For the purpose of this blog, low air flow is defined as indoor airflow in residential heat pump systems below the required minimum specified by the equipment manufacturer.
It is a documented fact that low airflow exists in more than 50% of heat pump systems in the U.S. (google “DOE/ENERGY STAR low airflow in heat pumps”). It is widely known that low airflow will cause auxiliary electric heaters to short- cycle by their auto-reset primary high temperature safety limits and become inoperative (as they are designed to do) by their secondary back-up safety limits. It is also widely known that low airflow will cause heat pump compressors to short- cycle by their auto-reset high head pressure limits. Both the electric heater and the compressor are subject to premature failure depending on the degree of low airflow and the length of time in use.
Please post your comments or questions.
Good Job! It’s about time
I agree. A large percentage of field calls my technical team go on, there is some airflow issue. The ability of the unit (any manufacture) to deliver capacity is directly related to air distribution. Poor duct systems = poor performance = poor comfort = poor indoor air quality etc.
Now look, you have me on my soap box. Reguards Joel
Great !! This I have felt like a lone ship at sea talking about airflow and all the problems associated with it. I have a burnt compressor that I use in classes that show the results of low air flow, But you put a different twist on it – This is vital information. We need this proof of what happens in heat pump applications. All I ever get is “this piece of crap ” “your equipment sucks” and it is not the equipment.
What ever you do keep this information coming as a trainer I will promote your findings and I will pass on the information to the other trainers that I deal with from the fractories I deal with all the way down.
Good job
I’m glad to see Warren finally take a step in the direction to educate the HVAC industry on a problem that has fore ever been on going in this business. Your statement in your most recent bulletin “The amount of compressor failures will increase with the mandated increased use of R‐410 refrigerant which has higher operating pressure than the soon to be banned R‐22 refrigerant” is without facts. I would suggest you don’t bash other OEM’s especially compressor manufactures without 1st making sure that your own house is in order. R410A units have been installed in large numbers since 1996 and these compressors (per Copeland publications) have lower failure rates than their R-22 compressors. I do agree with you that there are many a lingering issues in the field which does include low or improper air-flow. With the turn over in the HVAC industry it is an on going effort to continually train the personal in the field of the proper installation & service techniques. I suggest that in your next revised bulletin you provide detailed pictures of what type of heater failures occur due to a result of inadequate air-flow. I also recommend that you would include in your bulletin a minimum air-flow requirement for each Kw heater size along with an example using the electric heat temperature rise method formula(s) for determining air-flow in the field. I also might suggest that Warren go beyond the UL requirements & look at making their product more bullet proof to field installation practices by providing to the customer an air proving device that insures minimum air-flow. People continually ask me what is changing in our industry. I keep responding….”definitely not the basics, only the names & the faces”. Glad to see that you have jumped on the band wagon with the rest of us to help educate the field.
Reggie -
I do not believe that bashing is a correct phrase to use. Yes copeland has had a lower failure rate to this point. The key is 410 has had “limited” use. Large numbers? in comparing against traditional r-22 use “large numbers” is not quite a correct statement. Anything can be large and show huge increase in use when you start from zero. But I digress my point in support of the article is this – Without proper training, without proper understanding of airflow properties in all conditions there will be an increase in equipment failures.
For expample — Rememember the old Dail – a – Charge unit to weight in refrigerant ? that thing has been out for 25 + years. I get stunned looks when I tell students they need to weight in charges and verify static pressures and delta T when installing new units – Quite a few of these students have been in the business for those 25+ years. What do you think that these new fangled ideas about airflow are going to do to these guys??
I belive that IF we get OUR act together as an industry then most of the OEM’s will all be able to claim low failure rate on their compressors , BUT without proper airflow you will not get correct suction gas return temp and that is really what contributes to the longevity of the compressor. Regardless of the refrigerant. By Copelands own admission 80% of returned failed compressors are installation related – I agree and airflow is one of the most critical components of proper installation
Hi Reggie,
It is not our intention to bash any product – only to help solve the low airflow problem. We assumed that higher pressures from R-410 make the low airflow problem worse. As you point out, we cannot make that assumption because the R-410 compressors may even outlast R-22 compressors. We can’t say for sure that R-410 compressors are more sensitive to low airflow; we are only suggesting that possibility based on some reports from the field. We do know that both refrigerants require proper air flow.
