12 inch extractor fan to 8 inch reducer ?

[sid2444]

hi first post here, im about to set my groom up 5m x 3m x2m high. i have read i will need a 12 inch fan and 8 inch intake. i was going to put the 12 inch exhaust fan tube to a wood burning stove pipe not used anymore, 5 feet from the fan but the stove pipe is 8 inch. i can buy a 12 to 8 inch reducer funnel shaped. but would this hinder the flow of the 12 inch fan enough to make it worth while? any advise welcome cheers.

[ERBURT]

I should think it will be ok mate.

[sid2444]

i live in the middle of nowhere quarter of a mile to nearest neighbour, there is a public footpath 100 yards away used by dog walkers and farmer, post man delivers to letter box 40 yards from house. do you think i would still need a filter ?

[White Warg]

In some ways you're more visible in the middle of nowhere. If any one of those dog-walkers, farmers, ramblers, etc., is a self-righteous prick they'll be on the phone to the police. Especially if they notice it each day. And 5m x 3m implies you're going to be having a healthy grow going on in there. A filter doesn't cost much for peace of mind.

As for a reducer, I only did a 1-inch reduction but it worked, without an actual reducer. I used acoustic ducting, it has inner and outer layers. I used one of those metal rings on the inner layer, and a zip tie (actually two or three linked together) on the outer. Made a nice seal. Make sure you get a good quality 12" fan, like an RVK or suchlike.

[sid2444]

yes i will get a filter. the pipe goes into a 30 foot chimney but the house is down a slope from the track and post box so the chimney is actually lowered to less than 20 foot. probably going to blow towards them sometimes. will this room have to be completely airtight for the negative pressure to work ? the walls are 2 ft thick theres one window 6 ft by 4 ft which i will block with king span with curtains in front the door doesnt fit tight its an old house plenty of drafts. i get paranoid about the choppers.the police chopper training school is only a few miles away and they fly low over here at least 5 times a day and night. i was going to get the gear from hydro shop, he give me a quote with discount which i thought was reasonable, then i checked ebay it was 300 quid cheaper to get the bits seperate but then anybody can see what your buying and your address is there i have been reading on here for 5 days now picked up some great tips but also confused myself, information overload. i first thought get a few plants get the lights and away you go, bit more to it than that. me and the missis like a toke pissed off driving 5 miles into town for a couple of shit ten bags that dont last long

[British green]

Good morning and welcome your in the right place . To achieve negative pressure you just need to suck more air out than your pushing or pulling in . You should achieve negative pressure with 12inch extraction and 8inch intake . Depending on your lights and room you wil be able to achieve better negative pressure by just having the extraction of running and might not even need the intake

[White Warg]

How many plants are you expecting to grow?

You might find it cheaper and easier to buy a grow tent, of 1.2, or 1.5, or 2.0 meters, stick that in the room, and control that. You could use a smaller fan to the flue, would probably need nothing more than passive intake to it. You might find it easier with controlling the environment in there. I mean, is there any dampness about which can be an issue in non-centrally heated rural houses?

What size of light you intending on using? Is this house a bungalow or two-story? What floor is the grow on?

The more details the more help.

[sid2444]

thanks very useful info. on the subject of fans i looked at the rvk ones they look good but a bit pricy for the size i need . i was looking at a motor and fan company website not hydro . 12 inch metal fan 1800 mh3 99 quid and 10 inch 76 quid. they look solidly made powder coated. 800 positive feedback on site saying there stuff is good quality the fans are advertised for kitchen extractors. will a metal case fan be more noisy than rvk ? i was also thinking of getting the gse fan controller with humidity control 150 quid any body use one of these ? are they worth the money ? also the intake pipe would be 5 meters sucking in just under a slightly open window, do i put the fan in the middle of pipe or near one end ?

[sid2444]

ok the grow will be downstairs room 2 storey. i have been taking advise on the phone off stepson who lives 100 + miles away 10 plants 20 litre pots 6 x 600w dimmable lights so a tent would defeat the object i think ? for moving about etc he has been my mentor up to now but that could change soon after reading on this great site. no damp issues.

[White Warg]

It's difficult to guarantee your fan without some info on brand. Be wary of manufacturer's claims, you Google for Hydromagazine Fan Test Youtube you'll find some youtube tests of inline fans and in the description a link so you can go to the magazine online and read the reviews. Many of the manufacturer's claims are so wide of the tests the magazine had to go back and get all new testing equipment as they thought it must be them. But no, it was the fans. They review actual draw, noise, and wattage draw. For example the Fan Flow fans are slightly cheaper than Systemair, and do a great job, but they draw almost twice the amount of power - basically almost twice the cost to run. Given they're running 24 hours a day that's going to add-up.

So just make sure you know what you're getting into before saving a few quid.

On Ebay I found a Systemair RVK 10" for £75 (widely available) the 12" for £130 (Ebay ID 261979168371). Systemair do not make fans for the hydro hobby growers, and they do not make them for domestic kitchen and bathrooms. The make them for "industry": extraction in professional commercial units.