15A fuse/15A breaker

[beerbeerbeerbeerbeer]

I’m wiring in a 12V freezer.

 

Having trouble with finding the components to wire in a fuse.

I’ve got 10mm / 70A cable.

 

I thought a 15A circuit breaker would be ideal but can’t find one less than 20A that’ll take fat wire

I thought a mega fuse would be simple but they don’t go down to 15A.

The 15A in line fuse holders I can easily get a hold of have skinny wires.

If I go down the 15A in line fuse route: What’s the easiest, tidiest and most effective way to join my fat wire to thin?

How do I go about it? there don’t seem to be the connectors to do it. 

 

thanks 

[Alan de Enfield]

Reducing bootlace ferrules

 

(say) 10mm2 "in" and then sized for 4mm terminal.

 

 

[beerbeerbeerbeerbeer]

Just crimp them?

 

thanks

Edited April 19, 2022 by Goliath

[TheBiscuits]

3 minutes ago, Goliath said:

Just crimp them?

 

It's not a standard crimping tool, it's got different shaped jaws

[Jen-in-Wellies]

Since you are protecting a wire able to handle 70A, why not use a 70A fuse, or breaker? It is to protect the wiring, not the appliance on the end.

[beerbeerbeerbeerbeer]

4 minutes ago, Jen-in-Wellies said:

Since you are protecting a wire able to handle 70A, why not use a 70A fuse, or breaker? It is to protect the wiring, not the appliance on the end.

That would make it much simpler for me. 

And in that case, a 20A or 30A or 50A would be ok. Any as long as it ain’t over 70A?

 

 

 

[Jen-in-Wellies]

2 minutes ago, Goliath said:

That would make it much simpler for me. 

And in that case, a 20A or 30A or 50A would be ok. Any as long as it ain’t over 70A?

 

 

 

Yes.
Anything up to whatever the current rating of the wire is should be fine.

[beerbeerbeerbeerbeer]

Just now, Jen-in-Wellies said:

Yes.
Anything up to whatever the current rating of the wire is should be fine.

Great stuff. 
That’s what I’ll do
Many thanks

[Jen-in-Wellies]

A midi fuse holder should be able to take 10mm^2 wire fine, with the appropriate crimp connectors. There are a range of fuses to suit, including 70A, probably better than a mega fuse for this.

Jen

Edited April 19, 2022 by Jen-in-Wellies

[beerbeerbeerbeerbeer]

Thanks, I had looked at those but was put off thinking I need to use a 15A fuse. 
 

But now I know I can go bigger, I might look again. 
 

thanks again. 👍

[springy]

If the manufacturer has specified a 15A fuse then there may be INTERNAL cables only rated to 15A, I would be wary of exceeding this by much.

 

Would something like this allow you to connect to your breaker :-

 

https://www.altecautomotive.co.uk/copper-tube-pins------reduction-terminals----to-suit-10mm2---70mm2-cables-13992-p.asp

 

or these

 

https://www.altecautomotive.co.uk/non-insulated-pins--to-suit-10mm2---70mm2-cables-15645-p.asp

 

springy

Edited April 19, 2022 by springy
add second link

[ditchcrawler]

You could do what lots of people do and give the cable a hair cut to make it smaller

[MtB]

1 hour ago, TheBiscuits said:

 

It's not a standard crimping tool, it's got different shaped jaws

 

Or just blatt it with a hammer or squash it with a pair of grips. Once tightened firmly under a terminal screw, the ferrule will look like it's been chewed by a ferret whether or not the correct crimp tool has been used.

[jonathanA]

4 hours ago, Alan de Enfield said:

Reducing bootlace ferrules

 

(say) 10mm2 "in" and then sized for 4mm terminal.

 

 

I'm sure Alan knows these are insulated bootlace ferrules and not reducing pins. See the things springy has linked to.

 

The insulated ferrules can be crimped with a tool or the terminal screw will do it. But won't help you get a 10mm cable into a hole designed for 6mm 

 

I agree with @TheBiscuits if you use the first pins linked to by springy you would be best using a proper crimp tool of some sort (ebay has some for 20-25 quid chinese shite but good enough for occasional use). 

 

The second  type you could batter as suggested by MTB but still a bit poor IMHO.

 

You could fit a decent 20A midi type fuse at the battery end  (as Jen said) and if worried about protecting the appliance shove a 15A one close to the freezer. I would solder or crimp  a short length of smaller  cable to the end of the 10mm to connect to the 15a fuse/breaker near the freezer. Would slightly depend on what the freezer installation instructions say but I think I'd sooner not introduce another connection/ maintenance liability and personally would be happy with the midi 20A protecting the cable.

