Dumb questions about breakers

[noelex 77]

Originally Posted by catsketcher

I considered DIN rails but they don't seem to be easy to switch. I could use them as breakers only but I am more likely to use ATO car type fuses that fit in Blue Seas fuse blocks.

Switching DIN rail circuit breakers is a deliberate action, but should not be difficult. You don’t want the switching action to be very easy, as a knock could inadvertently turn off some vital piece of equipment such as the autopilot.

The nice thing about DIN rail breakers is that they are very easy and quick to exchange and not too expensive. Replacements from a multitude of manufacturers are available so you can switch even active DC loads without too much concern.

[team karst]

DIN rails also available in corrosion resistant metals. I have several aboard; one is holding a fairly chunky soft start box.

[catsketcher]

Thanks for the replies

I have the Nigel Calder book and have watched numerous vidoes by Jeff Cote on electrics, but I can't figure out the redundancy of breakers AND fuses. I teach Physics at High School and have wired and built this boat. I just don't get the basics behind having two different protections on a circuit.

I have read that fusing is for the wire but I can't see the point of having low resistance large wire with an inline fuse buried somewhere in the boat. I would like all my fuses to be in one place (apart from those from charging sources like solar panels). The last thing I want to do in the dark is start pulling bits of boat apart to try and find where the inline fuse is on a nasty night bumping around - I absolutely want to avoid inline fuses on any boat I have to run. If something goes dark I want to run to the board and have a look. I will have to ensure I don't get hot joins or resistant wire but I would prefer to put my money into good wire, great crimps and busses to ensure that the voltage at the panel is almost the same as at the device.

Protecting the equipment circuit is best nearer the battery, rather than near the appliance -is it not? So this would suggest that putting the appliance protecting fuse (always rated less than the wire protecting fuse) would be best next to the switch panel. This would mean putting a fuse block at the switch board. So if I put a breaker switch in, I have a breaker almost next to a fuse block.

Or to think of it another way. I can use fuses instead of breakers. If I use toggles and fuses I can place the fuses in a block next to the panel. If I can select them, why not use fuses that are lower in rating than the wire and do the job of fusing for the appliance as well as being a safety for the wire - why two devices for the same job? Especially if it will cost me $1000 or more to do so. How can sizing fuses for the appliance do anything but increase safety margins? So I could be safer and save a heap of money by going toggles and fuses, or not? It is really easy to find the correct ATC fuses for each circuit and I can get a tub of each individual size. Surely that is a good thing?

I should add, my boat is pretty darn simple. No AC, no power winches, a BD 50 fridge, no freezer, two outboards on their own circuit with starter battery (to protect the soon to be lithiums - I can't change alternators to suit lithiums), simple PUR watermaker. She is a low load boat.

Cheers

Phil

[Statistical]

Originally Posted by catsketcher

Thanks for the replies

I have the Nigel Calder book and have watched numerous vidoes by Jeff Cote on electrics, but I can't figure out the redundancy of breakers AND fuses. I teach Physics at High School and have wired and built this boat. I just don't get the basics behind having two different protections on a circuit.

I have read that fusing is for the wire but I can't see the point of having low resistance large wire with an inline fuse buried somewhere in the boat. I would like all my fuses to be in one place (apart from those from charging sources like solar panels). The last thing I want to do in the dark is start pulling bits of boat apart to try and find where the inline fuse is on a nasty night bumping around - I absolutely want to avoid inline fuses on any boat I have to run. If something goes dark I want to run to the board and have a look. I will have to ensure I don't get hot joins or resistant wire but I would prefer to put my money into good wire, great crimps and busses to ensure that the voltage at the panel is almost the same as at the device.

Protecting the equipment circuit is best nearer the battery, rather than near the appliance -is it not? So this would suggest that putting the appliance protecting fuse (always rated less than the wire protecting fuse) would be best next to the switch panel. This would mean putting a fuse block at the switch board. So if I put a breaker switch in, I have a breaker almost next to a fuse block.

Or to think of it another way. I can use fuses instead of breakers. If I use toggles and fuses I can place the fuses in a block next to the panel. If I can select them, why not use fuses that are lower in rating than the wire and do the job of fusing for the appliance as well as being a safety for the wire - why two devices for the same job? Especially if it will cost me $1000 or more to do so. How can sizing fuses for the appliance do anything but increase safety margins? So I could be safer and save a heap of money by going toggles and fuses, or not? It is really easy to find the correct ATC fuses for each circuit and I can get a tub of each individual size. Surely that is a good thing?

I should add, my boat is pretty darn simple. No AC, no power winches, a BD 50 fridge, no freezer, two outboards on their own circuit with starter battery (to protect the soon to be lithiums - I can't change alternators to suit lithiums), simple PUR watermaker. She is a low load boat.

