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Caravan Fuses and Circuit Breakers – how to know which to use

by Collyn Rivers

Caravan Fuses and Circuit Breakers

Circuit breakers and fuses in caravans both cut the current, but in different ways. Here's how to know which best suits circuits and appliances protected. Those for 230 volt grid or inverter supplied circuits must be specified and installed by a certified electrician - who will install caravan circuit breakers etc anyway. Circuit breakers and fuses for RVs (for 12/24 volt circuits) can be self-installed by those familiar with such work.

The problem with fuses

A fuse is a short piece of wire that heats up and melts when current flow exceeds the fuse's melting point. Caravan fuses are cheap and simple. They respond very fast to excess current. Fuses usefully safeguard sensitive and costly electronics - such as computers. Many such devices have fuses inbuilt.

A fuse's downside is that it will not cut the current quickly. This is a drawback with water pumps, fridges and electric motors etc. Some draw up to five times their working current whilst starting. A fuse must thus be oversized to cope. Whilst slow blow fuses overcome this, few RV owners know they exist. Let alone know why they are needed. Further, only the most costly can be relied on to blow at their intended current. Another failing is that a fuse must be replaced by when it blows. If that which caused it to blow remains, the replacement also will blow. On the plus side, caravan fuses are cheap. They are stocked by most hardware stores.

A further issue with fuses is that there are known problems with some blade fuses and fuse holders. These are mostly over 10 amps or so. See Blade Fuse Problems in Caravans. Fuses and fuse holders tend to corrode. This causes heat to be generated to the point where they may melt. They may catch fire - yet not necessarily blowing the fuse.

Caravan fuses - blade fuse mounted

RV fuses and circuit breakers - how circuit breakers work

Circuit breakers are a type of switch that turns off when they detect excess current. They are then manually reset. Some automatically reset, however these are best avoided - because the cause of such tripping may still remain.

The better-made caravan circuit breakers operate more reliably at their rated current. This is a plus with loads with a high starting current. They also double as manual on/off switches.

Fusible link blue seas web

Fusible link - the material above and below the fusible link dampens the explosive forces if/when the fuse link blows. Pic: Blue Seas.

Circuit breakers should be located close to the battery as possible. This protects the cable in the event of short circuits downstream from the circuit breaker. In some instances, caravan fuses are used in place of circuit breakers, but usually to save cost. It is not a good electrical practice to do so. If funds are really low, so-called fusible links (below) can be substituted for circuit breakers. This can be done in (say) the feed to a large inverter that may carry 200 amps or more.

High current fusible links go off like fireworks if/when they blow. They need locating so that any such debris is contained.

Circuit breaker dc 12 volt shop

This high-quality circuit breaker doubles as an on/off switch. Pic: 12-volt shop.

Caravan fuses and circuit breakers - which to use and why

An RV may have multiple cables that each feed a specific item - e.g, fridge, water pump, TV, computer etc. Here, the current flowing through that cable is reasonably constant, and thus readily known. This is the usage where suitably rated caravan fuses work fine. Each fuse is installed as close to the battery as feasible - yet accessible. It needs to so located as it thus also protects the supply cable if it is shorted out.

Many caravans and motorhomes have several main cable feeds. Each serves a number of different items that may or may not be used simultaneously. Here, the fuse rating must cope with the maximum load. It may blow slowly (or not at all) if a fault occurs when only one item is switched on. Circuit breakers, that accommodate the cable's total load, need locating as above. This protects the supply cable, but as the breaker must cope with the total load it may not act fast enough to adequately safeguard. Any connected appliance thus also needs an appropriately rated fuse. Locate that fuse as close as possible to the appliance.

A typical caravan or motorhome is thus likely to need one or more circuit breakers as close as feasible to the battery. Plus an individual fuse adjacent to each appliance.

There are major differences in circuit breaker quality. Good ones are not cheap but well worth the price.Make sure the ones you buy are designed for 12/24 volt dc. The best are stocked by marine suppliers, but there are many other sources.

Other information

If you liked this article, you will also like my books. All are technically correct yet written in everyday down-to-earth plain English.