We can and do make heaters more bullet proof, however that does not solve the low airflow problem for the compressors and often renders the heater inoperative resulting in ugly no heat calls. In fact, our heaters trip the secondary low airflow/high temperature limit when low airflow is present. At this point the heater is often blamed (even possibly bashed) and replaced with another heater which at some future point in time will more than likely be subjected to the same conditions (dirty filter, coil, etc.) and low airflow as the original heater was. During this period the compressor continues to be subjected to the uncorrected low airflow conditions. Making our product more bullet proof will only mask the low airflow problem. We believe that the system as a whole should be addressed by curing the common disease (low airflow) rather than continuing on the path of treating the symptoms. We need help from folks like you to make this happen. Thanks for your input.
I do training classes on Manual D and in this class I talk about proper airflow across electric heaters and this opened up many eyes . The problem with air flow is not just with heaters it affects cooling systems in a big way also. I want to let you know that I have been getting this word out for many years and will keep on trying
I have been doing customer technical support for distributors since the early ’90s. In that time I would guess that somewhere north of 75% of the problems I have encountered in the field, both heating and cooling, are indoor airflow related. I have also noticed (what a coincidence!) that most of the techs I talk to have no idea how to measure indoor airflow, or its importance.
I put together a class I call “Airflow measurement for the Working Serviceman” to teach techs cost and time efficient methods of measuring airflow in residential and light commercial systems using a digital manometer that they get as part of the class. The final homework assignment is to measure the airflow in the next 10 systems they work on. The reports back are staggering. 3 ton systems with about 700 cfm. 5 ton units running 1200 cfm (and 3 compressor failures in 4 years, I wonder why?). Needless to say, the classes are lightly attended. Four hours and $175.00 seems a lot to ask from somebody who makes their living by the hour.
It is clear to me that as an industry we have, and are, failing miserably in preparing the people who are working in our trade. In the words of my first service manger many years ago, “The first word in ‘Air Conditioning’ is ‘Air’, and if that isn’t right nothing else will be right either.” Somehow, as an industry, we have failed to get this across to generations of service techs and installers. Our problem is compounded by the way that, as efficiency levels go up, the tolerance for error in our equipment goes down. Airflow issues that were a minor nuisance in an 8 SEER system will kill a 13 SEER machine in short order.
Unfortunately the classes that I, and some of the others who have posted here, provide are just a drop in the bucket. We aren’t reaching enough people fast enough, and I don’t think we can. Also, typically, the guys who attend these classes are the ones who need it least. The guys we need to get to are the ones who can’t ever seem to find the time to take training classes.
I think that for the biggest improvement in the shortest time we need a better (read quicker and simpler) way to measure airflow in the field. A method and/or device that can give a fair estimate of airflow in a few minutes without disassembling the machine and without drilling holes. Probably temperature rise based, understandable by people who don’t speak “static pressure” or “inches of water column”. It may not tell them where the problem is, return or supply, but at least it will tell them that there is a problem, time to go get the manometer (and their service manager) and do some more checking.
Until that comes along, all we can do is keep on doing what we can do. I’m real glad to see a major player like Warren at least addressing the problem. Admitting that we have a problem has to be the first step to a solution.
I am also an instructor, I do mention in all classes about weighing in refrigerant and checking airflow, to the point of insisting that some sort of magnahelic gauge or manometer is used to check the air-flow before replacing any system.
