HVAC School - For Techs, By Techs

In this short podcast episode, Bryan talks about the TXV power element or power head. He explains what it does and why it's important. A TXV power element threads onto the top of the valve, and it's where the sensing bulb attaches to the valve. It is the component that applies the opening force to the TXV. When you lose the charge in the element, it stops exerting an opening force on the valve. So, the valve completely shuts and doesn't allow refrigerant to get to the evaporator coil. You'll get high superheat and a starved evaporator. Whenever you're checking one of those elements, it would be wise to check for a leak. The capillary tube that goes between the bulb and the element is usually easy to diagnose. You can usually see cracks, leaks, or rubouts quite easily. (If you're used to working with TXVs, you may even be able to hear or feel when the bulb is light on charge.) Because the element threads to the valve, it is usually quite easy to replace without condemning the entire TXV. If you're not sure that the TXV power element is the issue, you'll want to turn the superheat adjustment nut to the fully counterclockwise position (fully open). Once you do that, verify that the superheat is still too high. Then, remove the bulb from the suction line and warm it up in your hand for a little while. If the element still has charge, you'll notice more opening force on the valve. If the valve doesn't change at all, then the power element is the most likely problem. You should also not be able to depress the TXV's diaphragm with your thumb; if you can depress the diaphragm, then the element has lost its charge.   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.

In this episode, Bryan and Alex Meaney talk about value engineering. They discuss what it means to value engineer better when it comes to construction projects. Value engineering is about finding ways to reduce the costs of a project. However, we don't want to do a bad job or use extremely cheap materials just to bring the price tag down. In many cases, builders will want to reduce the cost as much as possible, but we also want to make sure the construction project works in the end. In other words, 2+2 doesn't quite have to equal 4, but we don't want it to equal 3. We can't afford to lose work or do bad work. When we value engineer, we have to bring some sales experience to the table. We will have to negotiate with builders, and the process of value engineering is transactional. We also have to be honest about solutions that will work and ones that won't. It's best to show builders previous value engineering solutions that have failed. You don't have to sound robotic in your meetings with builders, but you want to be sincere and have a consultation process that works for you. It's a good idea to let previous results speak for themselves. However, you will want to mention options that you think the builder will reject. More often than you could imagine, the builders do indeed take those more expensive add-ons. Alex and Bryan also discuss: Speaking your customer's language Coming to the table with the most expensive option Selling vs. consulting Printing your failures Approaching a sales conversation with pros and cons Changing solutions and technologies Finding a consultation process that works Price objections about parts warranties New constructions vs. retrofits Where builders usually want to cut costs Flex duct   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.

In this short podcast episode, Bryan talks about the placement of the TXV sensing bulb. He also explains how it affects the opening force on the TXV. The TXV sensing bulb (or sensor on an EEV) provides the opening force for the valve. The warmer the bulb gets, the more the valve opens; the colder the bulb gets, the more the valve closes. The TXV also has a closing force provided by the spring pressure and equalizer (usually the external equalizer). So, if you have a bulb that has been poorly mounted or insulated, you tend to have more opening force than the design. Your suction line will generally be colder than the airstream around the evaporator coil. If the sensing bulb has poor contact with the suction line, it will likely read warmer temperatures than it should. When the TXV opens more than it should, the valve loses control and could lead to flooded conditions. (If that liquid gets to the compressor, then you could get catastrophic damage.) Generally speaking, improper TXV bulb placement will result in low superheat and potential flooding. When you have a high superheat or a starved evaporator, the sensing bulb placement is rarely the actual problem. When mounting a sensing bulb, the suction line should be clean. Get rid of all Armaflex residue and ensure that the bulb is also clean. In some cases, you may need to insulate the bulb. You must also ensure that you mount the sensing bulb securely near the evaporator outlet, and you can be a few inches downstream of the external equalizer. Another common suggestion is to place the bulb on top of the line if the line is smaller than 7/8" (larger than 7/8", you can mount the bulb at 4 o'clock or 5 o'clock on the 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.

In this podcast episode, Bryan, Erich Vinson, and Anthony Marino talk about dealing with difficult customers in the HVAC industry. When working with customers in general, it is best to make eye contact with the customer, listen to them, and put yourself in their shoes. When dealing with difficult customers, we must remember that there are several potential causes for their "difficulty." You can't control that; you just have to let the anger run its course and diffuse the situation as much as possible. Some customers also try to stir up drama; in those cases, it is best to focus on the mission and stick to fixing the problem at hand to avoid adding negativity to the situation. Instead, we want to focus on communicating the appropriate information while avoiding overcommunication. Being thoughtful is the key to good customer service. So, follow-up is especially important because it shows that we care about the customer show attention to detail, and have been deliberate in our service. Commercial managers and owners also care about their bottom line. So, we need to be attentive to their business-related concerns. Price objections are common among difficult customers. You'll want to put yourself in the customer's shoes and give them the choice to order a cheaper part. You can use that situation to explain the value of your labor. If you keep your body language under control, you can handle those difficult conversations well. Erich, Anthony, and Bryan also discuss: Residential vs. commercial HVAC customer experiences Managing our own emotions before we approach customers Being dragged into corporate or landlord drama Being deliberate Where price objections come from What makes residential and commercial customers upset Dealing with disrespect   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.

