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Mismatched airconditioning equipment...


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My brother is paranoid because just found that the central air conditioning equipment at his home installed 30 years ago has always had a 3 ton exterior unit and a 2 ton interior.

What should the behavior of such mismatch ?  Am not an expert in the field to answer without 'maybes' and 'sometimes'  Anyone around knows ?

Question 2:  What behavior should be expected if some technician fed refrigerant R410 in equipment that calls for R22 ?  Anyone knows ?

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#1 - The bigger outside coil should be pushing more refrigerant to the smaller indoor unit than it can handle, which makes me wonder if your brother has this right. The inside unit should be bigger, but if it's smaller by a ton there would be some problems. Some of these units give a range (it can push 2-3 tons), so have him double check the size.

#2 - Carrier systems pushed R410A through the EPA, and it's caused compatibility issues. I'm told R410A operates under much higher pressure than R22, but as long as the system is tightly sealed you should be OK. 

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Thank you, sir.

What I have deduced in the last day is;

Being the location very tropical,

The higher cooling capability of the exterior unit overwhelms the inside unit forming ice in the fins, which blocks the air flow to the inside. The cold air not entering the inside; the thermostat is cranked to a lower temperature which makes the problem worse.  Small slits in the ice formation launch any condensation droplets with high velocity mist wetting the wall by the vent register instead of dripping into the condensate tray under the evaporator.  The pissed-off users crank the thermostat even lower worsening the behavior with a compressor that does not cycle.

Did not check reality, he is 4000 miles away.  As a larger matching proper 3 Ton indoor unit does not fit in the indoor niche; suggested to :

- increase the indoor fan speed as possible with the proper motor jumper setting;

-Set the thermostat to 24C and lower only if there is no ice formation,

-Look frequently at what is going on head-into the evaporator and flashlight on hand.

-Reduce cold losses by windows, doors, kitchen... 

Does it make sense; anything you would add ?

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