So here we are around nine months into this covid deal, and things are getting more unrealistic by the day.
We are hearing, but don’t have proof, that municipalities and other governmental orgs are requiring MERV 13 filters for buildings. Which brings us to a couple of problems.
I run an HVAC distributor and we are getting lots of calls for MERV 13 filters. We represent four filter companies. Two aren’t taking orders for MERV 13 product and of the other two, our best lead time is 4-6 months. For those who want to wait, we are encouraging them to buy a years supply and just store them.
We are even having trouble getting our standard pleated MERV 10 product due to factory production slowdowns because of covid. So we are getting some of the shooting of the messenger by our customers, but we can handle that OK.
Why the long lead times? Besides the crushing demand, the same companies that make media for masks, make media for MERV 13 filters. You can guess where priority is right now. Also, nobody has told me if the filters, presumably loaded with covid, will be someday declared a hazardous waste by OSHA, making their changeout completely ridiculous. Not to mention that MERV 13 filters create enormous amounts of static pressure, which will be terrible for a lot of systems, especially older ones. There are already rumblings of certain equipment manufacturers engineering departments getting ready to go to war with the authorities mandating these filters, and declaring “no warranty” on equipment failure due to lack of return air and MERV 13 filters putting their equipment out of engineering spec. This is super fun.
We have been recommending for a long time that people use standard pleats in combination with a bipolar ionizer or UV product, both of which in the past few months have received covid killing certification. We are hoping this MERV 13 train isn’t fully out of the station just yet and that everyone will start to get a bit more realistic. But since it is 2020 we aren’t expecting much.
So MERV 13 filters to HVAC systems is what masks are to human bodies: a symbol.
Masks are theater. The UV thing sounds like a good idea but I chose not to spend $700 on one. There are very few people in our house month after month.
All those bureaucrats in governments & companies have to do something while working from home. Writing a new policy to require the highest grade filters sounds like a good morning’s work to that kind of overhead person — done in total ignorance of the term “pressure drop”.
Most of what I hear from contacts in China is that life is pretty much back to normal there — albeit with many people having to work hard to fulfill the huge orders for exports to the West.
I cannot shake this feeling that future histories will record the CovidScam as the most successful example of economic warfare ever achieved. After two decades of preparing the ground by attracting much production from the West to China, penetrating Western Academia-media-bureaucracies, and greasing the palms of Western politicians, China’s authorities in 2019 released a not-particularly-deadly virus on the world along with a massive behind-the-scenes campaign to encourage Western Lock Downs. Western politicians fell for the trap, and by the time the dust settled, the West had destroyed much of what was left of its production base. Without realizing it, the West had become totally dependent on China for manufactured goods and for essential components of what Westerners thought of as “domestic” products, right down to nuts & bolts. It then became easy for China’s rulers to extend their sway over the entire planet– the equivalent of a winning a World War without firing a single shot.
I said months ago that this might be an example of a successfully deployed bio-weapon, prove me wrong.
To the point at hand: Most places have a very involved and slow process for changing building codes. It is even slower and more litigation prone when it concerns retroactive changes to existing buildings. I expect the politicians and “authorities” that are a couple of steps above assistant dog catcher will find their prerogatives don’t extend this far.
Even hospitals are millions of dollars away from a ventilation system that could be proved to limit exposure. Count the number of hospital rooms in the whole country considered capable of containing a dangerous airborne pathogen. From the Ebola outbreak, that number is less than 20.
As Mike said, they were willing to sell him something for $700. I doubt that $10,000 would be enough to actually test it AS INSTALLED to show whether or not it was effective. I’d be willing to bet that any written material included a very densely worded disclaimer of its ability to actually reduce or control an actual disease.
Then, there’s no particular reason to believe this is spread through ventilation systems. All of the supposed superspreader events I’ve heard of involved people in a single room. There should be ample evidence of whole apartment buildings and hotels being infected if that was the case.
MCS – well they have the proof of the effectiveness of bipolar ionizers and UV lights against covid. And you are right, it is all based upon supposed exposure times, something basically impossible to test in a real life system, as far as I know. However these items are certainly not doing any harm and are definitely helping with indoor air quality and are probably killing a lot of covid along the way.
