HVAC School - For Techs, By Techs

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Short #35 - Resolution, Precision & Accuracy Jan 01, 2019

Show notes

What is the difference between accuracy, precision, and resolution? In today's short podcast, Jim Bergmann explains the differences and why they matter.

People commonly confuse accuracy and precision. Accuracy refers to how close a measurement is to the correct value, but precision refers to the consistency of values. For example, you can get several infrared thermometers to measure the difference between circuit breakers, and the thermometer readings all come out close to the same value. They aren't necessarily accurate, but they are precise.

In cases where we use a voltmeter to measure for the presence of voltage, we don't need a high degree of accuracy. However, when we want to measure exact voltage values, we want to make sure our tools are accurate. Sometimes, voltage that is too low can cause issues with the circuit boards.

Resolution refers to the smallest possible amount of change you can detect. For example, one voltmeter may measure to the nearest whole volt, and another may measure to the nearest tenth of a volt. The resolution is higher on the latter voltmeter, as it detects a smaller change than the first voltmeter. Some tools measure with a high resolution, but the increased resolution may compromise the accuracy. For example, if a manometer reads into the Pascals range, it may only have a tolerance of +/- 5 Pascals, which leaves room for inaccuracy.

However, again, accuracy is not always the most important value. Sometimes, resolution and precision are more important than accuracy. After all, in the words of Jim Bergmann, it's pretty difficult to measure feet with your car odometer. One common example where precision and resolution are more important than accuracy is when techs try to measure microns with analog gauges. The accuracy means nothing when the precision and resolution are poor.

Learn more about Refrigeration Technologies HERE.

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Ventilation w/ John Semmelhack Dec 27, 2018

Show notes

John guides us through all aspects of ventilation and system design. He gives us a review of point ventilation, ASHRAE 62.2, whole-home strategies, and much more.

Nowadays, construction protocols instruct builders to make houses tighter than the builders of the past. The goal of building tighter homes is to give us more control over the temperature, quality, and energy impact of the outside air we bring into our homes.

Common sources of ventilation are local exhaust systems, including bath fans and kitchens. However, in tighter constructions, there is a greater need for whole-home strategies to bring in outside air and dilute indoor-generated pollutants. Some of those pollutants include VOCs, odors, and moisture. We must think about how to introduce that outside air into the home and how that outdoor air will impact heat loads, moisture levels, and air quality inside the home.

When we select equipment for airflow, we need to think about constant vs. intermittent flow. In humid climates, you also need to take extra steps to prevent moist outdoor air from leading to excess condensation in the home. Ventilation equipment either delivers outdoor air to each room or mixes that outdoor air with the return air. Try to ensure that the space temperature doesn't drop below the dew point, which can be a challenge in humid climates.

Ventilating dehumidification is a promising solution for HVAC system replacements and new constructions in humid climates. In cold, tight homes, ventilating dehumidification can keep a home dry enough to keep occupants comfortable in the winter.

John and Bryan also discuss:

Why do people want energy efficiency?
"Passive house" and airtightness standards
Mixing air and filtration
Carbon dioxide (CO2)
ERVs vs. HRVs for balanced ventilation
Fan cycler systems
Duct installation quality
Dedicated make-up air
Fireplaces and gas appliances under negative pressure

Learn more about Think Little, John's company, at think-little.com/.

Learn more about Refrigeration Technologies HERE.

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Gas & Combustion Tools w/ Bill Spohn Dec 20, 2018

Show notes

Bill and Bryan discuss gas and combustion tools. These tools include manometers, combustible gas detectors, personal CO detectors, draft gauges, and combustion analyzers.

Manometers measure gas pressure, and they require calibration but are usually quite accurate. Before using a manometer as a diagnostic tool effectively, you must understand your targets and resolution. Some digital manometers come with BlueTooth technology, so you can log, convert, and store your data on mobile devices.

