Survey after survey has shown that a large percentage of HVAC systems are not operating at peak efficiency due to insufficient indoor air flow. And, the chief reason for that condition is a problem with the supply air duct system. In many cases the heart of the problem is a leaky duct system that needs sealing, or, in some cases, the problem is a combination of a duct system problem along with negative factors regarding the building envelope.
In Figure One, we’re showing an elementary indoor air handling system and a simplified living space that should be able to handle air properly and maintain the desired comfort level in the building while operating efficiently.
It’s a simple process to understand the fundamentals of an air handling system as we’re showing it here, with the trunk and branch duct, along with the register boxes and diffusers delivering air on the supply side of the system while the air intake, duct and plenum on the return side allow for air to get back to the air handler with a little resistance as possible. Taking a simple approach to understanding the process of moving air throughout the structure also requires a more refined understanding of a supply duct system. For example, consider the two velocity bonnets shown in Figure Two.
In both cases, the design shown here is considered to be sufficient to allow air to be propelled from the air handler into the duct system in the proper volume and velocity, the first step in ensuring proper air flow throughout the building. To put it simply, either of these two installations would be considered ‘good’. In Figure Three, though, our two examples illustrate a different point.
In this case, one of these two static take-offs would ensure that the duct system would be off to a good start, while the other may not. The illustration on the left is considered a ‘good’ design, while the one on the right is only ‘acceptable’.
The point to consider here is that an overall evaluation of the performance of this system may show a temperature drop across the indoor coil that may be slightly higher than it should be, or ‘acceptable’ (indicating that the volume of air is not a sufficient as it could be) while it should be ‘good’ in order to ensure an efficient operation of the system. And, the follow-up point to understanding this situation is that it may not take a major modification to the duct system in order to get to ‘good’. Consider the two illustrations shown below.
In Figure Four we’re showing a supply duct system that is in trouble due to the fact that the design called for a static take-off very close to the elbow. And, as you can see, there is a problem with turbulence in this elbow, resulting in an air flow problem. In Figure Five, the problem is solved with the addition of turning vanes that will promote proper air flow, not only in the first branch of the duct system, but also throughout the entire supply and return air duct system.
Learn From Yesterday…..Live For Today….Look Forward To Tomorrow…
At the root of any study that compares human beings to all other animals on earth is the simple understanding that the one thing that makes humans different is their ability to reason. And, of course, that’s a good thing…..most of the time. However, after a lifetime of study of how human beings think, I’ve come to the conclusion that, in certain situations, due to the ability to reason, people sometimes uncessarily complicate somethng that isn’t complicated. For example, I recently presented the following troubleshooting problem, which is straightforward and not complicated:
AN A/C SYSTEM THAT’S NOT KEEPING THE HOUSE COMFORTABLE
In this troubleshooting situation, our customer’s description of the problem is “not cooling” and “blowing warm air”, and the equipment that is supposed to keep this residence comfortable is a split system that has been in service for sixteen years. The service history of this unit includes several electrical repairs, and in one instance, a leak in the sealed system was found and repaired.
When you arrive, you find the following conditions:
- The indoor temperature is near 85-degrees.
- The thermostat set-point is 70-degrees.
- The indoor fan motor is running normally, and you determine that the indoor air flow is sufficient.
When you go to the condensing unit to continue your evaluation, you find that the outdoor fan motor and compressor are operating on this R-22 system, and, after confirming proper air flow through the condenser coil, you measure an ambient temperature of 90-degrees. When you connect your gauges to the high and low side access valves, you read the following pressures.
- Low-side pressure: 90 PSIG.
- High-side pressure: 170 PSIG.
To complete your diagnosis, you apply the pressure readings to the temperature scales on your gauge set, and you also measure the current draw of the compressor as lower than normal.
Your troubleshooting question: What is the specific failure that is preventing this system from cooling properly?
