I came out for a condensate leak on the upstairs system. I checked the system over and tested the drain. There is a clog in the P-trap. I vacuumed out the excess water in the drain, cut out the P-trap and vacuumed out the drain line in both directions. I poured more water down the drain to check if there’s any other clogs. The rest of the drain is clear. I reconnected the drain, without the P-trap because it isn’t needed in that coil. I re-tested the drain with 2L of water. All working properly.