Is the condenser unit engineered to be optimal with a leaky cabinet? Any reason not to pimp it up, blocking air leaks?

While I was troubleshooting my 12+ yo Carrier AC this morning, I vacuumed out needles and debris that had built up on the floor of the condenser cabinet, and noticed that the cabinet is a bit leaky, with passages that allow air to bypass the condenser. Examples are the gaps between the condenser coil/radiator and it's cabinet, and several unused OEM holes, and several un-grommeted in-use holes.




FWIW, the canine pee pee corrosion blocks 10-15% of the condenser.

On another note, unless best-practices have changed, I will put some pipe insulation inside the cabinet around the low-temp low pressure refrigerant line.

Should I insulate air conditioner coolant pipes?

2 Answers 2


The only thing that doing what you suggest would do is theoretically lower the head pressure. When I service air conditioners often times I have my gauge hoses sticking through the door so there was about a 3/4” gap all around the door. I felt that this would raise the head pressure so I taped all around the door. What I found is that it made no difference. My general recommendation is don’t mess with the factory engineering, it can cause unintended consequences and best case it will do nothing. That condenser coil on the other hand is likely costing you quite a bit of efficiency.

  • If blocking the leakages and insulating the inside line would reduce head pressure, that sounds worthwhile since it would reduce the load on the aging compressor.
    – April
    May 24, 2018 at 3:40
  • The pee pee coil, not to be confused with the tape, I imagine is costing 10-15% efficiency from blockage, but gaining a bit back since there is 10-15% higher air flow through the rest of coil. If there is a DIY fix for the 10-15% of fins that are corroded, please let me know.
    – April
    May 24, 2018 at 3:40
  • About the only thing you can do is maybe straighten out the fins in the coil and keep the coil clean. If having a 3/4” gap around the panel produced no measurable difference in my test then plugging up the factory holes will make even less of a difference. It probably won’t hurt but I am always leery of unforeseen consequences. Old coils just loose efficiency. The aluminum fins delaminate from the copper coils over time and oxidation forms in between lowering efficiency. Dog pee accelerates this process.
    – user76730
    May 24, 2018 at 3:49
  • i'm building an enclosure for the unit to put a stop to the pee pee scandal, and to make some heady, possibly, on the aesthetics front. No fins are bent. Your conclusion would be stronger if you had compared a no-leak cabinet to the 3/4 gap config. I can do a feather test tomorrow to probe the bypass airflow. The fan is cooling the compressor as well as the coil, so maybe the leakage is important.
    – April
    May 24, 2018 at 5:04

The suction line should be insulated all the way to the unit. The holes in the condenser case really amount to nothing if you compare the air flow cubic feet per minute across the coil the small openings would be less than 1% at max , anything within 6" of the coil affecting the flow will affect the efficiency some units require 12-18" free flow for maximum efficiency. The largest gain I see is a good cleaning of the coils, I use a non acid coil cleaner like new brite from nu-calgon, these cleaners foam and strip dirt from between the fins without damaging. I have flushed coils several times they looked clean but when I use the cleaner it is amazing how much more dirt is flushed from the fins. Foaming coil cleaners have been the most effective for me I only mention nu-brite because it is one of the better performing cleaners I have tried. You know you need to prevent the dog pee and until that is done flushing with water to prevent the pee from from damaging the coil will be important.

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