Cheers

Phil

Why are you using fuses and breakers on the same circuit. Put a breaker in the panel. You are done. Fuses and breakers on wiring is to protect the wiring. If the device needs OCP it will have its own OCP.

As an example at home when you plug in a 1A laptop charger into a 15A outlet you you first replace the 15A breaker with a 1A breaker? No. The 15A breaker is designed to protect the wiring. Your laptop charger will have an internal 1A fuse.

The only part I agree with you on is inline fuses are horrible from a maintenance perspective. So I agree your OCP should be at the panel/busbar but you don't need two.

If you want to use toggles and fuses feel free to do that. I don't think it is going to save you as much as you think when you consider the cost of the fuse, fuse holder, and extra labor in terms of jumper wire but if you prefer that do it.

[SY Harmony]

IMHO; Fuses are just to fiddly and fragile for the marine environment.

[catsketcher]

Originally Posted by Statistical

Why are you using fuses and breakers on the same circuit. Put a breaker in the panel. You are done. Fuses and breakers on wiring is to protect the wiring. If the device needs OCP it will have its own OCP.

As an example at home when you plug in a 1A laptop charger into a 15A outlet you you first replace the 15A breaker with a 1A breaker? No. The 15A breaker is designed to protect the wiring. Your laptop charger will have an internal 1A fuse.

The only part I agree with you on is inline fuses are horrible from a maintenance perspective. So I agree your OCP should be at the panel/busbar but you don't need two.

If you want to use toggles and fuses feel free to do that. I don't think it is going to save you as much as you think when you consider the cost of the fuse, fuse holder, and extra labor in terms of jumper wire but if you prefer that do it.

I still don't quite get it. A breaker in the panel will be at 10 or 15 amps. So it doesn't protect the appliance. I don't want appliance fuses at the appliance because inline fuses are tricky. So I want them in a central location, like in a car - hence the fuse block. If my boat computer fuse goes out I would like it in an easy to find location - at the panel.

In a house you are putting a multitude of different appliances in the household circuits, so you size for the wire and hope that the appliance is protected. But I am building individual circuits for each appliance in the boat and can determine the max current each individual circuit will ever handle. I won't be changing the appliance in the circuit. There will be no upper variation in load in the circuit as the appliance load should not change. So why not rate the circuit protection for the appliance, move the inline fuse to the panel block and reduce complexity? I will still choose the wiring to handle larger loads in the future and to lower resistance.

I guess for me I will be using as fuse block anyway, as I don't like inlines, so may as well go switches and fuses and rate the fuse whichever way I like. I find the ATC fuses easy to check and replace so will p[robably go that way. Thanks for the advice.

[Statistical]

Originally Posted by catsketcher

I still don't quite get it. A breaker in the panel will be at 10 or 15 amps. So it doesn't protect the appliance.

Well it isn't the job to protect the appliance its job is to protect the wiring. However a breaker panel can contain breakers of any size from 5A to 100A. If you want a 5A rated circuit (pointless IMHO) use a 5A breaker.

If you want to use a toggle switch and connected fuse then do that instead but this isn't a limitation of circuit breakers.

In a house you are putting a multitude of different appliances in the household circuits, so you size for the wire and hope that the appliance is protected.

No we don't "hope" the appliance is protected the appliance has its own over current protection if UL listed. It has that because the amount of current the appliance can safely handle may vary significantly from the circuit it is plugged into. If it didn't that would be horribly unsafe. An fault in the internal wiring of the appliance capable of only 5A now drawing 20A won't trip the breaker when you house burns down.

[Chotu]

I think I see were Catsketcher is getting confused.

It might have to do with a lot of the documentation that comes with various things that we buy.

There are several little appliances that you can buy for your boat that come with an in-line fuse. They talk about protecting the appliance using that fuse.

It’s probably completely accurate in the case of those products because they didn’t move that fuse inside like they should have.

But it can lead to confusion when thinking about how to protect the circuit. The posts above mine are correct. I just think it’s a little bit misleading sometimes the way the DC appliances have it worded. And how they do it in physical reality. With a fuse inline half the time.

With those types of appliances you’re not going to get around that little inline fuse no matter what you’re doing with the panel near the battery.

But what you are doing at the panel has nothing to do with the appliance or that pesky fuse that they put on the leads to it.

Two distinct and separate issues as was said above.

The breakers or fuses at the battery area and electrical panel area are there to protect the wire run to the appliance.