I received a variety of answers to this question, most of them incorrect. And, like I said, I’m convinced that the underlying reason for this is the tendency of people to complicate something that is straightfoward and simple. In this case…..troubleshooting an HVACR system that’s not performing as it should…. the simplicity lies in two fundamental processes:
1. Troubleshooting is always a systematic elimination of the possibilities.
2. Knowing what right is in the first place so you’ll know what wrong is when you see it.
On the first point, we accomplished a lot of elimination in the description of the problem. The indoor air handler was operating…indoor air flow was sufficient, which proved that the evaporator coil wasn’t dirty…the the outdoor fan motor was operating and the condenser coil was clean…and the compressor was running. So, we eliminated all of the possibilities in regard to the air flow and electrical systems, which means that the problem lies in the refrigeration system.
And, that brings us to the second fundamental process…knowing what right is in the first place.
In our problem situation, we stated that the low side pressure reading was 90 PSIG. When you apply the fundamentals of the operation of a comfort cooling system, knowing that what you’re looking for is an indoor coil temperature of approximately 40-degrees, and you apply that knowledge to reading the R-22 scale of the gauge, what you find is that the low side operating pressure is supposed to be approximately 69 PSIG.
So, the conclusion here is that our low side operating pressure is higher-than-normal.
Regarding the high side operating pressure, we stated that our gauge showed it to be 170 PSIG. Again, consulting the R-22 scale on a gauge and adding 30-degrees to that figure to allow for the heat of compression (after all we did say that this unit was in service for 16 years, which means that it is a standard efficiency unit, so 30 is the number we add to the amibient temperature to calculate what the high side should be on this particular system), you’ll find that the operating pressure in a 90-degree ambient is supposed to be approximately 260 PSIG.
So, the conclusion here is that our high side operating pressure is lower-than-normal.
And, when you put our two conclusions that are understood from the fundamental perspective of knowing what right is in the first place….a higher-than-normal low side pressure reading and a lower-than-normal high side pressure reading… together, along with the other fact we stated (the current draw of the compressor is lower than it should be), the diagnosis is that the compressor is not working due to a valve failure. When comperssor valves fail to seat properly and no longer internally separate the low side from the high side, the compressor cannot pull down properly on the low side, nor discharge properly on the high side. In essence, it’s “not pumping.”
A simple and un-complicated conclusion, arrived at by applying the two simple and straightfoward factors we stated above.
Learn from yesterday….Live for today…..Look forward to tomorrow.
It’s funny how some simple thing can jog a person’s memory and make them think of some other minor thing that happened to them long ago. It happened to me the other day, and the image that came to mind from a very distant memory was a cartoon I saw in a magazine. It showed a man who was smiling broadly and standing at an apartment door, about to knock. He was holding a jug of wine in one hand, and he had a loaf of bread tucked under his arm. On the apartment door, it said “Thou.”
This cartoon made me chuckle…it still does today when I think of it.
And, maybe you understand why that cartoon made me laugh. Or maybe you don’t. If you’ve never had an interest in poetry, you likely don’t understand. If you do have an interest, perhaps you remember that the line “A jug of wine, a loaf of bread–and Thou” is from a poem written in the Persian language by somebody named Omar Khayyam, a writer whom history tells us was born in the year 1048, and died in 1131. Shortly after his poems (he wrote about thousand) were translated into English, the people who read the poem that the line above is from pretty much latched onto the idea that it was a romantic way for a man to say to a woman that all he needed to be happy was a jug of wine, a loaf of bread, and her.
And, I’m inclined to agree that that’s what Omar intended to say with that line, hence the reason for the cartoon being funny to me. The guy at the door has his wine and bread, and all he needs now is the person standing on the other side of that door….Thou….and he’ll have all he needs to be happy.
OK, it’s not fall-down laughing funny, but it’s still funny; that is if you know about the line from the poem and have an understanding about what it means to you.
So, in consideration of this cartoon….if one person looks at it and it makes them laugh, and then a second person looks at it and doesn’t see anything funny about it, does that mean the person who laughs is “smarter” than the person who doesn’t ‘get’ it?
No, it doesn’t. It just means that the first person had more information than the second person…information that isn’t hard to understand. It’s just information that any person who has the ability to read can understand, or the ability to listen can grasp if they are being taught by someone else on the subject, in this case, poetry, can understand.
