HVAC School - For Techs, By Techs

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Short 21 - Leak Detectors Sep 04, 2018

Show notes

Bryan talks about the top refrigerant leak detectors, the best refrigerant leak detection practices, and some good leak detection tips.

Leak detectors require some flow through them. Otherwise, they won't detect leaks. So, these tools have small pumps inside of them to move air through them for sampling. Leak detectors also require some time to warm up, so keep that in mind when you approach a job.

One type of leak detector is a heated diode (sometimes called a heated pentode). It is a heated electronic leak detector that takes a sample and analyzes it within. Infrared detectors also exist, but they require you to move the tool consistently; these tools constantly recalibrate themselves, so you can't hold it still while you're using it to locate a leak.

Once you confirm that you have flow, you need to determine that the detector is actually working. Make sure that your detector can pick up tiny leaks, not just large ones from cracking open a can of R-410a. So, we recommend using leak references that you can use to test your detector. One of those references is a leak test vial.

Some leak detectors have a tip filter, which prevents contaminants from getting into the system. Make sure that your detector has a filter and that you change it regularly. You don't want water or other contaminants getting into your leak detector and breaking it. Another surprising contaminant is leak bubbles; these bubbles can also set off a leak detector, so be careful to manage your order of operations to avoid false positives.

These tools work best if you store them in clean, dry places. It is also a good idea to keep a backup in case your main leak detector breaks or loses accuracy.

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.

Vacuum Pump Basics w/ Kevan Mayer Aug 29, 2018

Show notes

How does a vacuum pump work? When should you change the oil? What does that oil do anyway? Kevan Mayer of NAVAC comes on the podcast to answer these questions and more in this episode.

Vacuum pumps help remove moisture and non-condensables from the system. Moisture can freeze at temperature drops in the system, and it can block refrigerant flow to the system. Moisture can also combine with POE oil to become acidic, which causes burnouts. A vacuum pump uses an impeller to bring a system under negative pressure. Many of these pumps are two-stage pumps, meaning that they have multiple chambers that push the contaminants through the pump before they get discharged into the atmosphere. As with other tools, it is a good idea to confirm your vacuum pump's operation regularly to make sure you can use it effectively.

Vacuum pump oil is a type of highly refined mineral oil and should be clear. It is hygroscopic and attracts moisture, like POE oil, so you need to take care to avoid contamination. This oil both lubricates the vacuum pump and absorbs incoming moisture from the system. It's a good idea to replace your vacuum pump oil every job when you have a small pump; you may even need to change it multiple times per job. Larger pumps will typically handle a few jobs before you need to change the oil. In any case, change the oil if it starts looking amber or milky.

Kevan and Bryan also discuss:

Gas ballast valves
Vacuum gauges and micron gauges
Changing gaskets in hoses
Proper oil disposal
Vacuum pump size
Vacuum pumps with solenoids
NAVAC pumps and features
Dedicated vacuum hoses
Standing vacuum tests

Check out NAVAC at navacglobal.com, or look for their products at trutechtools.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.

Short #20 - Tips for Service Valves Aug 28, 2018

Show notes

In today's short podcast episode, Bryan covers some tips about HVAC/R service valves and caps for new technicians. While service valves may seem simple, there are some things you should know about them before you handle them in the field.

Before you connect your gauges, ask yourself if you even need to connect gauges. If you've already benchmarked the system and know what to expect, then you may be able to suffice with line temperatures. If you have a system with caps or Schrader cores and need to hook up your gauges, be careful not to cover any leaks in the cap or Schrader. You could potentially miss a leak on a cap or Schrader, so be sure to inspect those before you hook up your gauges.

Service valves require gentleness and care when you take caps off and on. You don't need to overtighten caps and Schraders, as they mostly come together at an O-ring fitting or with a flare; check to make sure that you're using the correct caps and that those caps have their proper seals, if applicable. If you need to use a thread sealant, a dab of Nylog comes in handy. If you're too hard on it with a wrench, you could break the entire service valve.

When you braze in or around a service valve, you'll want to protect it from heat. One of the best ways to do that is to tie a wet rag around it or use Refrigeration Technologies WetRag heat-blocking putty. (Remember, leave the Schraders out while brazing!) Overall, you'll really need to think about protecting that service valve from damage any time you work on it.

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.

Hard Shut Off TXVs Aug 23, 2018

Show notes

Jamie Kitchen returns to the podcast and talks all about hard shut off TXVs/TEVs. He discusses bleed and non-bleed valves and why the TXV type matters to your compressor.

When it comes to TXVs, there are two main types: bleed and non-bleed. The former may be referred to as a bleed TXV, and the latter may simply be called a TXV. However, OEMs may refer to TXVs as a "hard shut off TXV" (HSO), which is a non-bleed TXV.

