HVAC School - For Techs, By Techs

Bill Spohn with TruTech Tools joins us to talk about why being "approximately correct" is better than being "exactly wrong" when it comes to test instruments. When you see a number, that doesn't necessarily mean that you're dealing with a number you're supposed to see. For example, nitric oxide can present as "false CO" to a carbon monoxide sensor. Test instruments that mistake nitric oxide as carbon monoxide will give a different reading than ones that don't pick up nitric oxide as CO, but that doesn't necessarily make either of them wrong. So, some instruments can give you false positives based on exactly what they measure. On the other hand, false negatives may have to do with poor sensitivity. A common case happens with leak detectors; on occasion, a leak detector won't be sensitive enough to pick up a leak. You can't just say that a set of numbers on an instrument absolves you of responsibility for errors; you must understand the instrument, what it measures, and its sensitivity to use it appropriately. Being rigid in terms of specifications is also a mistake when communicating with customers; customer satisfaction is the goal, and it's okay if their comfort needs deviate from the specifications a bit. Overall, accommodation and mental/financial investment in your tools are the keys; for the sake of the customer, we need to make acceptable compromises, and that's something you must factor into your measurements. Bill and Bryan also discuss: NOx filtration Bacharach PGM-IR Personal protective CO detectors and overloading Laboratory-grade instruments vs. normal test instruments Getting valid wet-bulb readings and using sling psychrometers Analog gauge variables and inaccuracy Lab testing and controlled conditions Ductwork in conditioned spaces Flow hoods Using our senses Olfactory fatigue 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.

Bernadette Shahin of Aeroqual joins Bryan and Kaleb as they all dig very deep into indoor air quality (IAQ) sensors and instruments. They also cover the certainty and uncertainty of measurements. Reference method instruments generally have to operate within a set of parameters, notably a temperature range. Gas laws make the gases act differently, so you want the temperatures and pressures to stay within a range that allows you to measure the air conditions effectively. While we can use reference methods for full-scale instruments, there are no reference methods for IAQ sensors. The only way to make something close to a reference method on IAQ sensors is to use the near reference method. We measure humidity and temperature, and we do an atmospheric chamber and calibration. You have to pair sensors within an instrument to have a product that properly senses conditions. Measuring indoor air quality is important because we spend 90% of our time breathing indoor air with very little fresh air. Air pollutants build up in indoor spaces, and you could spend time in environments with harmful VOCs, allergens, and bacteria. Most people don't have the means of using HEPA filters or fresh air mixing in their homes; so, we need to focus on other solutions to control indoor air quality. Those solutions include air purifiers, but they also include sensors that monitor the air quality. One such sensor is the photoionization detection (PID) VOC monitor. With sensors, we must also think about sensitivity; we want the sensor to measure what it's supposed to measure in the amounts it's supposed to measure. Bernadette, Bryan, and Kaleb also discuss: Barometric pressure instrument calibration Algorithmic adjustments Sick building syndrome Formaldehyde off-gassing, ozone, and CO Aeroqual's solutions for BTEX Automatic baseline correction R2 factor AQI Automating IAQ strategies Pricing 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.

Jordan Cummings is back to discuss some of the most important points in the proper installation of VRF and VRV systems. We especially cover piping best practices. When it comes to piping, the biggest concerns on VRF and VRV systems are making sure the piping can handle the refrigerant velocity and ensuring proper oil return. Most VRF systems use PVE oil, but you still want to be cognizant of oil type, as not all manufacturers use PVE. You must consider fittings, length, and elevation changes when you pipe a VRF or VRV system. In our suction line, we want minimal pressure drop because too much suction drop reduces the mass flow rate through the compressor. You also need to think about avoiding too much of a pressure drop on the dual pressure line when it sends refrigerant to the compressor. You want your piping to be below the connections on the outdoor unit. The piping should be pitched up towards the unit when the outdoor unit is elevated on a stand. Of course, you'll also want to be mindful of where you place the outdoor units; the units should avoid the elements and be mindful of any awnings above. VRF/VRV systems come together at a variety of joints, including REFNETs and wyes (multi-chassis kits). Indoor units use REFNETs, which are basically engineered, balanced wyes. Outdoor units use typical wyes. Positioning these joints also makes a huge difference when it comes to proper feeding. Jordan and Bryan also discuss: Pipe sizing with software Dual pressure line PVE vs. POE oil Miscibility and oil carry Air-cooled vs. water-cooled condensers Condensate drains and trapping Reduced pumping/flow on water-cooled condensers External static pressure Alarms Piping limitations Cross piping on the branch selector box Expansion valve staying shut Pipe expansion 550 PSI, 24-hour pressure test Testing as you go 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.