What does this have to do with HVAC technicians? Well, a while back I was facilitating a training workshop on electrical and refrigeration system troubleshooting, and at the end of the workshop there was a test. For the most part, adults – especially adults who are technicians – are not comfortable taking tests. The anxiety mounts as the time to take the test nears, and they begin to doubt their ability to pass the test more and more. And this anxiety is rooted in the belief that only “smart” people can easily accomplish a test…a belief that isn’t true. As the title of this segment says, “Nobody is any “smarter” than anybody else.
So, “smart” doesn’t have anything to do with passing a certification exam. Being exposed to information that can be understood, either through self-study or by attending a training session that covers the subjects the test is going to cover is all it’s about.
Anybody who read my explanation of the cartoon and why it made me laugh can accomplish the same thing in regard to a NATE certification exam, or any type of exam. (Not that everybody will laugh at the cartoon. They may understand why I laughed, and still not laugh just because they don’t think it’s funny and they don’t share my sense of humor…but they still understand,)
Learn from yesterday…..Live for today…..Look forward to tomorrow
It’s been said that the “The customer is always right” came into being as a familiar slogan some time in the early 20th century and was championed by both Marshall Field, who established his first retail store in Chicago in the late 19th century, and also by another department store founder, Harry Gordon Selfrigde from the United Kingdom. The general consensus is that one of them coined the phrase, but no one is sure which one. However it came about, it’s something that everyone who is in any sort of business that provides goods and services to customers has heard (and possibly had it drilled into them).
From a common sense perspective, I don’t believe that these entrepreneurs intended that the slogan be taken literally in every situation. What they were attempting to do was to make the customer feel special by training their employees to behave as if the customer was right, even when they weren’t. And, I would agree that this is not entirely a bad idea. After all, when a customer makes a purchase and it turns out that something isn’t right about it, a person can be quite upset about the situation and not be vere pleasant to deal with because they are afraid that they may have wasted their money and the business they dealt with may not be willing to ‘make it right’, or that they’ve invested time and effort in a purchase that resulted in a problem and now they’re stuck with something they don’t need or want, or it doesn’t suit their needs the way they thought it would.
So, the bottom line is fear. In the human condition, fear is the basis for all negative emotions. Fear of loss of some sort, whether it be financial or personal. And, when you look at it from that perspective….that somebody is frightened and it’s resulting in their less-than-pleasant behavior, I believe that you, as a business person or customer representative, should be committed to doing the best job you can do to work through that, and hang on to the belief that the “customer” is always right.
However, I’m also convinced that once somebody does anything that is deemed untoward behavior, such as being dishonest or abusive in an attempt to get what they want, then they are no longer a “customer” and the philosophy that they are “always right” no longer applies to this person.
I recently was involved in a sitution in which I had to deal with a “person” who purchased one of our DVD training programs. It was “HVACR Electrical Troubleshooting: Deciding Where To Begin” and he purchased it through an on-line retailer, and he requested expedited shipping. We shipped the item the same day, and within a week received a notice from the re-seller that this person wanted to return the program because he claimed that it didn’t follow through with a complete diagnosis, and then complete instructions on part replacement for each of the problems discussed. When we responded that the title….”Deciding Where To Begin”…..and the description of the program content was clear, the story changed.
It wasn’t that the program didn’t turn out as advertised after all, it was that he had mistakenly purchased the wrong program, intending to buy the title “Electrical Fundamentals For HVACR Technicians.”
And, when I got involved further with this person, the story changed again. The real reason for the return, he said, was because he was sure that what we sent him was a ‘bootleg’ copy and not an originally produced and dubbed product.
And, once I got into a phone conversation with this person, I never even got to complete a sentence when I was told that the reason for his wanting a refund was “none of your F-ing business!”….twice.