The core difference between bleed and non-bleed TXVs is the equalization speed. That equalization speed affects how your compressor runs; equalizing the system reduces the pressure differential that the compressor will have to overcome on startup. Non-bleed/hard shut off TXVs may cause the compressor to draw locked rotor amps because the pressures did not equalize. To mitigate that issue, you can put in a start cap and relay on the compressor or replace the valve with a bleed TXV.

The main purpose of hard shut off TXVs is to prevent refrigerant migration and flooded starts when the system is off. The non-bleed TXV does not permit equalization, which builds pressure and but keeps refrigerant in the condenser, not the evaporator. Although the compressor will have to overcome more pressure upon startup, it will be less likely to fail due to a flooded start. However, some manufacturers may recommend using a hard start kit to overcome that pressure if you use a hard shut off TXV (even on scroll compressors!).

Jamie and Bryan also discuss:

Non-bleed TXVs on scroll compressors
Pressure rising and falling throughout the system
Opening/closing forces
Superheat spring
Liquid refrigerant migration
Shutting off the suction line vs. using a liquid line solenoid valve
Proper equipment sizing and short-cycling
Charging with bleed vs. non-bleed TXVs
Energy benefits

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 19 - Superheat, Evaporator vs. Compressor Aug 21, 2018

Show notes

In today's podcast, we cover why both compressor and evaporator superheat matter. We also address some common confusion related to each.

Evaporator and compressor superheat are two different readings that give you different indicators about the system's health. When you look at evaporator superheat, you see how far you feed boiling refrigerant into the evaporator coil. You don't want to overfeed your evaporator coil and risk flooding your compressor. However, you also don't want to starve your unit and reduce suction pressure. You'll want to stay between 5 and 14 degrees (F) of superheat at the evaporator outlet on typical A/C systems.

On TXV systems, we can control superheat at the evaporator outlet. Evaporator superheat is the reading that helps you optimize your capacity. Increasing it will decrease your evaporator capacity, as the evaporator coil won't be fed as much refrigerant. The lowest possible value is your best bet for maximizing efficiency and capacity.

Compressor superheat can be measured before the compressor. When you know that value, you can predict how hot your compressor will be when it runs. The temperature can increase from the evaporator outlet to the compressor inlet. Poor insulation in close proximity to the liquid line can be a cause; heat can transfer from the warm liquid line to the cool suction line. Our goal is to minimize heat gain in the suction line, so we want to insulate our suction lines and keep them as short as possible. However, you don't want the compressor superheat to be so low that you end up flooding the compressor.

In most cases, you should check both values to evaluate the heat gains or losses in your suction line.

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.

Pulling a Vacuum 2.0 w/ Jim Bergmann Aug 16, 2018

Show notes

In today's podcast, Jim Bergmann joins us to talk about evacuation. He discusses pulling a vacuum, conductance speed, microns, core removal, decay rate, and all that other nerdy vacuum stuff. Jim has helped develop some new BluVac hoses with AccuTools, and he's here to explain why we need those. He also explains why we need to be more educated on evacuation.

While we have many good hoses today, we still have a way to go when it comes to moisture removal. Jim Bergmann has seen the need for more durable hoses that perform better when there's moisture and acids in the system. Pulling a vacuum that makes the system dry is crucial for that equipment's longevity. You cannot over-vacuum a system, so the deeper vacuum you can make, the better your evacuation will be.

Evacuation often takes place on new pieces of equipment, and some people worry that deep vacuums will compromise the oil quality of those new systems. That is actually not a real issue to worry about during evacuation, and it's a piece of misinformation that makes people misunderstand the importance of evacuation. Not enough people understand how evacuation works, and that is how misinformation and distrust around evacuation spread throughout the HVAC industry.

Evacuation best practices come down to the materials you use. We'd like to use a dedicated evacuation rig with the highest possible conductance speed. So, to achieve that, you'll want as few fittings/connections as possible and wide, short, high-quality hoses that are impermeable and leak-free. Remember to remove all Schrader cores and use your micron gauge away from the pump. Pull the vacuum down as deep as you can get it and do a decay test.

Bryan and Jim also discuss:

Degassing and dehydration
Best evacuation technologies of yesterday and today
Evacuation education gap
TruBlu hoses
Pressure, density, and air "thickness"
Moisture adhesion
Behavior of water
Hose ratings
POE oil and moisture

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 18 - Can You Freeze Water in a Vacuum? Aug 14, 2018

Show notes

In today's short podcast episode, Jim Bergmann and Bryan answer the age-old question: Can you really freeze water in a vacuum by pulling down too fast? Is that a problem? What should you do about it?

Here is the short answer: NO. You CAN'T freeze water in a vacuum in a typical residential A/C system.

First of all, you would need to have water in the system to freeze water in the system. We typically don't see large amounts of water in JVAC systems, but there could be moisture in the evaporator coil in refrigeration. Coupled with the very low temperatures, you could see freezing under vacuum in those systems.

However, you will almost never see freezing moisture under vacuum in residential comfort cooling. On top of that, you would need to have enough water to freeze, not even considering the vacuum speed. We cannot achieve a vacuum that would cause that much water to freeze in a system.

