulley to the overhead beam and connecting the double one to a light “load” like a wrench or something similar. Tie one end of the rope to our overhead beam. Start threading by running the other end through one side of the double pulley then through the single, through the other side of the double. Now, you should have a nice mess of rope. Lower that weighted double pulley to the spot where the load is and secure the free end of the rope with a clove hitch just to keep it from falling and to keep a tiny amount of tension on the system.

The setup shown here was used to hoist a 15 hp blower motor onto the roof. Motor weight was something like 145# With 4 lines supporting the load, the effort to hoist that motor was less than
40#.

I like to stand on the roof while hoisting, so I make it a point when threading pulleys to wind up with the pull end of the rope going up. This also has the advantage of using every line to support the load and obtaining maximum effort reduction.

As before, connect to the load and hoist it slightly. Check for good balance, twisted ropes and crossed lines. Make any corrections and hoist away. Since we’re hoisting to an overhead beam, there won’t be any need to take 100% of the load at any time, so this method is much safer and, when we dig into the gantry build, we’ll find a great way to manage the load once it’s at the top of the lift. As the loads get heavier, you’ll be using heavier and heavier duty hardware to attach to them. Eye bolts, shackles and chains are the rule here.

— Jeremy

Shopping list…
Stanley National Hardware 3214BC 1-1/2″ Zinc Plated Fixed Double Pulley

Crosby 1018393 Carbon Steel G-209 Screw Pin Anchor Shackle, Galvanized, 3/4 Ton Working
Load Limit, 5/16″ Size

This is Part 2 series by Senior Refrigeration Tech (and prolific writer) Jeremy Smith. Pay attention to this one folks, I know rigging and safe lifting practices may be boring to some of you, but it could very well save your back or your life.


Disclaimer

This article is written by a technician representing his real-world experiences and his advice for best practices. You MUST understand the particular application, weight of materials and load strength of every item you use. From struts to pulleys, to anchors, ladders, ropes etc.. HVAC School is NOT giving OSHA approved safety advice. Refer to your managers, safety professionals and OSHA guidelines first and foremost. Apply any and all of these practices at your own risk with the knowledge that we are trying to help keep you from hurting (or killing) yourself.


Simple pulley systems

Let’s get into the meat of lifting and moving heavier loads…

One thing that I use a LOT is a basic pulley. Simply put, when using a pulley or a system of pulleys called a Block and Tackle, the amount of force required to lift a load is the total weight divided by the number of lines supporting the load. An overhead pulley system doesn’t reduce lifting force at all. It does nothing more than redirect the force applied. Since there is only one line supporting the load, there is no reduction in force required to lift the load.

A pulley connected to the load with one line tied off and pulling force exerted on the other end of the rope will cut the force required in half for lifting a load. Here, with 2 lines supporting the load, the force or effort required to lift the load is cut in half.

 

In practice, I limit this to loads of 50-100 pounds or so because at the end of the lift, you will be lifting 100% of the weight. For your first couple lifts, try to stay on the lower end of these weights until you build confidence in your techniques. We’ll get into more complicated systems with more pulleys and lines in a later section.

Start by tying off one end of the rope to something secure. This is your anchor point. Best case scenario, there is something they’re purpose-built to anchor to. Worst case scenario, I’ve actually tied a loop around the entire curb assembly of a rooftop unit.

Remember, use good knots. The ONLY knot that I trust in this situation is a bowline. Now that we’ve got our rope anchored, slide the pulley onto the rope and lower that pulley to your load. Tie the other end, the lifting end, of the rope off to something, anything really. A clove hitch is quick and easy here. All we’re doing is keeping the rope in place so it doesn’t fall. To connect the pulley to the load, I like to use a climbing carabiner with a screw lock. Cheap carabiners that you can get at most home improvement Warehouse stores are NOT suitable here. If all they do is bend under the load, count yourself lucky.

If there is a lifting eye or provision to install one on the load, use it and be sure to lock the eye bolt in place with the included nut, otherwise, the load can unscrew itself from the bolt and fall. That is going to be the best and safest place to connect your pulley to the load. Now, back up to the roof and take a couple seconds to straighten out the ropes. Get any twists out of the system and lift the load a short distance off the ground. Check everything. Is your anchor solid? Are you comfortable with the load? If everything is good and you’re comfortable with the lift, then continue pulling the load up to the roof edge.

Remember when I said to limit the weight? Now you’ll see why. You’ve got the load almost there…. You’re going to have to squat to the load, grab it and haul it over the roof edge. Yeah, it sucks but not as bad as hauling the whole load all the way up the side of the building. This is where a carabiner is nice because that big metal loop gives you a solid handle to grab
and hang on to.

