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OfflinePirouli
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Positive or negative pressure?
    #27047525 - 11/19/20 03:10 PM (3 years, 4 months ago)

I'm setting up a greenhouse as a temporary grow in a 3x5 area of the house until I get something bigger planned out. I am able to have only one vent connection to the outside and I'm stuck on what to do.

I would prefer to exhaust the air out but I'm not finding any cheap fans that are waterproof. But if I bring in fresh air from outside then I'm pumping the greenhouse full of freezing air.

If anyone has any suggestions on how to overcome my dilemma I would appreciate it.



Edited by Pirouli (11/19/20 06:43 PM)

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OfflineHarry Manbach
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Re: Positive or negative pressure? [Re: Pirouli]
    #27047992 - 11/19/20 08:00 PM (3 years, 4 months ago)

Seems like you answered your own question as far as intake or exhaust. 
Further more there's plenty of options of waterproof inline fans, the next question would be, "what are you set up for?". Most common option would be 4"

...
https://www.amazon.com/PF-100-Mitigation-190CFM-Waterproof-Outdoor/dp/B08BC6CMHY/ref=mp_s_a_1_11?dchild=1&keywords=waterproof+4"+exhaust+fan&qid=1605841046&sr=8-11

If on a budget,I've used these..they're great for the price and have a 2 year warranty as well..but not guaranteed "waterproof"
https://www.amazon.com/AC-Infinity-RAXIAL-Booster-Controller/dp/B07ZL6FDYG/ref=mp_s_a_1_3?dchild=1&keywords=waterproof+4"+exhaust+fan&qid=1605841046&sr=8-3

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OfflinePirouli
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Re: Positive or negative pressure? [Re: Harry Manbach]
    #27048045 - 11/19/20 08:41 PM (3 years, 4 months ago)

Yeah 4in. Thanks for the links, I didn't come across those on Amazon.

Edited by Pirouli (11/19/20 10:52 PM)

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OfflineHarry Manbach
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Re: Positive or negative pressure? [Re: Pirouli]
    #27048596 - 11/20/20 09:15 AM (3 years, 4 months ago)

Quote:

Pirouli said:
Yeah 4in. Thanks for the links, I didn't come across those on Amazon.



No problem, those were just two quick searches of different styles for different budgets, can't beat those waterproof inline tho! Especially when it comes to cleaning!

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OfflineSHROOMSISAY01M
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Re: Positive or negative pressure? [Re: Harry Manbach]
    #27049777 - 11/21/20 01:27 AM (3 years, 4 months ago)


Edited by SHROOMSISAY01 (11/21/20 01:34 AM)

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OfflineSHROOMSISAY01M
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Re: Positive or negative pressure? [Re: SHROOMSISAY01]
    #27049786 - 11/21/20 01:42 AM (3 years, 4 months ago)

You also might want something like this that will close the intake air hole when the exhaust air is not on. To help keep the humidity in...

https://www.amazon.com/Connector-Plastic-Straight-Heating-Ventilation/dp/B0822TDWNF/ref=sr_1_64?dchild=1&keywords=air+duct+damper&qid=1605947952&sr=8-64

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OfflinePirouli
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Re: Positive or negative pressure? [Re: SHROOMSISAY01]
    #27051186 - 11/21/20 09:25 PM (3 years, 4 months ago)


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OfflinePirouli
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Re: Positive or negative pressure? [Re: SHROOMSISAY01]
    #27051191 - 11/21/20 09:28 PM (3 years, 4 months ago)

Quote:

SHROOMSISAY01 said:
You also might want something like this that will close the intake air hole when the exhaust air is not on. To help keep the humidity in...

https://www.amazon.com/Connector-Plastic-Straight-Heating-Ventilation/dp/B0822TDWNF/ref=sr_1_64?dchild=1&keywords=air+duct+damper&qid=1605947952&sr=8-64




Yep, I'm definitely getting one of those, I don't think I can run the fan without one. There's allot of cold air that rushes through the vent hose so it would make the greenhouse way too cold.

