Air Conditioning - why do i have to run my window unit on a single circuit

I have a large capacity WINDOW unit almost a 1 ton unit 10,000 BTU AND a 1/2 and 1/4 ton unit 8,000 BTU that says use on single circuit outlet only WHY it works without it they both use standerd 110v household current.

P.S it says use time delay fuse why. Yes my house still has the old fashon fuses:o

The A/C units you have use nearly the full capacity of a standard circuit. They may even need a 30 amp circuit which can't be used for general purposes because lights and appliances are wired to be safe on 15 and 20 amp circuits only. During compressor start-up the units use more than the full capacity of the circuit, which is why they need a time delay fuse (most are these days). The time delay will allow the unit to pull considerably more electricity for the fraction of a minute it needs to start.

If you have other devices on the same circuit, you will 1) Likely exceed the capacity and blow the fuse often, which may encourage you to do something foolish like putting in a higher amperage fuse. 2) Place extra strain on the other devices during compressor start-up when they will be robbed of the electricity they need to run. 3) Place extra strain on the compressor during start-up when it may not get all the electricity it needs to start quickly due to the other devices.

Doug M.