Of course, my response to this was exactly what it should have been. Although I certainly understand that the basis for his anger was fear, it was no longer my obligation to consider him a customer, and he certainly was no longer right, so I fired him. Yes, sometimes a business has to ‘fire’ a “person” who might have started out as a “customer”, but turned out to be a dishonest ( actually, a thief and a liar in this case who convinced a huge corporation that he was entitled to a refund when he was not ) and unnecessarily abusive individual.
Learn from yesterday…..Live for today…..Look forward to tomorrow
This is a story about a house in Tucson, Arizona. A house that, like most that are in a neighborhood, is situated between two other houses. And, this particular house, also like a lot of houses that have been affected by the real estate market crash, wound up being owned by a bank, and subsequently became available on the market as a foreclosure and offered for sale at a cash price.
The sequence of events that followed were that the bank set a sales price, but then changed that price due to information they received from the tenant who was living in the house (and was in the process of being moved out so it could be sold). According to them, the air conditioning system, while it would keep the building comfortable in mild weather, didn’t perform properly once the middle-of-summer temperatures occurred.
Based on that information, the bank decided to adjust the price of the house down $5,000.00 to allow a credit for replacing the roof-top package unit on this 1100 square-foot building. They arrived at this figure after getting a quote from a service company that evaluated the situation and confirmed that, yes, the unit was ‘dead in the water’ when it came to performing up to full capacity in warmer weather. This diagnosis was ‘confirmed’ by an HVAC technician who happened to live next door on the North side of this house. He said that he had also had an opportunity to look at the equipment, and tried to add refrigerant in order to get it to perform better, but it didn’t help, and he therefore determined that the only solution was to replace the unit.
During all this, I happened to be working on a remodel on the home next door on the South side of this house. (And, yes, I’ll admit that I was pretty much enjoying this scenario as it played out.)
Once the sale of the house was accomplished at the $5,000.00 discounted price, and the building had been cleaned out and fumigated…lots of dust, dirt, filth, and roaches involved here…I now had the opportunity to get into the building and evaluate the performance of the air conditioning system.
My first task was to perform a temperature-differential test across the indoor coil, which showed that the temperature drop was an alarming 29-degrees Fahrenheit. Wow….far lower than it should have been. And, while I could have then gone further with the evaluation of this equipment by performing a static pressure test, I decided to just go ahead and access the indoor coil for a visual inspection. And, I’m sure many of you who are experienced technicians and reading this, know what I found: An indoor coil that was nearly totally covered with damp, dusty, musty, muddy dirt, dog hair, roach excrement etc… on its contact side, preventing any chance of proper air flow through the coil. Inspecting further, I also found something else you would expect. The fins of the squirrel-cage blower wheel were also caked with thick layer of some mostly indescribable, disgusting material.
As is often the case, accessing the indoor coil in order to get the contact surface clean, and then use a coil cleaner to complete the process of clearing the rest of the debris that had collected deeper into the fins and tubing wasn’t an easy (or pleasant) task. And, the removal of the air handler so it could be taken down off the roof to make sure it could be properly cleaned, also took some time.
But, once the clean-up work on the indoor coil, the air handler, and the condenser coil, was done, and an evaluation of the TXV metering device refrigeration system was performed to ensure that there wasn’t an overcharge, a subsequent test of the temperature drop across the indoor coil showed it to be a respectable 18-degrees, and a static pressure test showed a differential of only .04 WC (Water Column Inches).
And, within a short time on this 100-degree ambient temperature day, the building was perfectly comfortable, both in regard to indoor air temperature and humdity.
The bottom line here? The cost of a gallon of coil cleaner pumped through a pressure sprayer on the coils, along with the de-greaser used on the blower wheel that was removed for cleaning, didn’t add up to anything near $5,000.00.
Until next week…
Learn from yesterday….Live for today….Look forward to tomorrow
It’s always been my personal opinion that the residential HVACR technician is, as they say, a ‘different breed of cat’….a bit different than an electrician, a plumber. And when I say different, I don’t mean from a hands-on or craft perspective. I’m talking about the desire to be independently employed.
