50 amp fuse?

[oceanjake]

I just got the walk through on my new toy today...1983 60' EB. It was a warm day and the seller told me I need to be careful how much load I draw at the dock because if I exceed 50 amps a fuse would blow. The fuse is located in the cockpit adjacent to the shore power cord. Has anyone replaced this with a breaker or bypassed it altogether? Shouldn't there be a breaker on the AC panel for this instead of a fuse? I really don't want to be afraid of running 2 or even 3 AC units at once. Advice is appreciated.

 

[SEVEN]

Don't worry about running 2 or 3 AC units. The fuse will easily handle it. If they do blow they are easy to change and available at HD.

 

[oceanjake]

Thanks for the reply. Is there a breaker retrofit?

 

[KPTIM]

There is actually two fuses per shore power input connection.
Make sure the fuse holders are clean and not corroded this will cause excess build up of heat if they are corroded. Also consider putting a thin layer of di-electric grease on the ends of the cartridge fuses and on the threads of the screw in fuse holder. This again helps to reduce the generation of heat from poor connections. I would suggest that you not consider changing the cartridge fuses to breakers and definitely do not consider eliminating them. Fuses are a much more reliable fault protection then breakers and you have breaker protection on the electrical panel on the boat.

You should also consider putting a thin layer of di-electric grease on the blade contacts
of you shore power cable plugs.

Tim
1979 53' MY

 

[oceanjake]

Thank you. Noted about the grease and I will do that. I still don't understand the purpose of these fuses though. There are 50 amp breakers on the dock.

 

[SEVEN]

Protects the electoral system.

 

[jrbrein]

Oceanjake,

I believe what you are referring to are "slow blow" fuses located just at the shore power connection on your boat. These fuses are for over current protection from the point where the shore power cords are plugged in on your boat to the 50 amp breakers on your ships circuit breaker panel. The fuses are only protecting that run of wire starting at the the shore power plugs on your boat to the 50 amp breakers on your panel. The circuit breakers on the shore power dock pedestal are protecting that run of shore power cable from the pedestal to your shore power connection on the boat.

Last year, I had my marine electrician install 2 galvanic isolators (one on each 30 amp leg entering the boat). He discovered that the slow blow fuses in the boats shore power box had been removed and bypassed by one of the PO's. He did not recommend re-installing them. In effect, the dockside pedestal circuit breaker is now providing the over current protection from the pedestal to a master circuit breaker on my electric panel. It is all about protecting wires from over heating.



Jon

 

[Pete]

The purpose of a fuse or circuit breaker is to protect the wire on the load side of the circuit. Many if not all land building codes require such a fuse or circuit very close to the service entry. I suspect but am not sure ABYC would have a similar requirement, and even if the ABYC does not it is a good idea. The purpose of the fuses at the shore power connection of the boat is to protect the wiring between the connectors and the service panel in the boat. This protection includes fire, chaffing of electric lines that short to ground, and any other hazard that could cause a short.

The analogy on a building is the service entrance disconnect that runs to a main panel with a breaker, and on to sub panels.

Bottom line, it is safety and you want it working correct. Keep the connections clean and protect them as outlined in the post above by another member

Pete

 

[Pete]

Jon, what your electrician recommended in not replacing the connector entry fuses maybe a bet you want to take if you have absolute faith in what you are plugging into. I would not recommend such an action. And if you cruise in your Hatteras, you never know what you are plugging into, and these entry fuses become your only assured protection. While I would not recommend doing it, if you just have to eliminate these fuses popping before the marina pedestal circuit breaker, you may want to consider finding a 35 amp fuse, or if they are not available even a 40 amp fuse. You will be guaranteeing that you still have some amount of protection, but if everything is working correctly the pedestal breaker or your main panel breaker will always go first. My recommendation is to get some 30 amp slow blow fuses and put safety first.

Pete

 

[jrbrein]

Pete,

Point well taken. I think you are correct.

Jon

 

[SEVEN]

Oceanjake,

I believe what you are referring to are "slow blow" fuses located just at the shore power connection on your boat. These fuses are for over current protection from the point where the shore power cords are plugged in on your boat to the 50 amp breakers on your ships circuit breaker panel. The fuses are only protecting that run of wire starting at the the shore power plugs on your boat to the 50 amp breakers on your panel. The circuit breakers on the shore power dock pedestal are protecting that run of shore power cable from the pedestal to your shore power connection on the boat.

Last year, I had my marine electrician install 2 galvanic isolators (one on each 30 amp leg entering the boat). He discovered that the slow blow fuses in the boats shore power box had been removed and bypassed by one of the PO's. He did not recommend re-installing them. In effect, the dockside pedestal circuit breaker is now providing the over current protection from the pedestal to a master circuit breaker on my electric panel. It is all about protecting wires from over heating.

Seven, the electoral system is how we ended up with Donald Trump!

Jon

Good one Jon.

 

[sixty]

From what i recall ABYC requires circuit protection within the first 15' of boat entry. Ive had problems with my entry fuse holders and will remove them at some point and add a marine breaker box in the engine room near the entry point.Be sure to remove the panel, clean all connections and apply dielectric grease. Will save the fuses. Congrats on the new boat. I had my eye on it for awhile and would have pounced if i hadnt just bought mine. It was a very good deal.

 

[SEVEN]

Re: 50 amp fuse?l

One more thing that I did to make the replacement of the fuses easier. I bought a brass wire wheel for my drumel and ran it in and out of the opening until clean. Added the grease and re installed. No issues from that point on.

 

[oceanjake]

Thank you for all of the replies. I guess for now I will just buy some spares and see how bad it is. I know on a friend's Viking the electrician removed the breakers in the same location, claiming they were redundant and problematic. Those were breakers. Fuses I think should be replaced with breakers in every instance but I will not make it my first priority. Thanks again

 

[Pascal]

Abyc require protection when the main breakers are more than 8' away fromthe inlet, not 15' so tyoically you shoudlt remove the fuses.

What you can do is install a dual pole breaker near the shore power inlet. It s more convenienet and also safer as those fuses have caused fires. Depending on the layout you often can isntall the breaker inside from where the shore power inleet is, other wise either hubbel or marinco has a circuit breaker built in a stsndard shore power cover.

 

[Pete]

For those considering replacing the shore power inlet fuses with circuit breakers, keep in mind that there are two common types of breakers, thermal and magnetic. Thermal breakers are sensitive to the ambient temperature and will trip under their rated load in a hot environment, such as an engine room. Magnetic breakers are far more accurate in their trip point and maintain that accuracy with increased ambient temperature.

As a general rule, thermal breakers should be avoided on boats. All breakers used on Hatteras boats since the early 70's are magnetic. Prior to that both AC and DC breakers were more likely to be standard household thermal breakers. And as you no doubt suspect, magnetic breakers are more expensive than thermals.

Pete

 

[cenger]

Does anyone know where Ican find a 50a cartridge fuse holder? I found a spare on board, but Iwould like to replace them all (they are faded beyond redemption). ThePrevious owner purchased just the cap from Spencer Rybovich, but I don't thinkthey are around anymore. Does anyone now where I might get a few newholders or the whole fuse?

 

[bigbill]

have you tried calling sams?

 

[SEVEN]

Here you go.

 

[SKYCHENEY]

Sams currently has the plastic caps but not the whole screw in holder. Those are on order. But if you just need to replace the faded plastic covers, they have plenty of those.