Understanding refrigerant charge {Updated 2023}

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Understanding refrigerant charge {Updated 2023}

We have another post offering a refrigerant charge calculator, so if you’re in need of that, head on over to that post.

Particularly when it comes to field-assembled equipment, there’s a lack of quality understanding around what a refrigerant charge is and refrigerant charging in general. (Honestly, there’s a stunning lack of understanding about the overall refrigeration system in general, but that’s for a different post. And amazingly, consider how many people use it as a modern convenience, air conditioning isn’t too well-understood either. Neither are heat pump systems. We could go on and on.)

Let’s see if we can help you understand the overall refrigerant charge and even the very accurate refrigerant charge too. Effective refrigerant charge management can actually be considered a “blue ocean” ESG strategy because so few companies are doing it that well. (With our help, more are doing it well, but more on what we do later in the post. This is information, not sales. We want you to have a high-level understanding of your refrigeration system, and then ideally use us to calculate and manage refrigerant charge.)

Let’s roll.


The high-level overview on refrigerant charge

All HVAC/R systems are comprised of several key components:

  1. Compressor
  2. Condenser
  3. Evaporator
  4. Controls
  5. Piping to connect everything

Importantly, there are more than 100 million appliances installed in the US alone with charged particles, suction lines, and condenser fans. (Other terms you will hear a lot in this space are “heat pump systems,” “refrigerant charging cylinder,” “refrigeration system” in general, etc. The important thing to remember about Trakref is that you don’t and won’t need to know all the specific vocabulary and what it means. Rather, we’ll handle that for you.)

For the purpose of this specific discussion on liquid refrigerant charge, we are going to designate two types of systems:

(1) those that are field assembled, charged in the field, and have parts and pieces both in/outside; and

(2) those that are factory charged.

The factory charged systems are easy to identify. They are referred to as “packaged,” or stand-alone, and can include systems like vending machines (a few ounces) as well as all the way up to 150 ton packaged rooftop units (hundreds of pounds) with electrons and protons.

Other than the packaged equipment, many air conditioner and refrigeration systems are field-assembled.

Field-assembled equipment have three components that contain refrigerant and this contribute to refrigerant charge:

  1. The Compressor/Condenser section
  2. The Evaporator
  3. The Piping

No complicated math required, you simply add together the gas in the pipe, the compressor/condenser section, and the evaporator = total charge.

(Again, if you need just a few more refrigerant and charge calculator, here’s where to go.)

As simple as this process is, most commonly techs and staff only read the “nameplate” capacity on the label of vacuum pump and the compressor/condenser section and then they leave off the evaporator and the piping.

As a result, they only capture between 30-40% of the system charge and therefore under report capacity charge, which throws off the ecosystem of refrigerant charging.

This under-reporting of refrigerant temperature high pressure and charge causes more problems in the long run. More on that in a second.


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Some other terms you might increasingly hear around “refrigerant charge”

Again, if you hear these terms in conversation or demos or sales calls or webinars and have no idea what they mean, that’s OK. Our goal is to take care of all this stuff around refrigerant charge and correct refrigerant charge for you.

Here are some terms you could hear. You don’t need to know all of them:

  • Pressure drop
  • Refrigerant lines
  • Evaporator coil
  • Superheat temperature
  • Temperature probe
  • Pressure readings
  • Charging connection
  • Proper refrigerant charge
  • Liquid refrigerant
  • Liquid charging
  • Vacuum pump
  • HVAC system (ideally you understand that one)
  • Charging cylinder
  • Specific refrigerant
  • Correct charge
  • Refrigerant level

Don’t worry if you don’t know them all. We take care of all this for you. All you need to really understand is the existence of “refrigerant charge” and that you’re going to need to report it to one or more entities.


Get in touch with an expert


The total refrigerant charge isn’t necessarily what’s on the nameplate, though

Refrigerant charging standards have changed over time, which means how you calculate and determine a refrigerant charge has also changed.

In the semi-glorious days of yore, the refrigerant charge was always determined by the tonnage of the unit and then, depending on where you were located (cold vs warm climate), you would either choose 3 lbs per ton or 4 lbs per ton (if you weren’t measured in coulombs and use coulomb law).

Then, you had a few more options like refrigeration vs air conditioning system and whether there was a flooded evaporator or not, whether you’re using electric charge, whether there was a liquid line, whether you were negatively charged or had positive charge, etc. — but these were minor adjustments.

The overall refrigeration system seemed maybe a tad easier to figure out. Then climate concerns shifted, people became more aware of what was happening with heat pump systems and refrigerant in general, and the “how” of calculating refrigerant charge and exactly the refrigerant volume shifted.

Agencies began to write requirements that targeted equipment 50 lbs and over with electric field. And somewhere along the way, instead of reporting normal system charges, we as an industry began to report only the nameplate or using a metering device as a shortcut for charge flow.

Because if the nameplate was less than 50, then the tech didn’t have to record as much information.


