Monday, November 17, 2014

Turbo 200 Capacitors

NOTE: - This is a re-posting - I got Mona's e-mail wrong on the first one.
Have you ever had to replace a dual capacitor only to find you do not have the right one on the truck? There are so many different possible combinations it is nearly impossible to have every one you might need. Amrad Engineering makes capacitors here in the USA. They make replacement capacitors which have a wide range of capacitors built into a single part called the Turbo 200. With these, it is possible to replace most any dual capacitor you need. These capacitors are great for teaching students about series and parallel capacitors. Basically, the Turbo 200 is 6 capacitors connected together at the center post. Any two outside connections are essentially in series. Measuring the microfarad between any two outside terminals shows the effect of capacitors wired in series. Jumping any two outside terminals puts those two capacitors in parallel. Placing a jumper between any two outside terminals and measuring the microfarads between either outside terminal and the center terminal shows how capacitors connected in parallel work.  Amrad engineering is offering a free kit to all HVACR instructors. They want to send out a kit of their products with instructions to schools all over the country to promote their products. The stuff they sent me was fantastic. Here are a couple of pictures of the kit.





To get a kit for your school contact
Mona Tompkins Amrad Engineering
1-800-445-6033

Friday, November 7, 2014

EPA Announces R-22 Allocations for 2015 - 2020

The EPA has released their R-22 allocations for 2015 – 2020, and it looks like the days of free-flowing R-22 are about to come to an abrupt end. To put things in perspective, the R-22 allocation for this current year, 2014, was 51 million pounds. The allocation for 2015, coming up in a few months, is 22 million pounds. That is just over 43% of the 2014 allocation. From there the cutbacks are more gradual with a reduction of approximately 4 million pounds each year until 2020 when the allocation is 0. Trying to figure out R-22 prices has been a bit difficult these last few years. They have spiked twice but then gone back down as supply increased. This time look for the high prices to last  because there will be no turning the tap back on this time. The main question remaining is how long demand for R-22 will continue. Although there is still a very large installed base of R-22 air conditioning equipment, it is starting to get old. As older equipment fails and supplies tighten, it will be increasingly difficult financially to keep an older R-22 system operating. I remember with R-12 and other CFCs, prices climbed high enough to kill demand. A local wholesaler took a bath on a large quantity of 502 just to get rid of it because nobody wanted it at the “market” price. Consider that a dry ship unit costs about the same as a 410A builder grade, but you still have to buy the refrigerant. It is conceivable that a dry ship unit charged with R-22 at inflated prices would be as expensive as replacing both the condenser and evaporator with a builder grade 410A system. Who would want to keep their old system if it costs as much as a system with current technology, higher efficiency, and a refrigerant that is still available? To read more about the EPA's ruling, check out

https://www.federalregister.gov/articles/2014/10/28/2014-25374/protection-of-stratospheric-ozone-adjustments-to-the-allowance-system-for-controlling-hcfc

Friday, October 31, 2014

DOE Small Motor Efficiency Standards for 2015

You may have missed the news about required small motor efficiency minimum standards while you were focused on refrigerant changes; regional efficiency standards for air conditioners, furnaces, and heat pumps; and trying to stay ahead of the latest news on climate change. I know I did. I was looking at the Grainger web site the other day and up popped a bulletin regarding the Department of Energy requirement that certain small electric motors 3 horsepower and under meet a new minimum efficiency requirement beginning in March, 2015. I immediately thought “oh bother,” that would include most of the motors we deal with in residential HVAC. Then I looked up some details and breathed a bit easier.  Motors which are exempt include multispeed, enclosed, specific purpose, or special mounting bracket. That just exempted most of the motors in residential air conditioning equipment. If you deal with regular mount, general purpose, 42, 48 or 56 frame capacitor start or capacitor start-run motors, you WILL be affected. An example might be ventilation fan motors. Grainger was not saying replacement motors would not be available, just that they would now have run capacitors and would be longer due to the extra windings required to meet the new efficiencies. Basically, this DOE ruling makes what was once the premium, high efficiency motors the minimum motor design for certain motor types defined by NEMA. I found several links with discussion and details on this requirement. They are listed below. You might want to take a look at some of these links to determine if you work with any of the affected motors. That way you can develop a replacement strategy before you get to a job and find that you will not be able to replace the old motor with another just like it.