I don’t really know if my percentage estimate is right, but to say that somewhere in the neighborhood of 95% of the technicians in the heating and air conditioning business either have been, are, or have a stronger-than-average desire to be, in business for themselves, feels right. And, in my experience in working with the other crafts mentioned above, I don’t get the same feeling about those technicians. My feeling is that the being independent-and-owning-my-own business desire percentage is significantly lower for them than it is for HVAC technicians.
And, again, while I don’t claim to have hard statistics to support my hypothesis, my feeling about this is that this higher-than-average desire is the reason I often hear from HVACR contractors who are frustrated about losing an employee who has decided to “open their own shop”. I’ve heard things like, “I brought the guy on board as a green technician, and now that he’s got some field experience, he’s one of my competitors,” or, “After I invested two years in him, he walked out on me and started his own business.”
(By the way, the subject that’s kind of related to this is losing a technician to another service company….on this one, what I hear is something on the order of, “I spent all that time and money training him and he left me for a lousy 50-cents an hour.”….so, some of what I’ve got to say on this subject will apply here, but, back to the technicians who “want to be on their own”.)
The first problem are regarding this higher-than-normal desire is that many technicians really don’t have a clue about what it takes in regard to covering expenses in order to operate a successful (meaning profitable) HVACR service business. All they see is the fact that their employer charges a significant amount per hour for labor, and that what they are getting in their paycheck is what looks like a very insignificant amout per hour. And their reasoning is either, “Heck, I can run three calls a day, be done by noon, and make more money that I’m making now,” or, “If I work the same amount of hours I’m working now, I’ll make twice the amount of money (or maybe even three or four times more!) than I’m making now.”
Umm…that reasoning is a bit off the mark there….no, wait a minute. I would be more correct to say that it’s actually not true at all.
Without going deeply into the boring and seemingly mundane details about licensing, workman’s comp, sales, marketing, (yes, there is a difference between those two things) accounting, taxes, adminstrative support, etc…that many technicians wave off and decide to get to later in the excitement of planning their ‘freedom of being on their own’ and allegedly doubling or tripling their income, it’s sufficient to say that the things listed here are the reasons you may hear, “I was on my own for a while,” or, “I used to be in business for myself,” in a conversation with an older and wiser technician.
Which brings me around (finally) to the title of this week’s segment, which is directed toward service company owners and service managers.
“The only thing that’s more expensive than training someone and losing them….is not training them and keeping them.”
My point here is that, as a service company owner or service manager, you certainly know about all the stuff I’ve been rattling on about, but that doesn’t mean that it justifies not doing the best you can do to offer in-house training to the technicians you employ or supervise, all the while helping them to understand that they are, in fact, in business for themselves as an “owner” of “their company” within your company because, not only do they get paid via an hourly wage or salary as part of their earnings package, they also earn money via a fair and just incentive program that rewards them for providing outstanding customer service and doing the best job they can do on a daily basis.
And, if it turns out that after an employer/employee relationship that has been beneficial to both parties ends, and the employee does decide to leave and establish a business of their own, there’s no reason to look upon that situation from an angry and frustrating lack and limitation perspective, and that ‘there’s only so much business out there’, etc…
Instead, understand that life happens when you look at things via a prosperity consciousness perspective (I wrote an entire book on this subject if you’re interested in knowing more about it) and remember the benefits that you both derived from the relationship that you had, and move on to hiring and training another person who will be a part of helping you succeed in your business.
Until next week….
Learn from yesterday….Live for today….Look forward to tomorrow.
There are a lot of people who like to ride bicycles in Southern Arizona where the weather is often pleasant enough that they can ride almost year-round. And, there are a lot of people who drive cars and trucks (let’s just say vehicles) in Southern Arizona who don’t like to encounter bicycle riders on the roadways. Unfortunately, those encounters are sometimes dangerous for the bicycle riders, and, sometimes, there are even confrontations between the bicycle riders and the vehicle drivers.
From the perspective of the bicycle riders, this shouldn’t happen. After all, their philosophy is that all they want from vehicle drivers is to share the road. There are even signs on the rural highways frequented by bicycle riders that have a picture of a bicycle on them, along with the phrase “Share The Road”.
