Residential Combustion Analyzers

To measure combustion efficiency you need a tool that can measure either the oxygen or CO2 content of the combustion gasses. For many years, an hour glass shaped bubbler containing a fluid that absorbs CO2 or O2 was used. They are difficult to find these days. They have been replaced by electronic instruments. These use an electro-chemical reaction in an oxygen sensor to measure the O2 content in the flue gases. They use thermistors to read the flue gas temperature and ambient temperature, so they have all the information that need to calculate and display combustion efficiency. They use this information to display CO2 %, O2 %, combustion efficiency, % excess air, flue gas temperature, and net stack temperature. Most offer other measurements as well. Some of the more common additional features include:

• CO ppm – to read the CO in the flue gas

• CO ppm air free – to calculate the CO ppm after removing the excess air

• Draft pressure – to insure you actually have a draft

• Differential draft pressure – to insure the draft pressure is lower than the room pressure

• NOX – to comply with NOX regulations in areas that restrict furnace NOX emissions

• Printer – to print out reports from results

• Computer Connectivity – to import data from analyzer to programs on your computer

Prices vary a good bit. From just over $500 for no-frills analyzers intended for residential work, to several thousand for commercial instruments. Certificates of NIST traceability often cost more.  Most combustion analyzers use electro-chemical sensors. These have a limited life because the chemicals in them are used up as they work. Typical replacement time is every one to two years. Some are user replaceable, and others require sending in the tool for the sensors to be replaced. This will typically cost $200 - $300. The table below compares several of the lower priced models which are aimed at the residential market.

	Bacharach Intech	Testo 310	UEI C75	E Instruments BTU 900
O2	yes	yes	yes	yes
CO2	yes	yes	yes	yes
Efficiency	yes	yes	yes	yes
Excess Air	yes	yes	yes	yes
CO	yes	yes	yes	yes
Air Free CO	yes	yes	no	yes
Draft pressure	no	yes	no	yes
Differential Pressure	no	no	no	yes
NOX	no	no	no	Can upgrade
Printer	Available Extra Cost	Available Extra Cost	Available Extra Cost	Available Extra Cost
Computer Connectivity	no	no	No	USB & Bluetooth
Field replaceable sensor	yes	no	no	yes
Fuels	6	5	5	10
Warranty	2 years	2 years	3 years	2 year
Approximate Street Price	$520	$600	$500	$1000

Combustion Efficiency

Fall tune up season is here. A seasonal check on a gas or oil furnace should include a check of the combustion process. To do a good job you really need to measure the combustion efficiency. To measure combustion efficiency you need to take two temperature readings and one flue gas reading.  The temperatures are the flue gas temperature and the ambient temperature around the unit. You subtract the ambient temperature from the flue gas temperature to get what is called the net stack temperature. The flue gas reading can be either CO2 or O2.Generally oxygen is preferred. For a gas furnace, perfect stoichiometric combustion produces 12% CO2 in the flue gas. The CO2 percentage drops off if the process is either too rich (too much fuel) or too lean (too much air). At the perfect stoichiometric point the O2 will still be 0% because all of it is being used in the combustion process. As excess air is introduced into the process, the O2 begins to rise due to the oxygen content in the air that was not used in the combustion process. Excess air is introduced to insure complete combustion. Note that complete combustion is not the same as perfect combustion. In perfect (stoichiometric) combustion, ALL the fuel and ALL the oxygen are used up, producing ONLY carbon dioxide and water. In complete combustion, all the fuel is used up, but not necessarily all the oxygen. Lack of combustion air produces incomplete combustion. Incomplete combustion leaves some unburned carbon and carbon monoxide. Excess air is introduced on purpose to prevent the production of soot and CO in the flue gas. The figure below shows the relationship of CO2, CO, O2 , and excess air. Next week we will discuss some of the ore practical aspects of measuring the combustion process.

Ride All the Rides!

Ride All the Rides!

Undoubtedly, many of you will spent  some time this past summer at an amusement park, water park, or other recreational establishment. Many parks now have a single price for admission that lets you ride all the rides as many times as you like. After paying the price of admission, most folks try to ride as many rides as possible to get their money’s worth. I can remember planning out my day at Disney World so that I would make the most of my time. I can see many of you smiling because you have done the same thing and planned a manic day at a pricey amusement park so you would get your money’s worth. I read recently that a year’s pass to Disneyland was now over $1000. I would have to be riding stuff every day if I paid that. So here is my question. Why are we so intent on getting our money’s worth at an amusement park, but beg to be cheated in education? When you pay your tuition for the semester, you are paying to ride all the rides. Every lecture, every lab, every online assignment, and every test you already paid for when you paid tuition. Chances are, your tuition was more than $1000 and it was not for an entire year. If you think tuition and fees are high, why would you not take full advantage of all that you paid for? Try reading the assignments more than once. It does not cost any more, and you get more out of the assignment. When you miss a lecture, lab, or assignment you are cheating yourself. Not only are you not taking advantage of the services you have paid for, but you are also limiting your earning potential later on. My brother Richard has a saying “work hard at school, or work harder all your life.” People with jobs which require less education and skill work harder and longer for far less money. HVACR is a very performance based industry. If you can’t perform, your earning potential suffers. Your diploma may get you in the door, but it won’t keep your job. HVACR is also a very technical field. To excel, you need to understand the systems and how they operate. Sure, without a lot of training you can get a job holding the other end of heavy things or running to get tools for other people. But without training or education, you won’t advance much past that point. And of course, the folks holding the other end of the furnace don’t get paid the big bucks. Attending school is not the only way to learn your trade. There are many ways to educate yourself, but the easiest and fastest is to go to school. Throw yourself into your studies. Attend all the lectures, read all the assignments, and do all the labs. Ride all the rides!