Gas leak detectors are relatively inexpensive tools. These should NOT be confused with combustion analyzers, which are different tools altogether. You usually cannot calibrate these tools. When using a gas leak detector, the leak detection process on gas pipes is similar to the electronic leak detection process on straight-cool A/C units.

Draft gauges measure very fine pressure differentials in the combustion air zone. These may use flappers or vanes to give you data about the direction and amount of draft. Most importantly, you want to ensure that you have no backdraft. These tools take very fine measurements, so they have high resolution. Because of their high resolution, they require frequent calibration to stay accurate.

Personal (or ambient) CO monitors are also important gas and combustion tools. Carbon monoxide (CO) is odorless and colorless, and it can be deadly. To avoid CO poisoning, use one of these monitors to remain aware of the CO content in your space.

Combustion analysis has evolved a lot over the years. Today, we perform combustion analysis with a single tool. When combustion occurs, a chemical reaction occurs. Combustion analyzers determine what happens post-combustion by taking temperature and oxygen readings. However, they also account for the presence of CO, which indicates incomplete combustion.

Bill and Bryan also discuss:

Analog and Magnehelic manometers
BPI-1200
Precision
CO monitor upkeep/disposal
Perfect combustion
AHRI-1260
Nitric oxide filters
Choosing tools

Learn more about Refrigeration Technologies HERE.

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Short #34 - Heat Pumps Dec 18, 2018

Show notes

In this short podcast episode, Bryan speed-talks through all the basics of heat pumps and how they function.

Heat pumps are not physical pumps or components on an A/C system. A heat pump is an HVAC unit that is also capable of heating a home by reversing the refrigeration cycle. When that reversal happens, the traditional indoor "evaporator" coil acts as a condenser that rejects heat in the home. As such, the traditional outdoor "condenser" acts as an evaporator that absorbs heat from the outdoors so long as the refrigerant is colder than the outside. Due to how they function, heat pumps are more common in warmer climates.

The heat pump's reversal happens on the reversing valve, which diverts refrigerant right before the compressor. A solenoid shifts the valve when you enter heat mode from cool mode (or vice versa), and that's how refrigerant gets diverted. These just slide back and forth, and they are pretty reliable; they don't typically malfunction. Before a reversing valve can work, the system must be ON; the valve cannot shift if the unit is OFF.

Heat pumps typically have two metering devices, one by the indoor unit (cool mode) and one by the outdoor unit (heat mode). A check valve controls the flow of refrigerant to the correct metering device. Heat pump systems may also often have suction accumulators and crankcase heaters to help prevent oil loss and flooded starts in the compressor. The defrost controls for heat pumps typically have a timer and defrost sensors.

We also discuss:

Issues with heat mode TXVs
Checking the charge on a heat pump
Defrost sensor types and operation
Auxiliary heat
Economic balance point

Learn more about Refrigeration Technologies HERE.

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

EPA Regulation Uncertainty w/ Jason Obrzut Dec 13, 2018

Show notes

Jason from ESCO and Cengage comes on to talk about the varying landscape of EPA 608 regulations with what you need to know for now (circa 2018).

The EPA has proposed to roll back some regulations regarding HFC refrigerants, including leak rate and leak repair mandates. There are also questions about the regulation of refrigerants that do NOT have ozone-depleting substances, not just HFCs. This choice reinterprets language within the guidelines put forth in 2016 and the Clean Air Act. However, this choice completely disregards global warming potential and limits regulations of refrigerants with global warming potential but no ozone-depleting potential. EPA 608 still prevents the venting of non-natural refrigerants, but the proposed changes aim to clarify the language in those regulations.

EPA 608 Subpart F can potentially be rescinded entirely. That action could muddy the language as to what constitutes venting. HVAC businesses can also suffer, as technician certification may no longer be a requirement for purchasing refrigerants. (Not to mention, homeowners can ignorantly engage in harmful practices, like cross-contaminating refrigerants and venting. Substance abuse is also much more accessible if non-HVAC techs purchase refrigerant to huff it.)

