Circuit breakers or fused switch panel?

Things 12V and 24V
mahnamahna
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Circuit breakers or fused switch panel?

Post by mahnamahna » Fri Dec 16, 2011 7:11 pm

About to purchase a set of switch panels, (3 x 8 gangs!!! and then another 6 gang 240v) and was wondering if anybody uses fused switch panels any more or if everybody now goes for the circuit breaker panels now. Big difference in price, much cheaper for the fused panels, but much more convenient to just re-set a tripped breaker. And if you run out of fuses. On the other hand, how often is a fuse likely to blow (or the breaker trip)?

Who used or will use what and what do you now think having lived with it.

Smooth Cruiser
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Re: Circuit breakers or fused switch panel?

Post by Smooth Cruiser » Fri Dec 16, 2011 9:07 pm

For 12V I had fuses - really you should never blow one unless something is wrong, and then you can't just simply reset the circuit breaker, you will need to fix the fault. So I don't really see why they are more convenient.

For 240V you should have circuit breakers, you could overload these circuits if you plug in too many appliances so the resettable breaker is better, they also act a bit quicker and hence give better protection to you from electrocution. I don't think an electrician would ever set up 240V with fuses, in fact it may not be allowed any more.

Jim
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Re: Circuit breakers or fused switch panel?

Post by Jim » Sun Dec 18, 2011 8:38 am

I have a fused 12 volt switch panel and a circuit breaker on both the 240 volt shore power and a separate one for the gen set. So far, no fuses blown or circuits tripped.
Jim.

mahnamahna
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Re: Circuit breakers or fused switch panel?

Post by mahnamahna » Sun Dec 18, 2011 10:52 am

Reading Marine Electrical Bible by John Payne, (1994 edition, so there would have been even more improvement in technology since) he claims there is no place on a boat for fused panels:

Page 106 to quote: Fuses are still widely used, and although cheaper than circuit breakers, they have many disadvantages......From my own experience and that of many other vessel owners, there is no place for a fuse system unless you enjoy the adrenalin rush as your nav lights go out or auto pilot stops and you feverishly try to locate and install a failed fuse in the middle of the night in a force 9 gale off a lee shore"

An exaggeration I am sure, but as I have to buy one panel or another, I thought it prudent to get others advise.

He claims it is possible for fuses to fail through vibration, that fuses are often not accurately rated and can be as much as 50% out either way and that there is also resistance issues in fuses and holders. He also claimed it was possible to go through a number of fuses until you isolate the problem causing the fuses to blow, as opposed to simply re-setting a tripped breaker.

Other than the slight difference in initial purchase cost, my only real issue is that circuit breaker panels have fixed amperage breakers in fixed places on the panel which may not suit the way I was going to wire them, whereas a fused panel I can make whatever amps I want in each position by placing the appropriate fuse in that toggle location. I need approx 8 switches for each of port, starboard and bridgedeck so planned on 3 x 8 gang panels, one for each bank, and a separate 240v panel of which I only need 6 gangs (separate isolation switch, separate master breaker and the panel will be definitely be a breaker panel, but this system I am getting a sparky to wire for me, I believe I need that to get insurance). On the 12v side I will have 4 sub master breakers and isolation switches, one for each panel and one for the windless and then a master isolation switch. Is this overkill?

I guess another question worth asking is do those that have fused panels prefer the older glass tube fuses or the auto blade fuses?

Smooth Cruiser
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Re: Circuit breakers or fused switch panel?

Post by Smooth Cruiser » Mon Dec 19, 2011 9:58 am

I would suggest that if someone is blowing fuses in the way that author is describing then there is something seriously wrong with the electrical wiring in their boat . . . .

A fuse will only blow if there is a problem. Every car on the road has multiple fuses and these are subject to much more vibration etc than on a boat - how often do you blow fuses in your car??

I don't think it matters whether they are glass tube fuses or blade fuses. Purists might say that blade fuses are more accurate in their rating but a 20A fuse isn't going to blow because it sees a current of 21A - it is going to blow because there is a dead short with very large resultant current flow so it doesn't matter how "accurate" the fuse is really. Whichever type you buy just carry multiple spares which will ensure that you never blow one. Murphy's law dictates that you will only blow a fuse when you don't have a spare!!

rexd666
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Re: Circuit breakers or fused switch panel?

Post by rexd666 » Mon Dec 19, 2011 11:26 am

Don't tempt Murphy, go circuit breakers and you don't have to worry about having spare fuses. Of course that will just transfer the bad juju to some other part that you don't have a spare for.

I was cruising the Blue Sea website and they seemed to have 15A breakers by default on the 12V modules, but also it seemed that they came with empty slots so you could put in the different amperage ones where required. But at the same time the 12V/240V combo panels were list price of $700-1100 at Fisheries Supply.
Steve

Jim
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Re: Circuit breakers or fused switch panel?

Post by Jim » Mon Dec 19, 2011 11:47 am

I had a brain freeze with my last comment. I have a Blue Seas main board which is a circuit breaker type, but I do have quite a few individual fuses, both in line and blade. Smooth is correct, if a fuse blows something has just gone wrong, find it and fix it or you might be re-charging your recently emptied fire extinguishers.
Jim.

dazza
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Re: Circuit breakers or fused switch panel?

Post by dazza » Mon Dec 19, 2011 7:21 pm

Im a house electrician not marine so take this advise with a grain of salt.
The circuit breaker or fuse is there to protect the cabling to the appliance etc not the thing at the end ,so size really matters with cabling and circuit breakers .Go with circuit breakers as it will be easier to find a fault as you only have to flick a switch to reset , not replace an expensive fuse . You dont need a seperate circuit breaker for each appliance , its just easier to fault find that way. Merin Gerin use to make house type circuit breakers that were DC rated at a reasonable cost compared to marine ones , dont know if they still do.
Dazza

Smooth Cruiser
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Re: Circuit breakers or fused switch panel?

Post by Smooth Cruiser » Mon Dec 19, 2011 8:08 pm

At the end of the day like most things it probably comes down to cost. Keep in mind you will need to carry spare fuses anyway as there will be other items on your boat that have fuses, battery chargers, various electronic bits and pieces, outboards etc.

Also another aside on a similar topic, I would recommend installing panels with several spare slots - you will always add other shiny bits down the track which will be better with their own electrical circuit and it is easier to put the spares there during construction rather than try to add another panel later. I see a lot of boats where the electric board is full and then there are add on individual switches below, or even worse peoople put other circuits over existing ones so your "VHF Radio" circuit now suddenly has a VHF on it, and an HF and a weather fax etc! Makes fault finding even more difficult! I would suggest at least 6 blank slots at time of construction - if you need them they are there, if not it doesn't really matter.

mahnamahna
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Re: Circuit breakers or fused switch panel?

Post by mahnamahna » Mon Dec 19, 2011 8:33 pm

Yeah I have seen the Blue Seas panels and the BEP fancy ones, at over a grand.....

I have also found this.....

http://www.ebay.com.au/itm/280781238082 ... 275wt_1037

What am I missing here. I need 3 or maybe 4 of these, and then a separate 240v panel, but at $75 each for my 12v side, thats only $300.

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