A Lab Gone Wrong Sometimes Teaches More

Sometimes adversity is the best teacher. Recently one of our first semester students learned more than he bargained for when he had multiple issues with his lab. The lab was to recover the refrigerant from a packaged unit, evacuate the system, and weigh the charge back in. The recovery process went well, but things got off track during the evacuation. The system would not pull down low enough for the vacuum gauge to register. After waiting a while, he decided he must have a leak, so he disassembled his evacuation setup and began to put nitrogen in the system. The leak showed right away – it was on the stem of the Schrader valve. It may have been created while he was connecting and disconnecting hoses. He brazed up the leak, reassembled his evacuation setup, and evacuated the system down to 250 microns. However, when he closed the valves on the core tools the vacuum started to rise. I told him a little rise is normal because the pressure back in the recesses of the system is a little higher than right at the point where you are pulling out the gas. However, it continued to rise past 1000 and kept going. At which point he decided he must have another leak. Once again, he disassembled his evacuation setup and charged the system with nitrogen. When he took off the vacuum gauge, he noticed that the rubber O-ring was missing. Most likely, that was his second leak. He left a note on the system stating the nitrogen pressure and ambient temperature so he can check it on Monday after a weekend of sitting. If the temperature changes, he will have an opportunity to use the gas laws to determine what the holding pressure should be. The lab was really intended for practice in refrigerant recovery, evacuation, and charging. He will get that, but he also receives the bonus of seeing first-hand the effect a leak can have on system evacuation. This also illustrates the value of leak testing and using vacuum gauges. Without the vacuum gauge he would have charged a leaky system and a good bit of the refrigerant would be gone in a few days. Vacuum gauges don’t cost time, they save it. Using a vacuum gauge is the only way of knowing when you have a vacuum and when you don’t. If you can’t pull a deep vacuum, you need to find the problem. The time you save by ignoring the problem will be far outweighed by the time it will cost chasing down the problem later.

Sure Thing in VEGAS!

The upcoming 2014 Educators & Trainers Conference & Expo in Las Vegas is a SURE THING! You can’t lose! You won’t find this many different training sessions anywhere else, especially not for this price. The conference is from March 31 – April 2. There are over 40 sessions with top name speakers from all over the country. A big plus to a national training conference comes from networking with other instructors from all around the country. With several hundred instructors at the conference, you will most likely learn something from fellow attendees during discussions in the hall or lunch. Sharing ideas and offering support and encouragement are vital to the long term health of our industry. If you live within driving distance, this conference is definitely a no-brainer.

I know that times are tough and getting funding and permission to go is difficult. When presenting the idea to your school administrators be sure to forward a copy of the program for the conference. Be sure to note the large number of educational sessions. There are literally more sessions than you will have time to attend. There may also be topics of interest to school administrators – such as Getting Started in Hybrid Instruction, or Program Accreditation. There are also opportunities to get free equipment. At one of these conferences a few years ago I learned about the Appion program to donate recovery machines and vacuum pumps to schools. That alone would cover the cost of your trip. If all those arguments don’t work, just tell them that I will be speaking. I am sure that will seal the deal. I hope to see you all there!
You can read the details here http://www.hvacexcellence.org/nhetc/Faq.aspx

Compressor Amp Ratings

Trying to figure out what a compressor’s amp draw should be can be a bit confusing. Most hermetic compressors only have the LRA (locked rotor amps) on the compressor data plate. The locked rotor amps tell you what the compressor will draw if the rotor cannot turn when the compressor is energized. This typically is 5 to 7 times as high as the operating current. But the operating current is not a fixed quantity. Changes in condenser and evaporator pressures change the work load of the compressor, which changes the actual operating current. Equipment manufacturers label their equipment with the compressor RLA (rated load amps). On complete systems submitted to UL, the rated load amp value will be determined by actual system tests. The same model compressor in two different applications can have a different RLA in each application. However, the RLA is not really there to tell you what the compressor amp draw should be. It is there for the purpose of sizing the wire, controls, and overcurrent devices for UL listed equipment.

