Synthetic Marijuana Kills!

I found out recently what killed a promising student in my program this past year. His heart was stopped by synthetic marijuana. I have no idea why he was using it, I only know that it killed him. He was a promising young man with significant ability that is now lost. He left behind a son that he cared deeply for. One of his motivations for learning a trade was to improve life for his family. I admittedly know very little about this stuff, so I am providing some links to articles about it. Wikipedia Article   National Institute of Health

What I do know is that it makes no sense to inhale any kind of drug laced smoke into your body. Before FDA approved drugs are even tested in limited quantities on people, they are extensively tested in animals for safety. With these designer drugs, the customers are the lab rats. My message is simple: if you use this stuff - stop. If you know someone else who uses it - stop them. It is literally a matter of life and death.

I am pleased to introduce my first guest blogger - Kevin Thompson of Thompson Heating in Louisville, Kentucky. He has contributed an article on what homeowners can do to prolong the life of their equipment, and what they should leave to trained professionals. 


Home comfort technology has come a long way in a very short time. For some it seems like just yesterday our homes were cooled with a box fan in the front window or heated during the winter months with a heap of coal and a trusty stove. While some may still prefer those primitive methods, most of us have evolved into using more complex, electrical contraptions to heat and cool our homes. These modern machines have resulted in safer, long-term, and more efficient options for modern day homeowners, especially when they are treated with their recommended annual maintenance. For most heating and cooling units, changing the air filter every 3 months is critical to its long-term maintenance. Over time dirt, dust, dander, and pollen build up and your filter keeps it from circulating in your home. If the filter is not replaced regularly, it could become clogged and your blower begins to work overtime. When your blower becomes overextended, it results in higher monthly energy costs and it could overheat your unit. Most air filters are inexpensive and can be purchased at your local supermarket or hardware store year round. Staying on top of their air filters is one way homeowners can save money on their comfort system and prolong its use. 


While making sure the air flow in your unit is not obstructed is very important, there are a number of other tasks that should be inspected by a trained HVAC professional. Among the things a service professional should check on a furnace include the burner assembly, gas pressure, carbon monoxide testing, and the indoor blower wheel. For an air conditioner unit, they may inspect the refrigerant charge, capacitors, lubricate moving parts, and clean the condenser coil. Not only is it important to have your comfort systems checked annually, but it is equally as important to have them serviced during the peak of their respective seasons. For example, a furnace should be checked towards the end of the summer months at the beginning of fall. Air conditioning units should be serviced at the beginning of spring. That way your units will operate at their highest level of efficiency during the most important times of the year. All of the abovementioned maintenance should be inspected by a trained professional. Most states require HVAC professionals to complete a specified number of hours per year to remain certified. The training they receive prepares them for the injury risks and technical know-how that is entailed in each service call. Some homeowners erroneously attempt to service their heating and cooling units on their own, deferring to online forums and do-it-yourself (DIY) manuals as opposed to making a simple call to their local HVAC professional. DIY projects are great for many jobs around the home, but HVAC repairs should be left to the professionals. There are too many things that could go wrong to justify servicing a unit on their own. 


Today’s HVAC products are far more complex than the wood or coal-burning stoves and box fans of the past. Making repairs on these primitive commodities could more easily be taken care of by a homeowner or a local handyman with a little welding and some electrical work. These days one would be hard-pressed to find two similar heating or cooling units in two homes on the same street. The wide diversity of products speaks to the crucial importance of having a certified professional perform annual inspections and needed repairs on furnaces and air conditioning units. Proper do-it-yourself maintenance is appropriate for air filter replacements which may help to save on monthly utility payments and could serve to extend the life of a unit. All other repairs and service calls should be taken care of by a certified HVAC professional annually in the beginning of the spring and fall months, depending on the respective unit. Proper annual maintenance by a certified professional will not only ensure the longevity of HVAC units, but may also protect against unnecessary injuries that may occur during DIY projects. As the complexity of home comfort systems evolves, so must the mindset of HVAC consumers as it pertains to proper and safe maintenance for furnaces and air conditioning units.


If you would like to find out more about Kevin or his company, check out their web site at http://www.thompsonheating.net

Is You Refrigerant System Constipated?

I am hearing more stories about systems having problems with refrigerant restrictions. Many are from black scale created inside the pipes by brazing without a nitrogen purge. In the old days we often got away with this if we did not take a long time brazing the joints and did not overheat the pipe. Today, however, the POE lubricant and HFC refrigerants scrub off the oxides and carry them around in the system. This is especially problematic with metering devices of all sorts. TEV screens get plugged, orifice metering devices get plugged, and even filter driers get stopped up. The black oxides can also conduct electricity, so if they build up inside the compressor shell they can cause it to ground out. Prevention is the best remedy – not forming the oxides in the first place. You can do this by purging the lines with nitrogen while you braze. Of course you need to let the nitrogen out as you put it in so the system does not pressurize. You can’t braze up a hole under pressure. There are new flow meters that let a trickle through – just enough to keep the air out, which is all you need. No air means no oxygen to form oxides. The primary symptoms of refrigerant restriction are a low suction pressure, a high superheat, and a high subcooling. The head pressure may anywhere from slightly low to kind of high. If someone has tried to fix the problem by adding charge, the high side may be high. Normally, it will be a little low after a few minutes of operation unless the system has been overcharged. If the restriction is anywhere in the liquid line, like the filter drier, there may be a temperature drop at that point due to liquid flashing off.