Edited April 19, 2022 by jonathanA

[beerbeerbeerbeerbeer]

1 hour ago, jonathanA said:

I'm sure Alan knows these are insulated bootlace ferrules and not reducing pins. See the things springy has linked to.

 

The insulated ferrules can be crimped with a tool or the terminal screw will do it. But won't help you get a 10mm cable into a hole designed for 6mm 

 

I agree with @TheBiscuits if you use the first pins linked to by springy you would be best using a proper crimp tool of some sort (ebay has some for 20-25 quid chinese shite but good enough for occasional use). 

 

The second  type you could batter as suggested by MTB but still a bit poor IMHO.

 

You could fit a decent 20A midi type fuse at the battery end  (as Jen said) and if worried about protecting the appliance shove a 15A one close to the freezer. I would solder or crimp  a short length of smaller  cable to the end of the 10mm to connect to the 15a fuse/breaker near the freezer. Would slightly depend on what the freezer installation instructions say but I think I'd sooner not introduce another connection/ maintenance liability and personally would be happy with the midi 20A protecting the cable.

After looking online for bits and bobs, and reading what you and Jen have said, I would prefer to simply use a 20A midi fuse and leave it at that,

but the instruction are quite exact in using a 15A fuse.

 

thanks for ideas and help 👍

 

 

Edited April 19, 2022 by Goliath

[cuthound]

15 hours ago, jonathanA said:

I'm sure Alan knows these are insulated bootlace ferrules and not reducing pins. See the things springy has linked to.

 

The insulated ferrules can be crimped with a tool or the terminal screw will do it. But won't help you get a 10mm cable into a hole designed for 6mm 

 

I agree with @TheBiscuits if you use the first pins linked to by springy you would be best using a proper crimp tool of some sort (ebay has some for 20-25 quid chinese shite but good enough for occasional use). 

 

The second  type you could batter as suggested by MTB but still a bit poor IMHO.

 

You could fit a decent 20A midi type fuse at the battery end  (as Jen said) and if worried about protecting the appliance shove a 15A one close to the freezer. I would solder or crimp  a short length of smaller  cable to the end of the 10mm to connect to the 15a fuse/breaker near the freezer. Would slightly depend on what the freezer installation instructions say but I think I'd sooner not introduce another connection/ maintenance liability and personally would be happy with the midi 20A protecting the cable.

 

These are reducing crimps. Used them a lot when I was at work.

 

 

[beerbeerbeerbeerbeer]

Just looking on line again and the smallest midi fuse is 30A.

So I’m simply gonna go with that.

I’m all set up now.

Wiring done. Just waiting to get things straight on boat before wiring in the freezer itself. 

 

The worst was threading the cable through the boat.

Feeding a cable blind through holes. 

A lot of swearing seemed to do the trick.

[jonathanA]

9 hours ago, cuthound said:

 

These are reducing crimps. Used them a lot when I was at work.

 

 

Yes they are the ones pictured by  Alan arent. 

[Ronaldo47]

Talcum powder is an excellent dry lubricant for threading cables and pipes through things. It is inert and will not harm plastic or rubber.  

[David Mack]

1 hour ago, Ronaldo47 said:

Talcum powder is an excellent dry lubricant for threading cables and pipes through things. It is inert and will not harm plastic or rubber.  

Our old house had been rewired in pvc twin and earth with the lighting switch drops threaded through the original steel tube conduit embedded in the walls. When I took one of the light switches off while redecorating the back box was half full of green gloop that resembled swarfega. I reckon whoever did the rewiring had used washing up liquid as a lubricant, and the remains had dropped down into the back box and partially dried.

[Jen-in-Wellies]

Looking at this again and there are some more questions for @Goliath I should have asked earlier.

Where did the 15A figure come from? Is this something that the freezer manufacturer gave, or from your own calculation, based on typical current for the freezer? If it is a manufacturers recommendation to protect the freezers internal wiring, as @springy wonders, then one should definitely be one fitted. Either at the start of the circuit, where it leaves the bus distribution bars, or at the battery, or at the end of the circuit, by the freezer. If near the freezer, then there needs to be another fuse, which could be higher rated at the start to protect the wiring up to the 15A fuse. If the 15A isn't a manufacturers recommendation, then be aware that most fridges and freezers have a high surge of current for a fraction of a second when they first switch on the compressor. This is likely to exceed 15A. Fuses often take a longer time to blow, so may survive that, but circuit breakers are more likely to trip. Also fuses are often specc'd as their maximum sustained current, rather than their blow current, so are more likely to survive a short time of excess current when. A 15A breaker will most likely trip at >15A after a shorter time.

