544
edits
Changes
m
→Choosing a Water Heater
When selecting a water heater for your boat, ensure that it is designed for marine use, e.g., stainless steel. If you select a dishwasher with an internal heater, you can set your hot water heater to a normal 120°F (49°C); otherwise you will want one that can be set as high as 140°F (60°C). Some people recommend settings as high as 160°F to keep bacterial growth in check, but this could be dangerous for children unless you install anti-scald balanced-pressure valves on showers and taps.
== How to Size ==
Some rules of thumb for sizing hot-water tanks were given as part of the discussion in [[WaterCapacity]]. Another way of sizing the hot-water heater is based on flow rates. The table gives a range of flow rates for different water appliances. For a comfortable lifestyle, the water heater is sized based on peak demand.
Assume the following use case based on two couples on board preparing for an evening out. (Six people on board do not change the scenario significantly since there are only two showers.)
* Two people showering (separately in the two showers, silly) and washing their hair. A third person running a faucet in the galley and loading the dishwasher and a fourth person dawdling.
* Two more people showering after the first set. The dishwasher is started accidentally.
The two people showering for 10 minutes will draw a flow rate of 4 GPM, while the person running the faucet for the same period will draw 0.75 GPM, for a total of 4.75 GPM. When the next couple jumps in the showers we will again need 4 GPM plus 1 GPM for the dishwasher, for a total of 5 GPM.
In other words, over a 20-minute period we will consume 97.5 gallons of water. What is significant about this case is that we need a heater with a fast recovery rate or one with a larger tank to buffer more hot water for the second set of people stepping into the showers.
<table width="50%" border="1">
<caption>Flow Rates for 50° F (10°C) Inlet Temperatures</caption>
<tr><th>Appliance</th><th>Gallons per Minute</th><th>Liters per Minute</th></tr>
<tr><td>Faucets</td><td>0.75</td><td>2.84</td></tr>
<tr><td>Showerhead</td><td>1.2 – 2</td><td>4.54-7.57</td></tr>
<tr><td>Clothes washer</td><td>1.0</td><td>3.79</td></tr>
<tr><td>Dishwasher</td><td>1.0</td><td>3.79</td></tr>
</table>
== Types of Water Heaters ==