What kind of air conditioner system do I have

Given how low you're keeping the apartment temperature, and given that the ambient temperature is relatively warm, I think you can probably get away with leaving it in place. You'll lose some heat, but nowhere near as much as you would if the differential between inside and outside was greater.

Digressions:

I've seen some weird-and-sometimes-wonderful approaches to AC mounting. I've generally used smaller units that could get by without external brackets, but I've seen one (in NYC) which used a steel square-bar to bridge the opening and carry the weight rather than letting it rest against the upper sash.

The one time I had an AC which really was too heavy to lift, it did have outside brackets built into its case (rather than permanently installed to the wall). The proper solution was actually to mount the case by itself and then slide the guts into it, rather than trying to manhandle the whole thing at once. When dismounted, I kept the mechanism on a rolling cart that was almost at the right height, so I could slide it from cart to case and back without ever having to lift the full weight.

After reviewing the spec sheet for the unit i have found that the LX series has a variable speed blower that will allow the unit to operate under low ambient conditions. Is specifies the system can operate down to 20 degrees. Anything below this and the system will not operate. If you do not have the LX unit and do have the standard, the. The unit is not permitted for low ambient use.

Most central air conditioning systems do not work under low ambient operation and doing so can damage the system. Residential condensers will very rarely come with a crank case heater for the compressor as well as a low ambient control that can modulate the condenser fan speed to maintain proper operation of the system. This is however common practice on heat pumps and ductless units. Most will only allow operation down to 32 degrees. A low ambient kit is normally required to lower the minimum operating temperature of the system.

The issue on running an air conditioner in cold weather is that refrigerant will migrate underneath the oil in the compressor crank case. When the compressor is then energized the refrigerant will rapidly change state as it is agitated and absorbing heat. This will cause the oil to be forced out of the crank case and will cause the compressor to run dry on oil for a period of time until the crank case has refilled with oil in the system. This can cause the compressor to fail. A crank case heater is utilized to prevent this by keeping the compressor pre heated.

So in conclusion if your system is the LX model it will stop operating when the outdoor ambient is below 20 degrees. The fact that the system is advertised for low ambient operation means that it is ok to operate down to 20 degrees. If it is the standard model then you may have damaged the system from running it in low ambient conditions.