In this short podcast episode, Bryan explains how hydrostatic pressure can build up in refrigerant cylinders and present a hazard to technicians. Your refrigerant cylinders have tare weight and water capacity values stamped on the tank. You'll want to use these when weighing the refrigerant you recover because you don't want to exceed 80% capacity. However, capacity changes when the liquid density changes; that density will change with pressure and temperature. Hydrostatic pressure builds up when you have overfilled refrigerant vessels. When those vessels get warm, the density will decrease, and the liquid refrigerant expands. At some point, the vessel will contain 100% liquid and can no longer expand, so hydrostatic pressure will build. When that happens, you have a dangerous situation on your hands; the vessel may even explode. AHRI recommends using 77 degrees as a guideline for figuring out the vessel capacity. However, we recommend using 130 degrees out of an abundance of caution; the back of your van probably won't get much hotter than that, so we use it as an operational maximum. We only get hydrostatic pressure when we recover refrigerant as a full liquid. When we recover refrigerants like R-410A in the liquid phase, we get a 45-PSI increase for each degree (Fahrenheit) of temperature increase. For R-22, that number is about 60 PSI; with R-134A, that number is about 40 PSI. When we get temperature swings from an ice bucket (~32 degrees) to the back of a hot van (~130 degrees), the pressure can build up within the vessel. We also need to think about hydrostatic pressure when pumping down systems with microchannel coils. Hydrostatic pressure can build up in the receiver, and liquid can fill your condenser.   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.

In this podcast episode, Bryan, Trevor Matthews, and Jim Dick from Emerson give us all an introduction to industrial refrigeration. Jim works with contractors to provide tech support. He also does the startup and commissioning of refrigeration compressors and gas compression units. Industrial refrigeration refers to warehouses and distribution networks. Grocery refrigeration is commercial refrigeration for the end-user, but industrial refrigeration is commercial refrigeration for the distribution network before the product reaches the end-user. Many of these large systems use natural refrigerants (including ammonia) and are easier to work on because of their scale and easy-to-access valves. However, the ammonia charge is small and is almost never in the same space as people, and industrial equipment often uses a brine fluid for heat transfer. If techs want to move into industrial refrigeration, Jim recommends attending seminars on ammonia and natural refrigeration. Trevor believes that trade schools are currently lacking industrial refrigeration programs, and he hopes to see that change in the future. Most people who succeed in the industrial side of the business are good electrical troubleshooters. When working on large equipment, you will have many electrical sensors and controls. The piping side is usually easier to learn than the electrical side, so some electrical proficiency is desirable. Many techs struggle with electrical concepts, so we encourage going back to the basics; do whatever you need to do to get a solid foundation. There are also many electrical contractors who would love to teach people who struggle with electrical concepts. However, learning about electricity also requires commitment and honesty about when you're in over your head. Bryan, Trevor, and Jim also discuss: Emerson's Vilter brand Ammonia-CO2 cascade systems Propane refrigerant Gaps in industrial education Building electrical troubleshooting skills Manufacturer-contractor relationships and dealership networks   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.

In this short podcast episode, Bryan talks about the strategies we can use to prevent refrigerant migration during the off cycle. We often see refrigerant migration when the compressor is lower than the evaporator, especially in low-ambient conditions when the refrigerant can condense in the crankcase. When the compressor starts up, you get a violent reaction as the refrigerant boils off and ejects oil. That can wear out the compressor and reduce the lubrication. Crankcase heaters are some of the most common devices we use when preventing refrigerant migration. These can be of the insertion or belly-band variety. As their name suggests, crankcase heaters keep the crankcase warm during the off cycle to prevent the refrigerant from condensing. However, that isn't a complete solution for stopping flooded starts and other issues. In the cases of flooded starts, we can use liquid line solenoid valves. These valves close off the liquid line when de-energized (in the off cycle). In many cases, we can use these WITH a crankcase heater for more protection. We also use pump down solenoids to prevent refrigerant migration. In these cases, the liquid line solenoids will de-energize while the compressor and condenser fan keep running. Then, the system cycles off on a low-pressure switch. If there is any leakage in the valves, the compressor can short-cycle. You can prevent short cycling if you have a pump-out control. However, it is usually a good idea to use a pump down solenoid with a crankcase heater. We also use hard shutoff (HSO) or non-bleed TXVs in residential HVAC. These function a bit like a liquid line solenoid valve, but you'll also want to use a crankcase heater for added protection.   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.