Where did the 10mm^2 cross sectional area for the main wiring came from? Fridges and freezers don't like low voltages, so they usually recommend large area wires to them to prevent this. Is the 10mm^2 area from the freezer manufacturers recommendations, or your own calculations, based on allowable voltage drop? The further away the appliance is from the batteries, or large diameter cables and distribution bus bars, then the fatter the cable needs to be and fridge/freezer makers will often give a table of distance vs cable size. Note if this distance is based on one way, or out and back for  both positive and negative cables.

What is the make/model of freezer?

How long do the cables need to be to reach it? One way, or out and back?

Is the connection planned to a set of bus bars, or more directly to the isolator switch/batteries?

 

Jen

[cuthound]

1 hour ago, Jen-in-Wellies said:

.Fuses often take a longer time to blow, so may survive that, but circuit breakers are more likely to trip. Also fuses are often specc'd as their maximum sustained current, rather than their blow current, so are more likely to survive a short time of excess current when. A 15A breaker will most likely trip at >15A after a shorter time.

 

 

This is the wrong way round for BS rated fuses.

 

Fuses typically blow quickly at twice their rated current, whereas circuit breakers trip at 3-5 times their rated current, depending their "type" but can be much higher for motor rated types.

 

https://studyelectrical.com/2014/07/miniature-circuit-breakers-mcb-types-characteristic-curves.html

 

Fuses are always used where close protection is required.

Edited April 21, 2022 by cuthound
Clarification

[MtB]

The fuses I find in gas boiler electronics always have a specification/rating for the 'speed of blow', so (say) a 4A fuse can be slow, normal or fast blow. It is considered important to replace a blown fuse with the correct speed of blow as well as the correct current. 

 

[beerbeerbeerbeerbeer]

2 hours ago, Jen-in-Wellies said:

Looking at this again and there are some more questions for @Goliath I should have asked earlier.

Where did the 15A figure come from? Is this something that the freezer manufacturer gave, or from your own calculation, based on typical current for the freezer? If it is a manufacturers recommendation to protect the freezers internal wiring, as @springy wonders, then one should definitely be one fitted. Either at the start of the circuit, where it leaves the bus distribution bars, or at the battery, or at the end of the circuit, by the freezer. If near the freezer, then there needs to be another fuse, which could be higher rated at the start to protect the wiring up to the 15A fuse. If the 15A isn't a manufacturers recommendation, then be aware that most fridges and freezers have a high surge of current for a fraction of a second when they first switch on the compressor. This is likely to exceed 15A. Fuses often take a longer time to blow, so may survive that, but circuit breakers are more likely to trip. Also fuses are often specc'd as their maximum sustained current, rather than their blow current, so are more likely to survive a short time of excess current when. A 15A breaker will most likely trip at >15A after a shorter time.

Where did the 10mm^2 cross sectional area for the main wiring came from? Fridges and freezers don't like low voltages, so they usually recommend large area wires to them to prevent this. Is the 10mm^2 area from the freezer manufacturers recommendations, or your own calculations, based on allowable voltage drop? The further away the appliance is from the batteries, or large diameter cables and distribution bus bars, then the fatter the cable needs to be and fridge/freezer makers will often give a table of distance vs cable size. Note if this distance is based on one way, or out and back for  both positive and negative cables.

What is the make/model of freezer?

How long do the cables need to be to reach it? One way, or out and back?

Is the connection planned to a set of bus bars, or more directly to the isolator switch/batteries?

 

Jen

 

thanks Jen, I’ll try and cover all your questions.
 

The freezer is a 95L shoreline.

 

The manufacturers specify a 15A fuse

I will put one at the freezer end now for ease and convenience.

(I expect it’ll be a spade connection to freezer, I will look today.)

The 10mm cable is again manufacture’s recommendation for the freezer between 6m and 10m away from the battery.

My freezer is approximately 7m away from the batteries. 
The instructions do not refer to one way or both ways but only distance of the appliance from the batteries. 

I have installed an isolator switch at the freezer end.

Again manufacturers specification. 
 

At the moment I have no busbars but they are something I am considering installing

 

At moment the plan is;

connection direct to Batteries — 30A midi fuse—(7m through boat)— isolator switch—-15A fuse—Freezer.

 

 

 

[Jen-in-Wellies]

37 minutes ago, Goliath said:

At moment the plan is;

connection direct to Batteries — 30A midi fuse—(7m through boat)— isolator switch—-15A fuse—Freezer.

That sounds good. 😀