Piggy-back fuseholders - a right way and a wrong way?

I give up.. :).. Run your supply to your web cam right from the battery.. no worries about overloading your fuse box.
 
Pretty sure this video sums it up correctly, based on my research + reading through this thread:

 
Well... I was going to abstain from further comments in this thread.. But if you think the commentary at ~7:35 sums it up correctly.. or clearly.. my condolences.

One point the "other" video made that I had not thought of.. is... Do you want.. is it important.. to have your application continue to work should.. for what ever reason.. the original fuse blows. Installing the fuse tap one way it will.. and one way it wont..
 
Firstly this is in no way comparable to house wiring beyond having a few common components. Inside a car fusebox there will be at least two power feeds: Always on, and on only when the key is turned on (switched). Some of the newer cars have delayed off circuits which could add other power feeds into the fusebox. In some older cars these feeds are done with wire jumpers, not buss bars, although the functioin is exactly the same. All we need to know about this is that the power feed goes to one side of any given fuse, and the other side of that fuse goes to the load.

To make this easy to understand I'll use "12V" to identify the power feed to the fusebox, whether always on, switched, or delayed. So your interior dome lights go like this:
12V to fuse, other side of that fuse (downstream side) to the door switches, then from there to the dome light. Should an overload or short occur anywhere past the other "downstream" side of this fuse, the fuse will blow to protect the fusebox and other car wiring.

Now let's consider adding onto this. The car was designed so that the wiring in this circuit could sustain normal operation of the dome light at the expected load without the fuse blowing. If we add our new load to the 12V side of the fuse, the original car fuse for that circuit is not protecting the new load, but it stil protects the dome light circuit. If our new load shorts or overloads the circuit, the fusebox and car wiring will see that load unprotected and you've got problems.

Now lets add a fuse for our new load so that an overload or short in the new circuit will cause the new fuse to blow before the fusebox and car wiring are affected. You might think you're protected but you're not, because we haven't accounted for the extra power being used by the new load during normal operation. When that is added to the power used by dome light operation, you might be overloading the 12V power feed at the fusebox which was not designed to have this extra power drawn from it. Being that our new load is a dashcam which uses little power, there is probably enough capacity for it's new load but we cannot know this for certain. We have now increased the total load.

So let's change the new load to the other "downstream" side of the dome light fusewithout adding a new fuse for it. Now if the new load shorts or overloads, it has only the dome light fuse to protect the fusebox and car wiring, and the dome light fuse will protect these adequately, but it will not protect the new load wiring and load that is not designed to handle as much power as the dome light normally uses and is fused for. During normal operation the total load is the same as before. It is only when the new load malfunctions that we have a problem.

Now let's add a fuse to our new load which is now drawing power fron the "downstream" side of the larger dome light fuse. Again the total load remains the same during normal operation, but that total load my now be more than the car fuse can tolerate, thus it might blow without any malfunctions occuring. Normally the car fuse and wiring will have some extra capacity designed in so that increased resistance over time due to wire and connector aging will be handled while still covering a larger overload. If a short or overload occurs in the dome light circuit, the dome light fuse will blow and now our new load has lost it's power source, but the fusebox and car wiring go unharmed so we don't have a problem other than the loss of function of our new load (dashcam). Now instead of a malfunction in the dome light, lets consider it working normally and having an overload or short occur in our new load, whose fuse is smaller in capacity than the dome light fuse feeding it. This will blow the smaller fuse of the new load before affecting the dome light fuse, the fusebox, or the car wiring. The only problem we have is loss of function of the new load (dashcam) and the dome light will still function normally.

Now lets consider that everything is functioning normally in both the dome light circuit and with the new load, both of which are fused appropriately as shown above. Can we possibly have a problem? Yes, and here's why- we have increased the normal load into a higher total load which the 12V at the fusebox must supply. If it cannot supply the total power safely, then we can have a problem even with no fuses blowing and with everything functioning normally. Since we cannot know for certain whether the 12V at the fusebox can tolerate the added load there is still some risk, but being that our new load is a dashcam using very little power, this risk is very minimal. In engineering electrical circuits, thr normal practice is to size the wire to meet the expected load, then fuse at a level which will carry the expected load, but with a small safety margin built in because when the wiring and the fuse are the same rating it is impossible to be certain that the fuse will blow before the wiring gets harmed. So the wiring feeding any fuse in a car will be able to carry more power than the fuse does, even if only slightly. Since our power needs for a dashcam is also slight it's very unlikely that our new total load will exceed the ability of the car wiring to handle it safely. If we fuse things like I last described here, each circuit we're playing with will be protected with the lowest possibility of one malfunction causing another malfunction.

