HVAC School - For Techs, By Techs

In this short episode, we replace a dirty "M" word (mold) with another "M" word (moisture) that gets to the root of the problem. "Mold" and "mildew" can freak out your customers. For years, I've refrained from saying "mold" at my own company and trained my techs to avoid it AND "mildew." Instead, we have called it "biological growth" or "organic growth." Those still aren't great. Just recently, my friend Joe Medosh suggested referring to fungal growth as a "moisture problem" instead. "Moisture problem" is a fact-based and less disgusting term. We can focus on solutions with indoor air quality (IAQ) to address the overarching issue that causes the growth, not just the nasty growth. In some cases, parts of the home may hit the dew point in colder temperatures. So, drywall is particularly vulnerable to falling to dew point if the building envelope has been poorly sealed. So, we have a practical means of reducing relative humidity below 55%. We can also seal the envelope better and address potential issues related to infiltration. A duct with poor or compressed insulation may also be prone to "moisture problems." We can address those "moisture problems" by properly strapping the duct. In cases when air handlers sweat by an improperly sealed duct, we seal the duct correctly to nip the problem in the bud. In the case of sweating vents, we must analyze the supply air, check the blower fan speed, and look for restrictions. Make sure all components are clean and that you seal up any leaky areas. Remember, "moisture problems" do NOT occur because hot meets cold! The moisture content and dew point are the key factors, not just a temperature differential.   If you have an iPhone subscribe to the podcast HERE and if you have an Android phone subscribe HERE.

Here is part 2 of the discussion with Trevor Matthews about the causes and prevention of air conditioning and refrigeration compressor failure. Slugging occurs when the compressor attempts to compress oil or liquid refrigerant. A telltale sign of slugging is valve plate damage. On a semi-hermetic compressor, you can remove the screws on the head to access the valve plate. Wrist pin wear occurs during slugging the wrist pin is between the rod and the piston; you should test the wrist pin to see if it makes a knocking sound before you dismiss all other possibilities and replace the valve plate. Overheating occurs when there is a system-related issue. Compression ratio is an indicator of overheating, but few technicians check it often enough. A requirement for external cooling and dirty condenser coils can cause overheating. Overheating also causes oil issues; when a compressor gets too hot, oil breaks down and loses its ability to lubricate the bearings. Oil loss is a tricky cause for failure; it is hard to notice without a sight glass. Short-cycling can lead to oil loss over time, and bearings will begin to wear when there isn't enough oil to lubricate them. Contamination usually occurs when moisture corrodes the copper plating and introduces acid to the system. Acid and sludge are the most common contaminants. Proper reaming practices also keep copper out of the system and reduce the risk of acid contamination. Trevor also discusses: Slugging in scroll compressors Sight glasses and oil measurement System load and suction pressure Maintaining design compression ratio "Blow by" Oil separators Replacing line dryers Components to troubleshoot and inspect Verifying System Operation Sheet from Emerson http://hvacrschool.com/Emerson Verify Diagnosing Compressor Failures from Emerson http://hvacrschool.com/CompFailures  

In this short podcast, we start the conversation about "Energy? Compared to What?" and explore several energy comparison examples. When we think about energy, we can confuse some terms. For example, temperature and heat are related but NOT synonymous. Temperature is an average measurement of heat energy; when many molecules move at a bunch of different speeds, the temperature represents the average speed of those molecules. Temperature does NOT measure total heat content. Voltage and amperage are two more confusing terms, and they get even harder to understand and differentiate when you throw "power" around. In most diagnostic cases, we usually measure things to compare them, such as using a voltmeter to measure a difference in electrical charges. We could compare the usage of a voltmeter to a temperature difference between two rooms. The wall between the rooms presents resistance between the temperatures of the two rooms (R-value, which affects energy transfer), and the voltage is analogous to the potential difference between the rooms. In the HVAC industry, we can witness energy differentials in temperature, charges, and pressure. Resistance gets in the way of these differentials reaching equilibrium and must be accounted for in our readings. Resistance affects the rate of energy transfer; that resistance can show up as friction, R-value, and other values that affect the total amount of energy transferred. Many techs also go wrong when they assume that a 120V blower motor draws twice as many amps as a 240V blower motor. In truth, the 240V blower requires twice as many amps to hit the same work target. In a 240V motor at 120V, it would draw far less amperage and result in less than half the usual horsepower.   