Summer is Capacitor Replacement Season

Any practicing service tech will tell you that service calls involving dead capacitors are common, especially in hot weather. The two most common causes of capacitor death are heat and over voltage. However, there is another less known cause: old age. Many capacitors have a shelf life. I have seen shelf lives listed as little as one year. The oxides on the metalized film break down when the capacitor is not in use, weakening the capacitor. They do tend to self-heal during use. That is why a capacitor which cannot sit on the shelf for longer than a couple of years can last for ten years in use.

Always check the capacitance of any replacement capacitor with a capacitor tester or the capacitance scale on a digital multi-meter before using the capacitor. It may have already died of old age before you install it! A capacitor is a pretty simple device, basically, it is a couple of rolled up sheets of aluminum foil or metalized film with paper or plastic between them. Although a capacitor is a simple device, it is an extremely important part on most air conditioning systems. A bad capacitor can kill a system’s compressor. To protect your reputation and your customer’s equipment, only use capacitors that can pass the EIA-456 Highly Accelerated Life Test. The HALT test subjects a set of capacitors to 125 percent of their rated voltage and 10˚C above their rated temperature for 2,000 hours. For example, a capacitor that is rated at 5uf/440 vac, with an operating temperature of 70˚C, is tested at 550 vac and 80˚C for 2,000 hours.  

Determining which capacitors to stock on your truck is another problem. There are so many sizes of dual capacitors that it is nearly impossible to have all the necessary sizes. American Radionic, AMRAD, has a solution – a multiple capacitor with enough sizes to cover nearly any application. Better yet, they will send instructors sample capacitors to use in your lab. These are great for demonstrating the effect of connecting capacitors in series and parallel. Their web site is AMRAD

Fundamentals of HVAC/R 2nd edition has coverage of capacitors and their effect in circuits in Unit 34 Alternating Current Fundamentals, Unit 37 Electric Motors, and Unit 88 Troubleshooting Refrigeration Systems.

Courage

On this Memorial Day weekend we set aside time to remember the men and women who have given their lives for their country. The bravery and courage of our fallen heroes will be mentioned in speeches, songs, and gatherings all across the country. In a culture steeped in action movies with larger than life characters portrayed by the likes of John Wayne and Sylvester Stallone, it is easy to imagine that the men and women serving in our armed forces are fearless; caring nothing for their personal safety as they conquer the forces of evil in the world. However, courage is not the absence of fear. Courage is fully understanding the peril about you and proceeding anyway to perform your duty. The brave men and women who gave their lives were not cinematic action figures, immune to pain, suffering, or terror. They felt fatigue, pain, anguish, and fear the same as any of us do. Despite all these very human feelings, they found the courage to perform their duty. I hope on this Memorial Day we will also find time to pray for the brave men and women serving around the globe. Every day, fully aware of the peril, they overcome their fatigue, pain, anguish, and fear to perform their duty. That is courage far beyond Rambo. 

Simple Troubleshooting

One of the problems with knowing a lot about possible complex issues is that we tend to look for complex solutions to simple problems. After learning how to measure superheat and adjust expansion valves, we send to see every problem as a problem with the TEV. This is similar to buying a car that you swore you never saw on the road before, and then by next week you notice every other car seems to look like yours. Our brains have a kind of data pre-fetch routine that tries to speed up our recognition of our surroundings that leads us to jump to conclusions. It is just how we are wired. Recognizing this, we need a system to prevent us from confusing ourselves by making incorrect assumptions based on very limited input. This is one of the reasons that systematic troubleshooting saves time in the long run. Having a system helps us avoid the temptation to solve the problem by guessing. Although there are many ways to approach a problem, I try to remember to check easy things first. If you are going to run down a list of things to check first, at least make sure the list includes simple things that don’t take long to check and should normally be checked anyway. For example, it is never wrong to check the air filter. You really should always do this anyway, and trying to check the system operation with a dirty air filter just wastes time. Dirty air filters reduce the airflow, causing a host of other problems such as low superheat, floodback to the compressor, furnaces cycling on the limit, burned heat strips, and generally poor heating and cooling performance. Similarly, it never hurts to take a look at the condenser coil to make sure it is clean. Dirty condenser coils can lead to units tripping on high pressure switches and compressor internal overloads opening. Always check to see that the thermostat is actually set to bring the unit on. Don’t assume that the thermostat is set correctly. Customers often don’t know how to set their thermostats, especially with the newer electronic thermostats. If the thermostat uses batteries, a fresh set of batteries will often cure a thermostat that is acting erratically. While you are at the thermostat, set the fan switch to on. If the fan comes on, you know that you have power to the indoor unit and also control voltage. With digital thermostats that have batteries, seeing a display on the thermostat does not necessarily mean you have control voltage because the display can operate from the batteries alone. If a unit will not operate, you need to check power to the unit first, and then check control voltage. The problem will often become apparent during these initial checks. Even if the problem is not discovered during these preliminary observations, you have eliminated many common problems in a relatively short period of time.