Monday, October 20, 2014

NOx Nox Who's There?

Cracked. Cracked who? Cracked heat exchanger. OK – not the funniest knock knock joke – especially if it is YOUR furnace. Low NOx emission inserts are causing pre-mature furnace heat exchanger failures. You can read more about this at http://ncidavid.blogspot.com/


I want to talk a bit about what NOx is, why an insert can help reduce NOX emissions, and why NOx inserts can cause trouble. NOx is a generic term for nitrogen compounds NO and NO2 which are formed when nitrogen is present during combustion at high temperatures. These are major contributors to air pollution and acid rain. Laws requiring reduction of NOx emissions in areas of particularly high air pollution (California) have required the development of low NOx furnaces. Since the air is 78% nitrogen, any combustion process that uses air for its oxygen source has lots of nitrogen present. NOx will only form at high temperatures, but the burners in gas furnaces are definitely hot enough to form NOx. One quick and easy solution is to put something in the flame to cool it down. NOx rods and NOx inserts work by cooling the burner flame temperature, thus reducing the NOx emissions. These NOx rods or inserts are typically metal. Stick some metal in the flame, cool it down, and you have a low NOx furnace. The problem is that metal held directly in a flame eventually burns up. It does not burn quickly, but it does burn. That is why we don’t want the furnace flames actually touching the heat exchanger. The heat exchanger material cannot withstand direct flame contact, called impingement. NOx inserts stick inside a tubular heat exchanger. Unfortunately, the insert eventually degrades from being exposed to the flames. In some cases, it can twist or deform and change the flame pattern. This can cause the burner flames to touch the sides of the heat exchanger, and the heat exchanger fails prematurely. Before the heat exchanger fails, the furnace will be producing higher levels of carbon monoxide and carbon particulates because of the change in flame pattern. So you trade one type of pollution for another. If you work on furnaces with NOx inserts, be sure to check them – and watch the flames to see that they are not touching the heat exchanger. If you work in an area that does not require the NOx inserts, you can solve the problem by removing them. However, now you are increasing the amount of air pollution the furnace produces. Low NOx burner technology does exist – where NOx reduction is achieved through burner design, but I don’t know if there are any true low NOx burners for residential appliances. Keep an eye out for furnaces with low NOx inserts. It might be worth a few extra moments to wath the flame pattern and measure the CO in the flue gas. Abnormally high CO might indicate a developing problem. 

Sunday, October 12, 2014

Playing with Your Phone on the Job



Many companies now issue company cell phones to their service techs. The phones are intended for communication, so the company can find the techs and talk with them virtually anywhere, anytime. Now those phones may need to be considered part of the technician’s toolbox. There are already many great apps, including free pressure-temperature apps – usually from refrigerant companies. Equipment and parts manufacturers have started producing apps for looking up parts and equipment service specs. Now you can use your phone or tablet to read the system pressures, line temperatures, superheat, and subcooling. Stride Tools (Imperial) released the i-manifold last year. It is a four port manifold without a display. It sends the information wirelessly to your phone or tablet, and your device becomes the display. Since the display is literally on a small computer, the app can do all kinds of cool things. For one, they have wireless thermometers that can work with the i-manifold to determine system operating conditions, capacity superheat, and subcooling. But wait – there’s more! Now Yellow Jacket has come out with a small device they call the mantooth. It connects to the system and has a tethered temperature probe. It also has no display, but sends the information to your smart device via Bluetooth. So you can see system pressures, temperature, superheat, and subcooling all on your phone. The advantage of this device is that you don’t have to fill up a hose with refrigerant to get a reading – so refrigerant loss is minimal. The “short” gauge concept is perfect for simply testing system performance. Another well known manufacturer is also testing “short” gauges that connect to smart phones and tablets. Their devices are also “short” gauges – eliminating the refrigerant loss from connecting hoses. Their gauges do have their own display as well as connecting to your device through Bluetooth. They are developing wireless thermometers to work with these gauges. Again, you will be able to see all relevant system operating conditions on your smart device and you won’t have to lose several ounces of refrigerant just to perform a check-up. You may soon be playing with your phone on the job – to improve your productivity!