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OfflineSHROOMSISAY01M
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Re: Positive or negative pressure? [Re: Pirouli]
    #27051355 - 11/22/20 12:03 AM (3 years, 4 months ago)

You want negative pressure anyway. Just in case you have a spore drop. You will not fill your hose with spores with a negative pressure system. You will also need a 12-volt power supply with the bilge fan. I would double or triple the amp rating needed for the fan just in case you need another fan you can run it on the same supply. I am thinking of one of these for my circulation fan. You will need a circulation fan especially if you will be growing oyster mushrooms...



even with the power supply, they are half the price of the other fan that was $99 and water will not be a problem with a bilge fan.

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Offlinegt40
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Re: Positive or negative pressure? [Re: SHROOMSISAY01]
    #27480988 - 09/24/21 04:33 PM (2 years, 6 months ago)

guys, do the theory above relevant for mushies which grow with casing layers when we need a lot of evaportion from the casing? I'm building a tent right now and try to understand proper cycle game. I mention that with GH people uses positive pressure with no exhaust fan. I have exhaust fan already and now think do I really need a fan for intake to boost the evaporation

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Offlinegt40
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Re: Positive or negative pressure? [Re: gt40]
    #27481460 - 09/25/21 07:21 AM (2 years, 5 months ago)

:smirk:

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Offlinetaku
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Re: Positive or negative pressure? [Re: gt40]
    #27481482 - 09/25/21 07:43 AM (2 years, 5 months ago)

The exhaust fan is to refresh the air, not sure what effect it would have on evaporation. A circulation fan would be more likely to help with that.


--------------------

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OfflineSHROOMSISAY01M
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Re: Positive or negative pressure? [Re: gt40]
    #27482965 - 09/26/21 04:17 PM (2 years, 5 months ago)

Quote:

gt40 said:
guys, do the theory above relevant for mushies which grow with casing layers when we need a lot of evaportion from the casing? I'm building a tent right now and try to understand proper cycle game. I mention that with GH people uses positive pressure with no exhaust fan. I have exhaust fan already and now think do I really need a fan for intake to boost the evaporation




If you set it up like in the pic there is no need for an intake. An intake fan will not help with evaporation and if you have an exhaust it will probably hurt. I had a guy running both an intake and exhaust with the intake running slower to keep from pushing out spores. I told him to stop using the intake and he got better results. I do agree with the circulation fan just because it will keep co2 from building up around the mushrooms. But I guess that depends on what you are actually growing. I know of no edibles that benefit from a casing layer. In my opinion, it is not worth putting the casing on most actives either.

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OfflineFarm3r
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Re: Positive or negative pressure? [Re: SHROOMSISAY01]
    #27483417 - 09/27/21 06:25 AM (2 years, 5 months ago)

What do you mean a intake won't help with evaporation?
I'm only using intakes and if that were the case then the room would be a pool.
Esspecially if you have a preconditioning room, and if your intake fan, whether or not it blows through your humidifier, moves air similarly in direction and volume to that of a circulation fan, or a bildge fan like some use, I don't see how you lose circulation or lose evaporation.


Although I do think an intake blowing around fresh air may cause potential for it to dry out Fruits, this I believe can be mediated by fan placement, from your intake going through your ac and being pointed at the ceiling, compared to an exhaust sucking in air from wherever there's gaps. But this has made it so for me at least I haven't seen the need for a circ fan Or exaust.

I've tried both as well, not just exhaust. I set up some exhaust through the ceiling at one point and the vents filled with water and nearly tore them down. If I do exhaust again they will be on the floor.
I know have an exhaust vent running though the ceiling, but no fan in it.

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Offlinegt40
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Re: Positive or negative pressure? [Re: Farm3r]
    #27483750 - 09/27/21 11:07 AM (2 years, 5 months ago)

Thank for response, guys.

I agree with Farm3r, dry warm air which is moving through the space will definetly push out the water molecules from casing. Initially my thought was that exhaust fan will suck out the moist air = provide the window for evaporation, but after a week of experimentation casing stays on a wetter side than assumed and I guess it's not enough. First flush in new room are way worse than my old Martha's.  I focused on pans now and proper evaporation is a key here.

So it's better to put exhaust fan near the bottom? Now it mounted close to ceiling.

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OfflineSHROOMSISAY01M
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Re: Positive or negative pressure? [Re: gt40]
    #27483882 - 09/27/21 01:00 PM (2 years, 5 months ago)

If you have an exhaust set up the way I show in the picture an intake will not help with evaporation. I did not say an intake alone would not help with evaporation. But with an intake alone you will be pushing spores out into other areas and that is a health concern.

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