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Question DetailsAsked on 5/20/2017

do I have to use the exact same compressor in house ac or can I go bigger?

its copeland ZR21K5EPFV830 Do i have other choices?

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1 Answer


Basically yes - identical or functionally identical compressor has to be used.

You have to use a compressor with the same rating, because too small a capacity one or too low pressure will result in inefficiency and excessive runtimes, and too large a one (even if correct pressure capacity) will also be inefficient. If the TXV control valve is working right an oversized one will "loaf" or may overpressure itself but will not result in measureably greater cooling capacity because the TXV will only allow the same amount of refrigerant through it. The cooling capacity of the system is limited (assuming the compressor has at least the minimum required capacity) by the pressures which the TXV regulates and primarily by the evaporator coil sizing and heat transfer capacity.

In some older units with static TXV valves one could "overdrive" the system with higher than design flow and get more cooling - but it was vary bad for the compressors, and unless the system ovaerall was signfiicantly undersized, resulted in short-cycling which can cause mold issues on the coil and in the ducts.

It is illegal to install a component on an A/C system which cause it to function outside the design operating range - so basically you are limited to an OEM replacement or identically rated aftermarket components. Therefore, while going with a larger compressor and new/adjusted TXV and a larger capacity evaporator coil and larger capacity condensing coil and fan (meaning you have essentially replaced the entire system) might give you more cooling capacity (at more cost than a totally new system), it is still illegal to modify the system liek that because it voids the energy efficiency rating and certification of it.

If you system is not producing the required cooling or has to run too long each cycle to do so, your choices are (assuming it is operating in the design range) to replace it with a larger system, or install an additional system like maybe a mini-split or window air conditioner to make up the difference. This is a common solution in spread-out houses with long tubing runs, and in houses which have had an addition added.

Answered 3 years ago by LCD

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