This page contains a Flash digital edition of a book.
What’s the best heating system for your boat?


We would like to discuss some of the factors that will influence your choice on how to keep your boat warm and toasty. As in all choices on a boat, the starting point is how you plan to use the boat as temperature control. It relates to our bodies not just as a luxury- it is important at a certain level for our survival.


By Jack and Alex Wilken Boat Use As in all choices on a boat, the


starting point is how you plan to use the boat as temperature control as it relates to our bodies is not just a luxury- it is important at a certain level for our survival. This is going to range from weekend


use, living aboard, or leaving the dock for a beautiful winter weekend in the San Juans.


How much heat output do you need? This depends on insulation,


window size, thermal leaks and how cold it is outside. An easy rule of thumb is to calculate the interior volume of your boat in cubic feet and multiply by 12 for sailboats and 15 for powerboats. This will give you a good idea of the BTUs (British Thermal Units) needed. When sizing diesel heaters it is better to get the next size bigger, rather than the next size smaller, and have it running less of the time.


Electric heat at the dock Most of us spend a lot of time


tied up and therefore probably have shore power available to us. The most typical electrical service at a slip is 30 amps of 110/120AC. This is equivalent to approximately 3,600 watts of electrical power at 120 volts. Why


reading only 99 volts. At 99 volts you only have 2,970 watts available. Yes, that means running two 1500 watt space heaters on full at the same time is too much. This is all before you turn your battery charger back on or try to use the toaster. Your 30’ boat will need around


7,000 BTUs to have a little reserve on heating capacity. As we said above, this will depend on insulation, size of the windows, thermal leaks and how cold it is outside. This is not just to keep things from freezing but to make it really livable. So, although dock power is cheaper than diesel fuel, it has its limitation – a limited amount of watts – even before we try to leave the dock. One other little matter we should


not forget is hot water. If you have a 10 gallon or so electric water heater, it is drawing 15 amps some percentage of the time, and therefore competing for a big part of the available shore power. Note: When we think about


electrical space heaters we should consider installed as well as free standing. There is a brand of installed heaters that offers a large range of heat settings as well as thermostat control and a very quiet fan motor. If you have the space, the electrical and the diesel systems discussed below can be a good combo (Figure 1).


Figure 2. This is a typical exhaust fitting with the air intake and the combustion exhaust incorporated together.


Figure 1. This is part of a hybrid system with the electrical heater mounted above and the hydronic air handler or radiator below.


48° NORTH, JANUARY 2012 PAGE 50


“approximately”? Because, the actual voltage arriving to your boat depends on several things, some of which are not in your control. If we assume a solid 120 volts coming into the main breaker for your dock and a first class installation on the dock, we still must deal with the usage of the other boats on your dock which are upstream of you. “Upstream” in this case means between you and the power source. Other things that can cause voltage drop are the length and condition of your power cable (the longer the cable, the greater the voltage drop); corrosion or oxidation on the connectors will cause resistance and therefore voltage drop; and finally your power usage. We have seen boats at the end of a dock which are using 20 amps and are


Diesel fuel This is a power source that we


can tap that allows different choices in heating. Basically, there are two possibilities: 1) Use a diesel burner to heat air and then circulate it, or 2) Heat


Figure 3. This heat exchanger is plumbed into the engine’s cooling system. Note that it is mounted at an angle to promote circulation as the heating system preheats the engine.


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108  |  Page 109  |  Page 110  |  Page 111  |  Page 112  |  Page 113  |  Page 114