Common Condenser Problems
Number one on the list of common condenser problems is… ITS DIRTY!
Condenser are subjected to air or water that is contaminated with all sorts of stuff. The contaminants hinder the heat transfer and cause condensing pressure to increase, capacity to go down, higher compressor temperatures, high amp draw, etc. in short, everything must work harder if the condenser can’t shed the heat from the system.
On water cooled condensers, the small temperature difference is a good indicator of cleanliness. The small temperature difference is the actual temperature of the refrigerant leaving the condenser minus the temperature of the water leaving the condenser. For example, a unit with a refrigerant temperature of 100 F and a leaving water temperature of 95 F. That is a 5-degree small temperature difference. For copper and copper-nickel tubes, it should run from 5-15 degrees, steel, from 12-22 degrees, after that, clean the condenser.
Air-cooled condensers usually can be visually inspected to tell whether it needs cleaned. (Micro-Channel® condensers can be challenging to tell if they are blocked off, and hopefully you don’t get stuff stuck in between the layers).
If you can’t make a visual assessment, you can compare the heat exchanger thermal effectiveness with the design. Thermal effectiveness is, (Air out – Air in)/ (Air out – refrigerant saturation temperature). For a typical split system, A/C the calculation looks like the following – (130 – 95) / (120 – 95) = 1.4. If the effectiveness is less than expected it likely needs cleaned (or its under-charged). If you can’t measure the air out, a good estimate is the square root of the discharge temperature multiplied by the ambient. Sqrt (190 X 95) = 134
Other conditions that lead to high head pressure:
1. Head pressure control may not be working. Head pressure controls can be bypass or fan speed controls.
2. Bad fan motor.
3. Loose belt.
4. Worn sheaves allowing belt to slip.
5. Wrong sheave causing lower than needed fan speed.
6. Air-flow is blocked.
7. Bent over fins.
8. Damaged pump vanes cause internal bypass.
9. Pump impeller worn causing low volume.
10. Leaking pump discharge check valve.
11. Leaking hot gas bypass valve allowing discharge gas into evaporator when not wanted.
12. Broken/missing fan blade.
13. Plugged strainer.
14. Non-condensable in refrigerant.
15. System overcharge.
16. Condenser air short cycles from poor location i.e. too close to opposing walls.
And, believe it or not, low condensing pressure usually isn’t a condenser problem. You could have a fan cycling control that doesn’t turn the fan off when the head gets low, or, you could have a condenser water valve stuck wide open for some reason. Most likely, the unit isn’t charged correctly or has no load, but its not a condenser problem.
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I worked for over thirty years in the HVACR industry. I have designed, installed, serviced, and trouble shot units of various types throughout the years. The posts here are information based on that experience, I hope you find them useful. If you have a different experience, please comment.