Fuse taps using the hot side aka wrong side

Pbets

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#1
I've gone ahead and installed my pmp and decided to use a couple of fuse taps.

http://s776.photobucket.com/user/ronjenx/media/1CircuitDiagram.jpg.html

The problem is amazingly my fuse box won't allow me the room to install them the proper way (load on cold side). So what if I run it with the load on the hot side (have room for the wire to kick out).. Could I then:

A) use two 7.5 amp fuses to replace the 15 amp fuse that came out (cigarette lighter).

Or

B) use in line fuses (2amp?) with the taps in wrong.
 

jokiin

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#2
to the existing fuse it won't matter, works either way, should also continue to use the rated fuse for that circuit, for the extra lead you're tapping off that one effectively becomes unfused, if you add a suitable fuse inline will do the same thing
 

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#3
Huh?

jokiin, am I missing something here? It makes no difference which way the tap is inserted as you say. Either way the top fuse ( to the PMP) will still work correct?

In his diagram it makes no difference if the power from the fuse box goes in from the bottom right or bottom left thru the fuse, same thing. Then the power for the top left is fed either directly from the fuse box or thru the bottom fuse, so it will be hot. Then the top fuse will complete the circuit to the PMP correct?
 

jokiin

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#4
it would still work but if you put it in the wrong way the second outlet won't be protected by the fuse, original outlet works either way
 

CDNinHH

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#6
Untitled1.jpg Untitled2.jpg

I must be thick, but I can't figure this out. I have attached a couple diagrams for you to look at to see why I think it makes no difference, well except in one the PMP is protected by both the 30 amp and the 5 amp, whereas in the other way only the 5 amp. But if I'm wrong I need to check my installation because I never considered there was a right or wrong way to put in the fuse tap.
 

Nigel

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#7
View attachment 20358 View attachment 20359

I must be thick, but I can't figure this out. I have attached a couple diagrams for you to look at to see why I think it makes no difference, well except in one the PMP is protected by both the 30 amp and the 5 amp, whereas in the other way only the 5 amp. But if I'm wrong I need to check my installation because I never considered there was a right or wrong way to put in the fuse tap.
You should connect after the original fuse so that whatever is supplying the power is still correctly protected from overload by the original fuse. If you connect before the original fuse then it is possible to take more power than the circuit was designed for and it is possible to overload the supply.

In reality the supply is probably capable of supplying far more power than the rating of the original fuse so it wont matter, but you can't guarantee that without checking, it is possible it is supplied via your ECU and taking an extra amp over the original fuse will blow up your ECU which will be a very expensive mistake.
 

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#8
Huh?

If I get a dead short on the PMP side the 5 amp fuse will blow regardless of which way this is used, make no differance. Reread your post, the 30 amp fuse protects the original load in either direction.


I have to say, even though these things are made in China I would bet that if there was right and wrong way to install it there would some kind of warning or fool proof design.
 
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Nigel

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#9
Huh?

If I get a dead short on the PMP side the 5 amp fuse will blow regardless of which way this is used, make no differance.
But if the original fuse was 5 amps and at the time you get your short the original circuit was drawing 5 amps then you will draw 10 amps before you blow your 5 amp fuse. Do you know that 10 amps will not destroy the supply? The point is that it is possible to overload the supply if you tap from the hot side, but impossible and therefore safe if you tap from the cold side.
 
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Pbets

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#10
View attachment 20358 View attachment 20359

I must be thick, but I can't figure this out. I have attached a couple diagrams for you to look at to see why I think it makes no difference, well except in one the PMP is protected by both the 30 amp and the 5 amp, whereas in the other way only the 5 amp. But if I'm wrong I need to check my installation because I never considered there was a right or wrong way to put in the fuse tap.

Fixed my post.. sorry for confusion. This is what I got posting right after waking up.
 

CDNinHH

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#11
Ok, now I see what you are getting at. But at least for me I always choose a circuit that is at least twice if not 4 times the tap load.

Anyway, that is a bit off the original question about needing an inline fuse if installed one way or the other.

The OP should install a 15 amp in the bottom and a 5 in the top regardless of which way he installs the tap the PMP is protected by the 5 amp. The lighter still by the 15 amp.

Just seen that he wants to use a 2 amp not a 5, thats fine.
 
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#12
Think about it this way.. Suppose you used a tap on a 3o amp circuit to ADD another 30 amp service. One way would work and the other way would see 60 amps go through the original circuit and fail. In the image (above) the left hand side circuit "could" see a 35 amp load across the 30 amp fuse. The right hand picture will not see a combined load.
 
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CDNinHH

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#13
All true.....but that is not what the OP was talking about here....apples and oranges. We are talking about a 15 amp circuit versus a 2 amp tap load. And I repeat myself " IN THIS INSTANCE, it makes no difference which way the tap goes in"

And if read what I posted I alluded to that when I say "protected" by the 30 amp.
 
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Pbets

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#14
So I guess the better question is.. Is this safe rather than correct. I'm actually using two separate CLA 15amp circuits and 3amp fuses for the pmp on top.

Sorry again for confusion.
 

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#15
So you are using one tap on a 15 amp switched circuit with a 3 amp in the top slot and another tap in a HOT 15 amp circuit with a 3 amp in the top slot right? I see no problem in that instance regardless of which way the taps are inserted.
 
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Pbets

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#16
So you are using one tap on a 15 amp switched circuit with a 3 amp in the top slot and another tap in a HOT 15 amp circuit with a 3 amp in the top slot right? I see no problem in that instance regardless of which way the taps are inserted.
Yes exactly this..
 

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#17
Ok, glad we cleared that up. Which side of Canada are you on? SK boy myself...
 

Nigel

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#18
I see no problem in that instance regardless of which way the taps are inserted.
The big problem here is that overloading a circuit can potentially cause a fire and since cars are not made from flame resistant plastics and fabrics they tend to burn extremely well. Giving advice to someone that can potentially result in a death is not sensible even if it is unlikely to happen.

My suggestion is to either fit another fused circuit connected to something you know to be protected by its own fuse, or direct to the car battery with your own fuse, or use a circuit where you can reduce the size of the original fuse by enough to avoid an overload, eg use a 20amp circuit and replace the original fuse with a tap containing 15 amp and 5 amp fuses. You need to choose a circuit where the full capacity of the original fuse was not actually in use, probably the case in a CLA circuit.

Yes exactly this..
Sounds like you have connected the output of two fuses together? Not good if that is the case since the original equipment downstream of the fuses is no longer correctly protected...
 

CDNinHH

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#19
The big problem here is that overloading a circuit can potentially cause a fire and since cars are not made from flame resistant plastics and fabrics they tend to burn extremely well. Giving advice to someone that can potentially result in a death is not sensible even if it is unlikely to happen.
The sky is falling, the sky is falling......

Why do you think almost everyone is using fuse taps rather than direct to the battery, are we all in danger of being incinerated?

I'm done with this topic....
 

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