In this podcast episode, Eric Mele joins Bryan for some weird transformer talk. They discuss corner-tapped transformers and some thought experiments. We hadn't been able to get our heads around corner-grounded transformers until recently. "Grounding" doesn't necessarily change the phase or lead that you ground. If you take the secondary of a 24-volt transformer and measure from your two colors, you'll measure 24v. However, if you connect a lead to ground, you'll still read 24v. (Don't ground both, or you'll get a short.) Ground is just a path back to the power source. Electrons don't suddenly "leak" from something connected to ground. Grounded and neutral conductors can potentially be dangerous. There can still be potential even though your leads wouldn't pick it up. In residential HVAC, we're used to seeing neutral and ground connected at the main distribution panel. However, it's not always okay to connect ground and neutral or use ground as a current-carrying conductor. If you've got split-phase power going into a regular home, you've got 120 volts 180 degrees out of phase with each other. If we don't have a center-tap neutral, it would function similarly to a 24v transformer. In that case, it's not necessarily unsafe to read 0v on neutral. We get tripped up because we think in terms of using a meter, not in terms of actual potential voltage. In a delta configuration, you will have a high leg connecting to neutral (B phase is usually high; A and C phases are usually normal). You can't really center-tap a delta, so you have to tap the center of one phase. Eric and Bryan also discuss: Working out of a truck vs. a van Shunting high-voltage spikes to ground Center-tapped transformers and "wild legs" Ground is NOT necessarily the earth Hot legs on the primary AND secondary   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.

In this short podcast episode, Bryan compares internal and externally equalized valves. He also covers how forces act upon the TXV. Equalization does not happen on the off cycle. When we talk about equalization, we are merely talking about a force that balances against the bulb force. A TXV sets the superheat within an operating range at the evaporator outlet; the sensing bulb on the TXV detects temperature and pressure at the evaporator outlet. So, those readings apply an opening force to the bulb. (Think of this process as being quite similar to you measuring the superheat and suction pressure.) The equalizing force is a closing force. When the closing force is applied to the TXV, it balances against the opening force provided by the sensing bulb. So, we have two ways of providing the closing force: within the valve at the evaporator inlet (internal) or externally. In an internally equalized TXV, the closing force that equalizes the bulb's opening pressure is taken at the evaporator inlet. The measurement is internal to the valve at the evaporator inlet. However, in externally equalized valves, the closing force comes from the evaporator outlet, which is beyond the valve. Externally equalized valves work best on systems with significant pressure drops within the evaporator coil or on systems with distributors. If we were to use internally equalized TXVs in those cases, it would be like measuring superheat at the wrong location. If you don't have a significant pressure drop, then you can use an internally equalized valve. These systems will usually be small (less than one ton) and won't have distributors. Most of the time, we will see externally equalized TXVs; these will ideally take readings within six inches of the bulb.   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.

In this podcast episode, Bryan talks with Bill Spohn about his most recent project, SpohnHome. SpohnHome explores Bill's journey in custom home performance. Projects are complicated because so many trades work together to accomplish a building. However, custom homes are particularly challenging, especially in Bill Spohn's case. His home is a "personalized performance home," so he's prioritizing energy efficiency, indoor air quality, and comfort as well as aesthetics. The home's design and purpose resemble that of a passive building. Although much of the construction went smoothly, there was a misunderstanding about the sewer conditions; unbeknownst to the township, a nearby property had a private sewer installed, so Bill could no longer tie the plumbing into the existing sewer system. That development put a monkey wrench in the plans, and Bill's team had to come up with new ideas for a septic system (and had to follow a bunch of rules). Even though a project may seem to have a perfect plan, setbacks can still occur due to miscommunication or unfortunate events (such as the death of someone integral to the project, as Bill experienced). Bill also used an air-source heat pump with zones for his HVAC system. He had to experiment with his home's ventilation to strike the ideal hybrid solution, as IAQ and efficiency were very important to him on this project. Custom constructions also have plenty of room for the team to do some unconventional things, including making 3D models of the home that gives accurate volume measurements. Bryan and Bill also discuss: Customer follow-up Modular building Plumbing conditions Divining and drilling wells Fresh air and filtration solutions Air sealing and blower door testing Dealing with snow Humidity considerations TruTech Tools news   You can find out the details of Bill's home construction at spohnhome.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.