After several years of asking and not getting a response I now get many more positive responses about Scales and Manometers. But the issue is not the students that come to classes, its like church on Sunday mornings, you don’t see many of the big sinners there. The fact is there is a huge percentage of the HVAC technical and installation people out there that never attend any formal training and don’t know near as much as they think they do but are out working every day and the consumer doesn’t have a clue,(so it is the sorry equipments fault.) Educating the public to insist on state tested and licensed HVAC mechanics would be great but I don’t see it happening, but educating the public about NATE recognized technicians and installers is a start that we all can push and advertise. As Reggie said we have a lot of issues in this industry, and I do believe that education is the key. We must educate our work force, the public, and the manufacturers. For instance the only thing in the directions for strip installation in the N:WORKSHEETS-NEW\ICP 8-4-08 is (to assure maximum fan efficiencies and to avoid limit switch cycling conform to ASHRAE and/or SMACNA recommendations. Now most people are not going to know what you are talking about and if they do they won’t have the proper books available.
I agree with Reggie the 410A its self should not be any more issue than R-22 with Airflow issues. But we could mention best performance is recommended with a .5 or less dry coil static. I don’t disagree that air flow with heat pumps is a big issue, so is proper piping, clean installation, controlling the refrigerant charge, as well proper installation techniques. To over come this the ultimate solution is an informed consumer that knows to call for an accredited company and people properly trained to do the job, I believe those days are a long way off.
Great idea Ed!
Low airflow is a real problem. Maybe we can hear some of the problems that people are seeing in the field. No doubt it reduces the lifespan of components, particularly electrical heating elements and compressors, and it reduces the realized efficiency of the product. The question is by how much and is it getting worse? This brings to mind several questions that need real data. We can start with opinions based on experience, as in this blog. Then hopefully someone will pick up the banner and do some real R & D. In my opinion, the problem is getting worse, not because of R410A or higher efficiency equipment, but because duct systems are getting worse, not better. Designers have always tried to minimize the duct system. Modern designs like open floor plans and larger windows, and we want the ducts inside the conditioned space –where there isn’t any room. Thus, the problem starts with design. Then it’s installation, especially if flex duct is used. The flex duct is not pulled tight, is twisted into pretzels, is not sealed properly, etc. Then, finally, it’s because no-one thought to add the effect of accessories like duct heaters, or high efficiency filters, or dirt in the filters, etc., etc., etc. All this reduces airflow and problems manifest. Some of this can be solved by EC motors that deliver constant airflow (to a point). Then as the filters get clogged or because of a restrictive duct system, the motor simply runs faster and faster. Until it reaches its maximum – either in speed or power. Then it slows down. In fact, you might notice it more with an EC motor because it will be a sudden drop in airflow whereas a more traditional PSC motor would be gradual (not sure which is worse). The real shame of it all is that restricting can cause the efficiency of the system to degrade significantly. That 13 SEER unit you just bought might cost you the same to operate over a year’s time as the 10 SEER you just replaced.
No kidding!
There are a bunch of “PROCLAIMED” HVAC CONTRACTORS that do not even carry a ductilator, or know how to use one properly!
The best one is two 10″ flex ducts on a 2 or 2.5 ton system! This guy is all over Atlanta!
What is even more hillarious….no actually it is sad, that some of your larger HVAC companies fall into this category, yet consumers are continually fooled and paying the bill!
Atlanta and the surrounding areas has a bunch of them!
I am making a living off these knucle heads just on word of mouth, with a minimal advertising budget!!
Common sense: AIR IN = AIR OUT
We have been working diligently on various causes of low airflow, one of which is the impact of using the newly available high efficiency filters has on the degradation of airflow, and will be posting some updates very soon
Ed, I’d be very interested in knowing what filters you’re referring to. I sure hope that we aren’t carrying them.
In my own, admittedly informal, testing, we have found that the highly efficient 4″, 5″ and 6″ pleated filters have less resistance to airflow than a 1″ throw away does. The last part of my Airflow measurement class allows the students to gain some practice with their new meters by testing the airflow on a working furnace. So that it isn’t the same for everybody I change the filters for each student. The furnace sits on a 4″ filter base, so we try 4″ pleats, 1″ pleats (like a piece of wood, don’t use them!), 2″ and 1″ throw aways, poly filters and an electrostatic (another piece of wood) filter. The 4″ pleat is only .01″ or .02″ away from no filter at all.