I saw several of them on the rural road I drove along earlier today, and it occurred to me that these signs could be the reason that vehicle drivers are not happy about their encounters with bicycles on these two-lane highways. It occurred to me that the vehicle drivers don’t think that the “Share The Road” signs are really telling the truth, the whole truth, and nothing but the truth. It occurred to me that from the perspective of the vehicle driver, they’re not really “sharing” the road as much as they are “yielding” the road to bicycles.
Consider it from this perspective:
…A person is driving a vehicle down a rural roadway, on which the speed limit is 55 MPH.
…They find themselves coming up on a person riding a bicycle, which is not capable of achieving the 55 MPH speed limit.
…At the same moment, another vehicle is coming from the opposite direction in the other lane.
When this happens, the person driving the vehicle that has come up behind the bicycle, naturally has to avoid two things: 1. Running into the bicycle, and, 2. Moving into the other lane which would risk a head-on collision, or force the oncoming vehicle to go off the road. It’s possible that, instinctively, from the vehicle driver’s perspective, this is not “sharing” the road with the bicycle, but rather “yielding” to the bicycle. Which means that they (again instinctively, and not consciously) don’t think that the signs with the pictures are telling the truth, the whole truth, and nothing but the truth.
Which means that there is a simple solution to this problem. Replace the “share the road” signs with signs that read “Yield To Bicycles”, a sign that will tell the truth, the whole truth, and nothing but the truth. And when vehicle driver’s see a “Yield To Bicycles” sign, and they encounter a bicycle on the roadway in the situation described above, they’ll instinctively know that they’re being told truthfully what is necessary, and they’ll be willing to do it. No more dangerous pass-by’s for bicycle riders, no more confrontations that are a result of a misunderstanding between the people that ride the bicycles and the people that drive the vehicles.
And, what if we were to apply this idea, not to bicycle riders and vehicle drivers, but to technicians and customers?
Is it possible that there are times when a technician is, from their perspective, communicating correctly with a customer, but there is, in reality, a misunderstanding from the perspective of the customer, making them wonder if they are being told the truth, the whole truth, and nothing but the truth?
As a technical professional, it’s our job to be sure that the customer has a complete understanding of the service we’ve performed for them, why it costs what it costs, and why we were sure it had to be done the way we did it. Always make sure that the customer is certain that we’re telling them the truth, the whole truth, and nothing but the truth, even if it means you have to explain the same thing to them in more than one way, and ask them several times if they have any questions you can answer for them.
Until next week…..
Learn from yesterday….Live for today….Look forward to tomorrow
As we complete our discussion on the fundamentals of Carbon Monoxide in this segment, I want to point out that two other symptoms of low-level CO poisoning are headaches and confusion. And one example of these specific symptoms involves this case study of a situation involving an elderly resident. The factors in this case are as follows:
Complaint: Frequent headaches.
Observation: Elderly resident seems to be confused and disorientated at times, lucid at other times.
Building Type: New, energy efficient construction, one-bedroom, elderly housing unit.
HVACR Equipment: Heat pump.
Kitchen Equipment: Electric range and standard exhaust vent system.
Water Heater. Natural gas, in laundry room adjacent to kitchen.
Fuel-Burning Equipment Operation and Ambient CO Measurements: An initial test showed normal draft of water heater and no CO emissions from the vent into the living space. However, a secondary test with vent fan operating in the kitchen showed a significant loss of negative draft pressure in the water heater vent, resulting in a carbon monoxide spill, emanating from the laundry room.
To put it simply: Complaints from a resident of this specific type of housing unit could have easily been written off as a condition and/or other health issue related to advancing age. Instead, the actual source of the problem was insufficient combustion relief in the laundry room that wouldn’t allow the water heater to vent properly in the event of a drop in building pressure in the room adjoining the combustion appliance zone.
The two instruments necessary to accomplish the test procedures in this case study were a draft gauge, used for measuring the pressure in the vent system, and a device designed to measure ambient levels of CO in a building.