Sunday, October 5, 2014

Condenser Subcooling



What happens to the refrigerant subcooling when condenser airflow or water flow are reduced? Many people instinctively say that the subcooling would decrease if the airflow across the condenser decreased. After all, the air is what is cooling the refrigerant – if you have less of it, the refrigerant will not be cooled as well – so you might expect subcooling to decrease when airflow decreases. The only problem with this is that it is exactly backwards. In fact, decreased airflow in an air cooled condenser usually causes an increase in condenser subcooling. Remember subcooling is just telling you the difference between the condenser saturation and the liquid temperature leaving the condenser. Condenser pressure and saturation temperature both increase with reduced airflow. Most techs understand that. While the condenser saturation temperature increases a lot, the liquid temperature does not rise as quickly. The increased condenser pressure also contributes to increasing the compression ratio, so the compressor moves less refrigerant. The increased compression ratio and the increased saturation temperature cause the condenser to hold more liquid refrigerant than normal. The liquid sits longer in the condenser and has longer to be cooled below saturation temperature. Since the liquid is starting at a higher temperature compared to the air circulating over it, it tends to lose temperature faster than it normally would. All this adds up to increased subcooling. 

This is easy to verify. Start a unit, let it run a while, and check the subcooling. Now block the condenser airflow and watch the condenser pressure and liquid line temperature. You should see a big increase in the high side pressure while the liquid line temperature stays about the same or increases just a little. One caveat – don’t let the unit run too long with a blocked condenser – unless you want to run the “what happens when the compressor overheats” experiment. Monitor the compressor temperature to be on the safe side. I am not responsible for you destroying your unit while checking this out. Better to use one at school. (After asking the instructors of course)

Sunday, September 28, 2014

Manual J Resources



Are you looking for materials to teach load calculations? ACCA has free excel spread sheets they call speed sheets. You can download them from their web site. They also offer a curriculum for studying Manual J8, also free from ACCA. You do have to buy either Manual J8 or Manual J8 abridged to take full advantage of these. If you are looking for load studies coverage in a text, “Fundamentals of HVACR, 2nd ed” has a complete Unit on residential load studies. It includes examples using Manual J8 while working on a complete block load for a small house. Other Resources include Wright-Soft’s Right-J program or Elite Software’s RHVAC program. These are two very full featured commercial programs which are used a good deal in the industry. The good news is that you can download and use demo versions of them for free. Typically, there are a few limitations on the free download versions, such as not saving the files. However, you get a chance to try them out before purchase.

For teaching, I really like the ACCA Manual J Speedsheets. They are not too hard to learn, and I believe that students get a better understanding of Manual J because they do have to use the manual some to use the software. I also like the Manual D Speedsheet for ductwork. Both of these are a little limited – they are mainly for use in residential systems that are not too complex. But that is exactly where our students should be starting. We typically have our students do a block load on a small cabin and a room by room load on a 3 bedroom ranch style house. They then do a radial duct design on the cabin and an extended plenum on the ranch house. You will want to spend some time with the speedsheets before giving them to students. Although they are not difficult, there you do need to go through one a couple of times to feel completely comfortable. The instructions are in the sheets and there are ample examples on every tab. Links to the  resources mentioned are