Carbon filter, HEPA filter, mixed flowfan setup help

[panckage]

I have a hepa filter since Cannabis plants gives me allergy symptoms even during veg.

Currently my system is set up as carbon filter - > fan -> hepa filter. It works great with only the carbon filter, but once the hepa filter is added the airflow is drastically reduced.

I have read that pulling works better than pushing so I assume that carbon filter - > hepa - > fan would give the most airflow. But does it really? I have trouble finding any rational for this....

I would have tried this already but I am using a rectangular hepa filter (approx 8" by 12") this means I would have to build a box to put it between the fan and the carbon filter (both 6" diameter). It is also in a 2'x2' tent so space is minimal. This situation is far from ideal. Any other hepa filters I have found with the proper shape are ridiculously expensive and will only work in a push configuration.

Any ideas on this? Is having both the carbon filter and hepa filter before the fan the best option?

 

[queequeg152]

lol welcome to HEPA... do you have any manufacturer specs for this particular filter? what about the fan?

all hepa is extreemly high static pressure, so generally you need huge square footages to work efficiently. conversly you could use a smaller hepa filter like yours, but you would need an enormously powerful blower ... but this is going to cost more in the long run, so if space is not a premium, id reccomend against that.

it will make almost 0 difference the order that filters are placed. there are some issues with blower inlets ingesting turbulent air and such at high velocities, but here the velocities are so low that the air is going to be close to laminar save for the slower moving boundary layer air on the sides of the duct.

 

[Floridian]

I have always used Allerair portable carbon/hepa filters,you may want to check it out.The way they filter the smell is unbelievable and are supposedly fantasic for filtering out allergans too.

 

[panckage]

lol welcome to HEPA... do you have any manufacturer specs for this particular filter? what about the fan?

Not on hand, but good point about HEPA. A less strict (non-hepa) filter could let through more airflow while possibly still protecting from the allergens. However I have no idea what the allergens are so I have no guide when comparin micron/MER ratings of filters

As for push vs pull though the fan I notice that the air that comes out does not come straight. A lot of the air seems to be coming out in a big arc as opposed to pushing just straight ahead. Are you sure that this isn't a unique problem with pushing air through the hepa?

 

[queequeg152]

again the problem is one of static pressure first, then CFM second.
so unless you have a very very specific type of blower... like say a forward swept impeller blower, its not goinn to make any difference which direction it faces.

the reason why your hepa comes out at the center more... it probably because its a non channel fin type that one uses for sterile air work.

without the channel fins, air is allowed to migrate throughout the media and find its own path to the lower pressure exhaust face.

by all means though prove me wrong and swap the blower if you like. idk how you would quantify the results though.

the fact that you are getting a perceptible amount of flow is good though lol... you might be able to just get two of the same blowers, build a "pants" type horizontal tee, and use both to get enough cfm to keep the pressure in the room below static air pressure and hence keep what ever is irritating you inside the room.