If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In today's podcast, we talk with Trevor Matthews with Emerson. He tells us about the causes and prevention of air conditioning and refrigeration compressor failure. Most compressors don't die a natural death... they're murdered. Of course, that's to say that installation and maintenance play a major role in the compressor's operation and lifespan. Electrical and mechanical failures are the two broad causes of compressor failure. When it comes to electrical failures, Trevor often sees single-phase compressors fail early when their electrical components don't receive proper inspections and care. For example, contactors may go too long without inspection or replacement. Three-phase compressors are also prone to phasing issues and may run backward. Common mechanical failures deal with oil in the system. Oil lubricates the bearings inside the compressor. Unfortunately, that oil can mix with liquid refrigerant, become diluted, or experience acid contamination. Some oil-related failures include floodback, flooded starts, slugging, overheating, oil loss, and contamination. Compressors cannot compress liquids, so many of them fail when the refrigerant condenses to a liquid inside the compressor. Many failures occur because technicians don't think they have enough time to troubleshoot or inspect the whole system. Trevor recommends setting up a checklist with all of the tests you need to perform. Trevor also discusses: Service replacement compressors vs. OEM compressors Megohmmeter usage Causes of floodback/flooded starts Compressor superheat Suction accumulators Bearing wear Temperature control and pump cycles for controlling flooded starts Verifying System Operation Sheet from Emerson  http://hvacrschool.com/CompFailures 

In today's podcast episode, we talk with system and duct design educator Jack Rise about ACCA Manual J load calculation and Manual S system selection. Many people know about Manual J, but relatively few techs follow it properly. When people attempt to do Manual J calculations, many of them go wrong when they overestimate the difficulty of the equations in Manual J. However, many of these techs do better when they can use software like Wrightsoft to help with their load calculations. The best way to approach load calculations is to develop confidence in software programs and field experience (sizing equipment and sealing ductwork); you are more likely to make mistakes if you put all of your confidence in one or the other. Some techs also don't take the time to measure buildings properly if they are either over-reliant on technology or too confident in their field skills. Manual S is all about equipment selection after the load calculation. However, much of the manual is not useful for fieldwork. The rules are also not as regionally thoughtful as they could be, especially regarding furnace sizing and the consequential heat loss. Manual S is only useful if you perform a Manual J calculation first and use that result as a guide. Rise does not believe that Manual S is bad, but he thinks it gives installers way too much leeway on sizing as it stands. Jack and Bryan also discuss: Wrightsoft Manual J practices in different types of buildings Envelope leakage in retrofit applications Most important chapters of Manual S Accounting for sensible and latent heat load New ventilation requirements Odors, cooking, and building design Increasing airtightness in building construction Encapsulated attics   Learn more about ACCA standards and codes at acca.org. Learn more about Wrightsoft HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this podcast, Bill Johnson shares his practical tips to make low-voltage electrical diagnosis easier in HVAC work. Bill is one of the original authors of the Refrigeration and Air Conditioning Technology manual. A common issue that techs have in low-voltage diagnosis is that they overcomplicate the issue. Techs should take the time to trace out the system and see where all the wires lead. The techs can be more effective if they know a system's components and those parts' relationships. During diagnosis, some techs also don't allow themselves to use their hands. Bill recommends using an alligator clip on the system as you "walk your way" through the whole circuit for diagnosis. "Short" is a commonly used term. A true "short" occurs when the current takes an undesigned path with almost no resistance. Some of the things that we casually call "shorts" are actually open-circuit issues where the current doesn't make it all the way through the circuit. Real "shorts" include shunts on the load and blown fuses. If a fuse blows but everything else in the low-voltage circuit seems to be operating fine, check the amperage at the transformer outlet. Electronic boards give techs a lot of trouble because they seem complicated. But, in the end, these boards are just switches where a hot wire goes in and a hot wire goes out. (The common wire goes straight through the board.) The board is nothing more than a distributor of voltage, and the best way to work on them is to simplify them. You can simplify electrical boards by figuring out the inputs, outputs, and sequence of operation. Bill also discusses: Grounding on one leg Connecting to ground "Probing" the hot side Measuring amperage on a thermostat "Spark-tricians" Commercial vs. residential low-voltage electronics Stripping wires   If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this podcast episode, refrigeration tech Eric Mele talks us through some common characteristics of walk-in freezers and refrigerators. Eric recently discussed reach-in refrigerators on the podcast, and you can listen to him talk about those HERE. Common walk-in applications include coolers, freezers, and wine rooms. You may even see some package units. Condensers typically go on top of the box or the roof, and evaporators are inside the refrigerators. Many of these refrigerators also have pump down solenoids on their equipment. Thermostats mostly control the opening or closing of the solenoid valve. To cycle the unit, you shut off the liquid line and let the system pump all the refrigerant into the condenser. Evaporators tend to come in the side-discharge or pancake-style varieties. Wine rooms may also have ducted evaporators. Some older evaporators may not have fans; we call these gravity evaporators. Heaters are components that you'll see quite often on walk-in equipment. Drain pan and drain line heaters are critical for walk-in coolers, especially freezers. You can test them by touch or by using a thermal imaging camera. Freezers also have door heaters. Walk-ins also have low-ambient controls. Fan cycling is a low-ambient strategy, but commercial walk-in