You could use a temperature controller module such as this one https://www.amazon.com/Temperature-Controller-Display-Thermostat-Waterproof/dp/B07H2X4NNR/ref=sr_1_31?keywords=temperature+sensor+relay&qid=1574123185&sr=8-31
Say you have 50 fans in total , run 10 of them direct 24/7 , use a temperature controller on a contactor that controls the MCB of say 10 fans, and set the temp to say 28c , another set of 10 fans on 30c and so on , this way you get to save on power and fan's lifespan, this is just an idea i know people use in other fields aside from mining, it's efficient and pretty cheap to set up , so you might consider it , as for all the other small details , again , hire a professional.
That temp control module looks great. That is essentially what we are doing with automating the fans, but using a temp sensor we already have for temp alerts: https://store.wirelesstag.net/products/wireless-tag.
Fair to point us to a professional at our size, and maybe we will go that way, but I wonder if a professional is going to make up for their cost. The downtime and low power cost us around $10,000 this summer. We believe we can cut that by ~75% with some low cost improvements.
So on the cooling side it's something like this: $2500 per summer + low cost solution + labor to monitor and handle heat shutdowns vs. hiring a professional + work and materials to implement that. One reason for posting is to learn if there are a number of other efficiency improvements to be made that would warrant paying for a professional.
