What is the difference between these ventilators? Is bigger better?

Growroom Design
#1

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 which claims to do 2130mÂł/h. But then I did read in George Cervantes book (cannabis encyclopedia) that the smart grower uses 30mm 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 3230mÂł/h would cost me 150 bucks more than taking a 250mm fan which claims to do 2130mÂł/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…

#2

The diameter of the fan and ducting has a lot to do with power use, noise and amount of air moved.

For any given size room, a larger diameter fan and ducting, uses less power, and makes less noise, to move the same amount of air. Larger is also usually more $$.

You need to decide how much your willing to spend to get those benefits.

I dont think pressure is the best metric to look at in this application, but it does tie in. More pressure is needed in smaller diameter setups to move the same amount of air - which means faster air movement, which means more noise, which usually means more power needed.

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#3

I just realized that the greenhouse calculator was putting out cfm (cubic feet per minute) and the ventilators on the manufacturer page are mÂł/h (cubic meter per hour). (I corrected the mistake in my first post).

I didn’t plan to use bigger than 250mm ducting in my grow room. What would happen if I use 250mm ducting with a 355mm fan? Would that be the same as a 250 fan with 250 ducting? Or would 250 ducting with 355 fan be maybe even worse? Unfortunately I lack the theoretical knowledge for properly designing the air system.

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#4

Using smaller ducting than the fan diameter will be mostly a waste of the fan potential. The duct size is the limiting factor - smaller ducts have higher resistance to the flow. To move the same amount of air in a smaller duct, you will need more power, which means more noise and reduced efficiency.

Its always best to use the correct size duct with any fan.

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#5

I noticed a few years back that the motor size was the same in a 8in as a 10in inline fan. I used 10 in ducting on my 8in fans to increase flow and it worked. I don’t know if this is still true. (motor size)

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#6

Exactly. Larger diameter => less noisy because same amount of air can be moved at lower speed.

I always try to use largest diameter I can (of course with very large sizes it can become inpractical). But you have to use that diameter across all the tubing, don’t reduce it somewhere. Also don’t do unnecessary bends.

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#7

Ok I just calculated the values for the different units:

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

So if the greenhouse calculator says to exchange the whole volume of the room in one minute I would need a fan with 2941 m³/h. Is it really necessary to change the air so quickly? Isn’t every two or three minutes enough? Or does it depend on how hot the room gets?

I mean I would only need that capacity in summer when it is hot, when the room temperature gets to high and I can’t use CO2 anymore.

All the other times I would use the fan just for air circulation between the rooms. And I don’t want to use 355mm ducting in the rooms because it uses much more space and all the 355mm ducting parts are double the prize of 250mm. And I think I wouldn’t need 355mm to circulate the air between the rooms.

But the prize difference between 3230 mÂł/h and 2130 mÂł/h is 120 bucks only. So if nothing bad happens when using 250 mm ducting with the 355mm fan, I could take the bigger one and use it with 250mm in the room and when it gets hot, I can duct with 355mm.

#8

That depends what factors are priority for you…?

  • Costs
  • Less noise
  • Scalability

Then it is also matter of air you can bring in… How hot it can get?

For your more than 18m2 I’d go at least with 315mm tubing…

What do you mean by that? You need to supply fresh air to the grow not circulate used air (unless you are adding CO2).

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#9

For understanding the situation better:
In winter, when it is cold I am using CO2. I was thinking to have the CO2 generator in the motherplant room because of space issues. That would mean that I need to circulate the air into the flowering room properly, so the plants there benefit from the CO2. That is in winter.

When it is getting hot, I need to buy a mini split (which I postponed) or at the moment I plan to use intake and exhaust air from and to the outside. That would mean I can’t do CO2, which means it is not necessary to circulate the air between the rooms. In that case I would close the air connections between the two rooms and take the fan and use a Y-piece of ducting and connect each room to the Y-piece. Also each room would have its proper air intake hole. The fan would exhaust then in some air ventilation system which already exists there.

But I am not really sure if I can make two 355mm air intakes (because the airintake hole in the wall might not be big enough, and breaking the wall is not an option), or if I need to use a Y-piece of ducting again and have just one 355mm air intake for both rooms.

I am not sure what works properly from the physical standpoint.

Also I am not completely sure where to put the scrubber. If I put it into the flower room, what happens f I have different air flow resistances for each room (e.g. one room has a scrubber the other not) if at the end there is one fan who pulls it all. Could there be the case that air gets pulled preferably through the mother room if there is a scrubber which restricts air flow in the ducting for flower room ?

Sorry if it is difficult to understand what I mean. Actually it is a pain in the ass to properly figure this stuff out if you lack the knowledge.

#10

I guess I will go with the 355mm one. I will use it now when it is still cold with 250 mm ducting for air circulation between the rooms. and later when its too hot I will go for 355mm and pull air from the outside.

Actually there is an offer I found for a 2000 cubic meter per hour active charcoal scrubber which would cost me 80 bucks. (also has 250mm)

If I would use the fan for air circulation between the rooms, would that be sufficient?

Also found an offer for an 3500 cubic meter per hour scrubber (355mm) which would cost 190 bucks.

What would happen if I use the 3500 cubic meter per hour filter for the between room circulation? I mean I guess I would run the fan pretty low for between room air circulation… what happens if I run a 3500 filter with a low set fan? Does it still work properly?