When you perform a decay test, the pressure rise will taper. (If it doesn't rise, then you have a leak.) When the pressure tails off, you've likely come across moisture in the system. You can usually remove that moisture without having to worry about freezing; that moisture will merely exit the system under vacuum, and it typically will not freeze.

But what about water in a normal, non-HVAC vacuum? Can you freeze water in a vacuum then? YES.

The water would vaporize before it freezes, and it would sublimate off very quickly on most vacuum rigs. You can check out this article and video to watch an experiment in action.

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.

What We Learn From HVAC/R Trade School Aug 09, 2018

Show notes

In this episode, we talk with two techs recently out of trade school. We get their perspective on their trade education and how it compares to the field. Jeremy and Blake have been kind enough to share their experiences with us and give some advice.

Schooling undoubtedly gives technicians a leg-up once they got into the field. However, the knowledge you gain isn't all practical. Bookwork is still important for a solid foundation in theory, and it would likely benefit a lot of training programs. Bookwork, like trade school itself, is a good precursor to the hands-on material in the field. It also helps to do your research about classes you need to take and to see if a degree is more advantageous than a certificate or vice versa.

Your education won't end upon getting that certificate or degree. In the field, you will learn something new every day (and not in the air-conditioned classroom!). A lot of your familiarity with tools will come from working in the field. However, in trade school, you will learn best practices that you may not learn from other workers in the field.

When you enter the field, invest in your tools. You will work with classroom equipment, but once you enter the field, you will have to develop your own arsenal of tools—research new tools and set aside part of your paycheck to invest in your toolbox.

In many ways, this is the trade with homework. You have to want to learn to be successful in this field. Every day, you will come across new problems that require more knowledge, and nowadays, you have plenty of access to online sources of information to help you tackle difficult problems.

Well-rounded techs come from a solid education and apprenticeships with competent senior techs.

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 17 - MicroChannel Aug 07, 2018

Show notes

Bryan talks about MicroChannel coils, what issues could happen with them, and what the best practice is to clean them.

MicroChannel coils are kind of like car radiators; they have a small, honeycomb-like channel, and the sections that go between the crisscross fins carry refrigerant from the front surface to the back surface. These coils have a bit of a bad reputation. The refrigerant flows close to the surface of the coil. When the MicroChannel suffers damage, these coils can leak much more easily than other tube-and-fin coils. The channel is also more likely to be exposed to the elements and cleaners, where they can suffer from corrosion. Both alkaline and acid cleaners can cause corrosion on these coils.

The manufacturers usually advise against using a cleaner. However, we know that not using cleaners can be unrealistic. When you need to clean MicroChannel coils, you should use a cleaner that is not heavily alkaline (and certainly NOT acidic!). Refrigeration Technologies' Viper cleaner is an excellent product for cleaning coils without causing damage.

These small coils also hold less refrigerant than other coils. You have less flexibility with the charge, and the charge is so much more critical. A seemingly insignificant charge deviation on a normal system will have a greater impact on a system with these coils. You also have to use a chart to determine your subcooling on a spectrum to set your charge; the subcooling is not a fixed value. If you have MicroChannel coils shipped in, they may also not come with their full charge because they simply can't fit the refrigerant. Pump down is also dangerous in these coils. You can build up too much pressure and cause the coil to burst.

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.

Water Source - The Water Side w/ Eric Mele Aug 02, 2018

Show notes

In this episode, Eric Mele dives into the world of pumps, controls, cooling towers, and everything else related to the water side of a water source heating and cooling system. Many of these systems are water-to-water setups that use heat exchanges for heat transfer. You can listen to an introduction to water source heat pumps HERE.

A cooling tower is where we reject the heat that we put into water loops. Most of these towers are of the induced-draft variety, meaning that they have fans drawing/blowing air through them. Some cooling towers are "wet" towers, where water is open to the fluid you're working with, so some of that water is lost to evaporation. Contamination can be an issue with the wet open-type towers, but strainers, chemicals, and proper planning (for location) can prevent contamination. Dry towers do not need constant refilling and need fewer precautions against contamination.

These water-to-water systems use centrifugal pumps to push water through the system. These circulate water molecules, NOT compress them. Water source heat pumps get their heat from boilers, not the outdoor air in most air source heat pumps. When you have gas boilers, you have to think about your typical furnace concerns, including combustion air and carbon monoxide.

Air can sometimes circulate with the water, and you'll want to minimize that as much as possible, such as via air bleeds. These air bleeds may have ball valves that you can use to purge a lot of air. Other systems may not have air bleeds, but you will still need to get air out of the system.

Eric and Bryan also discuss:

Makeup water float assemblies
Strainers and cleaning procedures
Heat exchanger configurations
Water sources and quality control
Water treatment
Couplings and alignment
Boiler configuration
Bypass valves
Expansion tanks
Water source heat pump controls
Variable frequency drives
Aquastats

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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