Full details of every aspect of RV electrics and their installation is covered in my Caravan & Motorhome ElectricsSolar That Really Works covers solar in RVs. Solar Success covers home and property systems.

Caravan & Motorhome Book is a comprehensive guide to every aspect of caravans and motorhomes.  Likewise, all related issues are covered in the Camper Trailer Book. For information about the author please Click on Bio.

Articles by Category

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Electrical (general)
Batteries & Battery Charging
General
Travel
The Camper Trailer Book

Want to find out more? Our books cover all these topics and a lot more. 

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Whether you’re buying your first RV or updating to a bigger, more comfortable rig, there are a great many things you need to know and consider. How to Choose and Buy an RV breaks things down so that you can decide what you want and whether or not what you’ve found is right for you.

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Cover of solar success by collyn riversSolar Success explains how to design and build home and property systems that ensures affordable solar success first and every time.

 

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Between 1959 and 1961 Collyn Rivers and Antony Fleming drove a Bedford QLR off-road truck twice the length and breadth of Africa studying road surface conditions.

A 43 minute film about their adventure, produced and narrated by Antony Fleming, has been viewed on YouTube more than 1.6 million  times!

Picture from africa journey. Caravan and motorhome electrics by collyn rivers

To view the film, and also read Collyn's telling of the tale, just click the button below.

Africa 

Cover of how to choose and buy an rv by collyn riversWhether you're buying your first RV or updating to a bigger, more comfortable rig, there are a great many things you need to know and consider.  This book breaks things down so that you can decide what you want and whether or not what you've found is right for you. It's technically sound and comprehensive so that you can proceed with complete confidence.  How to Choose and Buy an RV is the ultimate guide for those times when you want to, well, choose and buy an RV.

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Cover of why caravans roll over by collyn riversCaravans and their tow vehicles rarely jack-knife and roll over - but when they do the results are catastrophic. The cause, and how to prevent it, is explained here.  Why Caravans Roll Over offers solid advice for keeping yourself safe on the road.

learn more

 

Cover of caravan and motorhome books by collyn riversCaravan & Motorhome Electrics is the totally rewritten successor to the original globally selling Motorhome Electrics. The book's content now also covers every aspect of designing, installing and fault finding of the electrics in fifth wheel and conventional caravans, camper trailers and motorhomes.

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Cover of solar success by collyn riversSolar Success explains how to design and build home and property systems that ensures affordable solar success first and every time.

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Home page - rv books, collyn rivers, rv books for beginners, solar books, best rv books, rv repair books, solar success, caravan and motorhome electrics, solar that really works, the caravan and motorhome book, why caravans roll over, how to choose and buy an rvThe Caravan & Motorhome Book covers every conceivable aspect of camper trailer, caravan and fifth wheel caravan, campervan and motorhome usage. Like all of Collyn Rivers' books it is technically sound yet written in plain English.

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How to Choose and Buy an RV

This is Collyn Rivers' newest book.  Building on his years of experience and extensive knowledge of engineering and all things caravan and RV, this is the book you need with you when shopping for an RV.

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Collyn Rivers has done it again! – if you need to know anything about motorhome electrics, then this book is for you... Collyn must be, without doubt, the foremost authority in Australia on this subject.

The Wanderer (Campervan & Motorhome Club of Australia Ltd)

Why Caravans Roll Over....and How to Prevent It​

Should be compulsory reading for everyone involved with Caravans: Design / Engineering, Marketing, Journalism (print & electronic), Regulations, Inspections, Driver-Training, Caravan Clubs, Towing and Modifications.

Colin Young

Founder and CEO, Caravan Council of Australia

Solar that Really Works!

Collyn is an accomplished engineer who knows how to design and build successful systems. It is refreshing to see practical advice written in plain language when there is so little solar information around. . . this is an essential text . . . you won’t find a better guide.

Alan T. Gray

Earth Garden Magazine

The Caravan & Motorhome Book

Without doubt, this is the best book we have ever read . . . it will be treasured, and read on a regular basis.

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