I feel as you do – from a practical standpoint the chances of covid spreading through an HVAC system and infecting someone else with that as a transit system (especially a commercial system where fresh air is most of the time introduced at some point) are teeny tiny. Maybe zero.
So MERV 13 filters to HVAC systems is what masks are to human bodies: a symbol.
Could be. Alternately, different people have different perceptions of risk and/or different preferred risk tradeoffs.
MERV 13 filters trap covid, that is an undisputable fact. Whether the tradeoff is worth it to trash your system (or if these filters someday get declared a hazardous waste) is another question.
Air handler spread.
Legitimizes Disease.
It will only take one sensational incident to have all the building code flaks demand it, the manufacturers to lobby it, the insurance companies to require it, the finance companies zots funding potential contaminated un-resellibke properties.
A more accurate characterization would be that they capture some virus particles.
Here’s the EPA ratings:
https://www.epa.gov/indoor-air-quality-iaq/what-merv-rating-1
They don’t show 13 but for 14 the rating is: 0.3 – 1.0 75% – 84%, 1.0 – 3.0 90% or greater. The numbers are microns. Note that the efficiency is 75% for particles down to 0.3 microns which is far larger than the actual size of the virus. the ratings go all the way to 16.
The particles in question are presumably composed of other materials as well and larger than individual viruses. I haven’t heard anything that indicates just what size particles would be of concern. They would have to be small enough to stay suspended in the air indefinitely while preserving the virus in a viable state long enough and in high enough concentration to cause infection. Of the four conditions above, only the particle size is reasonably established. All the rest are conjecture and highly uncertain.
As far as the harm this would cause, Imagine you are trying to restart or continue a business that’s been affected. You are now confronted with both a large cost and an indefinite delay for the installation of something that “can’t hurt” and satisfies someones “abundance of caution” with no actual evidence or, really, any reason to believe that it will accomplish a reduction of infection.
Dan from Madison:
If I recall my information on respirable aerosols, a typical range for human exhalation (not including coughs and sneezes, which emits much larger droplets) is around 5 to 10 microns. The virus itself has been claimed to be on the order of 0.5 to 0.75 microns, a factor of 10 smaller than the aerosols on which it presumably travels.
My background is limited; for the first bunch of years I was designing and building air conditioners and heat exchangers for cooling electronic enclosures. For the last three decades or so I’ve been involved in filtration and other associated systems for ground-based gas turbine inlets. The biggest systems I designed were for turbines pulling 1.3 million cubic feet per minute. These filter systems are typically the size of a intermediate office building, and have just under a thousand individual filter elements. Some were static, and even panel filters, others were cylindrical/conical combinations that were pulse-cleaned.
All of those elements were extensively tested, against both ASHRAE dust and other challenge media, as well as mists and aerosols.
What I do know is that the higher the media efficiency, the higher the static pressure (for a given air flow and number of elements).
– Isn’t it true that the vast majority of standard HVAC filters are relatively low efficiency, and are therefore associated with (relatively) low pressure drops at their rated flow?
Simply going to a (much) higher-efficiency filter without changing the size of the filter bank, or increasing the fan power, has to lead to a reduced rate of air flow through the system. This would affect things like the air-side delta-T across chilling and heating coils, which in turn will affect the efficiency and possibly the operation of the heating and A/C components (compressors and condensing coils).
– I would assume that this would be unacceptable in the majority of applications, but given your experience in the industry I’d rather someone like you address that issue.
Yet another problem is the typical “knee” in the fan curve for most systems. A big jump in system static pressure (again, just assuming only the filter elements are changed) could lead to significant fan/motor problems, where the same static pressure exists on both sides of the fan curve. The fans tend to surge under such conditions, making noise issues and degrading the life of the fan/motor.
From a system standpoint, I’d say that simply changing to higher-efficiency filter elements without addressing system-wide effects could lead to much worse problems that the (still hypothetical) HVAC-spread of a bad cold.
