Commerical HVAC Upgrade to HEPA Filters 1

[Roadwork]

MEs,

Looking to find out what is involved in upgrading commercial HVAC systems to HEPA filters. Just trying to get a feel for the magnitude of this kind of effort, so I can come up with a ROM. Currently have a variety of systems: Trane, Carrier, CoolAir, and AAON, with filters in the MERV 8 range. Do we need to hire a designer, or can a service company handle this? Or is it even possible for the systems we have?

Thanks in advance.

 

[BronYrAur]

You would want to keep the MERV 8 as pre-filters and then install HEPAs downstream. Your unit fans almost certainly do not have enough capability to handle the additional static pressure of the HEPAs. That could mean that you need larger fans, larger motors, larger electrical feeds, etc.

I assume this is a knee-jerk reaction to Covid-19 by some upper authority at your facility who doesn't know what they are asking for. What are you trying to accomplish with the HEPAs?

 

[Roadwork]

Yes, the goal is to lower the risk of transmitting COVID in occupied spaces via HVAC systems. So, sounds like we would certainly need a designer.

 

[miningman]

Roadwork , another cheaper and possibly more effective approach for your consideration

https://www.eng-tips.com/viewthread.cfm?qid=466759

 

[BronYrAur]

I know my "knee-jerk" comment was rather flipid, but I live in Illinois and do a lot of work in Chicago. I'm the victim of ignorant politicians drunk on their own power pretending to be scientists. The liberty-grab in this state has been crazy.

Here's my thoughts. Although HEPA filters have demonstrated the ability to remove coronavirus, how are you going to get the infected air to the HEPA filters? If someone is sick in an office setting for example, when they cough or sneeze they are spraying germs all over their neighbors. The hot humid air from their body is mixing in with the ambient air and traveling. There is no HVAC system that will grab the contaminated air away from the person and take it back to the HEPA filters. Office systems in particular are designed with low velocity so they're not noisy. There is no capture velocity to grab the contaminants. The contaminants will diffuse throughout the office space long before they get pulled back into the HVAC system.

So for this reason I don't have a lot of confidence in putting in HEPA filters as a solution to the virus. Someone else had suggested the possibility in another thread of converting their units to 100% outside air. Same situation. With nothing to capture the contaminants right at the source, they will propagate throughout the area.
I've done limited research on UV lights and they appear to kill the virus, but I think they need more contact time than a simple pass through a duct will give them. I'm no expert but that's what I've seen so far in my limited research. Again, the source of the contamination is not being captured.

I'm a design engineer but I work for a contractor. My primary job is to keep the construction Crews busy. There's nothing more that I would like than to retrofit every HVAC unit in my area, but I don't think that's the solution to the virus.

But to answer your question, yes you would need to hire an engineer to take a good look at your units. Chances are you would need significant upgrades in order to put in HEPA filter

 

[DBronson]

BronYrAur:

+1 on your post. Also, it pays to bear in mind that, as I understand it, the filters need to be Merv 16 - not 12 since the corona virus is only ~ 0.1 micron in diameter.

Regards,

DB

 

[Roadwork]

If MERV 8 is minimum ASHRAE design standard (and is infact what we have in all our facilities), how would I determine what the maximum MERV would be for the system before modifications would be needed? Just asking based on ASHRAE's current recommendation (i.e. If you can't use MERV 13, use the highest MERV you can).

 

[EnergyProfessional]

IMHO, MERV 8 is jsut good enough to protect the air handling equipment. if the space served is dirty (i.e. garage, shop), no further filtration needed.
for clean spaces, like offices, you should use MERV 11, 13 or something like that. If virus is a concern, you need HEPA.

But adding filter banks requires space and causes pressure drop, so this may require re-design.