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Electrical Installation

The intricacies of electrical installations are a mystery to most people not least the writers.

Fortunately owners don’t need to be electrical experts to operate their vessels but they should have a reasonable understanding of the principals involved.

Most systems are pretty much fail safe and even when troubles occur the vessel is never disabled completely.

Installations may be one of or a combination of the following types:

(1) Direct Current low voltage systems (DC).
(2) Alternating Current high voltage systems (AC).

Direct current systems operate on either 12 or 24 volt reticulation and a trawler yacht can be designed to operate quite satisfactorily, albeit restrictively, using these voltages.

The great disadvantage is that this voltage is unsuitable for high power demand equipment such as air conditioning systems, watermakers, coolers, washing machines and the like. If the owner is prepared to forego some of these comfits D.C. systems are generally the least expensive option.

Some of the disadvantages can be overcome by using a solid state D.C. to A.C. invertor for running such things as entertainment equipment, microwave ovens, lights and fridges.

The following table shows how D.C. ships services could be set up.

A 24 volt D.C. ship underway should be able to operate the following equipment satisfactorily. When not underway much of the electrical equipment would however be severely restricted.

EQUIPMENT

VOLTAGE

DUTY

Lighting
NAV. Lights
Electronics
Toilets
F.W. Press Set
F.O. Transfer Pump
Auto Pilot
Alarms
Macerator Pumps
Bow Thruster
Fridge
Freezer
Accommodation Fans
Entertainment Systems
Computer

24V
24V
24V
24V
24V
24V
24V
24V
24V
24V
24/110V
24/110V
24/110V
24/110V
24/110V

Selectively
Continuous
Continuous
Intermittently
Intermittently
Intermittently
Continuously
Intermittent
Intermittent
Intermittent
Static Inverter
Static Inverter
Static Inverter
Static Inverter
Static Inverter

Water Maker
Air Conditioning
Galley Hot Water
Hot Water Heater
Washing Machine
Dryer
Cooker/Oven
Bilge Pumps

-
-
-
-
-
-
-
-

Engine Heat Evaporator type
Not possible(under develop.)
Gas califont
Engine Heat Exchanger type
Not possible*
Not possible*
Gas
Mechanically driven

Engine Room Fans

24/110V

Static Inverter (possibly)

* It may be possible in some installations to run this equipment from the 24v/110v static inverter source.

In practice, for an owner contemplating a live aboard ocean cruiser, the best option is to install an A.C. system.

To meet the power demand one or more dedicated diesel generator sets are installed. These units are supplied by specialist manufacturers and are self contained, often acoustically encased machines.

The genset output has to be sized to meet the max. continuous power demand of all the ships services. This is the sum of the electrical load of all equipment expected to run consequently at any time plus a suitable load margin.

The trouble with this is that for much of the time the genset will be running at next to no load or very intermittent loads. Usually therefore a 24v/110v static inverter is fitted also.

On long ocean passages a separate cruise generator can be fitted to the main propulsion engine. This is designed to operate at the cruising rpm of the engine. Because alternators must run at a fixed speed this arrangement works well on long runs where the main engine speed is never varied. Not only does this give two separate sources of power aboard the vessel but it also means for much of the time the main genset can be shut down.

Appendix 1. is an Electrical Specification for our WATSON 72 which describes an electrical system in some detail and is typical of all our designs.

DESIGN AND INSTALLATION

(i) System Design
The system design should never be entrusted to someone not familiar with marine electrical systems. More over the contractor should be familiar with Class Society Rules and Regulations. Marine electrical installations are quite a different field to residential or industrial installations.

(ii) Installation
Once again the electrical contractor must be a specialist in the marine field. Only they are familiar with installation standards required. They must have had experience with wiring vessels to Classification Society standards.

Marine electrical systems must operate in an extremely aggressive environment and applying normal industrial standards anywhere is unacceptable and will only lead to maintenance headaches in the future.

Last Updated (Saturday, 29 August 2020 03:36)