If your system is constipated with black scale, ex-lax won’t help. You will need to recover the system refrigerant, disassemble it and flush it out using a solvent made specifically for refrigeration systems, such as Qwik Flush by Mainstream Engineering. Using carburetor cleaner will just add to your problems. Re-assemble it with a new filter-drier, pull a good vacuum, and weigh in the manufacturer’s specified charge. You will have to adjust the charge slightly for line length and the amount of refrigerant the filter holds. I recommend using flare filters because they are easier to change, and you won’t have to worry about making any more scale. For more details on this procedure, check out unit 91 Refrigeration System Cleanup in the 2^nd edtion of Fundamentals of HVACR.  

Desired Air Conditioning Temperature Drop

I was recently asked for a formula to determine the temperature drop between the return air and supply air of an air conditioning system. While it is logical to check the temperature drop, determining exactly what it should be is not as simple as plugging in readily available numbers into a formula. Two operating conditions can have a pronounced effect on the results: the relative humidity of the return air and the amount of airflow. Most air conditioning systems condition the air two ways. They cool the air, referred to as sensible cooling; and they take water out of the air, referred to latent cooling. Only sensible cooling creates a temperature drop. Removing water from the air takes system capacity. The more water the system removes from the air, the less capacity is left for reducing the air temperature. Standard airflow is 400 CFM per ton for most systems, but that does not mean your system is actually operating at 400 CFM per ton. If you move less air across the coil, the air will be cooled a little more. To determine the temperature drop you must know the outdoor ambient temperature, the return air dry bulb, the return air wet bulb, the CFM of airflow, and the system’s sensible cooling capacity at that condition.

Take for example, a system that is removing no water out of the air operating at 100% sensible cooling with a standard 400 CFM per ton of airflow and producing 12,000 Btuh per hour. The temperature difference is calculated as TD = 12000/(400 x 1.08) = 28°F TD. If the airflow is reduced, the TD becomes 12000/(350 x 1.08) = 32°F. Increasing the airflow would make the TD 12000/(450 x 1.08) = 25°F. In humid climates, the latent capacity can easily be as much as one third of the total capacity, reducing the sensible cooling capacity to 8,000 Btuh. These same airflows would then give TDs of: 8000/(400 x 1.08)=19°F, 8000/(350 x 1.08)=21°F,8000/(450 x 1.08)=16°. In reality, these TDs would be a little off because the overall system capacity would be a bit less with the decreased airflow and a bit more with increased airflow. The system capacity will also change depending upon the outdoor ambient. The 12.000 Btuh per ton is a nominal figure based on the AHRI rating condition of 95°F outdoor ambient, 80°F indoor dry bulb and 67°F wet bulb.

You can try to account for duct gain by reducing the expected TD by some amount: say 3°F - 5°F. However, it is really difficult to use TD at the registers because the duct gain from one system to another can vary a lot. Ducts in the attic will pick up more heat than ducts in a crawl space. Duct leakage also has a big effect. If 10% of the air entering the coil comes from a 150°F attic, that obviously will affect the delivered air temperature. The rule of thumb people have used for many years is a TD of 15°F to 20°F across the coil, not at the registers. Looking at the above calculations, you can see where this comes from. However, it is also easy to see how little you actually know if you don’t really know all the operating conditions, the system airflow, and the system capacity at those conditions. If all you do is measure the return and supply air temperatures at the registers, you don’t really know much.

Substitute Refrigerant Safety

As R22 prices increase and R22 availability decreases, many technicians have at least thought about using a substitute refrigerant in place of R22. Usually, we are looking for a drop-in which can be used to charge a system instead of R22. My primary consideration is safety. Of course I want any substitute refrigerant to work well and be environmentally friendly, but most of all, I want it to not hurt me or my customers. The refrigerant manufacturer should be able to show that their refrigerant is listed on the EPA SNAP list of acceptable replacement refrigerants. If they can’t, I would not use it. Another source of safety information is the required MSDS sheet. Any chemical sold in the United States must have an MSDS sheet. If the seller cannot provide an MSDS sheet, I would not consider using the refrigerant. The MSDS sheet will list important information such as toxicity and flammability. One replacement refrigerant that is advertised on the internet has enough information on the MSDS sheet to let me know I don’t want any part of it. The proper shipping name is “Petroleum Gasses Liquified.” Other statements include “Vapor may ignite if exposed to static discharge", and "Flammable vapor may form if allowed to mix with air. Accumulation of gas is an ignition hazard. Vapors are heavier than air and may travel to an ignition source." R22 systems are not built to operate safely with a flammable refrigerant. There is no way I would put this in a system designed for R22. Last year technicians were killed while working on refrigerated shipping containers that exploded.(See post about it). They were R22 systems which had been charged with a flammable substitute refrigerant. Although the EPA has recently approved the use of flammable refrigerant in limited charge applications, it is important to note that there are many requirements a system must meet to be safe with flammable refrigerants. R22 systems meet none of these. For more information on flammable refrigerants, take a look at my previous post on Flammable Refrigerants. For more information on R22, take a look at my previous post on R22 Conversion. A couple of simple rules to follow will help keep you safe. Can you buy the refrigerant at your local wholesaler? If you can only get it over the internet or from a guy at a flea market, you don’t want it. Is the refrigerant listed on the EPA SNAP list for the specific application? If not, you don’t want it. Does it seem too good to be true? If so, you probably should avoid it like the plague.