Duct Cleaning Cuts Allergies

Occasionally I have a "guest speaker" provide the weekly article. This week, Gary Arena provides a some insight into the benefits of duct cleaning. Enjoy.

Allergies
Allergies can be a serious problem for someone’s overall health. The high concentration of pollen has been at an all-time high this summer, and overall allergies are increasing each year. Sensitivities to mold, mildew, dust and dirt can make everyday life a struggle. When a home air adaption is supplying air that contains these allergens, life can be quite miserable.

Benefits of Air Duct Cleaning and HVAC Restoration:
By removing this containment from a home air adaption, the effect is greatly reduced. Clean, healthy, circulating air is a must for those highly sensitive people. It is not unusual for a person to realize immediate relief upon completing a cleaning of a home heating, ventilating, and air conditioning adaption.

 
Here are the top 9 triggers that contribute to asthma attacks and allergy symptoms:
1. Dust Mites

2. Mold

3. Second-Hand Smoke

4. Cockroaches and Pests

5. Pet Dander and Hair

6. Wood Smoke (solid burning fuels)

7. Outdoor Air Pollution

8. Nitrogen Dioxide (from gas burning appliances and utilities)

9. Chemical Irritants

When dirt and debris are removed from ductwork, the fans and motors that power a furnace no longer need to work as hard to distribute air. Advising people to routinely get their air ducts serviced and inspected is important. Not only does this properly maintain a building, but it keeps the quality of indoor air as pure as possible!

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Written by Gary Arena from DUCTZ of Greater Lancaster and York Cities. Gary is the owner of the professional air duct cleaning company in central PA and is proud to serve a locally and family-owned franchise.

Managing Large Numbers of Lab Students

The easiest way to manage your lab is to have one lab instructor for every five students. I have actually taught lab classes where we had this ratio and it was a lot of fun. We were able to spend a lot of time with each student and we were able to do things you just can’t do with larger groups. So what if you have more like 20 students per lab instructor? It is still possible to give them a good lab experience, but a lot more planning and organizing will be required up front, and there will be things that are just not practical. One management technique is to split up large groups into smaller ones and schedule them at different times, effectively making several smaller lab classes. Of course this means you must spend more time than usual since you will be repeating the lab for each group. This may not be an option for everyone depending upon the number of instructors, students, lab equipment, and available lab time. For most of us, there will come a time when we have to work with larger groups in the lab.

A common technique is to have students work in groups. I try to avoid this if possible because it often means a couple of confident students do the work and the rest of the group watches and writes down the results. In group projects, you can see the 80/20 rule at work: 80% of the work is done by 20% of the people. However, this can be managed if you know it is going to occur. Ask every member of the group a question that requires an understanding of the process. If they know they are going to be asked to perform a task or answer a question, they will at least pay more attention to what is going on.  For example, if the group is measuring the superheat on an air conditioning system you might ask different students

What is superheat?
What measurements are required?
How did you arrive at the current superheat?
What readings are necessary to use the manufacturer’s superheat charging chart?
What does the system charging chart say the superheat should be?
Compare the manufacturer’s specification to the actual operating superheat?


Some skills are so important, every student must perform them for you individually. Lighting an oxyacetylene torch is one example. An issue with large groups is simply the amount of equipment and tools available. Most of us would be hard pressed to come up with 15 oxyacetylene torch sets so that every student could have their own. Besides, I really do NOT WANT to have more than three rookies working torches at the same time. Once when I had a class of 18 students who needed to learn to braze, I worried about how I was going to teach all of them to handle an oxyacetylene torch safely. What I did was to demonstrate, as I always do and then ask questions to see what people remembered. We then went back over the procedure, paying particular attention to things that I felt they had missed the first time. Finally, I lined them up and had each student turn on the tanks, set the regulators, light the torch, adjust the flame, shut off the flame, and shut down the torch leaving it ready for the next student. If they hesitated, they repeated the process. I noticed that the students got progressively better, which was odd because the most confident students had stepped forward first. When I remarked to one student on how quickly and confidently he performed the task he replied “I saw it done 10 times before I had to do it.” In other words, the students waiting in line learned through the experience of their fellow students. This made me feel less guilty about having everyone wait in line to work with me. This method works well for procedures that can be demonstrated in a few minutes such as lighting torches, soldering, brazing, or installing gauges. If the students use their time wisely and pay attention to what is going on they will learn by watching others and everyone leaves with an important skill they did not have the day before.

