Central vac installation
The wires are low voltage and interchangeable. If you have multi strand telephone wire, i.e. 4 or more colored stands, I suggest running a matched color pair, if you can see where all wires terminate elsewhere in the house. If it is a 2 strand wire there is no requirement for left or right at your INLETS or the vac.
Be sure not to lose the springs under the terminal screws on the inlets when wiring. Only back the screw out enough to loop the wire fully around. If you have metal mounting plates in the wall be certain there is no excess bare wire from your terminals contacting the plates when you install the inlets in the wall.
The short screw if one is included with your inlets goes on the pipe side so as not to pierce the pipe in the wall. IE on the top floor, the pipe would be below the inlet, so short screw is used st the bottom.
When you mount the unit leave at least an extra 36 " of slack in the wire, coil it around a small screwdriver or pencil like a phone cord. This will provide a stress free terminal in case the unit is ever moved.
When done, the system is low voltage, you can jump start it without a shock by using a quarter to short across the terminals at each inlet. Listen for a hiss or flutter at each inlet when the door pops shut. Ideally the door should swing up, to prevent strain from the weight of the hose. If there is any noise as the machine shuts off, back out the inlet screws and adjust for flush fit to the wall.
One more tip, many Cvac INLETS have a narrow rubber O ring on the mounting plate in the wall, which creates an air tight seal to the neck of valve. When the valve is inserted, I wet the O ring with a drop of saliva on my finger tip so as not to pop the O ring out of place... Happy cleaning