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The operational issues around poor refrigerant charge calculations

Under-reporting of weight means that, as systems leak, the leak rate looks larger. For a

✔ 20-ton unit with 80 Pounds and leaks 10 pounds = leak rate of 12.5%
✔ 20-ton unit with 49 pounds and leaks 10 pounds = leak rate of 20%

In Scenario A, the leak rate is high, but not as high as it is with fewer pounds reported (i.e., Scenario B).

If you report fewer pounds in a refrigeration system, then your maintenance needs look lower than they actually are.

So, when developing budgets, you are always underestimating the need you have to keep these systems operational.

Additionally, in the event of a system failure, your new gas charge will be larger than what you reported. We call this “the can’t get 10 lbs of flour into a 5 LB sack” rule.


Once more: if this is confusing and you just want a way to easily calculate refrigerant charge, we can help with that.

Under-reporting can lead to fines and violations if exposed during an audit or investigation.

Inaccurate system reporting is compounded when you consider that:

  • Very few technicians use a scale when charging a system
  • Although R-410A has 25 lbs in each cylinder, it is well-documented that at least 10% of that charge remains in the cylinder at all times, meaning that you only can get 22-23 lbs. out of each cylinder.

Most people we talk to about air conditioning, heat pump systems, and refrigerant charge honestly don’t do what they should because the whole process is a time consuming method, and they’re focused elsewhere operationally. But then, on the back end, it bites them because they get audited and face potential losses around compliance. They think, “Oh, I’ll solve all this with a metering device,” but it’s not enough.

You don’t need to understand refrigerant charge at a high level, no. But you need to realize how refrigerant charge can play into your overall compliance position. That part is important about refrigerant charge and liquid refrigerant in general.

Refrigerant charge calculations are crucial for the functioning of your refrigeration system

Think of it this way: Refrigerant is to an HVAC/R system what antifreeze is to a car.  If you under or over fill, then the car won’t operate as needed.

Keep this in mind going forward when you calculate your refrigerant charge.


Get in touch with an expert


How does TrakRef help with Scope 1 emission management, refrigerant charge, and your refrigeration system?

Many companies are still just catching up on understanding the significant carbon emissions caused by refrigerants — and, again, what refrigerant charge even is.

Scope 1 emissions reporting, ESG reporting in general, or social cause reporting are becoming more top-of-mind for companies, but it’s not fully there yet. Companies don’t know how to do it properly, and it falls into poorly-managed, poorly-contextualized processes that use old tech.

Ideally, what you want from any refrigerant management and Scope 1 emission reporting tool is:

  • A way to see and understand the data
  • Task management
  • Some level of automation
  • Clear reporting capabilities

There are more bells and whistles that help out, but those are the core things you need to effectively report Scope 1 emissions.
Here’s what Trakref can do:

Refrigerant tracking: Trakref provides a centralized platform for tracking refrigerant use across an organization. This includes tracking the amount of refrigerant used, refrigerant charge, air conditioning, liquid refrigerant, the location of each refrigerant-containing device, and the dates of any maintenance or service activities. By tracking refrigerant use in this way, Trakref can help organizations identify opportunities to reduce their refrigerant use and associated emissions. Think of us as your refrigerant charge BFF. We handle everything about the terms and conditions associated with refrigerant charge. We know all the regulations and protocols that are impacting refrigerant charge calculations in each area, and we bake that into our systems so that you don’t need to worry about it. You can focus on operations.

Emissions calculations: Trakref can calculate an organization’s refrigerant-related emissions based on the type and amount of refrigerant used, as well as other factors such as equipment age and efficiency. These emissions can then be reported as part of the organization’s overall Scope 1 emissions.

Leak detection: Refrigerant leaks are a common source of emissions in many organizations. Trakref can help organizations detect and address refrigerant leaks quickly, reducing the amount of emissions released into the atmosphere.

Compliance tracking: Trakref can help organizations stay compliant with regulations related to refrigerant use and emissions, such as the Environmental Protection Agency’s (EPA) Refrigerant Management Program. By staying compliant with these regulations, organizations can avoid fines and penalties and demonstrate their commitment to sustainability and environmental responsibility. You can do this while keeping the air conditioning on, which is going to please your people.

Reporting: Trakref provides a range of reporting capabilities, including reports on refrigerant use, emissions, leak rates, and compliance. These reports can be used to inform decision-making and to demonstrate progress in reducing emissions and improving environmental performance.

Overall, Trakref can be an important tool for organizations looking to manage their Scope 1 emissions related to refrigerant use. By providing a centralized platform for tracking refrigerant use, detecting leaks, and calculating emissions, Trakref can help organizations reduce their environmental impact and meet their ESG goals.

And again, if you want a refrigerant charge calculator, we would recommend this tool. We have 28 years of experience in HVAC systems, liquid refrigerant, refrigerant charge calculation, heat pump systems, air conditioning, and much more. We can help you figure out what needs to be done.


Use our refrigerant charge calculator


  • avatar
    Muthusamy Gounder
    April 6, 2020 at 5:27 am

    What is the formula to calculate refrigerant charge

  • avatar
    October 12, 2021 at 5:52 am

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