Labor Day

As we celebrate this Labor Day I am reminded of the many Americans who don’t want a day off, they are looking for a day on. Your job provides you with more than the financial means to support yourself. For most of us, we are identified by our profession. One of the first things people ask when meeting is “what do you do?” Having regular earned income also gives us a way to be more in control of our destiny. With a predictable source of income, you can better manage your life. This is crucial for people wanting to improve their lot in life.

I truly believe all our political leaders want to help. We would all like for everyone seeking employment to find it. There have been many attempts by government at all levels to pass legislation that would stimulate the economy and create jobs. Many of these programs focus on training people for jobs of the future. The problem is that it is very difficult to accurately predict the future and create truly new jobs, particularly in new and emerging technologies. I believe we would have more success investing our time and money training people for jobs that already exist, particularly in fields where industry growth exceeds the available workforce. HVACR is one such industry.

Jobs are available now for skilled HVACR technicians. Money spent in technical education prepares students for real jobs that we know exist, not jobs that we wished exist. Further, if you want new emerging technologies – train folks for commercial refrigeration. Commercial refrigeration is undergoing a major transformation involving new energy-smart, earth-wise technologies.  So training people for a career in commercial refrigeration IS training for jobs of the future. The lack of qualified technicians is limiting HAVCR contractor’s growth, which limits the growth of the nation’s economy. Again, these job opportunities exist NOW.

Preparing people for a real job that pays real money makes them a contributing taxpayer. This means that the government gets the money back. Some HVACR students will be successful enough to start their own business. There are several in the Athens area who started as students at Athens Tech. One relatively small business with five employees can gross $1,000,000. That generates tax revenue of $150,000 at 15%. If those five employees are trained at Athens Tech, the cost of their training is less than one year’s tax revenue. Not all students will generate that kind of return, but even a student earning $12 an hour will likely pay back the cost of training in less than five years. For people who already have a job in HVACR, education makes them more productive and earns them more money. Increased productivity means a better bottom line for the government – more income to tax. It is not necessary to start new programs with new administrative costs; there are already programs and institutions in place with proven track records of training workers for skilled trades. All we have to do is support them.    

What Flavor is Your CO2 System?

If you work in any phase of refrigeration, you undoubtedly have heard about the emergence of CO2 refrigeration systems in commercial refrigeration. I had the pleasure of touring the HillPhoenix Refrigeration plant in Conyers today, and I was impressed by both the number and variety of CO2 systems they are currently building. They had Cascade systems, Trans-critical systems, Glycol systems and Booster Systems all using CO2. These are distinctly different approaches to working with CO2.

The transcritical has probably received the most press. It derives its name from the fact that the high side operates above the critical point while the low side operates below the critical point. The name indicates that the system operates on either side, or across, the critical point of the refrigerant. The critical point is the pressure and temperature at which the refrigerant can no longer condense to a liquid. So the “condenser” is really just a gas cooler. The refrigerant does not condense to a liquid until AFTER the pressure is dropped. The critical temperature of CO2 is 88°F, so any time the high side temperature rises above 88°F, the refrigerant will not condense. The pressures are bit higher than you might be used to – over 1200 psig, so not just any compressor and piping will do. However, in a way, the transcritical systems are a bit simpler than the other flavors.

Cascade systems use two complete refrigeration systems – one system’s job is really to cool the condenser of the other system. If you keep the CO2 cold enough, say 40°F, the pressures are not that high. However, to have a 40° condenser requires a system whose evaporator is in that same temperature range and whose condenser is at the normal operating temperature for an air cooled condenser. This system typically uses HFC refrigerant. So you have a heat exchanger and an HFC system to keep the CO2 system cool. This allows wider range of compressors because the CO2 compressors are not operating at 1200 psig. However, the system operating with the normal temperature condenser (80°F – 100°F) will have a refrigerant OTHER than CO2.

And then there are the booster systems. The booster systems incorporate both low and medium temperature racks into a single unit. The low temp CO2 compressors pump into the suction of the medium temp CO2 compressors, which operates at transcritical temperatures and pressures. This way the low temp compressors don’t have to be heavy duty transcritical compressors, just the medium temp compressors. The system uses only CO2, no HFC refrigerant is required, as in a cascade system.

There are also glycol systems, where the refrigeration system cools glycol, which is pumped through the store to the cases. This reduces the amount of refrigerant in the system and reduces leaks by reducing the amount of piping, fittings, and braze joints. What became apparent in my visit was that there are many ways to solve the same problem, and you can expect to see different solutions at different locations. It also is apparent that in commercial refrigeration, CO2 is here to stay and HFCs are on their way out.