Dense foam insulation provides better and longer heat retention than traditional fiberglass. The tank itself is protected by a 75 PSI T& P ( temperature and pressure) relief valve. The cylindrical design of the tank enables it to withstand more pressure than a cube shaped tank. Heat exchanger models can be connected to the engine cooling system. The innovative heat exchanger is over seven feet in length and is evenly coiled throughout the interior of the tank, providing hot water rapidly and efficiently. Raritan's water heaters use an ignition protected thermostat. Although it is factory set to 120F, it is adjustable from 110 to 160F and has a safety shut down limit of 190F. All models and sizes have the plumbing connections on the same side to simplify installation. Hot and cold water connections are 3/4 male NPT (National Pipe Thread). Heat exchanger connections are 3/4 female NPT.