In addition to accomplishing ambient measurements of CO in a living space to determine if fuel-burning appliances are operating properly in regard the vent system as mentioned in the case study above, a more advanced level of testing, known as a combustion analysis, can be accomplished to further evaluate the operation of equipment. This process requires a more sophisticated device, one that is capable of evaluating the overall operation of the burners. In the example in Figure Two, we’re showing the factors that are evaluated when device that is capable of these simultaneous measurements is employed.
The equipment in this case is forced-air gas furnace with an 80% efficiency rating, and the procedure for obtaining these measurements is to drill a hole in the equipment vent (re-seal it with a high temperature silicone once testing is completed) and inserting the instrument probe into the opening. While this analysis print-out is showing the measurement several factors, note the two listings that are highlighted, the Oxygen level shown at 10% and the Carbon Dioxide measurement shown at 6.1%.
In this specific instance, a furnace of this type should show an Oxygen reading of 6 to 8 percent, and a Carbon Dioxide measurement between 8.25 and 9.5 percent. When comparing data regarding what the measurements should be, and the actual measurements recorded by the device, we know that the Oxygen level is higher than it should be and the Carbon Dioxide level is lower than it should be. This means that the furnace is not operating properly, with the burner is functioning in a condition known as under-firing. What this analysis leads us to is a diagnosis that the fuel pressure being supplied to the burners in this equipment is lower than it should be, and an adjustment is necessary to bring the pressure up to a proper level. This will ensure the correct ratio of fuel to air, and the proper operation of the burner.
In addition to vented appliances, non-vented appliances such as the gas range shown in Figure Three, could also be responsible for a CO spill in a building if the burners are not operating properly. To be certain that a residence is not experiencing excessive CO levels and that fuel-burning equipment is operating properly, ambient measurements in the building, and a combustion analysis of vented equipment, are necessary.
Until Next Week….
Learn from yesterday….Live for today……Look forward to tomorrow.
Picking up where we left off last week, another factor to keep in mind about cabon monoxide generating equipment and draft measurements is that the water column-inch measurement scale we mentioned is a very fine measurement of pressure. One PSI is equal to 27.70 inches of water column, and the draft measurements we mentioned relative to a natural draft appliance are a fraction of a water column inch. The bottom line regarding the proper operation of atmospheric draft equipment such as a water heater or natural draft furnace is that if a given CFM of air is removed from the building due to the conditions mentioned above, then some method of allowing the re-entry of the same amount of air into the building must exist.
An important factor to understand about this situation is that it can be easily written off as extremely rare because the general belief is that if it did happen, somebody would be killed by the CO spill, or at least become gravely ill and wind up in the hospital. As I said last week though, there’s such a thing as low-level CO poisoning, which doesn’t always result in an emergency trip to the hospital. Here are some numbers for you to consider about CO levels in a building, measured in what is referred to as an ambient measurement in PPM (Parts Per Million):
009 PPM: Maximum allowable concentration for continuous 24-hour exposure. In an outdoor situation, this standard is often exceeded in urban areas due to auto exhaust.
10 to 35 PPM: Occupants should be advised of a potential health hazard, particularly to infants, small children, elderly people, and persons with respiratory or heart problems.
35 PPM: Common action level for fire department and other emergency personnel to use self-contained breathing apparatus.
50 PPM: OSHA requirement for maximum allowable concentration for workers continuous exposure in an 8-hour period.
70 PPM: Concentration required for UL2034 alarms to sound when CO at this level is present for as long as 60 minutes.
36 to 99 PPM: Medical alert. Ventilation required.
100 to 200 PPM: Dangerous, a commonly accepted building evacuation standard.
150 PPM: Concentration required for some UL2034 alarms to sound when CO at this level is present for 10 minutes.
220+ PPM: Extremely dangerous.
When you consider the listings above, you immediately recognize a possible health hazard for many people. Note that many alarms do not sound until the CO level in the building is beyond what is known to be a health hazard for the elderly, those with health issues, or children. A fundamental way to consider CO alarms is that they are designed to go off in the event that the carbon monoxide level in the building reaches a point where it would be hazardous for a healthy adult male….based on requirements that were initiated via testing and research involving military personnel.