The appliance should have a fuse inside. But many of them do not and they put it outside. I suppose it’s easier to actually change the fuse that is outside. So maybe it’s a good thing. But That’s the one that’s protecting the appliance. And there is nothing you can change or do anything about that fuse. It’s best to just completely ignore it. As long as the appliance is functioning it should be functioning. It won’t blow unless you have some kind of problem inside the appliance

[catsketcher]

Yeah Chotu, that is what I was getting at. My VHF and other electronics have a little ATC fuse or glass fuse that is outside the device. I was thinking that instead of having it somewhere random, I could put the provided fuse or one of the same rating at the start of the circuit and make it easier to keep an eye on. I really am not trying to be obscure or difficult, just trying to get my head around the basics and trying to figure out why a low current fuse can be at the device but not at the panel or switchboard.

cheers

Phil

[s/v Jedi]

Originally Posted by catsketcher

Yeah Chotu, that is what I was getting at. My VHF and other electronics have a little ATC fuse or glass fuse that is outside the device. I was thinking that instead of having it somewhere random, I could put the provided fuse or one of the same rating at the start of the circuit and make it easier to keep an eye on. I really am not trying to be obscure or difficult, just trying to get my head around the basics and trying to figure out why a low current fuse can be at the device but not at the panel or switchboard.

cheers

Phil

Most devices will have the fuse internally but some like radios use a fuse holder integrated in their power cord. You should never see that fuse blown. If it does, the appliance needs professional service or possibly replacement.

The breakers protect the wiring. They don’t care about the piece of wire, I can see how one misunderstands that…. they care about the boat catching fire when the wire burns. That’s all the do, but when they have this on/off handle you can also de-energize the circuit manually.

You should never try to replace the fuse of an appliance by using a smaller value breaker. This voids warranty immediately and for good reason: the appliance’s fuse value, as well as the type of fuse, provides the protection it needs to be safe. A different type of fuse or a breaker, even if it is the same value, may fail to provide the same level of protection and cause the appliance to catch fire. For example, a fast acting glass fuse of 5A is very different from a magnetic hydraulic circuit breaker of 5A.

[Ballsnall]

Originally Posted by catsketcher

In Australia, each hydraulic/magnetic breaker is about $30 and with about 25 switches on my boat, the panels are getting really pricey.
Phil

Contrary to people get their knickers in a knot over fusing smaller than the wire rating, there is nothing inherently wrong with this approach other than cost as you have realised.

25 circuits on your DC panel is unnecessary in my opinion unless you want to spend the money for little advantage. Consolidate your circuits down to 10 or 12 and use a fuse box where warranted like at the nav station.

Do you really need individual lighting circuits, individual pump circuits, charging outlet circuits etc etc etc?

The only equipment I can think of that needs protection is sensitive electronics and the risk is from power surges or spikes so think about other ways to mitigate that risk, some people use a dedicated electronics battery, BMS disconnect is also a risk, so prevention in addition to protection is also important.

Keep it simple, go sailing.

[team karst]

I will submit that at least in the vhf case, the ext fuse is meant to blow if the power wire is reversed, or small boat battery is reversed. It saves the radio. There are better ways to protect against rev pol, but the fuse is cheap.

[s/v Jedi]

Originally Posted by team karst

I will submit that at least in the vhf case, the ext fuse is meant to blow if the power wire is reversed, or small boat battery is reversed. It saves the radio. There are better ways to protect against rev pol, but the fuse is cheap.

Correct. I just default to recommending to change nothing to the original design. Not only did they have many technical reasons for doing things the way they did, but also compliance with standards is only guaranteed without any modifications.

For cost: if you find the toggle breakers too expensive, you can use other breakers. I also use these and they are only a couplebucks each: https://www.bluesea.com/products/cat...ton_Reset-Only

[CharlieJ]

@catsketcher: As said many times in this thread, the OCPD (fuse or circuit breaker) at the panel is to protect the conductor. As s/v Jedi said, typically the OTS breaker panels are loaded with 15A circuit breakers because they will easily protect AWG 14 wire which will generally run most anything.

There are some nuances and solutions.

The first nuance is the installed fuse at navigation equipment. As others stated, and your concern, is locating these to check if they are blown. My solution has been to feed a small ATO (blade) fuse block from one of the circuit breakers then clip the manufacture's in line fuse and extend the cut conductor to one of the poles on the new fuse block. Install the fuse block where you have good access. On boats with fly bridges, I have installed these on the access door to the area under the helm. In this example the main circuit breaker would be FLY BRIDGE and an appropriately sized breaker and conductor would supply the common feed of the new fuse block.

In the case of a marine centrifugal pump, the manufacture is required (in the USA) to provide the recommended size for the OCPD to prevent the possibility of a dangerous locked rotor condition. In this case, it is best (IMHO) to go with a one-to-one solution. The CB on the panel is conveniently sized to protect the conductors and there is an inline fuse as specified by the pump manufacture close by the pump it is protecting. I use "waterproof" ATO fuse holders and will often label the pump with directions on where the fuse holder is located.

[catsketcher]

Thanks everyone, the input is much appreciated