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1700cfm 4.1 amp 12" online fan speed controller?

Discussion in 'Grow Room Design & Setup' started by p0opstlnksal0t, Mar 4, 2018.


    p0opstlnksal0t Active Member

    Anyone have any ideas what fan speed controller I need? I've used the cheap rheostat versions and they just can't supply the amperage. I bought a 5 amp variac and it blows the 5 amp fuse on startup. I tried a 6 amp fuse and half the time it will blow that. When it doesn't blow it and I dim the voltage do around 78 volts everything runs OK for a few minutes then the fan shuts down due to the thermal overload protection and takes about an hour to cool down before I can plug it back in and have it work again.... not sure what I should try next?

    Zero_OS Member

    why not try a 15A variac? This should solve the fuse blow issue, not sure about the overload protection though. Check out the used Staco variacs on ebay.

    p0opstlnksal0t Active Member

    Ya my fear is buying another varia just to have the fan shutdown at lower speed due to the thermal overloadprotection. Would a vfd be a better choice?

    Zero_OS Member

    I haven't used a VFD, but it should work. I know they work wonders on grinders and other standard AC motors.
    Last edited: Mar 4, 2018

    HydroEnthused Member

    VFD’s work but always eventually break. When will they break? 5 yrs? 10yrs? Maybe less time? It’s hard to predict when but instead of fan speed control I use multiple carbon fan/filter sets in conjunction with inlet dampers. There are different combinations of fans turned on according to the outside temperature. Air flowing into the room is controlled with automatic round dampers that throttle open and closed according to the grow room thermostats.
    This eliminates the possibility of ventilation failure due to VFD breakdown and with a repeat cycle time delay to very slowly “inch” the dampers open/closed, you will smoothly maintain the exact temperature you desire if using mass air flow to vent heat and during cool months of the year. The method is implemented with 10 amp general purpose relays, delay timers, repeat cycle timers and other simple reliable electrical control components that are not likely to break down when their electrical contact terminals are drastically under loaded.
    I am able to maintain spot-on 84f at canopy height and 77f at the base of the stalk during 8.5 months of the year without air conditioners using this variable air volume method. I’m out on the east coast.

    p0opstlnksal0t Active Member

    That's a great idea man.

    My temp is very stable with my current setup using a pair of 12" electric dampers that open/close when temp hits above 79.5f and close when. Temp drops back below 79f. My only issue is the humidity. When the room exhausts the humidity drops 15% points then builds back up and repeats every 10 min or so.

    Below you can see the humidity cycles while the temp is almost linear at 79f


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