Another factor to consider regarding a CO alarm is when it was purchased. For the most part, the sensor in the alarm that reacts to the carbon monoxide has a shelf life of approximately two years from the date of manufacture. And most consumers are not aware of this, thinking that if they faithfully replace the battery and press the TEST button on their five-year-old alarm, initiating an audible warning, that they will be protected against a CO spill. The simplest way to explain this process to a customer is that then they press the button, what they’re testing is a button and a power supply only, not the ability of the sensor to function. The only way to properly assess the function of a CO alarm is to use a test kit that includes a plastic bag to surround the alarm and an aerosol container of a material that, once sprayed into the isolated area, will cause the sensor to react.
The technician advising a customer about CO should also be aware of other facts related to the dangers of carbon monoxide. Symptoms are often written off as being other health issues, such as the flu. In one hospital study of 100 patients who requested treatment for what they thought was the flu, 24 were found to be affected by low-level carbon monoxide poisoning. Health care providers, if they are going to confirm carbon monoxide poisoning, must accomplish a carboxyhemoglobin test, which requires taking a blood sample for analysis.
Until next week…
Learn from yesterday….Live for today….Look forward to tomorrow
It’s a tradition in the appliance and HVACR service industry that there will be a high level of concern about carbon monoxide in the fall, with technicians fielding questions from the customers about alarms and requests for testing equipment for proper operation. And, as the winter wears on, people tend to forget about the concerns they had at the beginning of the season because their assumption is that the threat of a (Carbon Monoxide, so identified with the chemical symbol “CO” since it is a product of carbon and oxygen) spill has been dealt with for another year, and they don’t need to be worried about it until the next heating season rolls around. The reason this is true is because most people equate a CO spill into a living space with a serious incident; the kind of thing you hear about on a news report about a furnace problem that results in someone getting killed.
However, from a technician’s perspective, there’s much more to the issue of CO safety, equipment operation and the alarms that are supposed to warn of an incident. One issue is what is commonly referred to as low-level carbon monoxide poisoning, which can be occurring in a residence or commercial building on an intermittent basis at any time of the year, and it goes largely unnoticed even though has an effect on the health of the building occupants. Consider the simplified building in Figure One.
The first thing to understand about this building is that its tight construction, along with several other factors, is that it’s possible to create a slightly negative pressure in the structure. Hence, the collapsed look of the house. And, in this typical home, the gas furnace, which is a natural draft type, the and water heater (which will almost certainly always be natural draft equipment), are in the basement along with the clothes dryer. On the main floor, there’s a range vent in the kitchen and a vent in the bathroom, and there’s a fireplace. And there is an attic vent system. Note what is happening to the vent system on the water heater and the furnace.
Both of these items, since they are connected to a common vent system, rely on a slightly negative pressure…likely in the range of -.02 to -.06 on water column-inch scale… to vent the by-products of combustion from the building. And when the pressure in the building is unaffected, or if there is either plenty of infiltration due to less-than-tight construction or a combustion relief system, this atmospheric vent system on these two appliances will operate as designed. However, in the event that the building pressure drops to a negative level, the vent system will back-draft, a condition we’re showing in our illustration.
One of the reasons for this condition is the vent on the clothes dryer, which expels approximately 150 CFM from the living space. Next is the kitchen vent, which, depending on the model, can send up to 250 CFM of air out of the building. In the bathroom on the second floor, the fan there, which is designed to vent moisture and odors, will also expel another 50 (or possibly more, depending on the design of the fan) CFM out of the building.
When you add the possibility that there could be infiltration from the living space up into the attic, and a possible open chimney damper on the fireplace, some, or all these factors, could create a negative pressure that allows for the back-drafting of any natural draft appliance. And, since carbon monoxide has a specific gravity of 0.98, meaning it is slightly lighter than air, an open basement door or infiltration from the basement to the living space will allow the CO to rise. And, since CO is so close to the weight of air, it will stratify and linger in the building.
Until next week….
Learn from yesterday….Live for today…..Look forward to tomorrow