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.
