garage door not working

I am adding some new curcuits to a panel box. I do not have any new knock outs to use. I have thought in the past that per code you can only put (1) NM cable thru a connector, but the bag of 3/8" NM connectors I have says "For one or two 14-2 to 10-2 nonmetallic sheathed cables". Which is correct? Thanks Jeff

Another question regarding the 220V 50Hz silent compressor I mentioned in my other post about Step-Up transformers: I have received conflicting answers on this question so I thought I would ask her also. From what I have researched it seems that a 50Hz electric motor will run allright on 60Hz power here in the U.S. but vice versa will damage the motor quickly. Would you concur with that? I called the U.S. branch office of the company that sells this compressor and asked the technician if I could run it on 60Hz power. He said he would have to check and then came back to the phone and told me that it "should be OK to run on 60Hz." I am wondering if that is the truth or if he just asked someone who may or may not have known? I also called another company that makes compressors almost exactly the same as these and the technician there told me that running it at 60Hz will work but that it will probably only last a year or so. So now I am wondering who is right and who is wrong? I appreciate any input you may have. Thanks Mike