What is the difference between these silenced 250, 315, 350 mm EC-ventilators? Is bigger better?

Hey guys,
need a short advice. My two rooms together have the size: 16.7 x 12.2 x 8.5 feet (1731 cubicfeet) (5.10m x 3.70m x 2.6m). One room flowering with 4x600Watt double ended and the other room is mother plants and clones.

My plan now is to buy an EC-fan which I will use for air circulation between the two rooms in winter. (Closed system with CO2). And in summer I will use the fan to suck in fresh air, scrub it and push it out the building (For this I will position the fan differently than in winter).

Now I am wondering about the size of the fan. This calculator here http://www.littlegreenhouse.com/fan-calc.shtml
says that I need a fan with 1732 cfm, so all my room is ventilated completely every minute.

So I thought I will go with a 250mm fan. But then I did read in George Cervantes book (cannabis encyclopedia) that the smart grower uses 300mm or more of ducting, because then he can run the fan lower which means less noise and longer material life.

So now I am undecided. I wanted to use 250mm max when Using it for circulation between the rooms.
Maybe in summer I can use bigger ducting for intake and exhaust. But one advantage I would see is to run the fan with lower rpm, which would mean a quieter operation.

Taking a silenced 355mm fan which claims to be able to do 3230m³/h would cost me 150 bucks more than taking a 250mm fan which claims to do 2130m³/h.

Here is a website of the manufacturer which compares the fans in differtent metrics (you can choose language in the right upper corner of the window):

https://www.ruck.eu/ventilatoren/rohrventilatoren1/rohrventilatoren-ec-motor/emix-ec?filterFrequency=50&filterErP=conform

Interesting would be the models:
Emix 250 EC11
Emix 315 EC11
Emix 355 EC11

I really wonder what is the difference between them? When you compare the metrics, it seems like that the 355 has less power (look in the column with the wattage) than the 250. Also the 250 seems to be able to handle a lot more Pressure PA (Look at the graph).

Also in the graph you can see the noise in dB (if you press on the models name, there will be a lot more detailed information for each ventilator). What do you think of the difference in dB shown there between the models?

Am I right in the assumption that the motor doesn't change between the three models, just the openings and the rotor size, which would result in more air movement at lower rpm?

What would happen if I run a 355mm fan with a reducer with 250mm ducting. Will that result in the need of higher rpm to have the same mass of air moved? Would that result in the same as a 250mm fan with 250mm?

Actually I need to answer these questions this weekend, because the price offers for these devices end soon...

EDIT: Actually I realized that the greenhouse calculator is cfm and the fan supplier is cubic meters per hour. So here are the values:

250mm fan = 2130 m³/h = 1254 cfm
315 mm fan = 2860 m³/h = 1683 cfm
355 mm fan = 3230 m³/h = 1901 cfm

If I trust the greenhouse calcultator and try to exchange the air every minute, I would need a 315 or 355mm fan.

ok change of plan.... I think it is better to buy a minisplit and distribute the air between the rooms and scrub it.

Ok I still got this offer for the EC-fans this weekend and also sourced two new very cheap charcoal filter (2000m³/h (25mm) for 80 bucks and 3500m³/h (35mm) for 190 bucks).
So considering I will buy a mini split and want to distribute the air between my two rooms and scrub the odor, what size of fan and charcoal filter would I need? (My two rooms together have the size: 16.7 x 12.2 x 8.5 feet (1731 cubicfeet) (5.10m x 3.70m x 2.6m). One room flowering with 4x600Watt double ended and the other room is mother plants and clones.) Is 3500m³/h filter and 355 mm fan overkill?

And I was wondering if a minisplit is able to transport smell to the outside?

Mini splits do not smell.
You get what you pay for, especially with carbon filters
There’s reasons why an Audi costs a lot more then a Dodge

The brand I talk about usually cost more than double. It is can filter lite. I guess it will be alright.

Sam&Max said:

The brand I talk about usually cost more than double. It is can filter lite. I guess it will be alright.

Click to expand...

They work, I have one in my flowering room
But the real Can works better then the lite tho.

So tell us......wot did you go for and did it work......?I'm in the same position. .....

I did go big 355mm. But I couldn't test it yet. But I was recommended to do so by a professional. The bigger you go the lower speed you can run the fan or the more air you can move. But keep in mind the charcoal filters seem huge then Unfortunately I was not able to test the equipment yet. So I can't give a verdict.

Maybe another variant would be to split the stuff on ventilators?

What decision you have to make?