The USA is actually well behind other industrialized countries when it comes to refrigerant usage. We're one of the only industrialized countries that have yet to really move forward from HFCs. So, rolling back HFC regulations may be a step back for environmental initiatives, refrigerant innovation, and even the refrigerant reclamation job market in the USA.

Jason and Bryan also discuss:

EPA exam changes
Individual state regulations and certifications
Who benefits from these changes?
Comparisons to other toxic chemicals
Air quality, pollution, and resource exploitation
Refrigerant recovery and mixing
How will this change affect the job market?
How will this change affect education and writing?

Learn more about Refrigeration Technologies HERE.

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Short #33 AMA - Business Tips Dec 11, 2018

Show notes

In this short podcast episode, Bryan shares his experience as an entrepreneur and his tips for anyone who wants to run and grow a successful business.

When growing a business, the best thing you can do is listen to others who have started a business. It's especially useful to listen to those who have already "made it" in the business world.

Growing a business requires you to stay focused. While you may have to work in your business, you also want to make time to work on the strategic parts of your business. Make goals, hire good people, and make sure your business has all the right people and tools to help it grow. Know your hirees' motives, and it's also important that the people in your personal life support you. Your business will also grow most effectively if you can keep your emotions under control.

On a financial level, you need to have a good grasp of your personal finances before tackling business finances. Make wise decisions, and don't make excuses to spend money on things your business doesn't actually need. One of our main business tips is that it's best to avoid dumping your money into things you don't understand. Marketing is something that a lot of HVAC businesspeople don't understand and may not actually need. So, keep your investments limited to things you understand early on.

Networking is a critical element of business. Your business needs to develop relationships with people you can trust. Trust-based relationships help foster an appreciation between your customers and your business. Appreciation for employees is another element of this. When everyone is aware of the value of your relationships, your business can grow with the right people within the company and the right people paying for your services.

Learn more about Refrigeration Technologies HERE.

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

AMA#1 - State of the HVAC School Union Dec 06, 2018

Show notes

In our first ever ask-me-anything (AMA) podcast, we talk about the trade as a whole and answer random questions about Kalos and myself.

Some people ask me if I'd encourage my children to get into HVAC/R. In my opinion, the trade offers plenty of good opportunities and room for growth. So, I will definitely encourage my children to get into the trades, but I will not pressure them into it. I think more of us should encourage our children to consider a career in the trades and understand the benefits of those careers. I'd even say that I'd choose this career path again if I were allowed to restart my life and take a new career path.

I'm optimistic about the future of the trade. The pay and opportunities are better than they've ever been before, and we have chances to attract young people to the trade. This trade is one of impact, and impact is becoming increasingly important to young people.

One of the main issues we need to address in our trade is unprofessionalism. From bad practices to blatant prejudice, we need to be professional, proud of the work we do, and fair to everyone.

We also discuss:

Which piece of equipment I identify with
Sleep schedules for people who work on many things at once
Providing tools and tool stipends
HVAC company finances and profit
Tech traits across trades
The separation between commercial and residential HVAC
Unprofessionalism in the trade
Taking time to read and do research
Time management and discipline
Mechanical diagnosticians vs. sales techs
What inspired me to get into HVAC
Innovation, marketing, and corporate culture among manufacturers
Onboarding and training green techs

Thanks to everyone who asked questions in this AMA.

Learn more about Refrigeration Technologies HERE.

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Short #32 - "It's Undersized" Dec 04, 2018

Show notes

When we replace equipment, we sometimes wonder if the old unit was undersized. Here are some things to consider before replacing that old A/C with a bigger one.

When we do load calculations, we figure out how much heat to remove or add to a home based on the building's design. We need to account for how much heat is entering or leaving a building and heat gains on the inside of a space. Heat gains can come from human body heat or electronics running, and heat losses are quite rare. Those factors are perhaps even more important for correct sizing than mere square footage.