refrigerators may also have a headmaster. When you first start working on walk-ins, you may feel overwhelmed if you don't have all the parts on you. However, if a unit has multiple fans and only one is not working, you can typically still run the equipment if you cover the faulty fan and seal up the opening in the shroud. The goal is to get (or keep) the equipment running to save consumable products. Eric and Bryan also discuss: Pressure switches Defrost controls Troubleshooting equipment (sight glasses, etc.) Adjusting charge Superheat values Patching coils   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 covers some basic best practices for wire routing and wire connections in HVAC work. When it comes to electrical work of any kind, the wires must have proper protection. For example, the wires must be in the proper conduits. They must also work on appliances that they are rated for. HVAC technicians must also understand their qualifications against local codes to ensure they have been authorized for electrical work. You also NEVER want to route the wire through an opening you can't shove your finger through. If you can cut your finger on an opening, then that opening will probably cut the wire. If you need to run a wire through one of those difficult places, use a grommet. In any case, make sure you properly strap the wire, such as with zip ties. Do NOT trim wires to make them fit a connection. When routing wire, you WILL be making connections inside the appliance. Make sure you know your connectors and their ratings to make the best, safest connections possible. Check if there is any tension at the connections and disconnects; if there is tension AGAINST the terminal, check your wire angles and adjust them until they sit still or have a little tension towards the terminal. The goal of creating a good connection is to avoid melting, arcing, and other unsafe conditions. Replace melted plugs and leads entirely if you come across them. When you make a crimp connection, make sure you give them a good tug to check their tightness. Make sure there are no exposed wires by your crimp connections. Soldered connections are usually excellent connections, especially with heat shrink over them. Bryan also discusses: Using torque screwdrivers Terminal crimping (insulated terminals, indentations, using ratcheting crimpers) Lineman splice "Doubling over"   If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In the second part of this podcast series, Jim covers the basics of furnace commissioning in more detail with some common-sense practices. (Listen to Part 1 HERE.) Even though installers set up a furnace system, the technicians help with the equipment startup and commissioning. That way, two parties can ensure that the installation is proper. The technician is perhaps better equipped to check the electrical connections. As technicians, we can also check the polarity of the power supplies (ensuring that the sine waves are in sync). If the polarity is backward, sometimes the hot wire has been switched with another wire, or you may have to switch the primary or secondary on the transformer. Flame rectification also ties directly into the electric components of a furnace. Inspection is also a critical component of furnace commissioning. As such, our eyes and ears will be our most important tools during the commissioning process. During the inspection, we should check over the original factory parts to ensure that everything is in order and that the furnace will operate safely. After we've calculated the temperature rise and set the blower speed, we must evaluate our static pressures. The static pressures let us know how our motors and ductwork are doing. The goal is to get our static pressures as close to 0.5" wc as possible. Be sure to perform a flame disruption test to ensure that the flame does not starve. Many technicians also fail to check the high limit cutout. When techs fail to check that cutout, the heat exchangers can break from stress. To check that high limit cutout, we can use a piece of cardboard to block the filter; that blockage raises the temperature, and it's our job to make sure that the limit cuts out and shuts the burners down. Jim also discusses: Grounding screws ECM motors Home insulation and furnace/ductwork sizing Furnace switches/safeties Flame rod microamps   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 blower taps in furnace systems. He explains how to set up their fan speeds and repair them. Before you even look at the blower taps in a system, you must know a bit about the system design. Is the system supposed to remove high amounts of sensible heat? What is the capacity? How quickly should the thermostat drop? When a system is supposed to move lots of heat and has a high capacity, it needs high airflow; to run optimally, the system needs higher fan speeds to move more CFM per BTU. Moreover, a Manual J calculation can tell you how much sensible and latent heat the system must move. Also, keep in mind that system tonnage does NOT always indicate the amount of BTUs a system is actually moving. Conversely, to calculate the airflow needed for heating, you must look at temperature rise. Ideally, your temperature rise should be near the middle of the temperature-rise range. So, how do you set the airflow and know how much you're producing? That's where you measure your static pressure and look at fan tables. Remember to make sure the blower is clean and to factor in additional resistance from components like heat strips or filters. Alternatively, you can measure airflow with a duct traverse or by using an airflow hood. Then, you set the fan speed accordingly. Overall, to set the blower taps, you need to be able to measure your airflow and read fan charts. If you're merely commissioning a new system, measuring airflow becomes less important; instead, you must ensure that the manufacturer's fan charts are correct. Remember, the airflow needs to be different for a customer's heating and cooling needs.   If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.