As long as the standard HVAC filters are not immediately downstream of cooling coils (where they would remain humid and moist) I would guess that most of the respirable aerosols will impinge on the surface of even the low-efficiency filter media and eventually evaporate. Any live virus, after some period of time, will eventually die (within hours, at most half a day) since it will tend to stay on the media (we’re not talking about anthrax spores, here), and the filter elements can be disposed of in an normal fashion without worry about being a biological hazard.
Blackwing 1:
– Isn’t it true that the vast majority of standard HVAC filters are relatively low efficiency, and are therefore associated with (relatively) low pressure drops at their rated flow? Yes. Our standard filter is a MERV 10.
Simply going to a (much) higher-efficiency filter without changing the size of the filter bank, or increasing the fan power, has to lead to a reduced rate of air flow through the system. This would affect things like the air-side delta-T across chilling and heating coils, which in turn will affect the efficiency and possibly the operation of the heating and A/C components (compressors and condensing coils). Absolutely. This is a huge problem, especially in older units. I’m guessing iced up evaporators will be a normal occurrence in hot/humid climates within minutes after subbing standard pleated filters with MERV 13. You can’t choke down the air flow over the coils and have the compressors running just as normal. It’s just as good as running a system on a filter that has never been changed.
And to your “knee” comment – I don’t think you will lose motors per se. I think other safeties in the systems will trip before the motors fatigue out but there is no reason that a motor couldn’t overheat in this type of problem as well (again, especially older systems). Basically we tell people that you are in effect replacing your MERV 10 filter with what amounts to a fully loaded MERV 10 filter when you go to MERV 13.
As far as the filters not being deemed a haz waste, I wish you were right, but I trust the overlords at different agencies (who want to make a name for themselves) to do the worst.
Mike K: I believe the subject is commercial HVAC – offices, retail, hospitality, etc – not the residential use.
Risk tradeoff: before getting to this step, let alone to perception of risk, there has to be full understanding of the risks involved. Meaning, understanding not just one element, but the system.
Not just masks, in general, but various types of masks, how each affects the wearer and its level of protection, the maintenance (how long the mask remains operational w/o causing secondary infection – so how often it has to be exchanged for a new one) and, in wider perspective – the place wearing of mask holds in an overall system of antiviral measures.
By the same token, for organizations and landlords, not just buying & contracting to install the MERV 13 filter, but designing new or RE-designing existing HVAC distribution, with all the elements engineered appropriately. Then developing a schedule and method of safe discarding of used filters. Of checks and tests of the system. Of maintenance of the elements.
In other words, an engineering approach – rather than checklist’ approach to the problem.
But it looks like in the haste to reopen, the engineering (complex) approach might not be popular.
“But it looks like in the haste to reopen, the engineering (complex) approach might not be popular.” I wouldn’t say not popular, I would say that there is no way your typical governmental creature would understand/care. So MERV 13 filters “check the box” and that will be it. System parameters be damned.
You also mention a schedule for changing the filters. Great point. These filters will have to be changed WAY more often than standard pleats. Their sieve is so tight (static pressure previously discussed) that they load up very quickly. So they are 3x the cost of a standard pleat and have to be changed probably 3x as often or more, depending on the environment. A huge budget buster.
So they are 3x the cost of a standard pleat and have to be changed probably 3x as often or more, depending on the environment. A huge budget buster.
I quit using these with my relatively new system because I was getting a “change filter” alarm with an almost new item with my eyeballs telling me it hadn’t actually collected any dust.
No thank you.
Dan from Madison:
The current edition of the ASHRAE Journal is also accompanied by a copy of “In Motion”, the journal of AMCA.
The lead/cover article is an assessment of the engineering criteria for the deployment of UV-C sanitizing for HVAC systems. If you haven’t seen it you might want to take a quick look at it. Here’s a link:
https://www.amca.org/educate/#inmotion
Thanks for your feedback in the comment above.
Blackwing 1 – thanks for that I will check it out. Before even reading it, I will say that UV-C is so much more complicated for commercial applications than residential because, as you know, there are so many more variables. We deal with the resi and light commercial world, and even in light commercial say up to 10 or 12 tons things are still fairly standardized, relatively speaking. Above that the majority of systems are fully engineered and custom. Those guys have a lot of challenges with this.