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Old 27-03-2011, 08:25   #1
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Fuse and circuit breaker question

A friend has a 1985 Hatteras Sportfisherman. There are two 30amp shore power receptacles. Each receptacle has two 30amp fuses, one each for the 120v and neutral leg. The wiring then runs directly to the 30amp circuit breakers at the main electrical panels. So you have a 30amp breaker at the shoreside connection running directly to a 30amp breaker on the boat with 30amp fuses wired in between. He is sure the manufacturer had a good reason for installing the fuses but nobody he has asked seems to know why. He is considering omitting the fuses as they always blow before the circuit breakers trip and are a nuisance to replace.
Does anyone know if the fuses are necessary and why?

Thank you.
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Old 27-03-2011, 08:41   #2
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Re: Fuse and circuit breaker question

You're only allowed to run a maximum distance of 10 feet from the Shore Power INLET to the OCPD. If the Panel (c/w main beakers) is more than 10' away from the Inlet, supplemental Over Current Protection (Fuses) is required.

Excerpted from ABYC E-11:

11.10.2.8.3 Additional Overcurrent Protection - If the location of the main shore power disconnect circuit breaker is in excess of 10 feet (three meters) from the shore power inlet or the electrical attachment point of a permanently installed shore power cord, additional fuses or circuit breakers shall be provided within 10 feet (three meters) of the inlet or attachment point to the electrical system of the boat.
Measurement is made along the conductors.
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Old 27-03-2011, 08:53   #3
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I would be worried that the fuses are blowing. Either the load is getting to high for the service or something is wrong with the wiring. Either way something else is a problem
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Old 27-03-2011, 08:58   #4
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Re: Fuse and circuit breaker question

Rather than looking for ways to eliminate a safety device, perhaps you might want to figure out why those fuses are blowing? Removing them will probably just result in a regular tripping of the breakers, as fuses will usually blow before a breaker of the same capacity will trip. Resetting a breaker doesn't solve the problem that caused it to trip in the first place.

A regularly blowing fuse should not be treated as merely an inconvenience, but as a warning that something is amiss.
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Old 27-03-2011, 09:04   #5
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Re: Fuse and circuit breaker question

Quote:
Originally Posted by GordMay View Post
You're only allowed to run a maximum distance of 10 feet from the Shore Power INLET to the OCPD. If the Panel (c/w main beakers) is more than 10' away from the Inlet, supplemental Over Current Protection (Fuses) is required.
On my Catlaina 27, there is no fuse or circuit breaker between the shore power connection and the single A/C outlet box. What are the risks associated with this set-up? I presume that most dock power stations are breakered?

Thanks,

John
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Old 27-03-2011, 11:26   #6
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Re: Fuse and circuit breaker question

Check the fuse holders for corrosion!!

Our previous boat had a Dynamote 40 amp charger mounted in the engine room.
It had a 40 amp glass fuse mounted on its face in a typical spring loaded type holder.
About once a year it regularly corroded just enough to cause local heating and that cracked the glass.
I finally got tired of replacing those fuses after cleaning the holder terminals, so I installed a marine breaker.
It ran perfectly with no problems when I sold the boat.
When the new owner of the boat replaced the charger (I don't know why) he gave me the charger.
It's still working great as an automotive charger and is currently on loan to a neighbor.
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Old 27-03-2011, 12:04   #7
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Re: Fuse and circuit breaker question

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Originally Posted by Feral Cement View Post
On my Catlaina 27, there is no fuse or circuit breaker between the shore power connection and the single A/C outlet box. What are the risks associated with this set-up? I presume that most dock power stations are breakered?

Thanks,

John
You hope they are.
Also the dock breakers might be rated higher than the wiring on your boat, which could lead to overheated wiring and fire etc etc.
Would you trust a marina/dock to keep up with the maintenance for the safety of you and your boat
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Old 27-03-2011, 13:53   #8
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Re: Fuse and circuit breaker question

At marina Nuevo Vallarta back in the '90's, the place was so run down, you had a DIY project just to hook up to shore power
(if you dared).

There were no dock boxes or shore power stations, just three LIVE wires sticking up from the edge of the dock!!!

There was no color code to the wiring either.

You had to either use a meter, or touch & guess as to which was hot.

