I checked the wiring tonight and it is ok. I'll get some 5a fuses tomorrow and see how that works later this week. I may be trying to fix a problem that didn't need fixing, but I just don't think this connection should be using a 15a fuse. If I was using all the heated gear I would leave it as shipped. By changing the fuse to a lower rated one I was trying to keep it in line with the usage. Thanks for the help guys I appreciate it.

 

http://www.gerbing.com/Downloads/12vInstructions.pdf
all I got was connect to the battery.... and run engine before using....
guess the HD gear comes with a manual.....
I don't see anything about playing with fuse size

Live and learn (still leaving the OEM 15amp fuse alone)

 

Years ago I was taught that you double the the amp range to allow for spikes in power.

 

gunkholes & cHarley speak well. Another term for the initial higher draw when you turn on an item is inrush current, and though you'll see it more on a bike's lighting circuits, heated clothing is another potential place. As noted, the current will also be slightly higher when the gloves are cold. As the thin wires heat their resistance increases and the current drops in a linear manner. Voltage is "potential difference" and will stay the same as long as the circuit's draw doesn't exceed the ampacity of the supply source. Depending on AC or DC circuit, resistance or inductive loads, etc it's not uncommon to see fuse sizings of 120%-150% of the rated device current. Wanna cut through the BS? Try a 5amp and if there never is another blown fuse you'll be pretty safe guessing it was either a bad fuse or your unit draws a little more than the median of that item. A 5 amp is plenty to protect the actual wiring. Use a slow or fast blow according to whatever the original one was, look for the AGC, ABC, etc # on the original fuse & replacements and go with that in a 5A. Normally I'd go along with using a slo-blo but I have no idea if the controller has inrush damping built in already to make that unneeded in this case.

 

I have all the Gerbing gear including the dual controller. The various sized fuses/instructions only came with one component and I don't recall which one.

It's clear from the instructions that Gerbing recommends the included 3amp fuse for the 2.2amp gloves. When multiple components are worn Gerbing says to calculate the total amps and use the lowest fuse possible. There's no mention of adding "spike" loads to the calculation.

I also find it interesting that they give you the amp draw for every product they make except for the controller and make no mention of increasing the fuse size when using it. The instructions for the controller state only that it only draws as much power as the user requests.

So the jury's still out in my mind as to whether the controller adds to the amp load requirement of the "system".

 

Whether the controller adds draw is no longer relevant, when you consider the "inrush" current that is spoke of in the posts above.
I have seen the inrush effect on AC motors, but until it was mentioned on this thread, I had never considered it in this application.

Thank you guys for the thorough explanations!

 

While I have not measured the "inrush" current on the Gerbing gloves, the Gerbing equipment is a DC resistive heating device much like an automotive type cigarette lighter.

A bit over a year ago, I installed a cigarette lighter on my bike. Since the lighter package contained no information on the current draw, I was careful to measure the amperage draw for the lighter before deciding on the wire gauge and fuse size for the power circuit and the results should be useful here.

The lighter while heating drew a nominal 3-5 amps. The hotter it got the lower the amps fell in the 3-5 range. However, during the 1st 1/4 second after the lighter was pushed in, the INRUSH current spiked to 19 Amps.

This lighter would probably have been rated at about 5 Amps had the manufacturer chosen to put that data on the package, but I can tell you from experience, that a 20 amp fast blow fuse in this circuit will blow after 6 to 8 uses of the lighter. A Slo Blo type fuse/circuit breaker, should be used in any application where a high inrush current occurs unless you like changing fuses and the above example demonstrates how much higher the inrush current may be compared to the manufactures "nominal" amp rating for a product. In the end, it took a 25 amp Slo Blo fuse to provide reliable operation of the lighter.

 

Just saw the added comments from the Edit...

While your theory is anecdotal, what could be occurring with an intermittent connection is that you're going to get numerous make-breaks, which would be like turning a light switch on & off many times. Each surge can cause a fuseable element to exercise a little, and after some time, it will just give it up, kinda like a light bulb filament will fail after too many rapid cycles.

Regarding the controller, the draw is very minimal, since it is not a thermostat -- it just interrupts the current flow at various duty cycles. However, each one of those make-breaks will have the same effect on a fuse I described above, so if you're operating close to the fuse's design limit, the chance for failure increases.

There is little harm in installing the largest fuse that the wiring can safely handle -- faults (shorts) usually don't cause just a slight increase in current flow; they usually cause a big increase, which will blow most fuses.

 

Just realized that according to Gerbing the combined amps of all my gear is 14.8. I'm running a 15 amp fuse which means I only have a .2 amp margin (less than the ops).

Guess I don't have any "inrush current"

 

Maybe you just have a "really good" fuse