The Installation of household water heaters in vessels

The installation of household water heaters in vessels.

Quite often, household water heaters are purchased for installation in boats. This decision is generally made in an effort to save money. These will typically be 120 volts units, 20 gallons or less with a heating element of 2000 watts. The following information is presented in the interest of safety. NOTE: always, read and heed manufacturer’s warnings and recommendations for any product.

Electric Marine Water Heaters: They come in many sizes, shapes and construction to accommodate installations in boats. Most offer optional heat exchangers. Marine water heaters are ignition protected (should be unless otherwise noted). The exterior jackets for most marine water heaters are made from materials that better withstand the marine environment (not all). The heating elements will normally range from 1200-1500 watts. The T&P (Temperature and Pressure) relief valves on Marine Water Heaters are set at 75 PSI. The T&P valves on household heaters are set at 150 PSI. Never use an old T&P valve. Generally, marine water heaters come with very good instructions applicable to installation in boats.

Prior to purchasing any water heater you should know the wattage of your current water heater. (After all it was working for some time until replacement was needed.) In all probability the electrical supply circuit was rated for the existing heater. Should a heater with a higher wattage element be installed, there may be problems with overloading the supply circuit resulting in circuit breaker tripping.

Some Facts To Consider About Household Electric Water Heaters:

Fact One: Household type water heaters are not ignition protected. If a household water heater were to be located in an area that requires ignition protected devices, the thermostat would have to be changed to one that is ignition protected.

Fact Two: This heater would probably be equipped with a 2000 watt heating element. This wattage may be excessive for the existing electrical supply circuit. Should this be the case, one of the following two things would have to be considered: 1.The purchase and installation of a heating element of less wattage (this would probably be the same wattage as the old water heater element.) 2. The Up-grading of the water heater electrical supply circuit.

NOTE: Instructions are normally provided with all new heaters that discuss the electrical requirements such as conductor and circuit breaker requirements. There are normally warnings with respect to safety issues, take them seriously. Prior to any up-grade to handle an increased in wattage, the effects of this up-grade would need to be considered. Even a small amp load increase on some vessels could be problematic. The difference in amp loads from 1200 watts to 2000 watts is approximately 6-8 amps, depending on voltage. Watts divided by voltage = amps.

Fact Three: The T&P valve if supplied with the heater would have to be changed to a 75 PSI valve as mentioned above. Again, never use an old T&P valve.

NOTE: Water temperature above 125 degrees can cause severe burns. This can happen instantly. The subject of burns/scalding, hydrogen gas generation and bad odor will be discussed in ‘TIPS" 14A.