Bryan and Eric Mele have a relaxed conversation on time management on the job. They also explain how to manage time in life as a whole. Some people are naturally fast because they cut corners in the name of time management. Instead, something Eric has learned to do is optimize his processes. He gets his work done a lot more quickly because he knows how to get the most out of the trips to his truck. Eric is also familiar with the tasks to perform them confidently, and he knows which diagnostic tools he'll probably need. Overall, repetition leads to efficiency. There are also plenty of ways to streamline evacuation and recovery. For example, Eric recovered refrigerant by piercing the liquid line from the air handler. His setup consisted of two charging hoses, a line dryer, and a recovery machine; it was an economic way to save his tools and recover refrigerant in the rain. Eric has done a lot of installs with people of varying experience levels. If there's one thing he learned, it's that you can streamline the process by starting at the outdoor unit, getting the old unit out, and getting the new unit set. The entire time, only one person should be working on the one-person jobs while the other gets supplies and makes preparations as needed. When it's time to work on the new unit, one person can work outdoors while the other works indoors. Eric and Bryan also discuss: Diagnostic tools to keep close or go without Dealing with paperwork Scavenging and saving small parts Cleaning the drain pan Pulling a vacuum through difficult fittings Working with people of diverse experience levels Using tin snips Efficiency and payment Work-life balance Prioritizing parts of your life Working with cranes 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 what suction line traps and inverted traps are. He also covers the purposes they serve. It's a bit hard to find literature on suction line traps, so it's always best to read the manual and follow the manufacturer's guidelines. We traditionally use P-traps on suction lines to hold oil and let it go up the walls of the refrigerant piping. You need enough velocity to lift oil (mineral or alkylbenzene) up the riser. We know that POE carries much easier with refrigerants than mineral oil; it is very miscible with common refrigerants. That's why it's especially important to get all of the mineral oil out of retrofit systems. In refrigeration, we have lower temperatures, pressures, and densities; that combination adversely impacts oil carry. Oil logging is a bigger concern even with POE oil. So, P-trapping with POE oil is a more common practice in refrigeration than it is in air conditioning. In air conditioning, we can make a case for the inverted trap: in an air handler that's higher than the condenser, we want the suction line to go above the air handler and then go down into the evaporator coil. When the system goes off, there is still refrigerant in the evaporator coil, so refrigerant will condense into a liquid. We don't want that liquid to rush down the suction line and into the compressor upon startup, so we use an inverted trap to prevent flooded starts from happening. However, we can use hard shutoff TXVs and other strategies to prevent liquid refrigerant migration. Unfortunately, inverted traps can also keep mineral oil stuck in the evaporator coil. 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 you can prevent and overcome price objections in your HVAC business. You can prevent price objections by avoiding the "budget" reputation. If your company establishes itself as a "budget" or "cheap" company, you will attract coupon-clipper customers. Coupon-clippers can be difficult to work with because of how cost-conscious they are. Customers who aren't looking for a deal will be less likely to object to pricing. You also don't want to shy away from money conversations with friends or family members. Once you get your business model and clientele established, you need to overcome pricing objections in yourself. "Expensive" isn't the issue; value is. If you set a price, then you need to be confident in it; pricing is a business decision, not a moral imperative, and you won't please everybody. If you're not comfortable with the prices, your discomfort can show in your body language and turn the customer away. Another tip is never to talk down your own value or make your work seem like it should be cheap; don't be afraid to explain labor or warranty costs if the customer asks. You can also prevent price objections by avoiding dramatic language. Instead of saying, "This will be expensive," or, "I've got bad news," you can just give the facts and the quote. If the customer gets emotional, you can empathize with them and give them a positive outlook on the situation. It also helps if you can keep money conversations as comfortable, clear, and fact-based as possible. Make sure you get customer approval and allow your customer to decline new procedures every step of the way. Bundle in extra value if you can. Oh, and remember to be empathetic and do a good job. 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, Bryan explains why latent capacity is prone to disappearing. He also explains what actually happens when the latent capacity drops. When you measure enthalpy split across the coil, you'll learn that the equipment design makes it perform to AHRI design conditions. Those design conditions are 95-degree outdoor temperature and 80-degree indoor temperature at 50% indoor relative humidity. So, the A/C system must remove a lot of moisture. However, we don't usually run A/C units for 80-degree indoor temperatures; we usually aim for a 75-degree indoor temperature. When we have 80 degrees, the sensible AND latent heat loads are higher. Things get tricky when we encounter disappearing latent capacity, which is when you remove less moisture. If we have equipment with a sensible heat ratio (SHR) of 0.75 at design conditions, we'll likely have a higher SHR with our typical conditions. When the dew point is lower, water condenses on the evaporator coil at a lower temperature; water holds up the surface temperature of the evaporator coil and optimizes heat removal, suction pressure, and compression ratio. When heat transfers to the water on the coil, the sensible heat in the air decreases via a latent process. When we don't have moisture on the coil, all of the heat going from the air into the refrigerant is making it in via conduction through the metal coil walls. Unless the coil gets below the dew point, it won't remove any moisture; we can still remove sensible heat, but you don't have the advantage of the moisture "holding up" the surface temperature. In very dry climates, we increase the airflow because we don't want to remove moisture from the air, but we still want heat to be available to the evaporator coil. However, we have to be careful about the bypass factor. 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, Jeremy Smith joins us to discuss demand cooling in low-temperature applications that use R-22 refrigerant. R-22 is NOT an ideal low-temperature refrigerant because it leads to high compression ratios. The discharge gas also gets really hot and can burn up the oil in the system. (The head of the compressor is even hotter than the discharge line, so if the temperature is high enough to cause oil breakdown in the discharge line, it's almost surely worse inside the compressor). However, R-22 is starting to go away in rack refrigeration. Demand cooling injects saturated refrigerant into the compressor to help mitigate the high discharge temperature and oil damage. It may seem like demand cooling intentionally slugs the compressor. However, the saturated refrigerant should boil off almost immediately, and it should not make it to the head of the compressor under typical conditions. On the diagnostic and repair side, demand cooling is usually pretty straightforward; if a sensor fails, then it's likely a thermistor issue. In the case of thermistor problems, you can diagnose those issues with the information given in the application engineering bulletin. Loose connections and valve restrictions can happen, but those are also pretty easy to diagnose and repair. Perhaps the most complicated issue occurs when rack systems have low liquid levels. The injector valves can't get a solid column of liquid, but many other components will work fine. Demand cooling solutions are usually brand-specific; each manufacturer has a slightly different setup. To learn more about the Copeland Discus compressors with demand cooling, check out the AE4-1287 bulletin. Jeremy and Bryan also discuss: Outdoor air and head pressure DTC valves Desuperheaters and hot gas bypass Tube-in-tube heat exchangers as "subcoolers" Seasonal changes in discharge temperature Why should we pay more attention to discharge line temperature? 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.

