Thank you for writing. They only takes 2 hot wires and a ground. Also an electrician needs to do the work and to bond the heater too the earth and pool equipment or you can lose your warranty if Hayward finds out. Everyone in the industry want you to use a licensed electrician to wire the heater. Anyone can glue the two water pipes though as that isn't rocket science. There is no neutral. Here is what they say on the Hayward web site copied below as of 08/14/2011. If someone is reading this in the future that might have changed. They say your breaker is too small. But it is possible that you also have a bad compressor, fan motor etc. or it is wired wrong somehow.
50,000 BTU Titanium Heat Exchanger High Efficiency Quiet Operation Electronic Control Easy Installation and Wiring 1 1/2 in Plumbing Connections 220 Volt / 30 Amp Service Required