What about venting a portable air condtioner into the cold air return of the furnace? Good idea or not? Trying not to go through a waal and no window access Thanks
No do not do this! The cold air return of the furnace goes into the house. You cannot vent a portable a/c into the space being cooled. It may seem to work for a while but will inject more heat into the space than the a/c removes.
I agree with Jim but it will cause the home to heat up not "may" AC units need to get rid of the heat outside the home or the net will be a hotter space because of the energy used to run the compressor and fans. Notice window units have part outside, central air systems have the evaporator and compressor out side, a portable unit pushes the hot air out the exhaust that needs to go outside.