In general, I don't recommend putting a bigger unit in. Focus on getting the equipment to work properly before considering an upsize, as the improper cooling could be caused by a mechanical issue and not an undersized unit. If you want to dig deeper and consider upsizing a unit, you have to consider a few things.

First of all, you want to look at the sensible and latent loads. Is the unit too small on the sensible or latent side? In either case, you can adjust the blower to try to address these first. If humidity is the issue, you do NOT want to oversize the unit.

Is leakage a factor? Check the integrity of the duct system and if you have cracks, can lights, or other sources of leakage. How's our ventilation? Attic ventilation is also a huge factor that will determine how well an A/C unit works.

We also discuss:

Shade and impact on radiant gains
Ductwork, wire, and copper pipe sizing
Heat load reduction (lighting, ventilation, etc.)

Learn more about Refrigeration Technologies HERE.

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Short #31 - U-Factor and R-Value Nov 27, 2018

Show notes

What is the difference between r-value and u-factor? Why should we care about the differences? In this short podcast, we'll explain what those differences between the two are and why you should care.

R-value and u-factor are actually pretty close to the same thing; they are inverse coefficients of the same phenomenon. R-value is the resistance to heat energy moving through conductance. R-value is not concerned with radiant gains, such as the sun's UV rays passing through a window; the heat gains occur strictly through conduction, molecule-to-molecule, like heat passing from the wall insulation to the actual wall upon contact. In terms of insulation, a higher r-value is desirable, Inversely, we like to see a lower u-factor.

The u-value is the coefficient of heat transfer. So, the r-value's resistance to heat acts directly against the heat transfer of the u-factor. You can convert the u-factor to r-value by dividing the u-factor into 1 (1/u-factor). Similarly, you can get your u-factor from your r-value by dividing the r-value into 1 (1/r-value).

We use these values in load calculations and plug them into Manual J programs. We figure out our BTUs per hour in an equation where we multiply the square feet by the u-factor and the delta t. So, our insulation plays into equipment sizing. Some products also have a rated u-factor. You also need to average out the u-factors if you use multiple materials. (Note: sometimes, manufacturer u-factor ratings are not entirely accurate.)

Learn more about Refrigeration Technologies HERE.

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Friction Rate and Duct Design w/ Dr. Bailes Nov 21, 2018

Show notes

This episode is very exciting to me because we get to have Dr. Allison Bailes on the show. Today, he shares his knowledge about friction rate and duct design. Allison got his start teaching college-level physics before getting into the building design industry.

If you have a forced-air system that blows heated or cooled air through a duct system, that blower creates a pressure difference. Some of the pressure is used up on the filter, registers, and dampers, so you will see pressure drops. Anything left over is the available static pressure, which pushes air through the ducts. When you do a duct design, you must account for pressure drops and your blower's static pressure rating.

When designing a duct system, you want to minimize friction as much as possible. Counterintuitively, you want a high friction rate. Friction rate refers to the availability of static pressure compared to friction provided by the effective length, not the total amount of friction. Fittings significantly impact your total effective length. By extension, fittings can have a major impact on friction. In flex duct designs, the turns add additional resistance.

Oversizing often happens due to poor load calculation. While you increase capacity with an oversized system, there are plenty of drawbacks. The capacity will rarely match the load, you may spend too much on the equipment, have ineffective dehumidification, and you will deal with short cycles, which lead to comfort problems.

Allison and Bryan also discuss:

Home energy ratings
Equivalent length and total effective length
Flex duct design
Seasonal runtime
Surface area challenges
Unconditioned spaces
Filtration

To find out more about everything Dr. Bailes has to say about building performance and duct design, visit his site at: https://www.energyvanguard.com/blog

Learn more about Refrigeration Technologies HERE.

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

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