Underwriter’s Laboratories requires that the compressor motor protection system will not permit a continuous current in excess of 156% of the rated load current. In commercial refrigeration, compressors and condensing units are often sold as separate component parts. Since there is no system to test, the compressor manufacturer must come up with an RLA. Compressor manufacturers work backwards to figure this out. They operate the compressor at different loading conditions to determine the MCC (maximum continuous current.) This is the highest amp draw the compressor can operate at continuously without tripping the overload. Since UL says the overload must trip no higher than 156% of the RLA (rated load amps), the RLA is calculated by dividing the MCC by 1.56. Some compressor manufacturers use lower safety factors of 1.4 to calculate the RLA. Either way, the RLA does not tell you what the amp draw should be for the particular operating condition in which you find the compressor in the field. In the case of individual compressors or condensing units, it does not even tell you what the amp draw should be at design point, because there is not a complete system, and thus, no system design point. To know what a compressor amp draw should be at any particular operating condition, you need a chart or table supplied by the compressor manufacturer. Some now have this data online. Bristol compressors will let you enter a specific operating condition and their web site will spit out all the relevant data – including the operating current.  

2014 HVACR & Mechanical Conference

I just got back home from the 2014 HVACR & Mechanical Conference in Baltimore. I am still sorting through all my contacts and to-do lists. Like all good things, it seemed to fly by. I learned some things, talked HVACR with old friends, and made some new friends. I am always impressed by the dedication and quality of the people who attend this conference. Jamie Kitchen gave an excellent session on CO2 refrigeration systems. Steve Coscia discussed soft skills for HVACR. Tom Grunstra discussed mini-splits. Jack Bartell gave a great overview of the new ACCA Manual Zr and John Brown covered Airflow Management with zone systems in a later presentation. There were many other excellent offerings as well - too many to mention. The two exhibit nights were lively, with several new products on display. I am sure there were many instructors who would have liked to attend but were unable to. Travel is particularly tough at many schools these days. If you missed this one, don’t despair – the Educators & Trainers conference in Las Vegas is right around the corner. I hope to see you there! You can get more info on it at http://www.hvacexcellence.org/nhetc/

Be Part of the Solution

Quick question. What credential can you possess that is more valuable to your employer and your career than professional certification? Answer: customer referrals. Although you may think you work for ABC Heating & Cooling, the truth is, you work for Mrs. Smith. If Mrs. Smith is not satisfied with your work, your attitude, your appearance, or your personality your company will hear about it. On the other hand, if Mrs. Smith calls in or writes and comments on the great job you did, how professional you are, or how pleased she was with your service, that is more valuable than almost any other asset you bring to the company. If Mrs. Smith asks for you by name when she calls, that is money in the bank for you. I have known customers who will follow a service tech when they switch companies because they want that particular technician to work on their systems. You want the customer to feel good about their decision to call you and your company.

My father always urged me to “be part of the solution, not part of the problem.” I can remember being at someone’s house working with dad on a piece of builder grade equipment that someone else put in. I remarked out load about the cheap brand furnace they had and was quickly and forcefully reprimanded. “NEVER insult the customer.” In dad’s eyes our job was to fix a mistake they had already made. He built his business by being part of the solution. People remember who helped them out of a jam and offered solutions to their problems.

Always try to keep the conversation positive. If you have identified problems, present solutions. Never belittle the customer for a poor decision they made. Instead, offer a better way or a way out of the problem. Never badmouth previous companies and techs. Instead, focus on your solutions. If the issue is a safety concern, you should certainly explain the risk, but offer a solution. In short, focus on solutions, not problems. Your job is to help the customer solve problems, not point out all their shortcomings. Dwelling on mistakes of the past, no matter whose they are, only leaves the customer with a negative feeling. Worse, they associate you with bad news and don’t want to see you again. Focusing on solutions and remaining positive makes the customer feel better. They associate you with good news and solutions. If you do this, I guarantee you customers will start asking for you by name. There is no better job security than having customers calling in and asking specifically for you.