Help_1: Thanks for the extra info.
Is there a By-law in place at your scheme which prevents, or governs a/c installation?
Town houses sometimes differ from multi level Lots with regard to common property. Townhouses may have different boundaries for common property (particularly if they are detached town houses) and different definitions of what is structural and who owns and is responsible for maintenance of the exterior walls etc. You may need to check up on this.
Section 110[1] may not even need to apply to you. The a/c will be installed within your own Lot boundary and the exterior wall may not be common property that is “in connection” with your Lot. This is clearly something that you will need to clarify.
110 Minor renovations by owners
(1) The owner of a lot in a strata scheme may carry out work for the purposes of minor renovations to common property in connection with the owner’s lot with the approval of the owners corporation given by resolution at a general meeting. A special resolution authorising the work is not required.
The requirement for an a/c to be approved by the OC as an Ordinary Resolution only applies if the a/c will impact on common property.
Perhaps that is why Lot 3 has installed an a/c without any paperwork or written approval.
If the OC has not requested the removal of the a/c at Apartment 3 then it appears that tacit approval has been given, or acquiescence has occurred.
However, if you do decide that the a/c installation is “in connection to common property” then you will need to submit a proposal to the OC regarding the a/c installation. This written notice should include all details you have about the system you’d like to install, including brands, installer information, photographs of where the system would be installed and any relevant plans.
As Jimmy has said, you will need approval via an Ordinary Resolution. Approval cannot be unreasonably withheld.
If you want to speed up the process then you could offer to pay the cost of holding an EGM. Depending upon the size of the strata scheme this suggestion may not be too expensive. Find out the cost before making the offer though.