— Jeremy

P.S. – Today’s Shopping list

Stanley National Hardware 3213BC 1-1/2″ Zinc Plated Fixed Single Pulley

Mad Rock Ultra Tech Screw Carabiner

 


We have been discussing a lot of methods for checking a refrigerant charge without connecting gauges over the last few months. This got me thinking about the “approach” method of charging that many Lennox systems require.

Approach is simply how many degrees warmer the liquid line leaving the condenser is than the air entering the condenser. The approach method does not require gauges connected to the system but it does require a good temperature reading on the liquid line and suction line (Shown using the Testo 115i clamp and 605i thermo-hygrometer smart probes).

When taking an approach reading make sure to take the air temperature in the shade entering the coil and ensure you have good contact between your other sensor and the liquid line.

The difference in temperature between the liquid line and the outdoor temperature can help illustrate the amount of refrigerant in a system as well as the efficiency of the condenser coil. A coil that rejects more heat will have a leaving temperature that is lower and therefore closer to the outdoor temperature. The liquid line exiting condenser should never be colder than the outdoor air, nor can it be without a refrigerant restriction before the measurement point.

Here is an approach method chart for an older 11 SEER Lennox system showing the designed approach levels.

While most manufacturers don’t publish an approach value, you can estimate the approach by finding the CTOA (Condensing Temperature Over Ambient) for the system you are servicing and subtracting the design subcooling.

6 – 10 SEER Equipment (Older than 1991) = 30°F(-1.11°C) CTOA

10 -12 SEER Equipment (1992 – 2005) = 25°F(-3.88°C) CTOA

13 – 15 SEER Equipment (2006 – Present) = 20°F(-6.66°C) CTOA

16 SEER+ Equipment (2006 – Present) = 15°F(-9.44°C) CTOA

I did this test on a Carrier 14 SEER system at my office so the CTOA would be approximately 20°

Then Find the design subcooling. in this case, it is 13°F(7.15°K)

Subtract 13°F(7.15°K) from 20°F(11°K) and my estimated approach is 7°F(3.85°K) +/- 3°F(1.65°K). I used the Testo 115i to take the liquid line temperature and the 605i to take the outdoor temperature using the Testo Smart Probes app and I got an approach of 4.1°F(2.25°K) as shown below.

More than anything else, the approach method can be used in conjunction with other readings to show the effectiveness of the condenser at rejecting heat.

If the system superheat and subcooling are in range but the approach is high (liquid line temperature high in relation to the outdoor air), it is an indication that the condenser should be looked at for condition, cleanliness, condenser fan size and operation and fan blade positioning. If the approach is low it can be an indication of refrigerant restriction when combined with low suction, high superheat and normal to high subcooling.

If the approach value is low with normal to low superheat and normal to high suction pressure and high subcooling it is an indication of overcharge.

The approach method is only highly useful by itself (without gauges) on a system that has been previously benchmarked or commissioned and the CTOA and subcooling or the approach previously marked, or on systems (like Lennox) that provide a target approach specific to the model.

— Bryan

This is an open letter sent to staff at Kalos Services


Hey Everyone,

First, I want to remind you that you are in no way obligated to read company emails or do anything work related when you aren’t working. So if you don’t want to be bothered by this on your day or time off then by all means save it and get back to it during work hours.

At Kalos we do a lot of training and developing people towards their goals. It always has been and always will be a big part of what we do.

Lately, I’ve had a lot of people stop me and say some version of “I would really like to learn about _________ (fill in the blank)”

Or

Can I sit in on a few of your classes it seems really interesting?

Or

What classes or certifications can I get / take to help me advance?

When I ask what they are already learning about the subject there usually isn’t much.

You aren’t going to like this answer, but it’s the truth.

If you haven’t already started learning something on your own then I’m not going to be much help.

I make 2 podcasts, 2 videos and send out 3 to 7 tech tip emails per week about all sorts of topics related to HVAC.

There are only a few of you who pay any attention to what I already make to help train you.

It isn’t just me, there are tons of books you can read, free videos you can watch, manufacturer manuals you can reference, online forums and groups you can leverage, code books you can refer to etc…

Before you start feeling defensive let’s be clear.

Most of you work a lot and watching videos or reading or listening to podcasts about AIR CONDITIONING of all things just isn’t a priority.

I get it…

But that means that you like the idea of learning or the recognition that comes along with showing an interest in learning but do you really want to learn?

Of course we all learn hands on doing our jobs. We learn from our mistakes, we learn from whomever we work with… that is all a type of learning that is forced upon on us and often it is valuable.

That is learning by force rather than by choice and you can do very well learning in that way.

When I started teaching classes in my 20’s I was an idealist. I thought everyone would be interested in knowing everything they could about their jobs and the world around around them. I figured they would take advantage of free education provided to them to advance in their careers.