Bryan and Kaleb cover the basics of low-voltage electrical applications. They focus on the practical stuff, not just the theory that confuses techs. Many techs have a hard time with low-voltage electrical concepts and components because it's not easy to visualize what happens; we only see wiring diagrams, not metaphors that help us understand what's going on. The low-voltage control circuit starts with the transformer. The transformer has a primary side (where the high voltage comes in) and a secondary side (where the lower voltage comes out). The secondary is only connected to the primary via electromagnetism; it helps to think of the secondary as an independent electrical circuit. Color coding is a simple concept, but it has changed over the years and can confuse techs. You can only truly understand the wires by doing a complete visual inspection and tracing the wiring. (Though generally, blue will be common/C, and red will be hot/R.) We also typically use yellow for Y1, but Y is a confusing concept. Y ISN'T the compressor or cooling! Y pulls in the contactor coil; it is really the high-stage contactor. Y2 is a higher staging, and Y1 is a lower staging. On heat pumps, the white wire is usually for heating, and the orange wire is usually for the reversing valve. G is for the indoor fan and often has a green wire. Kaleb and Bryan also discuss: Tapping transformers W and O calls on heat pumps G calls DH on 24v controls Communicating controls Float switch configurations and issues Breaking Y or R with the float switch Wire routing: air handler and condenser Preventing conductor corrosion NASA or lineman splice Stranded shielded wire vs. solid wire 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, Bryan talks about the impacts of compression and airflow changes. He also discusses some of the ramifications of those changes. In order for us to energize the second stage of a compressor, we need to energize both Y1 AND Y2. On stage 2, we're running that compressor at full speed (350-450 CFM per ton). The compressor will also perform at rated capacity. When you stage down to stage 1, your blower should ramp down, and the compressor should produce less capacity (move less refrigerant). When moving less refrigerant, the compressor should use less current but still be cooled properly. Naturally, the suction pressure goes up while the head pressure goes down when we ramp down the compressor. However, when you reduce the blower speed at the same time, your evaporator coil picks up less heat. In that case, the suction pressure would drop. You normally don't want the suction pressure to go up in the low stage from the high stage. The impacts of compression changes are multifaceted, and there are several moving parts to think about when it comes to capacity. When the compressor slows down, it moves less refrigerant over the same period of time; your compression ratio goes down if your airflow over the evaporator coil remains the same. However, if the airflow drops proportionally, then your suction pressure should stay close to the same. If the compressor pumps the same amount of refrigerant, the suction pressure will drop. If the compressor pumps less refrigerant proportionally to the airflow, then the suction pressure should remain the same theoretically, but it usually increases. An increase in suction pressure results in a lower compression ratio, which is good for efficiency. Bryan also discusses: Floating the evaporator temperature Broken valves on reciprocating compressors Improperly seated scrolls Improper tonnage ratings across components Oversized coils 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.