The model I have is the Yamaha 2400IS which is the older model. I have had this generator for about 8-10 years. This model was parallel capable and has the sockets for a special paralleling cable to be connected.
A few years ago, approximately 5, Yamaha came out with the 2400ISHC which has a little more surge capacity but does not have the parallel cable potential. Why I am not sure.
To my knowledge, these are the only two sub models of the Yamaha 2400 generator.
My generator, the 2400IS will run a 13500 ac most of the time but I have had incidents where it would not restart the ac compressor after it had been run awhile. Many of the users complained it would not start their ac at higher elevations also. I think the 2400ISHC was designed to correct this problem.