So as I posted before, the safest way to do this has this power flow: 12V > domelight (or other) car fuse > dashcam fuse > dashcam.
It is not the only way, and as I've shown above the car can be protected doing this differently, but this is the best way for the reasons already noted. Being that our power requirements are so small, I would not worry if we cannot determine which side of a car fuse is 12V and which side is downstream, since our smaller cam fuse will blow if it has a problem which protects the car anyway and that is our main goal.

Just remember that I've shown where even normal operation could possibly cause the car fuse to overload and blow, which is why you never want to tap into any fuse which could affect safe car functioning such as exterior lighting, engine controls, or airbags. This is the most important part of doing a dashcam install safely so never break this rule even if no other suitable power source can be found. Better to be safe without your cam than to risk death or injury just to have it.

Whew, I feel like I've just written a term paper for college but I hope that everyone can now understand what we're dealing with and how to best do it safely with the least risks in everything.
Phil
Basically what you said is sequential is best. Parrallel is OK but a secondary choice given that the amps required to power a dash cam is very low. Having said that would you say its appropriate to run sequentially off a circuit that currently has a 7.5A fuse for controlling the fuel filler door (and only the fuel filler door)? Or would you start messing with a 20A fuse circuit controlling stuff like lights and other things? I'm worried about the wire guages.
 
Well... I was going to abstain from further comments in this thread.. But if you think the commentary at ~7:35 sums it up correctly.. or clearly.. my condolences.

One point the "other" video made that I had not thought of.. is... Do you want.. is it important.. to have your application continue to work should.. for what ever reason.. the original fuse blows. Installing the fuse tap one way it will.. and one way it wont..
I think any logical person would rather preserve the core electrical system of the car over a sub $200 dash cam. Therefore sequential is best IMO.
 
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Hi
I have posted many replies as to the correct way to fit a fuse tap. First of all check to see if you have a spare fuse location in the fusebox this would be the best option as it is unlikely that the vehicle's fusebox is fully used. The add a fuse is used to add a second connection on the live side only. As for what size fuse to tap into it is more important that the fuse you are intending to use is not safety related for example use cigar lighter - heated rear screen. Use the recommended hard wire kit. This method it is simple and correct, use the correct fuse for the camera, find a fuse of the same or slightly higher size.
Remove the fuse.
With a simple tester find the live side.
Plug in the add a fuse with the red wire on the opposite side away from the live side.
Replace the original fuse, note this may now have to be replaced with a mini fuse as long as it is rated the same amperage as the original.
Now this is important for determining that it is correctly fitted.
The original circuit should work as before.
Now test the red wire on the add a fuse it should be dead - no current. If this is the case the add a fuse is correctly fitted.
The red wire should only be live when the second fuse is added, this is the live side starting point of whatever you wish to add. As for worrying about overloading the circuit this happens when you do not use the method I have just described. My way you are making two circuits independently fused the only thing shared with the original fuse is the live feed for the fuse.
It is important to use fuses of the same or similar ratings don't be put off by this because you are creating a new circuit. Should you fit lager rated fuses than what is recommended that will be the start of your troubles to come and dangerous.
Best ofmluck

I just finished reading all 9 pages of comments and interpret the conclusion as that it is generally more safe (preventing the more expensive worse case scenario) to connect the fuses in series (with the new/addon fuse being rated at equal or lesser than the existing fuse) so that you never pull more than the wire/circuit was made to handle.

My question now is if the above quoted procedure explains the process for series or parallel?
 
It's for parallel IMO. But he is wrong that the circuit cannot be overloaded as that is possible when using the parralel method. There is so much misunderstanding out there it creates confusion. Also, the sellers of dash cams and manufacturers add to the confusion but not addressing the topic or addressing it incorrectly IMO.
 
https://www.lumision.com/product/fusetap-mini/ Per Lumision, manufactuer of fuse taps the proper way to install.

Bussmann doesn't have instrucitons on thier site.

I am wondering how Nigel reconciles his view to Lumision's?????

Your link shows a parallel connection as indicated by the instructions at the bottom. If.. you have power at the new circuit.. WITHOUT the original fuse in place.. you have installed it in a parallel orientation. Whether you think this is the right or wrong way is up to you.
 