Anybody else here remember those "good old days"?
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Old 27-03-2011, 13:57   #9
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Re: Fuse and circuit breaker question

In adding AC to my boat all the AC is on the same side of the boat, mostly in the same are...with as short a run as possible.
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Old 27-03-2011, 14:10   #10
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Re: Fuse and circuit breaker question

Thank you for your replies. I apologize that I was not clearer in my original post in that his fuses are not blowing regularly. But in a situation where other boats breakers might trip his fuses will blow instead. He thinks the distance from his shore power receptacle to his main breaker is right about 10' and is going to measure the wiring. My guess is the ABYC regulation mentioned above is the answer.
Thanks again for your help.
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Old 29-03-2011, 06:48   #11
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Re: Fuse and circuit breaker question

If your friend finds that the fuse holders are deteriorated, not uncommon, replacements for these relatively hard to find components can be had from: Sam's Marine International

Charlie
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Old 29-03-2011, 07:19   #12
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Re: Fuse and circuit breaker question

No one has commented on fuses installed in the neutral lines. This seems to be contrary to normal practice, and possibly dangerous.

Also, if circuit protection is required at the fuse location (in the power lines) the fuses could be replaced with circuit breakers. It is possible that the fuses are "fast acting" types that may be blown with current inrush with a motor starting. A slower acting circuit breaker may help the situation. It also eliminates the need to carry spare fuses.
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Old 29-03-2011, 16:23   #13
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Re: Fuse and circuit breaker question

Quote:
No one has commented on fuses installed in the neutral lines. This seems to be contrary to normal practice, and possibly dangerous.
Under normal conditions that is true for a feed. However, these fuses are backed up by double pole circuit breakers at the main panel thus eliminating any danger. Hatteras has built there boat with these fuse holders at the inlets since the beginning.

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Old 29-03-2011, 17:06   #14
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Re: Fuse and circuit breaker question

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Originally Posted by gulfstar1 View Post
Each receptacle has two 30amp fuses, one each for the 120v and neutral leg. So you have a 30amp breaker at the shoreside connection running directly to a 30amp breaker on the boat with 30amp fuses wired in between. He is sure the manufacturer had a good reason for installing the fuses but nobody he has asked seems to know why. He is considering omitting the fuses as they always blow before the circuit breakers trip and are a nuisance to replace.
If the fuses always blow before the CB, and if only the fuse in the neutral leg happens to blow, then you will have all of the neutrals on the boat at 120 volts. That seems to be hazardous. Anybody know what ABYC says about a fuse in a neutral?
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Old 29-03-2011, 17:36   #15
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Re: Fuse and circuit breaker question

I found this previously ABYC information posted in another thread by Gord May:

E-8.11.9.2 Simultaneous trip circuit breakers shall be provided in power feeder conductors as follows:
E-8.11.9.2.1 120 volt AC, single phase - ungrounded and grounded conductors (white),

E-8.11.9.2.2 240 volt AC, single phase - both ungrounded conductors,
E-8.11.9.2.3 120/240 volt AC, single phase - both ungrounded conductors,
E-8.11.9.2.4 120/240 volt AC, delta three phase - all ungrounded conductors,
E-8.11.9.2.5 120/208 volt AC, Wye three phase - all ungrounded conductors.
E-8.11.9.3 If the location of the main shore power disconnect circuit breaker is in excess of three meters (10 feet) from the shore power inlet or the electrical attachment point of a permanently installed shore power cord, additional fuses or circuit breakers shall be provided within 10 feet (three meters) of the inlet or attachment point to the electrical system of the boat. Measurement is made along the conductors.
E-8.11.9.3.1 If fuses are used in addition to the main shore power disconnect circuit breaker, their rating shall be such that the circuit breakers trip before the fuses open the circuit, in the event of overload. The ampere rating of the additional fuses or circuit breaker shall not be greater than 125% of the rating of the main shore power disconnect circuit breaker. For 120 volt service, both the grounded and ungrounded current carrying conductors shall be provided with this additional over-current protection.

It seems that the two pole CB should be used at the entry point and the fuses employed should be rated for a higher load. The trouble with fuses is that uninformed users may replace them with different capacity fuses.
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