I mean now it is still cold enought that I dont need air from the outside. But if I need air from the outside to cool, do I need a 3500 filter or can I use the 2000 filter somehow by giving each room its own ducting connection to the fan and only scrub one room, which would reduce the workload for the filter by half. But would the 250 mm of the filter be a problem then? Or rephrased: Can you split a 355mm in two 250mm ductings or do you need to split a 355mm into two 355mm ductings (Considering you have two rooms and want to ventilate both and need to scrub one, would that work with a 355mm fan and a 250 mm filter or do you need a 355mm filter?)

Any air ventilation experts? :smiley:

#11

I believe the formula I use was LxWxH = cubic feet of area x 3 = amount of air one should be shooting for. Hope this helps.

#12

What concerns me a bit, if you consider a pressure drop of 180 Pa for the carbon filter, then looking at the graph
https://www.ruck.eu/ventilatoren/rohrventilatoren1/rohrventilatoren-ec-motor/emix-ec?filterFrequency=50&filterErP=conform

Then you see that the 355mm fan only delivers around 2300 mÂł/h which is 1000 mÂł/h less than the 3230 mÂł/h which it is marketed with.

Also if you look at the same for the 250mm fan, with a pressure drop of 180 Pa, you get around 1800 mÂł/h. Which is a difference to the 355mm fan of only 500 mÂł/h. (Considering the difference between the two fans in the beginning was over 1000 mÂł/h)

#13

Ok… I think I messed this thread a bit up. I did think now a bit and I looked a the prices for mini splits and 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 (2000mÂł/h (25mm) for 80 bucks and 3500mÂł/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 3500mÂł/h filter and 355 mm fan overkill?

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

#14

What the temperature of incoming air will be like?

What is the priority for you…?

  • Costs
  • Less noise
  • Scalability
  • something else?

Are you physically limited to some size?

#15

The size I planned it for (four 4x4 flowering tables) seems a good fit. So I dont plan to extend it. The rooms are set now and if I want to add tables, I would need to alter the room structure. Don’t plan to do that.

I am not planning to scale up.

If I am able to keep it quieter for a couple of hundred bucks extra, no problem. Less noise is more agreeable and good for security. And security is a priority.

Already have a CO2 generator which is water cooled and the room is also set up as sealed.

So if I only recirculate and scrub the air, this calculator (http://canfilters.com/resources/calculators) says that I need around 1200 cfm which would be like almost 2000 m³/h. For recirculation they calculate “length x width x height and divided by 1.5”. So every 1.5 minute complete airchange. (For exhaust they would calculate every 3 minutes an air change, because they want more contact time of the contaminant with the filter). They also say to calculate a 10 to 15% drop in airflow because of resistance of the filter.

So if I buy the 2130 mÂł/h (250mm) fan, and a 2000 mÂł/h (250mm) carbon filter and would use that for scrubbing and then put the ductwork in place for recirculation between the rooms (with different entry and exit points) I wonder in how much pressure drop that would result in, because it seems the amount of airflow quickly reduces with pressure drop. (https://www.ruck.eu/ventilatoren/rohrventilatoren1/rohrventilatoren-ec-motor/emix-ec?filterFrequency=50&filterErP=conform). Also would that mean that I would need to run the fan constantly on 100 percent? I did read that they can sound like a jet engine, even in silenced version.

Other variant would be to go bigger and buy the 355 mm 3230 m³/h fan. But this fan reacts even a bit worse on pressure drop. And I don’t know how the pressure drop will affect the air movement if I connect 250 mm ducting to it. Or should I run only 355mm ducting between the rooms and get an 355mm charcoal filter? Would it then work surely and I wouldn’t need to run on 100 percent? Or is that size absolutely not necessary for recirculation and scrubbing “only”? A 3500 cubic meter per hour scrubber (the only 355mm filter I could find), run on 80 percent fan, plus pressure drop, how will that behave? Might restrict the airflow even more. But to me it seems if I look at the numbers, I wouldn’t get it properly with 250mm only (considering pressure drop because of ductwork and filter) and I would need to run it on 100 percent (what I also dont want). So what to choose?

#16

no

yes

yes

you use warmer temps when using co2

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#17

they sell mufflers to quiet the noise coming from the duct exit. The can fans are loud but, inside the room.

http://ecx.images-amazon.com/images/I/71BUNco291L.SL1500.jpg

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#18

I will probably go the route and buy the mini split. And use the ventilator for scrubbing and air distribution.

I hope if I will install a big charcoal filter I still can use the fan for circulating the air between mother and flower room.

To use it for between room circulation means that I will need several air entry and exit points. I am not sure how to design it properly so there will be no air short circuiting because of different flow resistances in the ducting.

For example, I have the big charcoal filter in the flower room as an entry point, then also an entry point in the mother room, then these two ductings go together and run to the other end of the room into the fan (who pulls the air from these two air entries). Then after the fan (the fan pushes) air out of an air exit point into the flower room and an exit point into the mother room. Could this design cause an air short circuit between the air entry in the mother room and the air exist point in the mother room, because the air resistance between air entry flower room (charcoal filter) and air exit flower room is higher? I want dont want to set that up and realize I finally just recirculate the air in my mother room.

I think I will make a short drawing later, so it is understandable what I mean.