For starters, if you don't have a cooling source to bring the temp DOWN, I wouldn't use a brewbelt, which is designed to keep temps up.
It's VERY important to keep temps fairly stable and in the yeast's preferred range. At 24C you're too high. If this is the first big day of fermentation, the results are likely irreversible and you're going to get higher alcohols/fusols/jet fuel/hot type esters from the yeast. I'd get the belt off of there. If the temp dipped one degree below the target it won't hurt you. If the belt kicked in and thrust it 4 degrees ABOVE the target, it'll have a negative impact.