Tuesday, June 14, 2016
Frozen Air Conditioning
Let me reiterate my statement at the beginning of the video. Cleaning the evaporator coils on an AC system is not for the faint of heart, or for the accident prone. If you ding up some of the metal fins on the coils (as I kinda did) that’s not a big deal – unless you ding ALL of them really bad as too many mangled coil fins will restrict the air flow. However, if you puncture a refrigerant line, you will lose the refrigerant in the system and need and HVAC tech, incurring more expense.
Go slow and pay attention to the refrigerant lines.
There are two main reasons why an AC system will freeze over like this. One is restricted air movement caused by the air filter and/or coils can be so dirty that it is restricting air flow. The other is that the AC system is low on coolant. First try changing the air filter. Once you are confident that the air filter is not the problem, the next probable cause is dirty coils. This could be either or both the coils at the condenser outside the house, or the evaporator coil inside the HVAC unit inside the house. Dirty coils at either or both locations means that warm air is not flowing properly over the refrigerant lines inside the coils. Without warm air giving off heat to the coils, the coils will drop below 32 degree F and condensation will freeze on the lines. Over time, then entire system has ice on it. The AC system will basically freeze itself.
In my particular case, the AC system froze over because of a dirty air filter and a dirty evaporator coil.
So I turned off the AC system and just ran the whole house fan and after about an hour the coil had thawed out completely. While that was thawing out I hosed out the coils on the condenser outside. These were just cleaned a year ago by an HVAC tech using commercial grade coil cleaner, so this time I just hosed down the coils, then sprayed a fair amount of Simple Greene on the coils to help loosen up the dirt before I gave them a final rinse. Using a commercial grade coil cleaner too often will erode the finish on the coils and eventually necessitate replacement sooner than would have been necessary otherwise.
If I had the proper tools and refrigerant on hand, I could have removed the refrigerant lines from the evaporator coil and then removed the coil from the HVAC unit. This would have made cleaning the evaporator a lot easier and more thorough. However, that’s … not me, so I had to remove a triangular metal plate in order to get to the underside of the evaporator coil. This was difficult to do because the refrigerant lines were in the way of removing that metal plate easily. So I tried to cut the sheet metal in half with a pair of right-angle tin snips, so that I could remove it in two pieces. However, I couldn’t reach all the way across and I ended up having to shimmy out the sheet metal. I did this by gently lifting the evaporator coil up an inch or two (it is not bolted down), but not much as I did not want to put too much stress on the refrigerant lines. Then I was able to tip the triangular metal piece into the A frame of the evaporator coil. Then, again while lifting the coil up an inch or two, I was able to remove the sheet metal given the available clearance.
The evaporator coil was so dirty it was like a quarter inch thick layer of really nasty, dryer lint – yuck!
Below the A frame on my unit is the heat manifold and I didn’t want to knock all that dirt off and down into the system, so I carefully vacuumed it off by lightly tapping the vacuum duster and allowing the vacuum to do the rest of the work pulling the dirty lint off the coils. I probably could have stopped with that, but to do a thorough job there was still more cleaning to do.
I bought some no rinse evaporator coil cleaner and I sprayed on a heavy layer of that onto the top and bottom side of the evaporator coil. I let that soak in for a while to give it time to eat into the dust inside the coil fins. Even though this is a no rinse cleaner, I used a spray bottle of plain water to expedite the rinsing. I also poured some water into the collection tray to flush the dirt out and down to the drain.
Once the coils were all cleaned up, it was time to put this metal plate back in. I struggled to get that triangular metal sheet back into place and it was only after the job was done and I’m watching myself on video put it back in that I realized – I’m a dummy. Regardless if there was an easier way to remove it, at that point being that it was already removed, I could have finished cutting it in half and made the job of putting it back in a lot easier as two pieces. Duh!
Once the metal plate was screwed back in place I sealed up that cut I made with some aluminum tape.
Then I put everything back together and my house is cool again.
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