That just isn’t how it works

Most people want to FEEL like they are interested in learning or growing but they actually only learn or grow when their circumstances force them to.

Most people like the sound of “opportunity” but when opportunity looks like reading a boring book or manual then they look for a different opportunity.

So you may be feeling a bit like “what’s your point?!” Or “This dude is a real jerk”

People who know me best know that deep down I am a bit of a jerk and that that I also really care about seeing you all grow.

The point is this –

If you really want to learn you will start by learning without being forced to learn. If that’s you than I would be thrilled to help you along that journey.

Otherwise you will still learn by circumstances and if you are a talented, hard working, good person you will still have a home at Kalos whether you like learning or not.

However, there is no point in attending classes (other than ones directly related to your current role) or asking me about how you can learn more or progress. I can’t force you to learn and a few classes will only stand to create more confusion.

If you (actually) want to learn more about the HVAC/R trade then by all means, start down that path and I will be thrilled to help you along the way, give you classes, send you to classes, help you find resources etc…

But if you walk up to me or email me and say you want to learn be prepared for me to ask you what you’ve already been learning.

Remember –

A job is something you are given to do and you do it.

A career is something you create with intention and investment in yourself.

Thank you for all of hard work and I truly appreciate every one of you. No matter how you learn or the job you do.

— Bryan

This is ANOTHER series by Senior Refrigeration Tech (and prolific writer) Jeremy Smith. Pay attention to this one folks, I know rigging and safe lifting practices may be boring to some of you, but it could very well save your back or your life.


Disclaimer

This article is written by a technician representing his real world experiences and his advice for best practices. You MUST understand the particular application, weight of materials and load strength of every item you use. From struts, to pulleys, to anchors, ladders, ropes etc.. HVAC School is NOT giving OSHA approved safety advice. Refer to your managers, safety professionals and OSHA guidelines first and foremost. Apply any and all of these practices at your own risk with the knowledge that we are trying to help keep you from hurting (or killing) yourself.


I know, I know… everyone is super strong and nobody needs any help lifting those big, heavy compressors and motors. At least that’s what a guy could think if he just reads the HVAC pages
online.

Reality check. If you’re lifting anything over 50 pounds and are not using a mechanical device to do it, you’re risking serious injury. I speak from experience here. In 2016, I spent 16 weeks off of work progressing from Chiropractic care to physical therapy and ultimately had to have surgery to repair a herniated disc. The injury resulted from a twisting motion when a 200lb compressor we were throwing into a scrap bin went sideways and started to fall on me. I caught it but I didn’t avoid a painful injury…

Hopefully, I’ll be able to share more than a few tips, tricks and techniques to help you work more safely and more effectively and inspire you to learn more about this subject. By no means should this be taken as a comprehensive treatment of the subject of lifting and rigging, but just a primer with some cautions and warnings and the advice to go slow and always, ALWAYS double check yourself **before you wreck yourself** (**Added by Bryan in editing… because he’s a child)

Let’s lay down some baseline rules. Not to be “preachy crossfit guy” but keep your core strong. Sometimes, you just have to gut it out and move a heavy thing. Those core muscles are what prevent injury when your body goes outside of your normal range of motion and, if they aren’t strong, they can’t support your spine and skeletal system and that’s when you get injured.

Also, when you just have to lift using body strength, use proper techniques. We all know the words “Lift with your legs, not your back” but how many of us actually DO? I can tell you for 100% certain that any time I’m moving to lift something, I’m using proper techniques whether it’s a refrigerant drum or a screwdriver I dropped. Now get down and give me 20 squats!

As we get into the application of ropes and pulley systems, we will be tying knots. Knot tying can be a very involved topic but you can do everything were going to be doing with the bowline and the clove hitch. If you can’t tie either of those knots, here are links to simple videos that illustrate how to..

BOWLINE

CLOVE HITCH

If you attempt any of these techniques with inferior knots, you run a very real chance of losing control of that load and injuring yourself or someone else and damaging that expensive part.
Another thing to take a bit of time to learn about is basic rope care. A knotted, twisted rope isn’t as easy to set up and you’ll waste time dealing with twists, knots and tangles. Learn to coil and stow your rope well and this stuff will be a lot easier.

A quick note on rope. Buy good rope. Avoid the 3 strand twisted rope. It’s stretchy and the ends unravel and are difficult to manage. What you want is called Kernmantle rope. This is the type of rope that has a kind of braided “sheath” over inner fibers. It’s stronger, doesn’t stretch and it rides much easier through pulleys. Burn the ends well to prevent them from getting out of control.

One final note. Wear a decent pair of relatively snug fitting gloves while hoisting and lowering loads with a rope. If that rope starts to slide, the burns you will get on your hands take a long time to heal.

