When you build Erlang/OTP on OS X, it unfortunately defaults to handling a maximum of 1024 file descriptors. You can get around this limitation with the right combination of configuration options and manual changes to a generated config file.
First, go into your unpacked Erlang/OTP source directory and run the following command, replacing the value 10000 with whatever value you want for max file descriptors:
perl -i -pe 's/(define\s+FD_SETSIZE\s+)\d+/\1 10000/' erts/config.h.in
Next, when you run configure in your Erlang/OTP source directory, be sure to include the right CFLAGS setting, as shown below:
CFLAGS='-DREDEFINE_FD_SETSIZE -DFD_SETSIZE=15000 -D_DARWIN_UNLIMITED_SELECT' ./configure --enable-kernel-poll <other options>