Most Cities in the United States use the International
Mechanical Code, National Fuel Gas Code, Electrical
Code and a few other codes.

In new construction and upgrades, equipment that is replaced shall follow the manufactuers installation
instructions or the International Mechanical Code.
Where one is more restrictive than the other, that
shall be the procedure in which you follow.

If equipment is being re3pqaired or maintained it shall
follow under the code for which time the un it or house was built.

If you move a house into another location, then Im
pretty sure you will have to upgrade to the Code
that is up to date at that City