YO MOMMA

Nobody loves you like your momma. Regardless of your shortcomings, failings, or mistakes – your momma loves you. Perhaps that is why “yo momma” put downs are so successful at stirring people up. We all know that our momma is the one person in this world that loves us unconditionally. Attacking our momma is worse than attacking us. I am an expert on mommas because I have one and I am married to another.  Mommas are the toughest people on earth. Only a momma can endure nine months of physical hardship leading up to birth. A weaker being would not make it. The reward for enduring months of physically exhausting body changes is birth: the most physically excruciating event a human can experience. How do I know this? I was with my wife both times when she gave birth to our two beautiful children. She endured 24 hours of labor – the first 12 hours with no drugs – just backrubs. The final 12 hours with intravenous narcotics to “take the edge off.” I am pretty sure I could not have done that. Like I said – mommas are tough. Nobody is more interested in your well being than your momma. I know my own mother kept me from harm more than once when I was too stupid to recognize the life hazards before me. I specifically remember her sternly warning me to keep out of the old television set in the basement – telling me that you could receive a fatal electrical shock even if the set was unplugged. I thought, but did not dare say: “That is stupid. You can’t possible get shocked if it is not plugged in.” Neither I nor momma knew anything about capacitors, but she had read that experimenting inside the TV was dangerous, so she kept me away. Years later I learned that CRT screens had large capacitors capable of holding thousands of volts – enough to deliver a fatal shock! Momma was right! Momma knows things you don’t even if she can’t explain them. Your momma is more interested in your success than you are. At a recent high school honors night it was revealed that my son was tenth in a class of approximately 300. He thought that was pretty good. His momma wanted to know why he was so far down the list. She knows that he is extremely talented and has been coasting a bit. His sister just graduated from Vanderbilt with a degree in Biomedical Engineering and has accepted a job making more than I did after 20 years of teaching. I noticed that the proudest people with the broadest grins were not the graduates, but the mommas, witnessing the fruits of many years of labor. So let me tell you what I know about your momma – Yo Momma is AWESOME!       

Free Online HVACR Resources

Often, free advice is not worth what you pay for it. However, the HVACR Industry is full of philanthropists. There are many examples in our industry where people who really know what they are talking about offer help and information to the rest of us in the industry. This information is aimed at professionals in the HVACR industry, not DIY folks. I thought I would share some of the really helpful information I have been fortunate enough to find.

First, TruTech Tools offers a downloadable pdf book on combustion testing “Combustion Analysis of Gas and Oil Appliances” http://www.trutechtools.com/CombustionGuide
It is well written and very informative. While you are on their site you might look around – they have lots of the latest high-end HVACR tools. Just browsing their site is somewhat of an educational experience.

Yellow Jacket offers articles and instructional videos on using their tools an instruments at the “Yellow Jacket University” http://yellowjacketuniversity.com/
Of course they are showing you how to use their stuff, but the articles and videos are well done and information with just a bit of add.
  
On the ACCA site you can download free speedsheets. These speedsheets are excel files designed for using several of their more popular manuals, including J, N, S and D. https://www.acca.org/industry/system-design/speedsheets
Note that these do not replace the manuals. Rather, they are to be used in conjunction with the manuals. I use the Manual J speedsheet  to teach load studies. There is a little bit of a learning curve for the students, but really far less than with the traditional paper spreadsheets.

For a full package, you can download fully functional demos of EliteSoft design software on their web site http://www.elitesoft.com/web/prices/elite_order_info.html
Yes, they want to sell you something, but they are willing to let you use it first before you invest. Their software does the heavy lifting for you, and many people find that worth the cost.

And one of my favorite free resources is the NIOSH Safety and Health for Electrical Trades Student Manual available at http://www.cdc.gov/niosh/docs/2009-113/