AP AP3702I and AP3802I

[karlatentory]

Hi there's a big wifi issue in one of my sites. There are many equipment that can connect only to 2.4, so there's a lot of channel overlapping. There are 14 aps and around 350 devices that connect. My idea was to disable 2.4 and just live 5 band but 2.4 is necessary for the equipment there. Any ideas?

[Flavio Miranda]

Hi

 You can lower the power of 2.4Ghz and keep the power for 5.0Ghz on the top.  You can also enable band select. This can help but do it carefully. Have an asset of your devices just to make sure how many is using 2.4Ghz and how critical they are. 

  Do a site survey to check the coverage, maybe you can turn some 2.4Ghz radius down. 

[Leo Laohoo]

Do not turn on Flexible Radio Assignment and leave 2.4 Ghz alone.

[Rich R]

Use band select to push as many clients to 5 as possible.
If you have PCs using a driver which supports band preference (like Intel) then set the PCs to prefer 5.
Use data rate optimisation on 2.4 - disable the 11b data rates altogether (unless you still have devices which require them).  If you still have devices which require 11b then you probably need to have a chat with the owners about upgrades.
https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-6/b_Cisco_Wireless_LAN_Controller_Configuration_Best_Practices.html#concept_C84096B4070D4377BAA73AB7B4ED05C9
"If your design does not require low data rates, consider disabling the 802.11b data rates (1, 2, 5.5, and 11) and leave the rest enabled."
Check through the rest of that guide for other best practices too.

Interference and busy channels are completely normal on 2.4 these days.  As long as the channel utilisation is not too high you should be ok.

You didn't mention what model of WLC or software version you're using?