Now, basics covered, we can move on to actually lifting things.

— Jeremy

P.S. – Here is a good rope ROTHCO UTILITY ROPE 3/8” 100 FT / OLIVE DRAB

If you do any larger commercial work you’ve probably seen a DIN rail without knowing what it is called. It is simply a mounting standard that originated in Germany in the 80’s and slowly worked its way over here.

DIN rails can be used to mount terminal blocks, relays, starters, breakers… just about anything electrically. They aren’t designed to conduct electricity like a busbar, though they are used in some cases as a grounding assembly.

The most common DIN rail type is the “top hat” or TS35 shown in these photos.

Components that attach to a DIN rail have little release clips so that they can be easily installed and removed. In addition to the “top hat” style there are also some less common, heavier DIN rails with a C and G style configuration.

So if you ever see one of these don’t be alarmed, you can just sound cool when you call your boss and tell him “yeah, it’s one of those DIN rail mounted relays” and just wait for him to say “What??”

— Bryan

P.S. – There are Two Incredible Giveaways going on right now that you should signup for. Air Oasis is giving away a bi-polar and a Nano air purifier and you can signup HERE. Also my buddy Corbett Lunsford from Home Diagnosis TV is launching a new building performance mastermind course and giving away a TON of HVAC tools HERE


If you are new to the trade… welcome

If you are young and new to the trade, we need you, but if you aren’t thoughtful you might get fired.

No offense, millennials often just have a different way of looking at work than their GenX bosses and trainers.

Here are my 8 top tips to help you make it a great a career.

#8 – Act interested (even when you aren’t)

I know sometimes your trainer can be boring, but when he is talking, look alive. Literally… I’ve seen apprentices who I wondered if they were actually dead… smelly… unresponsive… you get it.

When someone is attempting to invest in you it’s important that you listen up and pay them the respect they deserve.

#7 – Learn the names of basic tools

I know it can be confusing if you are new but read up enough so that when your trainer asks for “channel locks” you don’t say “what’s that”. This isn’t difficult to do and if you want to get familiarized with some tools you can look through the HVAC School tool list

#6 – Keep the music off and the earbuds out

Work isn’t the time to be distracted for any reason. That is unless you are listening to the HVAC School podcast… then it’s OK

#5 – Ask questions and listen carefully to the answers

Listen more than you talk. Give eye contact when your manager or trainer is speaking. If you don’t understand something be specific about the part you aren’t grasping.

#4 – Repeat back what you heard

Say “I want to make sure I understood you correctly” and repeat back what you understood rather than saying OK if you didn’t fully understand

#3 – Look professional

I don’t care if your boss or trainer looks like a slob, YOU dress according to the company policy and come to work looking well kept. Obviously, you need to dress job appropriate but people naturally respect someone who has a professional appearance.

#2 – Show up on time

Show up 15 mins early. Show up 30 minutes early! This isn’t complicated and bad traffic isn’t a valid excuse.

#1 – STAY OFF YOUR PHONE

Your friends, Facebook, Snapchat… they can all wait. Give your work your full attention while at work

Oh… and while you’re at it… get good at working on and installing HVAC/R systems. That helps as well.

— Bryan

Enthalpy is easy… it’s just a state function that depends only on the prevailing equilibrium state identified by the system’s internal energy, pressure, and volume. It is an extensive quantity. Simple.

Like most things, the scientific definition is as clear as mud. In HVAC/R we use enthalpy measurement to come up with the total heat change in a fluid, whether it’s refrigerant, water or air.

That total change in heat content or enthalpy change is called Delta H (ΔH) which is just another way of saying “total heat split” and it is generally measured in BTU/lb in the US.

In air, we need to use probes that measure humidity and temperature like the HUB2 probes shown above or the Testo 605i probes in order to calculate the enthalpy of the air. Air has both the energy associated with the temperature of the air as well as the latent heat stored in the water vapor.

UEI HUB Screenshot

If you want to use the Δto calculate the total heat added or removed from the air you would then use this formula to calculate BTUs of heat added or removed from the air.

Total Heat = (H1-H2) x 4.5 x CFM

In the case above it would be

Total Heat = (29.68 – 22.77) x 4.5 x 730 (CFM we measured)

so

29.68 – 22.77 = 6.91 Δ

6.91 x 4.5 x 730 = 22,699.35 BTU/hr

This total air enthalpy change is a required part of calculating total system capacity and is a pretty simple thing to understand.

Don’t confuse ΔH (Total Heat Change) with ΔT (Temperature Difference). ΔH includes both latent and sensible heat and is a measure of heat quantity in BTU/lb while ΔT only calculates temperature difference and isn’t converted to BTUs at all.

— Bryan

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