The electrostatic claims to be highly efficient, but to use them in the field I think you would have to as much as triple or quadruple the filter area, which is impractical in most cases.
On a job I consulted on this last week we found the homeowner had used 1″ pleated filters (he had two returns). Those filters added .25″ to his return static by themselves. They weren’t big enough, either, which didn’t help, but even if they were the right size the static drop across them would still have been too much for the furnace to overcome and deliver rated airflow. His contractor will fix the size issue and sell him some 4″ pleats, but how many others on his block are buying these at Lowes or Home Depot thinking that they are protecting their systems?
The contractor I was with wasn’t aware of their effect before this either. Which brings up that education thing again…
Thanks for the info Bill. We would be interested in knowing exactly
what type(s) 0f 4, 5, and 6 inch pleated filters you are using, so that we can run some tests in our lab, and add that data to our reports. We are
posting some examples per your request of various filters, in various positions relative to the AHU, and their respective airflow degradations.
Please give us your thoughts after you have reviewed it.
The 4″ pleats that I use in the class are Honeywell FC100xxxx series filters. The last 4 digits change depending on the size of the filter. I have also checked pressure drop on the Aprilaire model 4200/4400 series. The media for these won’t fit in my training machine so I checked an installation in the field. The pressure drop on these also approaches that of no filter at all. The wider filters aren’t as common and I’ll have to check a little to get you some model numbers. I look forward to seeing your data.
I have a low flow problem, and would like to ask about some filter options based on the above discussions. I have a 24×24 return that will only fit a 1″ filter. However the duct behind the filter is 23x 23 or so and 18″ deep. Would I be better off getting a sheet metal insert made that would drop into the duct that would handle a 22×22x4 filter? Assuming the same filter material what pressure reduction could I see?
Rick,
In general, 4 & 5 inch thick filters will have lower clean filter pressure drops than the 1 inch type. However, you should still evaluate what minimum flow is required of the system you are referring to for proper operation of the electric heater and/or compressor, and what the degradation of the airflow is with the “clean” filter in place, keeping in mind that the flow will degrade further as the filter loads. Systems should never be allowed to operate below the minimum required airflow.
Ed
I was wondering if Bill’s statement “The 4″ pleat is only .01″ or .02″ away from no filter at all.” was a typo re: the measurments? The Aprilaire 4400 has an initial static of .16 / .37 at rated cfm respectively 1200 / 2000. I recently measured a 2″ MERV 8 pleated filter at .12 wg @ 1200 cfm. We also completed an independent lab study proving the AspenAir filter saves h/o’s up to 30% of their hvac utility bill. Thank you all for your dedication in improving airflow! Throw the 1″ filters away!
Ed thanks, Here is the update. My HVAC service company put a scope up the return to see if there are any restrictions, none. But the coil is tilted in a 4 ton unit and only providing 1100cfm of air flow. Could this restriction cause a failure of the compressor, I just had it changed out. The unit has been freezing up solid.
I am a homeowner in Port Orange, FL. I just moved in and found the sticker to this site on my air conditioner. How do I know if my system is right? It’s seems to work ok. Should I call my warranty company to have it checked? any advice is appreciated.
Ben,
Your airflow with a clean filter should be at least 65 cubic feet per minute (CFM) per KW of electric heat, and 375 cfm per Ton of cooling. Airflow should be meassured accurately with the proper instruments and procedure. Unfortunately, many service technicians do not have the proper training or instruments, and often use unreliable methods and misleading data from the equipment manufacturers. Suggest you ask for a written procedure before having this done. We can look at it and offer suggestions, etc. If your compressor is noisy in the heat pump heating mode, or your electric heater is cycling on & off frequently, you probably have insufficient airflow.
Freezing of the indoor coil during the cooling mode is another indicator of low airflow.
Interesting read! I’ve been looking for a way to save money on my energy costs since money is lower these days. I found your post extremely helpful. Thank you