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Your link shows a parallel connection as indicated by the instructions at the bottom. If.. you have power at the new circuit.. WITHOUT the original fuse in place.. you have installed it in a parallel orientation. Whether you think this is the right or wrong way is up to you.
Yes, I'm aware its parallel. My point is that a fuse tap manufacturer is stating that a parallel install is the proper way as implied by the instruction sheet on thier own website. Am wondering what Nigel has to say about it. If someone wnats to volunteer to call Bussman, who I think is a more credible manufactuer (part of Eaton, a major US industrial company), the number is 1 855 287 7626 for customer support. I may call later but am tied up today.
 
There is another way to FIGURE OUT both procedures, people are bound to read BOTH ways discussed in this thread, and USE BOTH ways, so my idea is to wait about 1 year and we will see how many cars/trucks BURN to the ground. The ones that burn to the ground or doing it the WRONG way, people who still are driving there original vehicle did it the RIGHT wayo_O:cool:
 
There is another way to FIGURE OUT both procedures, people are bound to read BOTH ways discussed in this thread, and USE BOTH ways, so my idea is to wait about 1 year and we will see how many cars/trucks BURN to the ground. The ones that burn to the ground or doing it the WRONG way, people who still are driving there original vehicle did it the RIGHT wayo_O:cool:
Then, how are you powering your cam now? Cig lighter socket?
 
LMJ since you know damn little about electronics and are acting like a parrot after reading what others say you are simply adding to the confusion!

PJones and Ralph (alphabetical listing) know more about electronics then I ever will so I will leave it up to them and a couple others to make a final decision (hopefully) and not add to a subject that I am not qualified to comment on in any way at this level.
 
LMJ since you know damn little about electronics and are acting like a parrot after reading what others say you are simply adding to the confusion!

PJones and Ralph (alphabetical listing) know more about electronics then I ever will so I will leave it up to them and a couple others to make a final decision (hopefully) and not add to a subject that I am not qualified to comment on in any way at this level.
You're lucky I have a good sense of humor.
 
Why would I be lucky that you think you have a good anything ?
 
FU.... I take it you ment Flowers for me, no thanks, I'm very picky about talking to strangers and idiots!
 
I'm sorry for the long delay for a reply. I didn't want to reply until I had a chance to collect examples to add to this discussion. Without new information then we're just saying the same thing over again. I've got the examples I just need to have a chance to make a response on the desktop computer because this phone just doesn't do it for me.

I appreciate that we have been able to have an adult discussion about this without getting defensive over someone else's different opinion and I hope it can stay that way. I don't care who is correct or incorrect, the whole purpose of this discussion it to determine a safe solution that everyone can use, and to come to that conclusion together. Like everything there are also scenarios where these rules could be broken. I don't believe those special rules will be consistent across the board so that is where people would need to use extreme caution and have a good grasp on what they are doing. With the information that comes out through discussion we can answer those questions as they come up so that hopefully everyone has a clear enough understanding at the end to be able to make those decisions or know well enough if it is beyond their current capabilities.

Work has had me swamped lately and December is tomorrow and I'm behind on my Christmas light sequencing... Life has kept me busy. I would like to bring some new information and explanations to the post soon, I'm just juggling a lot right now and just haven't had the chance yet. Again, I apologize for this.

Please don't feel like I'm picking on you Ralph2 when I bring this up but I do want to clarify a statement that you made. I understand you probably intended people to know that 240 can shock you easier because the potential can jump through a thicker insulation barrier with more ease than 110, but I worry that it may not be properly understood by all those that visit this forum looking for answers with how it was worded so I would like to clarify this one point right now since its safety related...

I know.. it is a safety thing.. at 240 volts a shock can kill.. at 110 most times it just hurts.

A shock can kill at both voltages. It's actually the amperage that kills (not the voltage). People have been killed working on circuits less than 48 volts before. People have also been shocked with thousands of Volts and lived. If the amperage is less Than 0.1 amps then you will most likely walk away, sore but alive. It's when the amperage increases to beyond that 0.1 amp threshold that problems occur. Get between the 0.1 and 0.2 amp range and it caused your heart muscle to seize and your heart stops, hope you said your goodbyes. Beyond that 0.2 range and you can often be brought back if someone is there to provide medical assistance within a reasonable time.

240 volt has the ability to jump through thicker insulting barrier but unless the amperage is there also then it's just going to hurt.

I work on 24 volt control circuits all the time and if my hands are sweaty or tacky at all then I can expect to get a shock if I touch the wires. With that in mind, the batteries in our cars can pass enough Amperage to weld a wrench to the chassis if you let it touch the terminals. We've welded drive shafts back together using a car battery, jumper cables, and some welding rod, when we were off road, so we could get home. Batteries can pack a punch even if it's only 12 volts.

Just something to keep in mind while you are working with the electricity.


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