This tech does not understand the source of the problem and has proposed an expensive and possibly unnecessary repair . What he is saying doesn't make sense. You should not have to replace a 13 year old condensing furnace. I suggest you call another HVAC company and get a second opinion.

I would almost count on the primary being clogged. Need to track down where it is and maybe you can get away with doing a shop vac on the outlet side.

Counter to what Austin sees, in NC at least, a/c condensate lines are not plumbed into plumbing systems. They go to random exterior locations. We also don't have conspicuous overhead locations for overflow lines. At least not that I have ever seen. I am pretty sure they go to the same relatively hidden condensate locations usually (But I am going to try pouring water in them like Austin suggested to be sure). And I am sure they are condensate lines because I see water coming out them when the a/c is running. We have floats and shut offs in the pans. So the usual set up is 2 switches - one in the condensate line and one in the pan. When the condensate line gets plugged, the first switch goes off and the system shuts down. The pan switch is a fail safe in case the first one fails. Leads to a lot of HVAC calls when the system shuts down. This is with attic installs. I have seen just my own systems but I have lived in several houses and this is how it is everytime. So even with attic installs, we never have pipes over doorways (or in garage ceilings). Our hot water pans in attics also go to random exterior locations and the pans have no switches. Interesting variations in practices. Oklahoma is more like Texas than NC of course (Is slab construction one of the reasons for the difference?). This thread just made my next project to install an alarm on my attic hot water heater pan. I think I have an extra one from a basement HVAC pan install on the last house that was never hooked up and I took when we moved. In that case, the condensate line had a pump. I have to say, I don't like the look of those garage pipes but it is the garage.

What causes excessive condensation in your air conditioning? https://www.heating-air-conditioning.org/ So what exactly is causing this excessive condensation in your air conditioning system in the first place? There are a number of factors that could help explain this phenomenon. For starters, this excess condensation could be due to bacteria found in your air conditioner that is creating a clog inside the drain. This clog causes the condensation pan to overfill, and leak water. Another contributor to this excess condensation could be the condensation pan itself, which perhaps is rusted or damaged and is causing water leaks in your homes. Another cause of excessive condensation in your air conditioning system could be a dirty air filter. This is why regular AC maintenance and air duct cleaning is so important. Your AC's dirty air filters could be blocking the airflow over your system's evaporator coil. This causes the coil to freeze, and when it melts, it could be dripping water into the evaporation pan, leading to water leaks.