I don't think anyone makes a 240V portable air conditioner unit. Even if they did, it would not be switchable between 120V and 240V. That a feature would be very expensive to include in the product. There are window units which require 240V. These typically units larger than 10,000 BTU.

This is forum is really good at keeping you from doing something not so smart. You will be moving heat twice as Brickeeye said. So it will double your electric use for cooling the attic. It would also kill your protable a/c faster since that return vent won't provide enough circulation for the portable a/c. There is just no way around the window placement ... except a through the wall placement. The outside part needs to be outside. Now - if you want to try a blower fan at the vents in the attic - go for it (these are fans only that pull extra conditioned air into spaces that don't get enough circulation). These don't do as much as you'd think and rarely work adequately but might be worth a shot. Best option is to redo the ducting.... Stories like this are way too common. How did these houses get built or areas get finished? Unpermitted? B/C in my area, any finished space needs full HVAC with thermostats on every floor (I think with either separate units or full zoning controls)

aceh, have you been talking to my grandmother? :-) A window unit does not work the way you described. For one thing, on any air conditioner, it's the evaporator that cools the room air, not the condenser. The condenser dumps the collected heat. Have a look at . The partition is shown partially cut away, but in actuality it extends across the width of the unit in front of the compressor to keep the indoor and outdoor airflow path separated. Room air is pulled by the blower through the filter and evaporator in front of the unit and blown back into the room. The separate outdoor fan pulls outdoor air into the grills on the outside of the unit's cabinet, and blows it through the condenser at the rear. Some window units have a fresh air setting, which opens a small panel through which a very small amount of outdoor air is supposed to be brought into the room, but most of them don't have much effect.

As Fotostat said, the portable a/c is often not as efficient as a window unit (especially if you have a portable a/c with just one hose -- the ones with two hoses are more efficient). But it's going to draw about 800 to 1,000 watts, which is a lot less than your central a/c unit. If you can cool your bedroom with it at night, I think you would save energy over your central a/c unit, but only if you exhaust the unit's output hot air to the outdoors, not to another room of your house. To answer your question, there are no bad health effects that would come from exhausting the hot air to an adjacent room, but you'll just be adding 8,000 BTU of heat to your house, plus the heat of the compressor itself, plus humidity, so you'll be adding maybe 12,500 BTU of heat to your house, which would erase any savings you'd get from turning your central a/c up to 76. So you do need to exhaust the air to outdoors, but I can understand your security concerns. Could you modify the door's latch mechanism, or make a new latch of some type that would allow you to secure the door when it's open a few inches, so it could not be opened further. What about a metal bar or block of wood placed in the track to keep the door from being opened more than the few inches you need it to be?