Rivco 6 circuit fuse block

[Cajunrider]

Has anyone installed the Rivco 6 circuit fuse block? I'm going to pick one up this week and install it behind my left side cover. I already have the Hoppy Converter wired directly to my battery and will be installing the Stebel horn hopefully next weekend. This fuse block comes with a #8 wire which connects to the positive pole on the battery. According the the wiring capacity chart in the link below, for 12V DC, #8 wire maximum capacity is 150 amps. The Stebel Horn requires a 20 amp circuit and I forget what the Hoppy is. This will be ideal for future accessories such as the Powerlet for the GPS and other goodies. There are several retailers online where these can be purchased but I have three local dealers who sell them. Best price I've found online is $35.95 + shipping. One of the local dealers may be able to beat that. Scroll down after opening the link below. There is a chart which compares the maximum amp capacity of wiring in 120v AC and 12v DC circuity. I was surprised at the difference between the two.

http://www.rowand.net/Shop/Tech/WireCapacityChart.htm

[Yellow Jacket]

I'm not sure I believe the amp ratings that chart shows for the 12 VDC.

The heat generated by current is what limits the safe amount of current through a particular size of wire.

As far as I know, 1 amp of current will produce the same amount of heat going through a wire regardless of the voltage which is pushing it.

There may be some difference between DC current and AC current due to the fact that AC current flow in one direction, comes to a stop and then flows in the opposite direction. Standard household 120 VAC has a frequency of 60 hz which means the current flow (and polarity) reverses direction 60 times a second.

If we have any electrical engineers on board they may be able to shed more light on this issue.

[Cajunrider]

Bob, I showed the chart to two of our electricians today and they agreed that the wiring will carry much more amperage on 12v DC than it will on 120v AC. One actually thought it was more extreme than the chart showed. Our electrical engineer will be here Thursday. I'll get his opinion on the chart and post what he thinks. I know that the circuits I will use will more than likely not exceed 60 - 80 amps if that much. I will hook up my Hoppy, a Stebel horn, and a Powerlet to it for running my little air compressor. I'll pick up power for the GPS from the headlight bucket. Thanks for your insight.

[Sin City Stan]

I'm not sure I believe the amp ratings that chart shows for the 12 VDC.

The heat generated by current is what limits the safe amount of current through a particular size of wire.

As far as I know, 1 amp of current will produce the same amount of heat going through a wire regardless of the voltage which is pushing it.

There may be some difference between DC current and AC current due to the fact that AC current flow in one direction, comes to a stop and then flows in the opposite direction. Standard household 120 VAC has a frequency of 60 hz which means the current flow (and polarity) reverses direction 60 times a second.

If we have any electrical engineers on board they may be able to shed more light on this issue.

You are right. An amp is an amp. You can run 150 amperes through a #8 wire. It's really no problem. However, unless you are using teflon insulation the insulation will melt off leading to bare wires and very spectacular short circuit. Although I don't know of any motorcycle that can produce 1800 watts and if one does exist it would eat up 8-10 HP doing it. (1800 watts equals 150 amperes at 12 volts)

A 480 watt alternator which is an upper middle of the road alternator for a motorcycle will produce 40 amperes. Note it will take quite a bit more than idle speed to produce this much power. Take note, the National Electric Code (NEC) rates a #8 wire at 40 amperes. Coincidence . . . I don't think so.

So . . . Use a #8 wire to connect your fuse block. Protect it with a 40 ampere fuse. Then go forth and illuminate.

[Cajunrider]

Our electrical engineer just viewed the chart and says it is accurate in his viewpoint.
This is his explanation as to why:

Current (amps) X voltage = power = heat
The smaller the wire, the less ability it has to dissipate heat. That's why the 22 gauge wire capacity is equal for 120v AC and 12v DC. Make sense??

[Sin City Stan]

Our electrical engineer just viewed the chart and says it is accurate in his viewpoint.
This is his explanation as to why:

Current (amps) X voltage = power = heat
The smaller the wire, the less ability it has to dissipate heat. That's why the 22 gauge wire capacity is equal for 120v AC and 12v DC. Make sense??

Doesn't make sense.
Have your engineer check the Neher-McGrath formula for allowable ampacity on a conductor. This is a conservative formula but the one that is approved per the National Electric Code 310.15(C). This formula covers 0 – 2000 volts

The passing of current through a wire develops heat. In order to not melt the insulation and cause a “short circuit” you limit the current to a safe level that does not cause heat sufficient to melt the insulation.

Assume you use THHN/THWN wire the insulation rating is 90C (194F) and the ambient air around the wire is 60C (140F). Remember this is right above the engine. The resistance of #8 wire is .000778 per foot the highest safe amperage that can be carried is 59 amperes.

If you use a higher ambient such as 70C (158F), which is a safer guess considering the location of the wire. The allowable amperage would calculate to 39.6 amperes which is really what I would consider safe.

If you want to safely carry more amperage on a #8 wire you can use the Teflon insulation I mentioned before. FEP insulation is rated 200C (392F) and you could run 257 amperes through it. Although, the wire insulation will not melt, whatever it’s connected to would act as a heat sink and it would melt..

I would have included the formula but my computer does not have all the fancy symbols to show it. Just Google it and do the math yourself.

[cactusjack]

Our electrical engineer just viewed the chart and says it is accurate in his viewpoint.
This is his explanation as to why:

Current (amps) X voltage = power = heat
The smaller the wire, the less ability it has to dissipate heat. That's why the 22 gauge wire capacity is equal for 120v AC and 12v DC. Make sense??

If I remember what I learned in Mr. Crook's 10th grade electronics class,
amps * volts = watts
watts / volts = amps

[dogdoc]

who remembers 10th grade honestly? :-)

[blowndodge]

CJ does! He just finished it!! http://s2.images.proboards.com/grin.gif

[Todd]

LOL!!! Have feeling that will cost you a beer BD!!

[cactusjack]

LOL!!! Have feeling that will cost you a beer BD!!




aw, no.......it's going to cost him 2!

At least I finished 10th grade, BD!