Carbon filter and air handling unit

[Uhtred]

I've been using a window unit for my100 sq Ft grow room and a mini-split system for my 300 sq ft office. The two rooms I built in my well insulated 1300 sq ft garage which leaves 900 sq ft remaining for the garage. Well my office mini split went out and I bought a Goodman 2 ton condensing unit located outside and air handler which I will locate in the attic. I'll rarely use the garage ducts but if a project comes up it would be nice to open the supply dampers for that area. The unit is cooling only. My concern is could I use a carbon filter in the return duct of the grow room or should it be in my office supply duct and will it remove the shared return air smell? If the filter won't hide the smell then I'll have to go back to using the window ac unit for the grow room and the new air handler for my office air. I'll control the dampers with thermostats located in the 3 areas. I'm a retired electrician and hope to only need to use an AC company for the refrigerant lines as I am sure I can do everything else myself. Also I'm planning on running a fresh air duct for possibly part time operation. Any helpful comments will be greatly appreciated...

[smoorman]

I've found carbon filters to help, but not totally eliminate the smell if that helps. If you plan on re-circulating any air there may be smell. Depends on how many plants and strains.

[Booger789]

Carbon filter will not remove the smell of most strains when in full flower. If you needed to really get rid of the smell an electronic air cleaner added to the air handler may pull it off. But I would not be 100% sure the electronic air cleaner would be able to pull all the smell out. I’m an Hvac guy, and the only way to be sure would be a hepa filter with carbon pre-filter.

[Uhtred]

After reading a bit more I'm thinking I need a carbon scrubber that is independent of the air handler duct work. Any thoughts on this? Also is Phresh a good company to buy from? Booger since your an HVAC man what size ducts should I run in the rooms? I've read equal size ducts and then I've read go for neg air pressure so I'm a bit lost. Ha. I was thinking 12" for the 300' office and 8" for the 88' grow room but that may be overkill. I've 5 led lights in the grow room. Also what size fresh air duct running into the return? Thanks... Uhtred

[Booger789]

Well first figure how many total watts your lights and fans are drawing then multiply by 3.413 and that will give you the btu load of your lights. That’s what will determine what size ducts to run to the grow room not its square footage. The 300 sq ft off ice will need to be wyed into at least two ducts to properly get adequate air flow to the office. But a 300 sq ft office will need about 300 cfm give or take depending on how many people computers and other equipment you may potentially have in the office.